fix: embed Console versioning error handling and cover checksum messages

Signed-off-by: Feng Ruohang <rh@vonng.com>

.github/workflows/go.yml

@@ -102,6 +102,11 @@ jobs:
       - name: Run tag replication tests under race detector
         run: go test -race ./cmd -run '^TestAPITagging' -count=1 -timeout=5m
 
+      - name: Run Object Lock authorization and overwrite tests under race detector
+        env:
+          MINIO_API_REQUESTS_MAX: "10000"
+        run: go test -race -tags kqueue,dev ./cmd -run '^Test(APIPutObjectRetention|APIVersionAddressedWrite|PutObjectRetention|DirectoryObjectLock|ObjectLockOverwrite|APICopyObjectPreservesVersionAfterSuspension|MultipartNullObjectLock|PoolsObjectLockOverwrite|MultipartVersioningTransitions|PlanReview|RecoveredMultipartUpload)' -count=1 -timeout=5m
+
   crosscompile:
     name: Cross Compile
     runs-on: ubuntu-latest

.github/workflows/release.yml

@@ -70,6 +70,12 @@ jobs:
           buildscripts/verify-rebrand.sh
           dockerscripts/docker-entrypoint_test.sh
 
+      # Keep this gate aligned with the Object Lock race regression in go.yml.
+      - name: Gate release on Object Lock authorization and overwrite tests under race detector
+        env:
+          MINIO_API_REQUESTS_MAX: "10000"
+        run: go test -race -tags kqueue,dev ./cmd -run '^Test(APIPutObjectRetention|APIVersionAddressedWrite|PutObjectRetention|DirectoryObjectLock|ObjectLockOverwrite|APICopyObjectPreservesVersionAfterSuspension|MultipartNullObjectLock|PoolsObjectLockOverwrite|MultipartVersioningTransitions|PlanReview|RecoveredMultipartUpload)' -count=1 -timeout=5m
+
       - name: Compute release variables
         env:
           # Passed through the environment, never interpolated into the script

Dockerfile.goreleaser

@@ -1,4 +1,4 @@
-FROM golang:1.27.1-alpine@sha256:cf6fca6641884b8433441b2b0652976f975e1d0fdd26d177eaaf8596087f3125 AS curl-build
+FROM golang:1.27.2-alpine@sha256:f92b6ef800e499660581efdabdf25d9d817a9d124eaf900924f0504e7e27e12d AS curl-build
 ARG TARGETARCH
 COPY dockerscripts/build-static-curl.sh /build/build-static-curl
 RUN /bin/sh /build/build-static-curl
@@ -9,7 +9,7 @@ COPY --from=curl-build /go/bin/curl /curl
 COPY --from=curl-build /etc/ssl/certs/ca-certificates.crt /etc/ssl/certs/ca-certificates.crt
 ENTRYPOINT ["/curl"]
 
-FROM golang:1.27.1-alpine@sha256:cf6fca6641884b8433441b2b0652976f975e1d0fdd26d177eaaf8596087f3125 AS build
+FROM golang:1.27.2-alpine@sha256:f92b6ef800e499660581efdabdf25d9d817a9d124eaf900924f0504e7e27e12d AS build
 
 ARG TARGETARCH
 

Makefile

@@ -4,7 +4,7 @@ LDFLAGS := $(shell go run buildscripts/gen-ldflags.go)
 
 GOOS ?= $(shell go env GOOS)
 GOARCH ?= $(shell go env GOARCH)
-GOLANGCI_VERSION ?= v2.13.1
+GOLANGCI_VERSION ?= v2.14.0
 
 VERSION ?= $(shell git describe --tags)
 REPO ?= docker.io/pgsty

buildscripts/checkdeps.sh

@@ -7,7 +7,7 @@ _init() {
 
 	## Minimum required versions for build dependencies
 	GIT_VERSION="1.0"
-	GO_VERSION="1.27.1"
+	GO_VERSION="1.27.2"
 	OSX_VERSION="10.8"
 	KNAME=$(uname -s)
 	ARCH=$(uname -m)

cmd/api-errors-checksum_test.go

@@ -0,0 +1,45 @@
+// Copyright (c) 2026 PGSTY
+//
+// This file is part of SILO Object Storage.
+// SPDX-License-Identifier: AGPL-3.0-or-later
+//
+// This program is free software: you can redistribute it and/or modify
+// it under the terms of the GNU Affero General Public License as published by
+// the Free Software Foundation, either version 3 of the License, or
+// (at your option) any later version.
+//
+// This program is distributed in the hope that it will be useful
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+// GNU Affero General Public License for more details.
+//
+// You should have received a copy of the GNU Affero General Public License
+// along with this program. If not, see <http://www.gnu.org/licenses/>.
+
+package cmd
+
+import (
+	"fmt"
+	"net/http"
+	"testing"
+
+	"github.com/minio/minio/internal/hash"
+)
+
+func TestChecksumMismatchAPIMessage(t *testing.T) {
+	for _, algorithm := range []string{"CRC32", "CRC32C", "SHA1", "SHA256", "CRC64NVME", ""} {
+		t.Run(algorithm, func(t *testing.T) {
+			mismatch := hash.ChecksumMismatch{Algorithm: algorithm, Want: "expected", Got: "actual"}
+			want := errorCodes.ToAPIErr(ErrContentChecksumMismatch).Description
+			if algorithm != "" {
+				want = fmt.Sprintf("The %s you specified did not match the calculated checksum.", algorithm)
+			}
+			for _, err := range []error{mismatch, fmt.Errorf("upload: %w", mismatch)} {
+				got := toAPIError(t.Context(), err)
+				if got.HTTPStatusCode != http.StatusBadRequest || got.Code != "XAmzContentChecksumMismatch" || got.Description != want {
+					t.Fatalf("toAPIError(%v) = %+v, want 400 XAmzContentChecksumMismatch: %s", err, got, want)
+				}
+			}
+		})
+	}
+}

cmd/api-errors.go

@@ -550,7 +550,7 @@ var errorCodes = errorCodeMap{
 	},
 	ErrBadDigest: {
 		Code:           "BadDigest",
-		Description:    "The Content-Md5 you specified did not match what we received.",
+		Description:    "The Content-MD5 you specified did not match what we received.",
 		HTTPStatusCode: http.StatusBadRequest,
 	},
 	ErrEntityTooSmall: {
@@ -2505,6 +2505,14 @@ func toAPIError(ctx context.Context, err error) APIError {
 	case errors.Is(err, errMissingPartChecksum):
 		apiErr.Description = strings.TrimPrefix(err.Error(), errMissingPartChecksum.Error()+": ")
 	}
+	// PutObject/UploadPart checksum mismatches name the algorithm in the
+	// message, matching S3 (e.g. "The CRC32 you specified did not match the
+	// calculated checksum."). Falls through to the generic table description
+	// when the algorithm is unknown.
+	var checksumMismatch hash.ChecksumMismatch
+	if errors.As(err, &checksumMismatch) && checksumMismatch.Algorithm != "" {
+		apiErr.Description = fmt.Sprintf("The %s you specified did not match the calculated checksum.", checksumMismatch.Algorithm)
+	}
 	switch apiErr.Code {
 	case "NotImplemented":
 		apiErr = APIError{

cmd/auth-handler.go

@@ -28,13 +28,10 @@ import (
 	"mime"
 	"net/http"
 	"net/url"
-	"strconv"
 	"strings"
 	"sync/atomic"
-	"time"
 
 	"github.com/minio/minio/internal/auth"
-	objectlock "github.com/minio/minio/internal/bucket/object/lock"
 	"github.com/minio/minio/internal/etag"
 	"github.com/minio/minio/internal/hash"
 	xhttp "github.com/minio/minio/internal/http"
@@ -733,48 +730,6 @@ func setAuthMiddleware(h http.Handler) http.Handler {
 	})
 }
 
-func isPutRetentionAllowed(bucketName, objectName string, retDays int, retDate time.Time, retMode objectlock.RetMode, byPassSet bool, r *http.Request, cred auth.Credentials, owner bool) (s3Err APIErrorCode) {
-	var retSet bool
-	if cred.AccessKey == "" {
-		return ErrAccessDenied
-	}
-
-	conditions := getConditionValues(r, "", cred)
-	conditions["object-lock-mode"] = []string{string(retMode)}
-	conditions["object-lock-retain-until-date"] = []string{retDate.UTC().Format(time.RFC3339)}
-	if retDays > 0 {
-		conditions["object-lock-remaining-retention-days"] = []string{strconv.Itoa(retDays)}
-	}
-	if retMode == objectlock.RetGovernance && byPassSet {
-		byPassSet = globalIAMSys.IsAllowed(policy.Args{
-			AccountName:     cred.AccessKey,
-			Groups:          cred.Groups,
-			Action:          policy.BypassGovernanceRetentionAction,
-			BucketName:      bucketName,
-			ObjectName:      objectName,
-			ConditionValues: conditions,
-			IsOwner:         owner,
-			Claims:          cred.Claims,
-		})
-	}
-	if globalIAMSys.IsAllowed(policy.Args{
-		AccountName:     cred.AccessKey,
-		Groups:          cred.Groups,
-		Action:          policy.PutObjectRetentionAction,
-		BucketName:      bucketName,
-		ConditionValues: conditions,
-		ObjectName:      objectName,
-		IsOwner:         owner,
-		Claims:          cred.Claims,
-	}) {
-		retSet = true
-	}
-	if byPassSet || retSet {
-		return ErrNone
-	}
-	return ErrAccessDenied
-}
-
 // isPutActionAllowed - check if PUT operation is allowed on the resource, this
 // call verifies bucket policies and IAM policies, supports multi user
 // checks etc.

cmd/batch-handlers.go

@@ -583,7 +583,11 @@ func toObjectInfo(bucket, object string, objInfo minio.ObjectInfo) ObjectInfo {
 func (r BatchJobReplicateV1) writeAsArchive(ctx context.Context, objAPI ObjectLayer, remoteClnt *minio.Client, entries []ObjectInfo, prefix string) error {
 	input := make(chan minio.SnowballObject, 1)
 	opts := minio.SnowballOptions{
-		Opts:     minio.PutObjectOptions{},
+		Opts: minio.PutObjectOptions{
+			Internal: minio.AdvancedPutOptions{
+				ReplicationRequest: true,
+			},
+		},
 		InMemory: *r.Source.Snowball.InMemory,
 		Compress: *r.Source.Snowball.Compress,
 		SkipErrs: *r.Source.Snowball.SkipErrs,

cmd/bucket-handlers.go

@@ -1273,6 +1273,12 @@ func (api objectAPIHandlers) PostPolicyBucketHandler(w http.ResponseWriter, r *h
 		writeErrorResponseHeadersOnly(w, toAPIError(ctx, err))
 		return
 	}
+	if isDirObject(object) {
+		if _, _, _, s3Err := checkPutObjectLockAllowed(ctx, r, bucket, object, objectAPI.GetObjectInfo, ErrNone, ErrNone, false); s3Err != ErrNone {
+			writeErrorResponse(ctx, w, errorCodes.ToAPIErr(s3Err), r.URL)
+			return
+		}
+	}
 	opts.WantChecksum = checksum
 
 	fanOutOpts := fanOutOptions{Checksum: checksum}

cmd/bucket-object-lock.go

@@ -20,8 +20,8 @@ package cmd
 import (
 	"context"
 	"errors"
-	"math"
 	"net/http"
+	"strconv"
 	"strings"
 	"time"
 
@@ -164,76 +164,129 @@ func enforceRetentionBypassForDelete(ctx context.Context, r *http.Request, bucke
 	return nil
 }
 
-// enforceRetentionBypassForPut enforces whether an existing object under governance can be overwritten
-// with governance bypass headers set in the request.
-// Objects under site wide WORM cannot be overwritten.
-// For objects in "Governance" mode, overwrite is allowed if a) object retention date is past OR
-// governance bypass headers are set and user has governance bypass permissions.
-// Objects in compliance mode can be overwritten only if retention date is being extended. No mode change is permitted.
+// isRetentionActionAllowed evaluates action for a PutObjectRetention request
+// with the object-lock condition keys derived from the requested retention.
+// The keys come from the request, not from the stored version, so the
+// handler can decide s3:PutObjectRetention before reading any object state.
+func isRetentionActionAllowed(action policy.Action, bucket, object string, objRetention *objectlock.ObjectRetention, r *http.Request, cred auth.Credentials, owner bool) bool {
+	if cred.AccessKey == "" {
+		return false
+	}
+	t, err := objectlock.UTCNowNTP()
+	if err != nil {
+		return false
+	}
+	conditions := getConditionValues(r, "", cred)
+	conditions["object-lock-mode"] = []string{string(objRetention.Mode)}
+	conditions["object-lock-retain-until-date"] = []string{objRetention.RetainUntilDate.UTC().Format(time.RFC3339)}
+	// Relative days from now, for "object-lock-remaining-retention-days".
+	// Clearing retention (<Retention/>) has a zero RetainUntilDate, which must
+	// evaluate as 0 remaining days rather than a large positive math.Abs delta
+	// from year 0001.
+	days := 0
+	if !objRetention.RetainUntilDate.IsZero() && objRetention.RetainUntilDate.After(t) {
+		// Time.Sub saturates after about 292 years. Count seconds instead so
+		// maximum-retention policies also apply to distant RFC3339 dates.
+		seconds := objRetention.RetainUntilDate.Unix() - t.Unix()
+		days = int(seconds / 86400)
+		if seconds%86400 != 0 || objRetention.RetainUntilDate.Nanosecond() > t.Nanosecond() {
+			days++
+		}
+	}
+	conditions["object-lock-remaining-retention-days"] = []string{strconv.Itoa(days)}
+	return globalIAMSys.IsAllowed(policy.Args{
+		AccountName:     cred.AccessKey,
+		Groups:          cred.Groups,
+		Action:          action,
+		BucketName:      bucket,
+		ConditionValues: conditions,
+		ObjectName:      object,
+		IsOwner:         owner,
+		Claims:          cred.Claims,
+	})
+}
+
+// enforceRetentionBypassForPut enforces the stored retention of oi against a
+// PutObjectRetention request. The caller must already hold
+// s3:PutObjectRetention; this only decides changes that depend on the stored
+// state. Expired or absent retention may be changed freely. Unexpired
+// GOVERNANCE retention may be shortened, removed or have its mode changed only
+// with the bypass header and s3:BypassGovernanceRetention. Unexpired
+// COMPLIANCE retention may only be extended.
 func enforceRetentionBypassForPut(ctx context.Context, r *http.Request, oi ObjectInfo, objRetention *objectlock.ObjectRetention, cred auth.Credentials, owner bool) error {
-	byPassSet := objectlock.IsObjectLockGovernanceBypassSet(r.Header)
+	ret := objectlock.GetObjectRetentionMeta(oi.UserDefined)
+	if !ret.Mode.Valid() {
+		return nil
+	}
 
 	t, err := objectlock.UTCNowNTP()
 	if err != nil {
 		internalLogIf(ctx, err, logger.WarningKind)
 		return ObjectLocked{Bucket: oi.Bucket, Object: oi.Name, VersionID: oi.VersionID}
 	}
+	if ret.RetainUntilDate.Before(t) {
+		return nil
+	}
 
-	// Pass in relative days from current time, to additionally
-	// to verify "object-lock-remaining-retention-days" policy if any.
-	days := int(math.Ceil(math.Abs(objRetention.RetainUntilDate.Sub(t).Hours()) / 24))
-
-	ret := objectlock.GetObjectRetentionMeta(oi.UserDefined)
-	if ret.Mode.Valid() {
-		// Retention has expired you may change whatever you like.
-		if ret.RetainUntilDate.Before(t) {
-			apiErr := isPutRetentionAllowed(oi.Bucket, oi.Name,
-				days, objRetention.RetainUntilDate.Time,
-				objRetention.Mode, byPassSet, r, cred,
-				owner)
-			if apiErr == ErrAccessDenied {
-				return errAuthentication
-			}
-			return nil
+	weakens := objRetention.Mode != ret.Mode || objRetention.RetainUntilDate.Before(ret.RetainUntilDate.Time)
+	if !weakens {
+		return nil
+	}
+	switch ret.Mode {
+	case objectlock.RetGovernance:
+		// https://docs.aws.amazon.com/AmazonS3/latest/userguide/object-lock.html#object-lock-bypass-governance
+		if !objectlock.IsObjectLockGovernanceBypassSet(r.Header) {
+			return ObjectLocked{Bucket: oi.Bucket, Object: oi.Name, VersionID: oi.VersionID}
 		}
-
-		switch ret.Mode {
-		case objectlock.RetGovernance:
-			govPerm := isPutRetentionAllowed(oi.Bucket, oi.Name, days,
-				objRetention.RetainUntilDate.Time, objRetention.Mode,
-				byPassSet, r, cred, owner)
-			// Governance mode retention period cannot be shortened, if x-amz-bypass-governance is not set.
-			if !byPassSet {
-				if objRetention.Mode != objectlock.RetGovernance || objRetention.RetainUntilDate.Before(ret.RetainUntilDate.Time) {
-					return ObjectLocked{Bucket: oi.Bucket, Object: oi.Name, VersionID: oi.VersionID}
-				}
-			}
-			if govPerm == ErrAccessDenied {
-				return errAuthentication
-			}
-			return nil
-		case objectlock.RetCompliance:
-			// Compliance retention mode cannot be changed or shortened.
-			// https://docs.aws.amazon.com/AmazonS3/latest/dev/object-lock-overview.html#object-lock-retention-modes
-			if objRetention.Mode != objectlock.RetCompliance || objRetention.RetainUntilDate.Before(ret.RetainUntilDate.Time) {
-				return ObjectLocked{Bucket: oi.Bucket, Object: oi.Name, VersionID: oi.VersionID}
-			}
-			apiErr := isPutRetentionAllowed(oi.Bucket, oi.Name,
-				days, objRetention.RetainUntilDate.Time, objRetention.Mode,
-				false, r, cred, owner)
-			if apiErr == ErrAccessDenied {
-				return errAuthentication
-			}
-			return nil
+		if !isRetentionActionAllowed(policy.BypassGovernanceRetentionAction, oi.Bucket, oi.Name, objRetention, r, cred, owner) {
+			return errAuthentication
 		}
 		return nil
-	} // No pre-existing retention metadata present.
+	default:
+		// Compliance retention mode cannot be changed or shortened.
+		// https://docs.aws.amazon.com/AmazonS3/latest/dev/object-lock-overview.html#object-lock-retention-modes
+		return ObjectLocked{Bucket: oi.Bucket, Object: oi.Name, VersionID: oi.VersionID}
+	}
+}
 
-	apiErr := isPutRetentionAllowed(oi.Bucket, oi.Name,
-		days, objRetention.RetainUntilDate.Time,
-		objRetention.Mode, byPassSet, r, cred, owner)
-	if apiErr == ErrAccessDenied {
-		return errAuthentication
+// checkObjectLockedForOverwrite re-checks under the object write lock whether an
+// in-place write to the null version (such as a directory object) would
+// overwrite a locked version in an Object Lock bucket.
+func checkObjectLockedForOverwrite(ctx context.Context, bucket, object string, getObjectInfoFn GetObjectInfoFn) error {
+	if isMinioMetaBucketName(bucket) {
+		return nil
+	}
+	retentionCfg, err := globalBucketObjectLockSys.Get(bucket)
+	if err != nil {
+		return err
+	}
+	if !retentionCfg.LockEnabled {
+		return nil
+	}
+	objInfo, err := getObjectInfoFn(ctx, bucket, object, ObjectOptions{
+		VersionID:  nullVersionID,
+		NoLock:     true,
+		NoAuditLog: true,
+	})
+	if err != nil {
+		if isErrObjectNotFound(err) || isErrVersionNotFound(err) || errors.As(err, &MethodNotAllowed{}) {
+			return nil
+		}
+		return err
+	}
+	if objectlock.GetObjectLegalHoldMeta(objInfo.UserDefined).Status == objectlock.LegalHoldOn {
+		return ObjectLocked{Bucket: bucket, Object: decodeDirObject(object), VersionID: nullVersionID}
+	}
+	r := objectlock.GetObjectRetentionMeta(objInfo.UserDefined)
+	if r.Mode == objectlock.RetCompliance || r.Mode == objectlock.RetGovernance {
+		t, err := objectlock.UTCNowNTP()
+		if err != nil {
+			internalLogIf(ctx, err, logger.WarningKind)
+			return ObjectLocked{Bucket: bucket, Object: decodeDirObject(object), VersionID: nullVersionID}
+		}
+		if r.RetainUntilDate.After(t) {
+			return ObjectLocked{Bucket: bucket, Object: decodeDirObject(object), VersionID: nullVersionID}
+		}
 	}
 	return nil
 }
@@ -274,16 +327,24 @@ func checkPutObjectLockAllowed(ctx context.Context, rq *http.Request, bucket, ob
 	if err != nil {
 		return mode, retainDate, legalHold, toAPIErrorCode(ctx, err)
 	}
+	if isDirObject(object) && opts.VersionID == "" {
+		opts.VersionID = nullVersionID
+	}
 
 	if opts.VersionID != "" && !replicaTrusted {
-		if objInfo, err := getObjectInfoFn(ctx, bucket, object, opts); err == nil {
+		objInfo, err := getObjectInfoFn(ctx, bucket, object, opts)
+		if err != nil {
+			if !isErrObjectNotFound(err) && !isErrVersionNotFound(err) && !errors.As(err, &MethodNotAllowed{}) {
+				return mode, retainDate, legalHold, toAPIErrorCode(ctx, err)
+			}
+		} else {
 			r := objectlock.GetObjectRetentionMeta(objInfo.UserDefined)
 			t, err := objectlock.UTCNowNTP()
 			if err != nil {
 				internalLogIf(ctx, err, logger.WarningKind)
 				return mode, retainDate, legalHold, ErrObjectLocked
 			}
-			if r.Mode == objectlock.RetCompliance && r.RetainUntilDate.After(t) {
+			if (r.Mode == objectlock.RetCompliance || r.Mode == objectlock.RetGovernance) && r.RetainUntilDate.After(t) {
 				return mode, retainDate, legalHold, ErrObjectLocked
 			}
 			mode = r.Mode

cmd/erasure-metadata-utils_test.go

@@ -20,6 +20,7 @@ package cmd
 import (
 	"context"
 	"encoding/hex"
+	"errors"
 	"fmt"
 	"math/rand"
 	"reflect"
@@ -110,6 +111,96 @@ func TestReduceErrs(t *testing.T) {
 	}
 }
 
+// TestReduceWriteQuorumErrsCommitMetaMissing verifies that an in-quorum
+// errCommitMetaMissing reduces to the sentinel, which renameData() converts
+// to errErasureWriteQuorum, while below-quorum reduces directly to
+// errErasureWriteQuorum.
+func TestReduceWriteQuorumErrsCommitMetaMissing(t *testing.T) {
+	errs := make([]error, 16)
+	for i := range 9 {
+		errs[i] = errCommitMetaMissing
+	}
+	if err := reduceWriteQuorumErrs(t.Context(), errs, objectOpIgnoredErrs, 9); !errors.Is(err, errCommitMetaMissing) {
+		t.Errorf("expected %s, got %s", errCommitMetaMissing, err)
+	}
+	// The sentinel must be distinguishable from errFileNotFound so that
+	// commit failures are never mapped to ObjectNotFound (404).
+	if errors.Is(errCommitMetaMissing, errFileNotFound) {
+		t.Error("errCommitMetaMissing must not match errFileNotFound")
+	}
+
+	// Below quorum the reduction must yield a write-quorum failure (503);
+	// eight sentinels against eight committed drives is not a quorum.
+	belowQuorum := make([]error, 16)
+	for i := range 8 {
+		belowQuorum[i] = errCommitMetaMissing
+	}
+	if err := reduceWriteQuorumErrs(t.Context(), belowQuorum, objectOpIgnoredErrs, 9); !errors.Is(err, errErasureWriteQuorum) {
+		t.Errorf("expected %s, got %s", errErasureWriteQuorum, err)
+	}
+}
+
+// renameDataFailingDisk is a StorageAPI stub returning a fixed error
+// from RenameData, enough to drive renameData() in unit tests.
+type renameDataFailingDisk struct {
+	StorageAPI
+	err       error
+	undoWrite bool
+}
+
+func (d *renameDataFailingDisk) RenameData(context.Context, string, string, FileInfo, string, string, RenameOptions) (RenameDataResp, error) {
+	return RenameDataResp{}, d.err
+}
+
+func (d *renameDataFailingDisk) DeleteVersion(_ context.Context, _, _ string, _ FileInfo, _ bool, opts DeleteOptions) error {
+	d.undoWrite = opts.UndoWrite
+	return nil
+}
+
+// TestRenameDataCommitMetaMissing verifies that renameData() converts an
+// in-quorum errCommitMetaMissing into errErasureWriteQuorum (HTTP 503),
+// while an in-quorum errFileNotFound keeps its meaning so that
+// PutObject() still reports IncompleteBody for client disconnects.
+func TestRenameDataCommitMetaMissing(t *testing.T) {
+	for _, tc := range []struct {
+		name     string
+		failures int
+		diskErr  error
+		wantErr  error
+	}{
+		{"all_commit_metadata_missing", 16, errCommitMetaMissing, errErasureWriteQuorum},
+		{"quorum_commit_metadata_missing", 9, errCommitMetaMissing, errErasureWriteQuorum},
+		{"neither_side_has_quorum", 8, errCommitMetaMissing, errErasureWriteQuorum},
+		{"successful_write_quorum", 7, errCommitMetaMissing, nil},
+		{"staging_failure", 16, errFileNotFound, errFileNotFound},
+	} {
+		t.Run(tc.name, func(t *testing.T) {
+			metadata := make([]FileInfo, 16)
+			disks := make([]StorageAPI, 16)
+			for i := range disks {
+				metadata[i] = FileInfo{Deleted: true} // valid without erasure info
+				disk := &renameDataFailingDisk{}
+				if i < tc.failures {
+					disk.err = tc.diskErr
+				}
+				disks[i] = disk
+			}
+			_, _, _, err := renameData(t.Context(), disks, minioMetaTmpBucket, "tmp", metadata, "bucket", "object", 9)
+			if !errors.Is(err, tc.wantErr) {
+				t.Fatalf("expected %v, got %v", tc.wantErr, err)
+			}
+			for i, disk := range disks {
+				// Failed writes undo only the drives that committed. A
+				// successful quorum must never be rolled back.
+				wantUndo := tc.wantErr != nil && i >= tc.failures
+				if got := disk.(*renameDataFailingDisk).undoWrite; got != wantUndo {
+					t.Errorf("disk %d: UndoWrite = %v, want %v", i, got, wantUndo)
+				}
+			}
+		})
+	}
+}
+
 // TestHashOrder - test order of ints in array
 func TestHashOrder(t *testing.T) {
 	testCases := []struct {

cmd/erasure-multipart-cleanup_test.go

@@ -0,0 +1,177 @@
+// Copyright (c) 2026 clown15
+//
+// This file is part of Silo Object Storage stack
+//
+// This program is free software: you can redistribute it and/or modify
+// it under the terms of the GNU Affero General Public License as published by
+// the Free Software Foundation, either version 3 of the License, or
+// (at your option) any later version.
+//
+// This program is distributed in the hope that it will be useful
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+// GNU Affero General Public License for more details.
+//
+// You should have received a copy of the GNU Affero General Public License
+// along with this program.  If not, see <http://www.gnu.org/licenses/>.
+
+package cmd
+
+import (
+	"context"
+	"encoding/base64"
+	"fmt"
+	"net/url"
+	"os"
+	"path/filepath"
+	"testing"
+	"time"
+)
+
+func TestExtractModTimeFromUploadIDDir(t *testing.T) {
+	now := time.Unix(1792056747, 123456789).UTC()
+	nano := now.UnixNano()
+	uuid := "d16ad42a-6fe5-4a3b-8092-69983142238f"
+
+	testCases := []struct {
+		name        string
+		dirName     string
+		expectedMod time.Time
+		wantZero    bool
+	}{
+		{
+			name:        "Modern Plaintext Format (<UUID>x<UnixNano>)",
+			dirName:     fmt.Sprintf("%sx%d", uuid, nano),
+			expectedMod: time.Unix(0, nano),
+			wantZero:    false,
+		},
+		{
+			// This valid UUID decodes to bytes containing 'x'. Checking
+			// for that byte before parsing plaintext loses the timestamp.
+			name:        "Plaintext Also Decodes To Base64 Containing x",
+			dirName:     fmt.Sprintf("4eacd477-e733-4851-b821-6fd42785ff87x%d", nano),
+			expectedMod: now,
+		},
+		{
+			name:        "Legacy Format Without Timestamp (<UUID>)",
+			dirName:     uuid,
+			expectedMod: time.Time{},
+			wantZero:    true,
+		},
+		{
+			name:        "Base64 Encoded Format",
+			dirName:     base64.RawURLEncoding.EncodeToString([]byte(fmt.Sprintf("%sx%d", uuid, nano))),
+			expectedMod: time.Unix(0, nano),
+			wantZero:    false,
+		},
+		{
+			name:        "Encoded Format With Deployment Prefix",
+			dirName:     base64.RawURLEncoding.EncodeToString([]byte(fmt.Sprintf("%s.%sx%d", uuid, uuid, nano))),
+			expectedMod: now,
+		},
+		{
+			name:        "Malformed Suffix (<UUID>xinvalid)",
+			dirName:     fmt.Sprintf("%sxnotanumber", uuid),
+			expectedMod: time.Time{},
+			wantZero:    true,
+		},
+		{
+			name:     "Timestamp Overflow",
+			dirName:  uuid + "x9223372036854775808",
+			wantZero: true,
+		},
+		{
+			name:     "Malformed Plaintext UUID",
+			dirName:  fmt.Sprintf("not-a-uuidx%d", nano),
+			wantZero: true,
+		},
+		{
+			name:        "Empty Directory Name",
+			dirName:     "",
+			expectedMod: time.Time{},
+			wantZero:    true,
+		},
+	}
+
+	for _, tc := range testCases {
+		t.Run(tc.name, func(t *testing.T) {
+			got := extractModTimeFromUploadIDDir(tc.dirName)
+			if tc.wantZero {
+				if !got.IsZero() {
+					t.Fatalf("expected zero time for %q, got %v", tc.dirName, got)
+				}
+				return
+			}
+			if !got.Equal(tc.expectedMod) {
+				t.Fatalf("extractModTimeFromUploadIDDir(%q) = %v; want %v", tc.dirName, got, tc.expectedMod)
+			}
+		})
+	}
+}
+
+type multipartCleanupDisk struct {
+	StorageAPI
+	root    string
+	modTime time.Time
+	readErr error
+	reads   int
+}
+
+func (d *multipartCleanupDisk) Endpoint() Endpoint {
+	return Endpoint{URL: &url.URL{Path: d.root}}
+}
+
+func (d *multipartCleanupDisk) ReadVersion(context.Context, string, string, string, string, ReadOptions) (FileInfo, error) {
+	d.reads++
+	return FileInfo{ModTime: d.modTime}, d.readErr
+}
+
+func (d *multipartCleanupDisk) StatVol(context.Context, string) (VolInfo, error) {
+	return VolInfo{Created: time.Now()}, nil
+}
+
+func TestCleanupStaleUploadsOnDisk(t *testing.T) {
+	const uuid = "d16ad42a-6fe5-4a3b-8092-69983142238f"
+	expiry := globalAPIConfig.getStaleUploadsExpiry()
+	for _, tc := range []struct {
+		name, prefix string
+		age          time.Duration
+		legacy       bool
+		readErr      error
+		wantReads    int
+		wantDeleted  bool
+	}{
+		{name: "recent", prefix: uuid, age: expiry / 2, readErr: errFileNotFound},
+		{name: "plaintext_base64_collision", prefix: "4eacd477-e733-4851-b821-6fd42785ff87", age: expiry / 2, readErr: errFileNotFound},
+		{name: "expired", prefix: uuid, age: 2 * expiry, readErr: errFileNotFound, wantDeleted: true},
+		{name: "legacy_recent", prefix: uuid, age: expiry / 2, legacy: true, wantReads: 1},
+		{name: "legacy_expired", prefix: uuid, age: 2 * expiry, legacy: true, wantReads: 1, wantDeleted: true},
+		{name: "legacy_metadata_missing", prefix: uuid, age: 2 * expiry, legacy: true, readErr: errFileNotFound, wantReads: 1},
+		{name: "malformed_metadata_missing", prefix: "not-a-uuid", age: 2 * expiry, readErr: errFileNotFound, wantReads: 1},
+	} {
+		t.Run(tc.name, func(t *testing.T) {
+			modTime := time.Now().Add(-tc.age)
+			id := tc.prefix
+			if !tc.legacy {
+				id = fmt.Sprintf("%sx%d", tc.prefix, modTime.UnixNano())
+			}
+			disk := &multipartCleanupDisk{root: t.TempDir(), modTime: modTime, readErr: tc.readErr}
+			uploadDir := filepath.Join(disk.root, minioMetaMultipartBucket, "sha", id)
+			if err := os.MkdirAll(uploadDir, 0o755); err != nil {
+				t.Fatal(err)
+			}
+			erasureObjects{}.cleanupStaleUploadsOnDisk(t.Context(), disk)
+			if disk.reads != tc.wantReads {
+				t.Errorf("ReadVersion calls = %d, want %d", disk.reads, tc.wantReads)
+			}
+			_, err := os.Stat(uploadDir)
+			if tc.wantDeleted {
+				if !os.IsNotExist(err) {
+					t.Errorf("expired upload must be removed: %v", err)
+				}
+			} else if err != nil {
+				t.Errorf("upload must be preserved: %v", err)
+			}
+		})
+	}
+}

cmd/erasure-multipart-fullobject_test.go

@@ -253,7 +253,7 @@ func testAPICompleteMultipartFullObjectChecksumMismatch(obj ObjectLayer, instanc
 	if apiErr.Code != "BadDigest" {
 		t.Fatalf("%s: expected BadDigest, got %q", instanceType, apiErr.Code)
 	}
-	if want := "The CRC32 checksum you specified did not match the calculated checksum."; apiErr.Message != want {
+	if want := "The CRC32 you specified did not match the calculated checksum."; apiErr.Message != want {
 		t.Fatalf("%s: expected message %q, got %q", instanceType, want, apiErr.Message)
 	}
 
@@ -361,7 +361,7 @@ func testAPICompleteMultipartCompositeChecksumMismatch(obj ObjectLayer, instance
 	if apiErr.Code != "BadDigest" {
 		t.Fatalf("%s: expected BadDigest, got %q", instanceType, apiErr.Code)
 	}
-	if want := "The CRC32 checksum you specified did not match the calculated checksum."; apiErr.Message != want {
+	if want := "The CRC32 you specified did not match the calculated checksum."; apiErr.Message != want {
 		t.Fatalf("%s: expected message %q, got %q", instanceType, want, apiErr.Message)
 	}
 	if _, err := obj.GetObjectInfo(t.Context(), bucketName, objectName, ObjectOptions{}); err == nil {

cmd/erasure-multipart.go

@@ -174,6 +174,24 @@ func (er erasureObjects) deleteAll(ctx context.Context, bucket, prefix string) {
 	wg.Wait()
 }
 
+// extractModTimeFromUploadIDDir extracts creation time from the upload ID directory on disk.
+// On-disk directory names are of the form <UUID>x<UnixNano>.
+// Parse the native format first: plaintext UUIDs can also be valid Base64.
+// Preserve the previous encoded-format parser for compatibility.
+func extractModTimeFromUploadIDDir(uploadIDDir string) time.Time {
+	if modTime, ok := multipartUploadTime(uploadIDDir); ok {
+		return modTime
+	}
+	if b64, err := base64.RawURLEncoding.DecodeString(uploadIDDir); err == nil {
+		if split := strings.Split(string(b64), "x"); len(split) == 2 {
+			if t, err := strconv.ParseInt(split[1], 10, 64); err == nil {
+				return time.Unix(0, t)
+			}
+		}
+	}
+	return time.Time{}
+}
+
 // Remove the old multipart uploads on the given disk.
 func (er erasureObjects) cleanupStaleUploadsOnDisk(ctx context.Context, disk StorageAPI) {
 	drivePath := disk.Endpoint().Path
@@ -181,16 +199,7 @@ func (er erasureObjects) cleanupStaleUploadsOnDisk(ctx context.Context, disk Sto
 	readDirFn(pathJoin(drivePath, minioMetaMultipartBucket), func(shaDir string, typ os.FileMode) error {
 		readDirFn(pathJoin(drivePath, minioMetaMultipartBucket, shaDir), func(uploadIDDir string, typ os.FileMode) error {
 			uploadIDPath := pathJoin(shaDir, uploadIDDir)
-			var modTime time.Time
-			// Upload IDs are of the form base64_url(<UUID>x<UnixNano>), we can extract the time from the UUID.
-			if b64, err := base64.RawURLEncoding.DecodeString(uploadIDDir); err == nil {
-				if split := strings.Split(string(b64), "x"); len(split) == 2 {
-					t, err := strconv.ParseInt(split[1], 10, 64)
-					if err == nil {
-						modTime = time.Unix(0, t)
-					}
-				}
-			}
+			modTime := extractModTimeFromUploadIDDir(uploadIDDir)
 			// Fallback for older uploads without time in the ID.
 			if modTime.IsZero() {
 				wait := deleteMultipartCleanupSleeper.Timer(ctx)
@@ -1696,6 +1705,32 @@ func (er erasureObjects) CompleteMultipartUpload(ctx context.Context, bucket str
 		defer lk.Unlock(lkctx)
 	}
 
+	if !opts.ReplicationRequest && !opts.ReplicaLockReconcile && !opts.DataMovement {
+		getObjectInfo := er.getObjectInfo
+		if opts.replicaObjectInfo != nil {
+			getObjectInfo = opts.replicaObjectInfo
+		}
+		if fi.VersionID == "" || fi.VersionID == nullVersionID {
+			if err := checkObjectLockedForOverwrite(ctx, bucket, object, getObjectInfo); err != nil {
+				return oi, toObjectErr(err, bucket, object)
+			}
+		} else {
+			_, gerr := getObjectInfo(ctx, bucket, object, ObjectOptions{
+				VersionID:        fi.VersionID,
+				Versioned:        opts.Versioned,
+				VersionSuspended: opts.VersionSuspended,
+				NoLock:           true,
+			})
+			switch {
+			case gerr == nil, errors.As(gerr, &MethodNotAllowed{}):
+				return oi, toObjectErr(errAuthentication, bucket, object)
+			case isErrVersionNotFound(gerr) || isErrObjectNotFound(gerr):
+			default:
+				return oi, toObjectErr(gerr, bucket, object)
+			}
+		}
+	}
+
 	er.cleanupMultipartPath(ctx, paths...) // cleanup all part.N.meta, and skipped part.N's before final rename().
 
 	defer func() {

cmd/erasure-object.go

@@ -150,6 +150,17 @@ func (er erasureObjects) CopyObject(ctx context.Context, srcBucket, srcObject, d
 		}
 	}
 
+	if !dstOpts.ReplicationRequest && !dstOpts.ReplicaLockReconcile && !dstOpts.DataMovement &&
+		(versionID == "" || versionID == nullVersionID) {
+		getObjectInfo := er.getObjectInfo
+		if dstOpts.replicaObjectInfo != nil {
+			getObjectInfo = dstOpts.replicaObjectInfo
+		}
+		if err := checkObjectLockedForOverwrite(ctx, dstBucket, dstObject, getObjectInfo); err != nil {
+			return oi, toObjectErr(err, dstBucket, dstObject)
+		}
+	}
+
 	modTime = UTCNow() // We only preserve modTime if dstOpts.MTime is true.
 	// in all other cases mtime is latest.
 
@@ -1072,6 +1083,12 @@ func renameData(ctx context.Context, disks []StorageAPI, srcBucket, srcEntry str
 	errs := g.Wait()
 
 	err := reduceWriteQuorumErrs(ctx, errs, objectOpIgnoredErrs, writeQuorum)
+	if errors.Is(err, errCommitMetaMissing) {
+		// Commit metadata went missing on a quorum of drives; the write
+		// did not commit. Return a 503 class error so clients retry
+		// instead of treating the object as absent (404).
+		err = errErasureWriteQuorum
+	}
 	if err != nil {
 		dg := errgroup.WithNErrs(len(disks))
 		for index, nerr := range errs {
@@ -1594,6 +1611,17 @@ func (er erasureObjects) putObject(ctx context.Context, bucket string, object st
 		defer lk.Unlock(lkctx)
 	}
 
+	if !opts.ReplicationRequest && !opts.ReplicaLockReconcile && !opts.DataMovement &&
+		(fi.VersionID == "" || fi.VersionID == nullVersionID) {
+		getObjectInfo := er.getObjectInfo
+		if opts.replicaObjectInfo != nil {
+			getObjectInfo = opts.replicaObjectInfo
+		}
+		if err := checkObjectLockedForOverwrite(ctx, bucket, object, getObjectInfo); err != nil {
+			return ObjectInfo{}, toObjectErr(err, bucket, object)
+		}
+	}
+
 	// Rename the successfully written temporary object to final location.
 	onlineDisks, versions, oldDataDir, err := renameData(ctx, onlineDisks, minioMetaTmpBucket, tempObj, partsMetadata, bucket, object, writeQuorum)
 	if err != nil {

cmd/erasure-server-pool-multipart-http_test.go

@@ -265,6 +265,7 @@ func TestPoolsMultipartConditionalLatestVersionAndCallbackOnce(t *testing.T) {
 			if explicit {
 				current = putConsistencyObject(t, z, bucket, object, 1, "latest-other-version", ObjectOptions{Versioned: true, MTime: UTCNow().Add(-time.Minute)})
 			}
+			opts.VersionID = ""
 			id, parts := multipartConditionUpload(t, z, bucket, object, 1, opts)
 			called := 0
 			opts.CheckPrecondFn = func(oi ObjectInfo) bool { called++; return oi.ETag != current.ETag }

cmd/erasure-server-pool-put-conditional_test.go

@@ -633,6 +633,8 @@ func TestPoolsConditionalPutReplicaAvailability(t *testing.T) {
 	}
 }
 
+// A public client cannot address a destination version, with or without a
+// precondition; only trusted replication may (SN-2026-016).
 func TestPoolsConditionalPutDestinationVersionHTTP(t *testing.T) {
 	z, _ := consistencyPools(t)
 	bucket, router := conditionalPutBucket(t, z, "versioned")
@@ -641,21 +643,14 @@ func TestPoolsConditionalPutDestinationVersionHTTP(t *testing.T) {
 	current := putConsistencyObject(t, z, bucket, object, 1, "current", ObjectOptions{Versioned: true, MTime: UTCNow().Add(-time.Minute)})
 	defer conditionalPutPool(t, z, object, 0)()
 	url := getPutObjectURL("", bucket, object) + "?versionId=" + old.VersionID
-	for _, stale := range []bool{true, false} {
-		tag, status := current.ETag, http.StatusOK
-		if stale {
-			tag, status = old.ETag, http.StatusPreconditionFailed
-		}
+	for _, tag := range []string{old.ETag, current.ETag} {
 		put := multipartConditionRequest(t, router, http.MethodPut, url, "replacement", map[string]string{xhttp.IfMatch: fmt.Sprintf("%q", tag)})
-		if put.Code != status {
-			t.Fatalf("version-addressed public PUT: %d want %d: %s", put.Code, status, put.Body.String())
-		}
-		if got := put.Header()[xhttp.AmzVersionID]; !stale && (len(got) != 1 || got[0] != old.VersionID) {
-			t.Fatalf("write version changed: %v", put.Header())
+		if put.Code != http.StatusForbidden {
+			t.Fatalf("version-addressed public PUT: %d want 403: %s", put.Code, put.Body.String())
 		}
 	}
 	get := multipartConditionRequest(t, router, http.MethodGet, url, "", nil)
-	if get.Code != http.StatusOK || get.Body.String() != "replacement" {
+	if get.Code != http.StatusOK || get.Body.String() != "old" {
 		t.Fatalf("addressed GET: %d %q", get.Code, get.Body.String())
 	}
 }

cmd/erasure-server-pool.go

@@ -1199,6 +1199,10 @@ func (z *erasureServerPools) PutObject(ctx context.Context, bucket string, objec
 
 	if opts.ReplicaLockReconcile || opts.DataMovement {
 		opts.ReplicaLockReconcile = true
+	}
+	// Public overwrites need all pools for Object Lock. Unaddressed replica
+	// callbacks retain their set-local reads unless reconciliation is needed.
+	if opts.ReplicaLockReconcile || !opts.ReplicationRequest {
 		opts.replicaObjectInfo = z.replicaObjectInfo
 	}
 	oi, err := z.serverPools[idx].PutObject(ctx, bucket, object, data, opts)
@@ -1510,9 +1514,9 @@ func (z *erasureServerPools) CopyObject(ctx context.Context, srcBucket, srcObjec
 		return objInfo, err
 	}
 
-	if !z.SinglePool() && dstOpts.ReplicaLockReconcile {
+	if !z.SinglePool() && (dstOpts.ReplicaLockReconcile || !dstOpts.ReplicationRequest) {
 		dstOpts.replicaObjectInfo = z.replicaObjectInfo
-		if !dstOpts.DataMovement {
+		if dstOpts.ReplicaLockReconcile && !dstOpts.DataMovement {
 			defer func() {
 				if err == nil {
 					err = z.retireReplicaCopies(ctx, dstBucket, dstObject, poolIdx, objInfo)
@@ -1549,13 +1553,16 @@ func (z *erasureServerPools) CopyObject(ctx context.Context, srcBucket, srcObjec
 		ServerSideEncryption:       dstOpts.ServerSideEncryption,
 		UserDefined:                srcInfo.UserDefined,
 		Versioned:                  dstOpts.Versioned,
+		VersionSuspended:           dstOpts.VersionSuspended,
 		VersionID:                  dstOpts.VersionID,
 		MTime:                      dstOpts.MTime,
 		NoLock:                     true,
 		EncryptFn:                  dstOpts.EncryptFn,
 		WantChecksum:               dstOpts.WantChecksum,
 		WantServerSideChecksumType: dstOpts.WantServerSideChecksumType,
+		ReplicationRequest:         dstOpts.ReplicationRequest,
 		ReplicaLockReconcile:       dstOpts.ReplicaLockReconcile,
+		DataMovement:               dstOpts.DataMovement,
 		replicaObjectInfo:          dstOpts.replicaObjectInfo,
 	}
 
@@ -2305,6 +2312,8 @@ func (z *erasureServerPools) CompleteMultipartUpload(ctx context.Context, bucket
 
 	if opts.ReplicaLockReconcile || opts.DataMovement {
 		opts.ReplicaLockReconcile = true
+	}
+	if opts.ReplicaLockReconcile || !opts.ReplicationRequest {
 		opts.replicaObjectInfo = z.replicaObjectInfo
 	}
 

cmd/erasure-sets.go

@@ -869,11 +869,17 @@ func (s *erasureSets) CopyObject(ctx context.Context, srcBucket, srcObject, dstB
 		ServerSideEncryption:       dstOpts.ServerSideEncryption,
 		UserDefined:                srcInfo.UserDefined,
 		Versioned:                  dstOpts.Versioned,
+		VersionSuspended:           dstOpts.VersionSuspended,
 		VersionID:                  dstOpts.VersionID,
 		MTime:                      dstOpts.MTime,
+		NoLock:                     dstOpts.NoLock,
 		EncryptFn:                  dstOpts.EncryptFn,
 		WantChecksum:               dstOpts.WantChecksum,
 		WantServerSideChecksumType: dstOpts.WantServerSideChecksumType,
+		ReplicationRequest:         dstOpts.ReplicationRequest,
+		ReplicaLockReconcile:       dstOpts.ReplicaLockReconcile,
+		DataMovement:               dstOpts.DataMovement,
+		replicaObjectInfo:          dstOpts.replicaObjectInfo,
 	}
 
 	return dstSet.putObject(ctx, dstBucket, dstObject, srcInfo.PutObjReader, putOpts)

cmd/object-api-errors.go

@@ -162,7 +162,7 @@ func toObjectErr(oerr error, params ...string) error {
 			apiErr.Type = v.Type
 		}
 		return apiErr
-	case errErasureWriteQuorum.Error():
+	case errErasureWriteQuorum.Error(), errCommitMetaMissing.Error():
 		apiErr := InsufficientWriteQuorum{}
 		if len(params) >= 1 {
 			apiErr.Bucket = params[0]
@@ -668,7 +668,7 @@ var (
 func completeMultipartChecksumMismatch(algorithm string) error {
 	description := "The checksum you specified did not match the calculated checksum."
 	if algorithm != "" {
-		description = fmt.Sprintf("The %s checksum you specified did not match the calculated checksum.", algorithm)
+		description = fmt.Sprintf("The %s you specified did not match the calculated checksum.", algorithm)
 	}
 	return fmt.Errorf("%w: %s", errCompleteMultipartChecksumMismatch, description)
 }

cmd/object-api-options.go

@@ -347,6 +347,11 @@ func putOpts(ctx context.Context, bucket, object, vid string, hdrs http.Header,
 	versionSuspended := globalBucketVersioningSys.PrefixSuspended(bucket, object)
 
 	vid = strings.TrimSpace(vid)
+	// A caller-chosen version ID writes that version in place. Only trusted
+	// replication may recreate a source version under its original ID.
+	if vid != "" && !trustedReplication {
+		return opts, errAuthentication
+	}
 	if vid != "" && vid != nullVersionID {
 		_, err := uuid.Parse(vid)
 		if err != nil {

cmd/object-handlers-chunked-checksum_test.go

@@ -62,12 +62,13 @@ func testAPIPutObjectChunkedChecksum(obj ObjectLayer, instanceType, bucketName s
 	// A well-formed 4-byte value that does not match the content.
 	wrongCRC := base64.StdEncoding.EncodeToString([]byte{0x01, 0x02, 0x03, 0x04})
 
-	apiCode := func(rec *httptest.ResponseRecorder) string {
+	apiErrOf := func(rec *httptest.ResponseRecorder) APIErrorResponse {
 		var apiErr APIErrorResponse
 		b, _ := io.ReadAll(rec.Body)
 		_ = xml.Unmarshal(b, &apiErr)
-		return apiErr.Code
+		return apiErr
 	}
+	apiCode := func(rec *httptest.ResponseRecorder) string { return apiErrOf(rec).Code }
 
 	// newChunkedJavaForm builds a non-trailer signed chunked PutObject request that
 	// mirrors the AWS Java SDK v2 wire form: the checksum value sits in the header
@@ -131,8 +132,12 @@ func testAPIPutObjectChunkedChecksum(obj ObjectLayer, instanceType, bucketName s
 		if rec.Code != http.StatusBadRequest {
 			t.Fatalf("%s: chunked+wrong CRC32: expected 400, got %d", instanceType, rec.Code)
 		}
-		if code := apiCode(rec); code != "XAmzContentChecksumMismatch" {
-			t.Fatalf("%s: chunked+wrong CRC32: want XAmzContentChecksumMismatch, got %q", instanceType, code)
+		gotErr := apiErrOf(rec)
+		if gotErr.Code != "XAmzContentChecksumMismatch" {
+			t.Fatalf("%s: chunked+wrong CRC32: want XAmzContentChecksumMismatch, got %q", instanceType, gotErr.Code)
+		}
+		if gotErr.Message != "The CRC32 you specified did not match the calculated checksum." {
+			t.Fatalf("%s: chunked+wrong CRC32: message = %q, want S3 algorithm-specific wording", instanceType, gotErr.Message)
 		}
 	}
 }

cmd/object-handlers.go

@@ -3435,27 +3435,16 @@ func (api objectAPIHandlers) PutObjectRetentionHandler(w http.ResponseWriter, r
 		return
 	}
 
-	// Check permissions to perform this object retention operation
 	if s3Error := authenticateRequest(ctx, r, policy.PutObjectRetentionAction); s3Error != ErrNone {
 		writeErrorResponse(ctx, w, errorCodes.ToAPIErr(s3Error), r.URL)
 		return
 	}
 
-	if _, err := objectAPI.GetBucketInfo(ctx, bucket, BucketOptions{}); err != nil {
-		writeErrorResponse(ctx, w, toAPIError(ctx, err), r.URL)
-		return
-	}
-
 	if !validateLengthAndChecksum(r) {
 		writeErrorResponse(ctx, w, errorCodes.ToAPIErr(ErrMissingContentMD5), r.URL)
 		return
 	}
 
-	if rcfg, _ := globalBucketObjectLockSys.Get(bucket); !rcfg.LockEnabled {
-		writeErrorResponse(ctx, w, errorCodes.ToAPIErr(ErrInvalidBucketObjectLockConfiguration), r.URL)
-		return
-	}
-
 	objRetention, err := objectlock.ParseObjectRetention(r.Body)
 	if err != nil {
 		apiErr := errorCodes.ToAPIErr(ErrMalformedXML)
@@ -3467,6 +3456,24 @@ func (api objectAPIHandlers) PutObjectRetentionHandler(w http.ResponseWriter, r
 	reqInfo := logger.GetReqInfo(ctx)
 	reqInfo.SetTags("retention", objRetention.String())
 
+	// Check permissions to perform this object retention operation. The
+	// object-lock condition keys come from the request body, so this is
+	// decided before any bucket or object state is read.
+	if !isRetentionActionAllowed(policy.PutObjectRetentionAction, bucket, object, objRetention, r, reqInfo.Cred, reqInfo.Owner) {
+		writeErrorResponse(ctx, w, errorCodes.ToAPIErr(ErrAccessDenied), r.URL)
+		return
+	}
+
+	if _, err := objectAPI.GetBucketInfo(ctx, bucket, BucketOptions{}); err != nil {
+		writeErrorResponse(ctx, w, toAPIError(ctx, err), r.URL)
+		return
+	}
+
+	if rcfg, _ := globalBucketObjectLockSys.Get(bucket); !rcfg.LockEnabled {
+		writeErrorResponse(ctx, w, errorCodes.ToAPIErr(ErrInvalidBucketObjectLockConfiguration), r.URL)
+		return
+	}
+
 	opts, err := getOpts(ctx, r, bucket, object)
 	if err != nil {
 		writeErrorResponse(ctx, w, toAPIError(ctx, err), r.URL)

cmd/object-multipart-handlers.go

@@ -1166,7 +1166,7 @@ func (api objectAPIHandlers) CompleteMultipartUploadHandler(w http.ResponseWrite
 		return
 	}
 
-	if _, _, _, s3Err := checkPutObjectLockAllowed(ctx, r, bucket, object, objectAPI.GetObjectInfo, ErrNone, ErrNone, false); s3Err != ErrNone {
+	if _, _, _, s3Err := checkPutObjectLockAllowed(ctx, r, bucket, object, objectAPI.GetObjectInfo, ErrNone, ErrNone, trustedReplication); s3Err != ErrNone {
 		writeErrorResponse(ctx, w, errorCodes.ToAPIErr(s3Err), r.URL)
 		return
 	}

cmd/object-retention-authz_test.go

@@ -0,0 +1,679 @@
+// Copyright (c) 2015-2026 MinIO, Inc.
+// Copyright (c) 2026 PGSTY
+//
+// This file is part of MinIO Object Storage stack
+//
+// This program is free software: you can redistribute it and/or modify
+// it under the terms of the GNU Affero General Public License as published by
+// the Free Software Foundation, either version 3 of the License, or
+// (at your option) any later version.
+
+package cmd
+
+import (
+	"archive/tar"
+	"bytes"
+	"context"
+	"crypto/md5"
+	"encoding/base64"
+	"encoding/xml"
+	"fmt"
+	"io"
+	"net/http"
+	"net/http/httptest"
+	"net/url"
+	"strings"
+	"testing"
+	"time"
+
+	"github.com/minio/madmin-go/v3"
+	"github.com/minio/minio/internal/amztime"
+	"github.com/minio/minio/internal/auth"
+	objectlock "github.com/minio/minio/internal/bucket/object/lock"
+	xhttp "github.com/minio/minio/internal/http"
+	"github.com/pgsty/silo-pkg/v3/policy"
+)
+
+func retentionAuthzRequest(t *testing.T, router http.Handler, creds auth.Credentials, method, target string, body []byte, headers map[string]string) *httptest.ResponseRecorder {
+	t.Helper()
+	var rd io.ReadSeeker
+	if body != nil {
+		rd = bytes.NewReader(body)
+	}
+	req, err := newTestSignedRequestV4(method, target, int64(len(body)), rd, creds.AccessKey, creds.SecretKey, headers)
+	if err != nil {
+		t.Fatal(err)
+	}
+	rec := httptest.NewRecorder()
+	router.ServeHTTP(rec, req)
+	return rec
+}
+
+func retentionBody(mode string, until time.Time) []byte {
+	if mode == "" {
+		return []byte(`<Retention xmlns="http://s3.amazonaws.com/doc/2006-03-01/"></Retention>`)
+	}
+	return fmt.Appendf(nil, `<Retention xmlns="http://s3.amazonaws.com/doc/2006-03-01/"><Mode>%s</Mode><RetainUntilDate>%s</RetainUntilDate></Retention>`,
+		mode, until.UTC().Format(time.RFC3339))
+}
+
+func putRetention(t *testing.T, router http.Handler, cred auth.Credentials, bucket, key, vid, mode string, until time.Time, bypass bool) int {
+	t.Helper()
+	body := retentionBody(mode, until)
+	sum := md5.Sum(body)
+	headers := map[string]string{xhttp.ContentMD5: base64.StdEncoding.EncodeToString(sum[:])}
+	if bypass {
+		headers[objectlock.AmzObjectLockBypassRetGovernance] = "true"
+	}
+	rec := retentionAuthzRequest(t, router, cred, http.MethodPut,
+		makeTestTargetURL("", bucket, key, url.Values{"retention": {""}, "versionId": {vid}}), body, headers)
+	return rec.Code
+}
+
+func newRetentionPolicyUser(t *testing.T, instanceType, policyJSON string) auth.Credentials {
+	t.Helper()
+	ctx := t.Context()
+	accessKey, secretKey, err := auth.GenerateCredentials()
+	if err != nil {
+		t.Fatalf("%s: generate credentials: %v", instanceType, err)
+	}
+	creds := auth.Credentials{AccessKey: accessKey, SecretKey: secretKey}
+	if _, err = globalIAMSys.CreateUser(ctx, creds.AccessKey, madmin.AddOrUpdateUserReq{
+		SecretKey: creds.SecretKey,
+		Status:    madmin.AccountEnabled,
+	}); err != nil {
+		t.Fatalf("%s: create user: %v", instanceType, err)
+	}
+	parsed, err := policy.ParseConfig(strings.NewReader(policyJSON))
+	if err != nil {
+		t.Fatalf("%s: parse policy: %v", instanceType, err)
+	}
+	policyName := "retention-authz-" + mustGetUUID()
+	if _, err = globalIAMSys.SetPolicy(ctx, policyName, *parsed); err != nil {
+		t.Fatalf("%s: install policy: %v", instanceType, err)
+	}
+	if _, err = globalIAMSys.PolicyDBSet(ctx, creds.AccessKey, policyName, regUser, false); err != nil {
+		t.Fatalf("%s: attach policy: %v", instanceType, err)
+	}
+	return creds
+}
+
+// TestAPIPutObjectRetentionAuthorization covers SN-2026-015: the governance
+// bypass header is intent only; s3:PutObjectRetention is always required and
+// weakening unexpired GOVERNANCE also requires s3:BypassGovernanceRetention.
+func TestAPIPutObjectRetentionAuthorization(t *testing.T) {
+	defer DetectTestLeak(t)()
+	ExecObjectLayerAPITest(ExecObjectLayerAPITestArgs{
+		t:          t,
+		objAPITest: testAPIPutObjectRetentionAuthorization,
+	})
+}
+
+func testAPIPutObjectRetentionAuthorization(obj ObjectLayer, instanceType, bucket string, router http.Handler, root auth.Credentials, t *testing.T) {
+	enableBucketObjectLock(t, bucket)
+
+	noRet := newObjectAttributesAuthzUser(t, instanceType, bucket, `"s3:GetObject"`)
+	retOnly := newObjectAttributesAuthzUser(t, instanceType, bucket, `"s3:PutObjectRetention"`)
+	retBypass := newObjectAttributesAuthzUser(t, instanceType, bucket, `"s3:PutObjectRetention","s3:BypassGovernanceRetention"`)
+	bypassOnly := newObjectAttributesAuthzUser(t, instanceType, bucket, `"s3:BypassGovernanceRetention"`)
+	condDenyShort := newRetentionPolicyUser(t, instanceType, `{
+		"Version": "2012-10-17",
+		"Statement": [
+			{
+				"Effect": "Allow",
+				"Action": ["s3:PutObjectRetention", "s3:BypassGovernanceRetention"],
+				"Resource": ["arn:aws:s3:::`+bucket+`/*"]
+			},
+			{
+				"Effect": "Deny",
+				"Action": ["s3:PutObjectRetention"],
+				"Resource": ["arn:aws:s3:::`+bucket+`/*"],
+				"Condition": {"NumericLessThan": {"s3:object-lock-remaining-retention-days": "60"}}
+			}
+		]
+	}`)
+	explicitDenyBypass := newRetentionPolicyUser(t, instanceType, `{
+		"Version": "2012-10-17",
+		"Statement": [
+			{
+				"Effect": "Allow",
+				"Action": ["s3:*"],
+				"Resource": ["arn:aws:s3:::`+bucket+`/*"]
+			},
+			{
+				"Effect": "Deny",
+				"Action": ["s3:BypassGovernanceRetention"],
+				"Resource": ["arn:aws:s3:::`+bucket+`/*"]
+			}
+		]
+	}`)
+
+	far := UTCNow().Add(365 * 24 * time.Hour).Truncate(time.Second)
+	nearer := UTCNow().Add(30 * 24 * time.Hour).Truncate(time.Second)
+	farther := far.Add(24 * time.Hour)
+
+	put := func(t *testing.T, object, mode string) string {
+		t.Helper()
+		payload := []byte("retention authorization")
+		opts := ObjectOptions{Versioned: true, UserDefined: map[string]string{}}
+		if mode != "" {
+			opts.UserDefined[strings.ToLower(xhttp.AmzObjectLockMode)] = mode
+			opts.UserDefined[strings.ToLower(xhttp.AmzObjectLockRetainUntilDate)] = amztime.ISO8601Format(far)
+		}
+		info, err := obj.PutObject(t.Context(), bucket, object,
+			mustGetPutObjReader(t, bytes.NewReader(payload), int64(len(payload)), "", ""), opts)
+		if err != nil {
+			t.Fatal(err)
+		}
+		return info.VersionID
+	}
+	stored := func(t *testing.T, object, vid string) objectlock.ObjectRetention {
+		t.Helper()
+		info, err := obj.GetObjectInfo(t.Context(), bucket, object, ObjectOptions{VersionID: vid})
+		if err != nil {
+			t.Fatal(err)
+		}
+		return objectlock.GetObjectRetentionMeta(info.UserDefined)
+	}
+
+	for _, test := range []struct {
+		name     string
+		creds    auth.Credentials
+		existing string // stored retention mode on the version, until far
+		mode     string // requested mode, "" removes retention
+		until    time.Time
+		bypass   bool
+		want     int
+		changed  bool
+	}{
+		{name: "no-permission removal", creds: noRet, existing: "GOVERNANCE", bypass: true, want: http.StatusForbidden},
+		{name: "no-permission mode change", creds: noRet, existing: "GOVERNANCE", mode: "COMPLIANCE", until: nearer, bypass: true, want: http.StatusForbidden},
+		{name: "no-permission new compliance", creds: noRet, mode: "COMPLIANCE", until: nearer, bypass: true, want: http.StatusForbidden},
+		{name: "retention-only shorten with header", creds: retOnly, existing: "GOVERNANCE", mode: "GOVERNANCE", until: nearer, bypass: true, want: http.StatusForbidden},
+		{name: "retention-only removal with header", creds: retOnly, existing: "GOVERNANCE", bypass: true, want: http.StatusForbidden},
+		{name: "retention-only mode change with header", creds: retOnly, existing: "GOVERNANCE", mode: "COMPLIANCE", until: nearer, bypass: true, want: http.StatusForbidden},
+		{name: "retention-only shorten without header", creds: retOnly, existing: "GOVERNANCE", mode: "GOVERNANCE", until: nearer, want: http.StatusBadRequest},
+		{name: "retention-only extend with header", creds: retOnly, existing: "GOVERNANCE", mode: "GOVERNANCE", until: farther, bypass: true, want: http.StatusOK, changed: true},
+		{name: "retention-only new retention", creds: retOnly, mode: "GOVERNANCE", until: nearer, want: http.StatusOK, changed: true},
+		{name: "bypass shorten with header", creds: retBypass, existing: "GOVERNANCE", mode: "GOVERNANCE", until: nearer, bypass: true, want: http.StatusOK, changed: true},
+		{name: "bypass removal with header", creds: retBypass, existing: "GOVERNANCE", bypass: true, want: http.StatusOK, changed: true},
+		{name: "bypass shorten without header", creds: retBypass, existing: "GOVERNANCE", mode: "GOVERNANCE", until: nearer, want: http.StatusBadRequest},
+		{name: "bypass shorten compliance", creds: retBypass, existing: "COMPLIANCE", mode: "COMPLIANCE", until: nearer, bypass: true, want: http.StatusBadRequest},
+		{name: "bypass-only extend", creds: bypassOnly, existing: "GOVERNANCE", mode: "GOVERNANCE", until: farther, bypass: true, want: http.StatusForbidden},
+		{name: "conditional-deny-put-retention with bypass header", creds: condDenyShort, existing: "GOVERNANCE", mode: "GOVERNANCE", until: nearer, bypass: true, want: http.StatusForbidden},
+		{name: "conditional-allow-put-retention satisfied", creds: condDenyShort, existing: "GOVERNANCE", mode: "GOVERNANCE", until: farther, bypass: true, want: http.StatusOK, changed: true},
+		{name: "explicit-deny-bypass shorten with header", creds: explicitDenyBypass, existing: "GOVERNANCE", mode: "GOVERNANCE", until: nearer, bypass: true, want: http.StatusForbidden},
+		{name: "owner shorten with header", creds: root, existing: "GOVERNANCE", mode: "GOVERNANCE", until: nearer, bypass: true, want: http.StatusOK, changed: true},
+	} {
+		t.Run(instanceType+"/"+test.name, func(t *testing.T) {
+			object := "retention-authz/" + strings.ReplaceAll(test.name, " ", "-")
+			vid := put(t, object, test.existing)
+			before := stored(t, object, vid)
+
+			body := retentionBody(test.mode, test.until)
+			sum := md5.Sum(body)
+			headers := map[string]string{xhttp.ContentMD5: base64.StdEncoding.EncodeToString(sum[:])}
+			if test.bypass {
+				headers[objectlock.AmzObjectLockBypassRetGovernance] = "true"
+			}
+			target := makeTestTargetURL("", bucket, object, url.Values{"retention": {""}, "versionId": {vid}})
+			rec := retentionAuthzRequest(t, router, test.creds, http.MethodPut, target, body, headers)
+			if rec.Code != test.want {
+				t.Fatalf("status = %d, want %d: %s", rec.Code, test.want, rec.Body.String())
+			}
+			after := stored(t, object, vid)
+			if changed := after.Mode != before.Mode || !after.RetainUntilDate.Equal(before.RetainUntilDate.Time); changed != test.changed {
+				t.Fatalf("retention changed = %v, want %v (before %s, after %s)", changed, test.changed, before.String(), after.String())
+			}
+		})
+	}
+
+	t.Run(instanceType+"/no-permission missing bucket", func(t *testing.T) {
+		body := retentionBody("", time.Time{})
+		sum := md5.Sum(body)
+		target := makeTestTargetURL("", "retention-authz-missing", "object", url.Values{"retention": {""}})
+		rec := retentionAuthzRequest(t, router, noRet, http.MethodPut, target, body,
+			map[string]string{xhttp.ContentMD5: base64.StdEncoding.EncodeToString(sum[:])})
+		if rec.Code != http.StatusForbidden {
+			t.Fatalf("status = %d, want 403 before bucket lookup: %s", rec.Code, rec.Body.String())
+		}
+	})
+}
+
+// TestAPIVersionAddressedWriteRequiresReplicationTrust covers SN-2026-016: a
+// caller-chosen destination versionId is honored only for trusted replication,
+// and write paths cannot overwrite locked versions via directory keys or
+// version-addressed multipart completions.
+func TestAPIVersionAddressedWriteRequiresReplicationTrust(t *testing.T) {
+	defer DetectTestLeak(t)()
+	ExecObjectLayerAPITest(ExecObjectLayerAPITestArgs{
+		t:                 t,
+		objAPITest:        testAPIVersionAddressedWriteRequiresReplicationTrust,
+		makeBucketOptions: MakeBucketOptions{VersioningEnabled: true, LockEnabled: true},
+	})
+}
+
+func testAPIVersionAddressedWriteRequiresReplicationTrust(obj ObjectLayer, instanceType, bucket string, router http.Handler, root auth.Credentials, t *testing.T) {
+	writer := newObjectAttributesAuthzUser(t, instanceType, bucket, `"s3:GetObject","s3:PutObject"`)
+	original := []byte("original version content")
+	info, err := obj.PutObject(t.Context(), bucket, "addressed",
+		mustGetPutObjReader(t, bytes.NewReader(original), int64(len(original)), "", ""), ObjectOptions{Versioned: true})
+	if err != nil {
+		t.Fatal(err)
+	}
+	vid := info.VersionID
+
+	unchanged := func(t *testing.T) {
+		t.Helper()
+		got, err := obj.GetObjectInfo(t.Context(), bucket, "addressed", ObjectOptions{VersionID: vid})
+		if err != nil {
+			t.Fatal(err)
+		}
+		if got.Size != int64(len(original)) || got.ETag != info.ETag {
+			t.Fatalf("version %s was rewritten: size %d etag %s", vid, got.Size, got.ETag)
+		}
+	}
+
+	for _, creds := range []struct {
+		name  string
+		creds auth.Credentials
+	}{{"writer", writer}, {"owner", root}} {
+		t.Run(instanceType+"/"+creds.name+"/put", func(t *testing.T) {
+			body := []byte("replacement")
+			target := makeTestTargetURL("", bucket, "addressed", url.Values{"versionId": {vid}})
+			rec := retentionAuthzRequest(t, router, creds.creds, http.MethodPut, target, body, nil)
+			if rec.Code != http.StatusForbidden {
+				t.Fatalf("status = %d, want 403: %s", rec.Code, rec.Body.String())
+			}
+			unchanged(t)
+		})
+		t.Run(instanceType+"/"+creds.name+"/null-version", func(t *testing.T) {
+			body := []byte("replacement")
+			target := makeTestTargetURL("", bucket, "addressed", url.Values{"versionId": {nullVersionID}})
+			rec := retentionAuthzRequest(t, router, creds.creds, http.MethodPut, target, body, nil)
+			if rec.Code != http.StatusForbidden {
+				t.Fatalf("status = %d, want 403: %s", rec.Code, rec.Body.String())
+			}
+		})
+		t.Run(instanceType+"/"+creds.name+"/copy", func(t *testing.T) {
+			target := makeTestTargetURL("", bucket, "addressed", url.Values{"versionId": {vid}})
+			req, err := newTestSignedRequestV4(http.MethodPut, target, 0, nil, creds.creds.AccessKey, creds.creds.SecretKey,
+				map[string]string{xhttp.AmzCopySource: "/" + bucket + "/addressed?versionId=" + vid, xhttp.AmzMetadataDirective: "REPLACE"})
+			if err != nil {
+				t.Fatal(err)
+			}
+			rec := httptest.NewRecorder()
+			router.ServeHTTP(rec, req)
+			if rec.Code != http.StatusForbidden {
+				t.Fatalf("status = %d, want 403: %s", rec.Code, rec.Body.String())
+			}
+			unchanged(t)
+		})
+		t.Run(instanceType+"/"+creds.name+"/multipart", func(t *testing.T) {
+			target := makeTestTargetURL("", bucket, "addressed", url.Values{"uploads": {""}, "versionId": {vid}})
+			rec := retentionAuthzRequest(t, router, creds.creds, http.MethodPost, target, nil, nil)
+			if rec.Code != http.StatusForbidden {
+				t.Fatalf("status = %d, want 403: %s", rec.Code, rec.Body.String())
+			}
+		})
+		t.Run(instanceType+"/"+creds.name+"/complete-multipart-existing-version", func(t *testing.T) {
+			// Simulate a pending upload persisted with an existing version ID
+			// (e.g. initiated pre-upgrade or by a replication peer).
+			up, err := obj.NewMultipartUpload(t.Context(), bucket, "addressed", ObjectOptions{
+				Versioned: true,
+				VersionID: vid,
+			})
+			if err != nil {
+				t.Fatal(err)
+			}
+			defer obj.AbortMultipartUpload(t.Context(), bucket, "addressed", up.UploadID, ObjectOptions{})
+
+			partPayload := []byte("replacement-part")
+			pi, err := obj.PutObjectPart(t.Context(), bucket, "addressed", up.UploadID, 1,
+				mustGetPutObjReader(t, bytes.NewReader(partPayload), int64(len(partPayload)), "", ""), ObjectOptions{})
+			if err != nil {
+				t.Fatal(err)
+			}
+			completeBody := fmt.Appendf(nil, `<CompleteMultipartUpload><Part><PartNumber>1</PartNumber><ETag>"%s"</ETag></Part></CompleteMultipartUpload>`, pi.ETag)
+			target := makeTestTargetURL("", bucket, "addressed", url.Values{"uploadId": {up.UploadID}})
+			rec := retentionAuthzRequest(t, router, creds.creds, http.MethodPost, target, completeBody, nil)
+			if rec.Code != http.StatusForbidden {
+				t.Fatalf("status = %d, want 403: %s", rec.Code, rec.Body.String())
+			}
+			unchanged(t)
+		})
+	}
+
+	t.Run(instanceType+"/locked-directory-object", func(t *testing.T) {
+		far := UTCNow().Add(365 * 24 * time.Hour).Truncate(time.Second)
+		for _, lockCase := range []struct {
+			name string
+			meta map[string]string
+		}{
+			{
+				name: "governance",
+				meta: map[string]string{
+					strings.ToLower(xhttp.AmzObjectLockMode):            "GOVERNANCE",
+					strings.ToLower(xhttp.AmzObjectLockRetainUntilDate): amztime.ISO8601Format(far),
+				},
+			},
+			{
+				name: "compliance",
+				meta: map[string]string{
+					strings.ToLower(xhttp.AmzObjectLockMode):            "COMPLIANCE",
+					strings.ToLower(xhttp.AmzObjectLockRetainUntilDate): amztime.ISO8601Format(far),
+				},
+			},
+			{
+				name: "legal-hold",
+				meta: map[string]string{
+					strings.ToLower(xhttp.AmzObjectLockLegalHold): "ON",
+				},
+			},
+		} {
+			t.Run(lockCase.name, func(t *testing.T) {
+				dirKey := "locked-dir-" + lockCase.name + "/"
+				if _, err := obj.PutObject(t.Context(), bucket, dirKey,
+					mustGetPutObjReader(t, bytes.NewReader(nil), 0, "", ""),
+					ObjectOptions{Versioned: true, VersionID: nullVersionID, UserDefined: lockCase.meta}); err != nil {
+					t.Fatal(err)
+				}
+				target := makeTestTargetURL("", bucket, dirKey, nil)
+				rec := retentionAuthzRequest(t, router, writer, http.MethodPut, target, nil, nil)
+				if rec.Code != http.StatusBadRequest {
+					t.Fatalf("PUT locked dir status = %d, want 400: %s", rec.Code, rec.Body.String())
+				}
+				got, err := obj.GetObjectInfo(t.Context(), bucket, dirKey, ObjectOptions{VersionID: nullVersionID})
+				if err != nil {
+					t.Fatal(err)
+				}
+				for k, wantVal := range lockCase.meta {
+					if got.UserDefined[k] != wantVal {
+						t.Fatalf("metadata %s = %q, want %q", k, got.UserDefined[k], wantVal)
+					}
+				}
+			})
+		}
+	})
+
+	t.Run(instanceType+"/snowball-archive-version-id", func(t *testing.T) {
+		var tarBuf bytes.Buffer
+		tw := tar.NewWriter(&tarBuf)
+		entryData := []byte("snowball-overwrite")
+		if err := tw.WriteHeader(&tar.Header{
+			Typeflag:   tar.TypeReg,
+			Name:       "addressed",
+			Size:       int64(len(entryData)),
+			Format:     tar.FormatPAX,
+			PAXRecords: map[string]string{"minio.versionId": vid},
+		}); err != nil {
+			t.Fatal(err)
+		}
+		if _, err := tw.Write(entryData); err != nil {
+			t.Fatal(err)
+		}
+		if err := tw.Close(); err != nil {
+			t.Fatal(err)
+		}
+
+		// Untrusted writer cannot overwrite an existing version via PAX minio.versionId.
+		target := makeTestTargetURL("", bucket, "archive.tar", nil)
+		rec := retentionAuthzRequest(t, router, writer, http.MethodPut, target, tarBuf.Bytes(),
+			map[string]string{"x-amz-meta-snowball-auto-extract": "true"})
+		if rec.Code != http.StatusForbidden {
+			t.Fatalf("untrusted snowball status = %d, want 403: %s", rec.Code, rec.Body.String())
+		}
+		unchanged(t)
+
+		// Trusted batch replication (with outer MinIOSourceReplicationRequest) preserves PAX minio.versionId.
+		replicaVID := mustGetUUID()
+		var repBuf bytes.Buffer
+		repTW := tar.NewWriter(&repBuf)
+		repData := []byte("replicated-via-snowball")
+		if err := repTW.WriteHeader(&tar.Header{
+			Typeflag:   tar.TypeReg,
+			Name:       "snowball-replicated",
+			Size:       int64(len(repData)),
+			Format:     tar.FormatPAX,
+			PAXRecords: map[string]string{"minio.versionId": replicaVID},
+		}); err != nil {
+			t.Fatal(err)
+		}
+		if _, err := repTW.Write(repData); err != nil {
+			t.Fatal(err)
+		}
+		if err := repTW.Close(); err != nil {
+			t.Fatal(err)
+		}
+		repRec := retentionAuthzRequest(t, router, root, http.MethodPut, target, repBuf.Bytes(),
+			map[string]string{
+				"x-amz-meta-snowball-auto-extract":  "true",
+				xhttp.MinIOSourceReplicationRequest: "true",
+			})
+		if repRec.Code != http.StatusOK {
+			t.Fatalf("trusted snowball status = %d, want 200: %s", repRec.Code, repRec.Body.String())
+		}
+		if _, err := obj.GetObjectInfo(t.Context(), bucket, "snowball-replicated", ObjectOptions{VersionID: replicaVID}); err != nil {
+			t.Fatalf("trusted snowball replication did not preserve version ID: %v", err)
+		}
+	})
+
+	t.Run(instanceType+"/trusted replication", func(t *testing.T) {
+		replicaVID := mustGetUUID()
+		body := []byte("replicated version")
+		target := makeTestTargetURL("", bucket, "replicated", url.Values{"versionId": {replicaVID}})
+		rec := retentionAuthzRequest(t, router, root, http.MethodPut, target, body,
+			map[string]string{xhttp.MinIOSourceReplicationRequest: "true"})
+		if rec.Code != http.StatusOK {
+			t.Fatalf("status = %d, want 200: %s", rec.Code, rec.Body.String())
+		}
+		if _, err := obj.GetObjectInfo(t.Context(), bucket, "replicated", ObjectOptions{VersionID: replicaVID}); err != nil {
+			t.Fatalf("trusted replication did not keep its version ID: %v", err)
+		}
+	})
+}
+
+func TestPutObjectRetentionClearMinimumDaysPolicy(t *testing.T) {
+	ExecObjectLayerAPITest(ExecObjectLayerAPITestArgs{
+		t:                 t,
+		makeBucketOptions: MakeBucketOptions{VersioningEnabled: true, LockEnabled: true},
+		objAPITest: func(obj ObjectLayer, instance, bucket string, router http.Handler, root auth.Credentials, t *testing.T) {
+			for _, conditionalAllow := range []bool{false, true} {
+				t.Run(fmt.Sprintf("%s/conditional-allow-%v", instance, conditionalAllow), func(t *testing.T) {
+					statement := `{"Effect":"Allow","Action":["s3:PutObjectRetention","s3:BypassGovernanceRetention"],"Resource":["arn:aws:s3:::` + bucket + `/*"]}, {"Effect":"Deny","Action":["s3:PutObjectRetention"],"Resource":["arn:aws:s3:::` + bucket + `/*"],"Condition":{"NumericLessThan":{"s3:object-lock-remaining-retention-days":"60"}}}`
+					if conditionalAllow {
+						statement = `{"Effect":"Allow","Action":["s3:BypassGovernanceRetention"],"Resource":["arn:aws:s3:::` + bucket + `/*"]}, {"Effect":"Allow","Action":["s3:PutObjectRetention"],"Resource":["arn:aws:s3:::` + bucket + `/*"],"Condition":{"NumericGreaterThanEquals":{"s3:object-lock-remaining-retention-days":"60"}}}`
+					}
+					cred := newRetentionPolicyUser(t, instance, `{"Version":"2012-10-17","Statement":[`+statement+`]}`)
+					key := fmt.Sprintf("review-minimum-%v", conditionalAllow)
+					far := UTCNow().Add(365 * 24 * time.Hour).Truncate(time.Second)
+					info, err := obj.PutObject(t.Context(), bucket, key, mustGetPutObjReader(t, bytes.NewReader(nil), 0, "", ""), ObjectOptions{
+						Versioned: true,
+						UserDefined: map[string]string{
+							strings.ToLower(xhttp.AmzObjectLockMode):            "GOVERNANCE",
+							strings.ToLower(xhttp.AmzObjectLockRetainUntilDate): amztime.ISO8601Format(far),
+						},
+					})
+					if err != nil {
+						t.Fatal(err)
+					}
+					if status := putRetention(t, router, cred, bucket, key, info.VersionID, "GOVERNANCE", UTCNow().Add(30*24*time.Hour), true); status != http.StatusForbidden {
+						t.Fatalf("shortening to 30 days status = %d, want 403", status)
+					}
+					status := putRetention(t, router, cred, bucket, key, info.VersionID, "", time.Time{}, true)
+					after, err := obj.GetObjectInfo(t.Context(), bucket, key, ObjectOptions{VersionID: info.VersionID})
+					if err != nil {
+						t.Fatal(err)
+					}
+					ret := objectlock.GetObjectRetentionMeta(after.UserDefined)
+					if status != http.StatusForbidden || ret.Mode != objectlock.RetGovernance {
+						t.Fatalf("clearing retention status = %d, stored retention = %s; want 403 and original GOVERNANCE", status, ret.String())
+					}
+				})
+			}
+		},
+	})
+}
+
+type hookBeforeWrite struct {
+	ObjectLayer
+	key    string
+	before func()
+}
+
+func (p *hookBeforeWrite) fire(key string) {
+	if key == p.key && p.before != nil {
+		f := p.before
+		p.before = nil
+		f()
+	}
+}
+
+func (p *hookBeforeWrite) PutObject(ctx context.Context, bucket, key string, r *PutObjReader, opts ObjectOptions) (ObjectInfo, error) {
+	p.fire(key)
+	return p.ObjectLayer.PutObject(ctx, bucket, key, r, opts)
+}
+
+func (p *hookBeforeWrite) CopyObject(ctx context.Context, srcBucket, srcObject, dstBucket, dstObject string, srcInfo ObjectInfo, srcOpts, dstOpts ObjectOptions) (ObjectInfo, error) {
+	p.fire(dstObject)
+	return p.ObjectLayer.CopyObject(ctx, srcBucket, srcObject, dstBucket, dstObject, srcInfo, srcOpts, dstOpts)
+}
+
+func (p *hookBeforeWrite) CompleteMultipartUpload(ctx context.Context, bucket, key, uploadID string, parts []CompletePart, opts ObjectOptions) (ObjectInfo, error) {
+	p.fire(key)
+	return p.ObjectLayer.CompleteMultipartUpload(ctx, bucket, key, uploadID, parts, opts)
+}
+
+func TestDirectoryObjectLockAfterPreflight(t *testing.T) {
+	ExecObjectLayerAPITest(ExecObjectLayerAPITestArgs{
+		t:                 t,
+		makeBucketOptions: MakeBucketOptions{VersioningEnabled: true, LockEnabled: true},
+		objAPITest: func(obj ObjectLayer, instance, bucket string, router http.Handler, root auth.Credentials, t *testing.T) {
+			writer := newObjectAttributesAuthzUser(t, instance, bucket, `"s3:GetObject","s3:PutObject"`)
+			srcDir := "other-dir/"
+			if rec := retentionAuthzRequest(t, router, writer, http.MethodPut, makeTestTargetURL("", bucket, srcDir, nil), nil, nil); rec.Code != http.StatusOK {
+				t.Fatalf("srcDir PUT: %d %s", rec.Code, rec.Body.String())
+			}
+
+			for _, mode := range []string{"GOVERNANCE", "COMPLIANCE", "LEGAL-HOLD"} {
+				for _, op := range []string{"PutObject", "CopyObject", "SelfCopy"} {
+					t.Run(instance+"/"+mode+"/"+op, func(t *testing.T) {
+						key := fmt.Sprintf("review-race-%s-%s/", mode, op)
+						if rec := retentionAuthzRequest(t, router, writer, http.MethodPut, makeTestTargetURL("", bucket, key, nil), nil, nil); rec.Code != http.StatusOK {
+							t.Fatalf("initial PUT: %d %s", rec.Code, rec.Body.String())
+						}
+
+						var locked ObjectInfo
+						hook := &hookBeforeWrite{ObjectLayer: obj, key: key}
+						hook.before = func() {
+							if mode == "LEGAL-HOLD" {
+								body := []byte(`<LegalHold><Status>ON</Status></LegalHold>`)
+								sum := md5.Sum(body)
+								rec := retentionAuthzRequest(t, router, root, http.MethodPut, makeTestTargetURL("", bucket, key, url.Values{"legal-hold": {""}, "versionId": {nullVersionID}}), body, map[string]string{xhttp.ContentMD5: base64.StdEncoding.EncodeToString(sum[:])})
+								if rec.Code != http.StatusOK {
+									t.Fatalf("set legal hold: %d %s", rec.Code, rec.Body.String())
+								}
+							} else if status := putRetention(t, router, root, bucket, key, nullVersionID, mode, UTCNow().Add(365*24*time.Hour), false); status != http.StatusOK {
+								t.Fatalf("set retention: %d", status)
+							}
+							var err error
+							locked, err = obj.GetObjectInfo(t.Context(), bucket, key, ObjectOptions{VersionID: nullVersionID})
+							if err != nil {
+								t.Fatal(err)
+							}
+						}
+						setObjectLayer(hook)
+						defer setObjectLayer(obj)
+
+						var rec *httptest.ResponseRecorder
+						switch op {
+						case "PutObject":
+							rec = retentionAuthzRequest(t, router, writer, http.MethodPut, makeTestTargetURL("", bucket, key, nil), nil, nil)
+						case "CopyObject":
+							rec = retentionAuthzRequest(t, router, writer, http.MethodPut, makeTestTargetURL("", bucket, key, nil), nil, map[string]string{
+								xhttp.AmzCopySource: pathJoin(bucket, srcDir),
+							})
+						case "SelfCopy":
+							rec = retentionAuthzRequest(t, router, writer, http.MethodPut, makeTestTargetURL("", bucket, key, nil), nil, map[string]string{
+								xhttp.AmzCopySource: pathJoin(bucket, key), xhttp.AmzMetadataDirective: "REPLACE", "x-amz-meta-updated": "true",
+							})
+						}
+						if hook.before != nil {
+							t.Fatalf("%s never reached backend: %d %s", op, rec.Code, rec.Body.String())
+						}
+						after, err := obj.GetObjectInfo(t.Context(), bucket, key, ObjectOptions{VersionID: nullVersionID})
+						if err != nil {
+							t.Fatal(err)
+						}
+						if rec.Code != http.StatusBadRequest {
+							t.Fatalf("locked null write via %s: %d %s", op, rec.Code, rec.Body.String())
+						}
+						multipartConditionError(t, rec, "InvalidRequest")
+						retentionOverwriteUnchanged(t, locked, after)
+					})
+				}
+			}
+		},
+	})
+}
+
+func TestMultipartVersioningTransitions(t *testing.T) {
+	ExecObjectLayerAPITest(ExecObjectLayerAPITestArgs{
+		t: t,
+		objAPITest: func(obj ObjectLayer, instance, bucket string, router http.Handler, root auth.Credentials, t *testing.T) {
+			t.Run(instance+"/unversioned-to-enabled", func(t *testing.T) {
+				key := "review-upload-before-versioning"
+				initRec := retentionAuthzRequest(t, router, root, http.MethodPost, makeTestTargetURL("", bucket, key, url.Values{"uploads": {""}}), nil, nil)
+				if initRec.Code != http.StatusOK {
+					t.Fatalf("init: %d %s", initRec.Code, initRec.Body.String())
+				}
+				var mp InitiateMultipartUploadResponse
+				if err := xml.Unmarshal(initRec.Body.Bytes(), &mp); err != nil {
+					t.Fatal(err)
+				}
+				part := retentionAuthzRequest(t, router, root, http.MethodPut, getPutObjectPartURL("", bucket, key, mp.UploadID, "1"), []byte("ordinary pending upload"), nil)
+				if part.Code != http.StatusOK {
+					t.Fatalf("part: %d %s", part.Code, part.Body.String())
+				}
+				if _, err := globalBucketMetadataSys.Update(t.Context(), bucket, bucketVersioningConfig, []byte(`<VersioningConfiguration><Status>Enabled</Status></VersioningConfiguration>`)); err != nil {
+					t.Fatal(err)
+				}
+				body := fmt.Appendf(nil, `<CompleteMultipartUpload><Part><PartNumber>1</PartNumber><ETag>%s</ETag></Part></CompleteMultipartUpload>`, multipartConditionResponseETag(part))
+				rec := retentionAuthzRequest(t, router, root, http.MethodPost, makeTestTargetURL("", bucket, key, url.Values{"uploadId": {mp.UploadID}}), body, nil)
+				if rec.Code != http.StatusOK {
+					t.Fatalf("ordinary upload initiated before versioning fails completion: %d %s", rec.Code, rec.Body.String())
+				}
+			})
+			t.Run(instance+"/addressed-upload-after-suspension", func(t *testing.T) {
+				key := "review-addressed-before-suspension"
+				original := []byte("original")
+				info, err := obj.PutObject(t.Context(), bucket, key, mustGetPutObjReader(t, bytes.NewReader(original), int64(len(original)), "", ""), ObjectOptions{Versioned: true})
+				if err != nil {
+					t.Fatal(err)
+				}
+				up, err := obj.NewMultipartUpload(t.Context(), bucket, key, ObjectOptions{Versioned: true, VersionID: info.VersionID})
+				if err != nil {
+					t.Fatal(err)
+				}
+				part := []byte("replaced existing version")
+				pi, err := obj.PutObjectPart(t.Context(), bucket, key, up.UploadID, 1, mustGetPutObjReader(t, bytes.NewReader(part), int64(len(part)), "", ""), ObjectOptions{})
+				if err != nil {
+					t.Fatal(err)
+				}
+				if _, err := globalBucketMetadataSys.Update(t.Context(), bucket, bucketVersioningConfig, []byte(`<VersioningConfiguration><Status>Suspended</Status></VersioningConfiguration>`)); err != nil {
+					t.Fatal(err)
+				}
+				writer := newObjectAttributesAuthzUser(t, instance, bucket, `"s3:PutObject"`)
+				body := fmt.Appendf(nil, `<CompleteMultipartUpload><Part><PartNumber>1</PartNumber><ETag>"%s"</ETag></Part></CompleteMultipartUpload>`, pi.ETag)
+				rec := retentionAuthzRequest(t, router, writer, http.MethodPost, makeTestTargetURL("", bucket, key, url.Values{"uploadId": {up.UploadID}}), body, nil)
+				after, err := obj.GetObjectInfo(t.Context(), bucket, key, ObjectOptions{VersionID: info.VersionID})
+				if err != nil {
+					t.Fatal(err)
+				}
+				if rec.Code != http.StatusForbidden || after.ETag != info.ETag {
+					t.Fatalf("suspended-bucket existing UUID overwritten: status=%d old-etag=%s new-etag=%s body=%s", rec.Code, info.ETag, after.ETag, rec.Body.String())
+				}
+			})
+		},
+	})
+}

cmd/object-retention-overwrite_test.go

@@ -0,0 +1,546 @@
+// Copyright (c) 2026 Feng Ruohang
+// SPDX-License-Identifier: AGPL-3.0-or-later
+//
+// This file is part of Silo Object Storage stack.
+//
+// This program is free software: you can redistribute it and/or modify
+// it under the terms of the GNU Affero General Public License as published by
+// the Free Software Foundation, either version 3 of the License, or
+// (at your option) any later version.
+//
+// This program is distributed in the hope that it will be useful,
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+// GNU Affero General Public License for more details.
+//
+// You should have received a copy of the GNU Affero General Public License
+// along with this program. If not, see <http://www.gnu.org/licenses/>.
+
+package cmd
+
+import (
+	"bytes"
+	"context"
+	"crypto/md5"
+	"encoding/base64"
+	"errors"
+	"fmt"
+	"io"
+	"net/http"
+	"net/http/httptest"
+	"net/url"
+	"strings"
+	"sync"
+	"testing"
+	"time"
+
+	"github.com/minio/minio/internal/amztime"
+	"github.com/minio/minio/internal/auth"
+	objectlock "github.com/minio/minio/internal/bucket/object/lock"
+	xhttp "github.com/minio/minio/internal/http"
+)
+
+func retentionOverwriteUnchanged(t *testing.T, before, after ObjectInfo) {
+	t.Helper()
+	if after.ETag != before.ETag || after.Size != before.Size || after.VersionID != before.VersionID || !after.ModTime.Equal(before.ModTime) {
+		t.Error("rejected write changed the stored object")
+	}
+	if objectlock.GetObjectRetentionMeta(after.UserDefined).String() != objectlock.GetObjectRetentionMeta(before.UserDefined).String() || objectlock.GetObjectLegalHoldMeta(after.UserDefined).Status != objectlock.GetObjectLegalHoldMeta(before.UserDefined).Status {
+		t.Error("rejected write changed the stored lock")
+	}
+}
+
+func TestObjectLockOverwriteConfigUnavailable(t *testing.T) {
+	previous := newObjectLayerFn()
+	setObjectLayer(nil)
+	defer setObjectLayer(previous)
+	err := checkObjectLockedForOverwrite(t.Context(), "lock-config-unavailable", "object", func(context.Context, string, string, ObjectOptions) (ObjectInfo, error) {
+		t.Fatal("object must not be read without a bucket configuration")
+		return ObjectInfo{}, nil
+	})
+	if !errors.Is(err, errServerNotInitialized) {
+		t.Fatalf("unavailable lock configuration must fail closed, got %v", err)
+	}
+}
+
+func TestPutObjectRetentionMaximumDaysPolicy(t *testing.T) {
+	ExecObjectLayerAPITest(ExecObjectLayerAPITestArgs{
+		t:                 t,
+		makeBucketOptions: MakeBucketOptions{VersioningEnabled: true, LockEnabled: true},
+		objAPITest: func(obj ObjectLayer, instance, bucket string, router http.Handler, _ auth.Credentials, t *testing.T) {
+			for _, conditionalAllow := range []bool{false, true} {
+				t.Run(fmt.Sprintf("%s/conditional-allow=%t", instance, conditionalAllow), func(t *testing.T) {
+					statement := fmt.Sprintf(`{"Effect":"Allow","Action":["s3:PutObjectRetention"],"Resource":["arn:aws:s3:::%s/*"],"Condition":{"NumericLessThanEquals":{"s3:object-lock-remaining-retention-days":"200000"}}}`, bucket)
+					if !conditionalAllow {
+						statement = fmt.Sprintf(`{"Effect":"Allow","Action":["s3:PutObjectRetention"],"Resource":["arn:aws:s3:::%s/*"]},{"Effect":"Deny","Action":["s3:PutObjectRetention"],"Resource":["arn:aws:s3:::%s/*"],"Condition":{"NumericGreaterThan":{"s3:object-lock-remaining-retention-days":"200000"}}}`, bucket, bucket)
+					}
+					cred := newRetentionPolicyUser(t, instance, `{"Version":"2012-10-17","Statement":[`+statement+`]}`)
+					key := fmt.Sprintf("maximum-retention-%t", conditionalAllow)
+					initial, err := obj.PutObject(t.Context(), bucket, key, mustGetPutObjReader(t, bytes.NewReader(nil), 0, "", ""), ObjectOptions{Versioned: true})
+					if err != nil {
+						t.Fatal(err)
+					}
+					// Both dates exceed time.Duration's range (~292 years). A saturated
+					// Time.Sub would report 106752 days and incorrectly allow 1000 years.
+					if status := putRetention(t, router, cred, bucket, key, initial.VersionID, "GOVERNANCE", UTCNow().AddDate(1000, 0, 0), false); status != http.StatusForbidden {
+						t.Fatalf("1000-year retention: want 403, got %d", status)
+					}
+					after, err := obj.GetObjectInfo(t.Context(), bucket, key, ObjectOptions{VersionID: initial.VersionID})
+					if err != nil {
+						t.Fatal(err)
+					}
+					retentionOverwriteUnchanged(t, initial, after)
+					if status := putRetention(t, router, cred, bucket, key, initial.VersionID, "GOVERNANCE", UTCNow().AddDate(500, 0, 0), false); status != http.StatusOK {
+						t.Fatalf("500-year retention: want 200, got %d", status)
+					}
+				})
+			}
+		},
+	})
+}
+
+func TestAPICopyObjectPreservesVersionAfterSuspension(t *testing.T) {
+	ExecObjectLayerAPITest(ExecObjectLayerAPITestArgs{
+		t:                 t,
+		makeBucketOptions: MakeBucketOptions{VersioningEnabled: true},
+		objAPITest: func(obj ObjectLayer, instance, bucket string, router http.Handler, root auth.Credentials, t *testing.T) {
+			t.Run(instance, func(t *testing.T) {
+				key := "self-copy-after-suspension"
+				original, err := obj.PutObject(t.Context(), bucket, key, mustGetPutObjReader(t, bytes.NewBufferString("payload"), 7, "", ""), ObjectOptions{
+					Versioned: true, UserDefined: map[string]string{"x-amz-meta-state": "original"},
+				})
+				if err != nil {
+					t.Fatal(err)
+				}
+				if _, err := globalBucketMetadataSys.Update(t.Context(), bucket, bucketVersioningConfig,
+					[]byte(`<VersioningConfiguration><Status>Suspended</Status></VersioningConfiguration>`)); err != nil {
+					t.Fatal(err)
+				}
+				rec := retentionAuthzRequest(t, router, root, http.MethodPut, makeTestTargetURL("", bucket, key, nil), nil, map[string]string{
+					xhttp.AmzCopySource: "/" + bucket + "/" + key, xhttp.AmzMetadataDirective: "REPLACE", "x-amz-meta-state": "replacement",
+				})
+				if rec.Code != http.StatusOK {
+					t.Fatalf("copy: %d %s", rec.Code, rec.Body.String())
+				}
+				old, err := obj.GetObjectInfo(t.Context(), bucket, key, ObjectOptions{VersionID: original.VersionID})
+				if err != nil {
+					t.Fatal(err)
+				}
+				if old.UserDefined["x-amz-meta-state"] != "original" {
+					t.Errorf("copy changed metadata of existing UUID %s: %v", original.VersionID, old.UserDefined)
+				}
+				current, err := obj.GetObjectInfo(t.Context(), bucket, key, ObjectOptions{VersionID: nullVersionID})
+				if err != nil {
+					t.Fatalf("copy must create the null version: %v", err)
+				}
+				if current.UserDefined["X-Amz-Meta-State"] != "replacement" {
+					t.Errorf("new null version metadata: %v", current.UserDefined)
+				}
+			})
+		},
+	})
+}
+
+// A persisted null upload can survive an upgrade or a versioning transition.
+// The completion must see locks committed after the handler's preflight.
+func TestMultipartNullObjectLockAfterPreflight(t *testing.T) {
+	ExecObjectLayerAPITest(ExecObjectLayerAPITestArgs{
+		t:                 t,
+		makeBucketOptions: MakeBucketOptions{VersioningEnabled: true, LockEnabled: true},
+		objAPITest: func(obj ObjectLayer, instance, bucket string, router http.Handler, root auth.Credentials, t *testing.T) {
+			writer := newObjectAttributesAuthzUser(t, instance, bucket, `"s3:PutObject"`)
+			for _, mode := range []string{"GOVERNANCE", "COMPLIANCE", "LEGAL-HOLD"} {
+				t.Run(instance+"/"+mode, func(t *testing.T) {
+					ctx := t.Context()
+					key := "multipart-null-" + mode
+					opts := ObjectOptions{Versioned: true, VersionID: nullVersionID, ReplicationRequest: true}
+					if _, err := obj.PutObject(ctx, bucket, key, mustGetPutObjReader(t, bytes.NewBufferString("original"), 8, "", ""), opts); err != nil {
+						t.Fatal(err)
+					}
+					mp, err := obj.NewMultipartUpload(ctx, bucket, key, opts)
+					if err != nil {
+						t.Fatal(err)
+					}
+					part, err := obj.PutObjectPart(ctx, bucket, key, mp.UploadID, 1, mustGetPutObjReader(t, bytes.NewBufferString("replacement"), 11, "", ""), ObjectOptions{})
+					if err != nil {
+						t.Fatal(err)
+					}
+					var locked ObjectInfo
+					hook := &hookBeforeWrite{ObjectLayer: obj, key: key, before: func() {
+						if mode == "LEGAL-HOLD" {
+							body := []byte(`<LegalHold><Status>ON</Status></LegalHold>`)
+							sum := md5.Sum(body)
+							rec := retentionAuthzRequest(t, router, root, http.MethodPut, makeTestTargetURL("", bucket, key, url.Values{"legal-hold": {""}, "versionId": {nullVersionID}}), body, map[string]string{xhttp.ContentMD5: base64.StdEncoding.EncodeToString(sum[:])})
+							if rec.Code != http.StatusOK {
+								t.Fatalf("set legal hold: %d %s", rec.Code, rec.Body.String())
+							}
+						} else if status := putRetention(t, router, root, bucket, key, nullVersionID, mode, UTCNow().Add(365*24*time.Hour), false); status != http.StatusOK {
+							t.Fatalf("set retention: %d", status)
+						}
+						var err error
+						locked, err = obj.GetObjectInfo(ctx, bucket, key, ObjectOptions{VersionID: nullVersionID})
+						if err != nil {
+							t.Fatal(err)
+						}
+					}}
+					setObjectLayer(hook)
+					defer setObjectLayer(obj)
+					body := []byte(multipartConditionCompleteBody([]CompletePart{{PartNumber: 1, ETag: part.ETag}}))
+					rec := retentionAuthzRequest(t, router, writer, http.MethodPost, makeTestTargetURL("", bucket, key, url.Values{"uploadId": {mp.UploadID}}), body, nil)
+					if hook.before != nil || rec.Code != http.StatusBadRequest {
+						t.Fatalf("completion after locking: %d %s", rec.Code, rec.Body.String())
+					}
+					multipartConditionError(t, rec, "InvalidRequest")
+					after, err := obj.GetObjectInfo(ctx, bucket, key, ObjectOptions{VersionID: nullVersionID})
+					if err != nil {
+						t.Fatal(err)
+					}
+					retentionOverwriteUnchanged(t, locked, after)
+					parts, err := obj.ListObjectParts(ctx, bucket, key, mp.UploadID, 0, 100, ObjectOptions{})
+					if err != nil || len(parts.Parts) != 1 || parts.Parts[0].ETag != part.ETag {
+						t.Fatalf("rejected completion removed upload parts: %v %+v", err, parts.Parts)
+					}
+				})
+			}
+		},
+	})
+}
+
+// The newer, unlocked copy is in the write pool; the lock exists only in the
+// other pool. A set-local check would miss it even while holding a write lock.
+func TestPoolsObjectLockOverwrite(t *testing.T) {
+	z, _ := consistencyPools(t)
+	bucket, _, err := initAPIHandlerTest(t.Context(), z, nil, MakeBucketOptions{VersioningEnabled: true, LockEnabled: true})
+	if err != nil {
+		t.Fatal(err)
+	}
+	for _, state := range []string{"GOVERNANCE", "COMPLIANCE", "LEGAL-HOLD", "expired", "unlocked", "unreadable"} {
+		for _, op := range []string{"put", "copy", "self-copy", "multipart"} {
+			t.Run(state+"/"+op, func(t *testing.T) {
+				ctx := t.Context()
+				key := encodeDirObject("null-" + state + "-" + op + "/")
+				meta := map[string]string{}
+				switch state {
+				case "GOVERNANCE", "COMPLIANCE":
+					meta[strings.ToLower(xhttp.AmzObjectLockMode)] = state
+					meta[strings.ToLower(xhttp.AmzObjectLockRetainUntilDate)] = amztime.ISO8601Format(UTCNow().Add(365 * 24 * time.Hour))
+				case "LEGAL-HOLD":
+					meta[strings.ToLower(xhttp.AmzObjectLockLegalHold)] = "ON"
+				case "expired":
+					meta[strings.ToLower(xhttp.AmzObjectLockMode)] = "GOVERNANCE"
+					meta[strings.ToLower(xhttp.AmzObjectLockRetainUntilDate)] = amztime.ISO8601Format(UTCNow().Add(-24 * time.Hour))
+				}
+				seed := ObjectOptions{Versioned: true, VersionID: nullVersionID, ReplicationRequest: true, MTime: UTCNow().Add(-time.Hour), UserDefined: meta}
+				putConsistencyObject(t, z, bucket, key, 1, "original", seed)
+				seed.UserDefined = map[string]string{}
+				seed.MTime = UTCNow()
+				putConsistencyObject(t, z, bucket, key, 0, "original", seed)
+				before := make([]ObjectInfo, len(z.serverPools))
+				for i, pool := range z.serverPools {
+					var err error
+					before[i], err = pool.GetObjectInfo(ctx, bucket, key, ObjectOptions{VersionID: nullVersionID})
+					if err != nil {
+						t.Fatal(err)
+					}
+				}
+				defer conditionalPutPool(t, z, key, 0)()
+				var restore func()
+				if state == "unreadable" {
+					restore = conditionalPutSwapDisks(z.serverPools[1], key, func(d StorageAPI) StorageAPI {
+						return consistencyReadFaultDisk{StorageAPI: d, bucket: bucket, object: key}
+					})
+					defer restore()
+				}
+				opts := ObjectOptions{Versioned: true, VersionID: nullVersionID, UserDefined: map[string]string{"x-amz-meta-updated": "true"}}
+				var writeErr error
+				switch op {
+				case "put":
+					_, writeErr = z.PutObject(ctx, bucket, key, mustGetPutObjReader(t, bytes.NewBufferString("replacement"), 11, "", ""), opts)
+				case "copy", "self-copy":
+					source := key
+					if op == "copy" {
+						source = "source-" + state
+						putConsistencyObject(t, z, bucket, source, 0, "replacement", ObjectOptions{Versioned: true})
+					}
+					gr, gerr := z.GetObjectNInfo(ctx, bucket, source, nil, nil, ObjectOptions{})
+					if gerr != nil {
+						t.Fatal(gerr)
+					}
+					defer gr.Close()
+					info := gr.ObjInfo
+					info.UserDefined = opts.UserDefined
+					info.metadataOnly = op == "self-copy"
+					info.PutObjReader = mustGetPutObjReader(t, gr, info.Size, "", "")
+					info.Reader = info.PutObjReader.Reader
+					_, writeErr = z.CopyObject(ctx, bucket, source, bucket, key, info, ObjectOptions{VersionID: nullVersionID}, opts)
+				case "multipart":
+					id, parts := multipartConditionUpload(t, z, bucket, key, 0, opts)
+					_, writeErr = z.CompleteMultipartUpload(ctx, bucket, key, id, parts, ObjectOptions{Versioned: true})
+				}
+				allowed := state == "expired" || state == "unlocked"
+				if allowed {
+					if writeErr != nil {
+						t.Fatalf("unlocked write: %v", writeErr)
+					}
+					return
+				}
+				if state == "unreadable" {
+					if !isErrReadQuorum(writeErr) {
+						t.Fatalf("unreadable pool: want quorum error, got %v", writeErr)
+					}
+					restore()
+				} else if !errors.As(writeErr, &ObjectLocked{}) {
+					t.Fatalf("lock in other pool: want ObjectLocked, got %v", writeErr)
+				}
+				for i, original := range before {
+					after, gerr := z.serverPools[i].GetObjectInfo(ctx, bucket, key, ObjectOptions{VersionID: nullVersionID})
+					if gerr != nil {
+						t.Fatal(gerr)
+					}
+					retentionOverwriteUnchanged(t, original, after)
+				}
+			})
+		}
+	}
+}
+
+type planReviewGatedBody struct {
+	io.ReadCloser
+	first   sync.Once
+	ready   chan struct{}
+	release chan struct{}
+}
+
+func (g *planReviewGatedBody) Read(p []byte) (int, error) {
+	g.first.Do(func() { close(g.ready); <-g.release })
+	return g.ReadCloser.Read(p)
+}
+
+func TestPlanReviewSlowDirectoryPut(t *testing.T) {
+	ExecObjectLayerAPITest(ExecObjectLayerAPITestArgs{
+		t:                 t,
+		makeBucketOptions: MakeBucketOptions{VersioningEnabled: true, LockEnabled: true},
+		objAPITest: func(obj ObjectLayer, instance, bucket string, router http.Handler, root auth.Credentials, t *testing.T) {
+			writer := newObjectAttributesAuthzUser(t, instance, bucket, `"s3:PutObject"`)
+			t.Run(instance, func(t *testing.T) {
+				key := "slow-body-directory/"
+				before, err := obj.PutObject(t.Context(), bucket, key, mustGetPutObjReader(t, bytes.NewBufferString("original"), 8, "", ""), ObjectOptions{Versioned: true, VersionID: nullVersionID})
+				if err != nil {
+					t.Fatal(err)
+				}
+				payload := []byte("replacement-body")
+				req, err := newTestSignedRequestV4(http.MethodPut, makeTestTargetURL("", bucket, key, nil), int64(len(payload)), bytes.NewReader(payload), writer.AccessKey, writer.SecretKey, nil)
+				if err != nil {
+					t.Fatal(err)
+				}
+				gate := &planReviewGatedBody{ReadCloser: req.Body, ready: make(chan struct{}), release: make(chan struct{})}
+				req.Body = gate
+				var once sync.Once
+				release := func() { once.Do(func() { close(gate.release) }) }
+				defer release()
+				rec := httptest.NewRecorder()
+				done := make(chan struct{})
+				go func() { router.ServeHTTP(rec, req); close(done) }()
+				select {
+				case <-gate.ready:
+				case <-done:
+					t.Fatalf("PUT finished before body: %d %s", rec.Code, rec.Body.String())
+				case <-time.After(5 * time.Second):
+					t.Fatal("PUT did not reach body read")
+				}
+				locked := make(chan int, 1)
+				go func() {
+					locked <- putRetention(t, router, root, bucket, key, nullVersionID, "COMPLIANCE", UTCNow().Add(365*24*time.Hour), false)
+				}()
+				select {
+				case status := <-locked:
+					if status != http.StatusOK {
+						t.Fatalf("set lock while body paused: %d", status)
+					}
+				case <-time.After(5 * time.Second):
+					t.Fatal("retention update blocked behind paused body")
+				}
+				release()
+				select {
+				case <-done:
+				case <-time.After(5 * time.Second):
+					t.Fatal("PUT did not finish")
+				}
+				after, err := obj.GetObjectInfo(t.Context(), bucket, key, ObjectOptions{VersionID: nullVersionID})
+				if err != nil {
+					t.Fatal(err)
+				}
+				if rec.Code != http.StatusBadRequest || after.ETag != before.ETag || objectlock.GetObjectRetentionMeta(after.UserDefined).Mode != objectlock.RetCompliance {
+					t.Fatal("paused ordinary PUT overwrote the COMPLIANCE null version after the lock was acknowledged")
+				}
+			})
+		},
+	})
+}
+
+type planReviewReadFault struct {
+	ObjectLayer
+	key       string
+	fired     bool
+	putCalled bool
+}
+
+func (p *planReviewReadFault) GetObjectInfo(ctx context.Context, bucket, key string, opts ObjectOptions) (ObjectInfo, error) {
+	if key == p.key && opts.VersionID == nullVersionID && !p.fired {
+		p.fired = true
+		return ObjectInfo{}, InsufficientReadQuorum{}
+	}
+	return p.ObjectLayer.GetObjectInfo(ctx, bucket, key, opts)
+}
+
+func (p *planReviewReadFault) PutObject(ctx context.Context, bucket, key string, data *PutObjReader, opts ObjectOptions) (ObjectInfo, error) {
+	if key == p.key {
+		p.putCalled = true
+	}
+	return p.ObjectLayer.PutObject(ctx, bucket, key, data, opts)
+}
+
+func TestPlanReviewPreflightReadFailure(t *testing.T) {
+	ExecObjectLayerAPITest(ExecObjectLayerAPITestArgs{
+		t:                 t,
+		makeBucketOptions: MakeBucketOptions{VersioningEnabled: true, LockEnabled: true},
+		objAPITest: func(obj ObjectLayer, instance, bucket string, router http.Handler, _ auth.Credentials, t *testing.T) {
+			writer := newObjectAttributesAuthzUser(t, instance, bucket, `"s3:PutObject"`)
+			t.Run(instance, func(t *testing.T) {
+				key := "locked-directory-read-fault/"
+				_, err := obj.PutObject(t.Context(), bucket, key, mustGetPutObjReader(t, bytes.NewBufferString("original"), 8, "", ""), ObjectOptions{
+					Versioned: true, VersionID: nullVersionID, ReplicationRequest: true,
+					UserDefined: map[string]string{
+						strings.ToLower(xhttp.AmzObjectLockMode):            "COMPLIANCE",
+						strings.ToLower(xhttp.AmzObjectLockRetainUntilDate): amztime.ISO8601Format(UTCNow().Add(365 * 24 * time.Hour)),
+					},
+				})
+				if err != nil {
+					t.Fatal(err)
+				}
+				initial, err := obj.GetObjectInfo(t.Context(), bucket, key, ObjectOptions{VersionID: nullVersionID})
+				if err != nil {
+					t.Fatal(err)
+				}
+				fault := &planReviewReadFault{ObjectLayer: obj, key: key}
+				setObjectLayer(fault)
+				defer setObjectLayer(obj)
+				rec := retentionAuthzRequest(t, router, writer, http.MethodPut, makeTestTargetURL("", bucket, key, nil), []byte("replacement"), nil)
+				if !fault.fired {
+					t.Fatal("preflight fault was not injected")
+				}
+				if fault.putCalled {
+					t.Fatal("preflight read error allowed PutObject to proceed to storage layer")
+				}
+				after, err := obj.GetObjectInfo(t.Context(), bucket, key, ObjectOptions{VersionID: nullVersionID})
+				if err != nil {
+					t.Fatal(err)
+				}
+				if rec.Code < 400 {
+					t.Errorf("metadata read quorum error was treated as absence: status=%d", rec.Code)
+				}
+				retentionOverwriteUnchanged(t, initial, after)
+			})
+		},
+	})
+}
+
+func TestPlanReviewLegacyMPUCompliance(t *testing.T) {
+	ExecObjectLayerAPITest(ExecObjectLayerAPITestArgs{
+		t:                 t,
+		makeBucketOptions: MakeBucketOptions{VersioningEnabled: true, LockEnabled: true},
+		objAPITest: func(obj ObjectLayer, instance, bucket string, router http.Handler, root auth.Credentials, t *testing.T) {
+			writer := newObjectAttributesAuthzUser(t, instance, bucket, `"s3:PutObject"`)
+			t.Run(instance, func(t *testing.T) {
+				key := "legacy-mpu-compliance"
+				initial, err := obj.PutObject(t.Context(), bucket, key, mustGetPutObjReader(t, bytes.NewBufferString("original"), 8, "", ""), ObjectOptions{Versioned: true})
+				if err != nil {
+					t.Fatal(err)
+				}
+				up, err := obj.NewMultipartUpload(t.Context(), bucket, key, ObjectOptions{Versioned: true, VersionID: initial.VersionID})
+				if err != nil {
+					t.Fatal(err)
+				}
+				payload := []byte("replacement-part")
+				part, err := obj.PutObjectPart(t.Context(), bucket, key, up.UploadID, 1, mustGetPutObjReader(t, bytes.NewReader(payload), int64(len(payload)), "", ""), ObjectOptions{})
+				if err != nil {
+					t.Fatal(err)
+				}
+				if status := putRetention(t, router, root, bucket, key, initial.VersionID, "COMPLIANCE", UTCNow().Add(365*24*time.Hour), false); status != http.StatusOK {
+					t.Fatalf("set compliance: %d", status)
+				}
+				before, err := obj.GetObjectInfo(t.Context(), bucket, key, ObjectOptions{VersionID: initial.VersionID})
+				if err != nil {
+					t.Fatal(err)
+				}
+				body := fmt.Appendf(nil, `<CompleteMultipartUpload><Part><PartNumber>1</PartNumber><ETag>"%s"</ETag></Part></CompleteMultipartUpload>`, part.ETag)
+				rec := retentionAuthzRequest(t, router, writer, http.MethodPost, makeTestTargetURL("", bucket, key, url.Values{"uploadId": {up.UploadID}}), body, nil)
+				after, err := obj.GetObjectInfo(t.Context(), bucket, key, ObjectOptions{VersionID: initial.VersionID})
+				if err != nil {
+					t.Fatal(err)
+				}
+				if rec.Code != http.StatusForbidden {
+					t.Errorf("legacy upload replaced locked UUID: status=%d", rec.Code)
+				}
+				retentionOverwriteUnchanged(t, before, after)
+			})
+		},
+	})
+}
+
+// A recovered upload retains an authentic server-generated version ID while a
+// surviving replica reintroduces its already-completed version and lock.
+// Only the fixture uses replication privileges; completion uses PutObject only.
+func TestRecoveredMultipartUploadAfterReplica(t *testing.T) {
+	ExecObjectLayerAPITest(ExecObjectLayerAPITestArgs{
+		t:                 t,
+		makeBucketOptions: MakeBucketOptions{VersioningEnabled: true, LockEnabled: true},
+		objAPITest: func(obj ObjectLayer, instance, bucket string, router http.Handler, root auth.Credentials, t *testing.T) {
+			writer := newObjectAttributesAuthzUser(t, instance, bucket, `"s3:PutObject"`)
+			t.Run(instance, func(t *testing.T) {
+				z := obj.(*erasureServerPools)
+				key := "recovered-generated-upload"
+				up, err := obj.NewMultipartUpload(t.Context(), bucket, key, ObjectOptions{Versioned: true})
+				if err != nil {
+					t.Fatal(err)
+				}
+				er := z.serverPools[0].getHashedSet(key)
+				fi, _, err := er.checkUploadIDExists(t.Context(), bucket, key, up.UploadID, true)
+				if err != nil {
+					t.Fatal(err)
+				}
+				_, err = obj.PutObject(t.Context(), bucket, key,
+					mustGetPutObjReader(t, bytes.NewBufferString("protected-original"), 18, "", ""),
+					ObjectOptions{Versioned: true, VersionID: fi.VersionID, ReplicationRequest: true})
+				if err != nil {
+					t.Fatal(err)
+				}
+				if status := putRetention(t, router, root, bucket, key, fi.VersionID, "COMPLIANCE", UTCNow().Add(365*24*time.Hour), false); status != http.StatusOK {
+					t.Fatalf("setting compliance lock: %d", status)
+				}
+				before, err := obj.GetObjectInfo(t.Context(), bucket, key, ObjectOptions{VersionID: fi.VersionID})
+				if err != nil {
+					t.Fatal(err)
+				}
+				partRec := retentionAuthzRequest(t, router, writer, http.MethodPut,
+					makeTestTargetURL("", bucket, key, url.Values{"uploadId": {up.UploadID}, "partNumber": {"1"}}),
+					[]byte("attacker-replacement"), nil)
+				if partRec.Code != http.StatusOK {
+					t.Fatalf("upload part: %d %s", partRec.Code, partRec.Body.String())
+				}
+				etag := multipartConditionResponseETag(partRec)
+				body := []byte(multipartConditionCompleteBody([]CompletePart{{PartNumber: 1, ETag: etag}}))
+				rec := retentionAuthzRequest(t, router, writer, http.MethodPost,
+					makeTestTargetURL("", bucket, key, url.Values{"uploadId": {up.UploadID}}), body, nil)
+				after, err := obj.GetObjectInfo(t.Context(), bucket, key, ObjectOptions{VersionID: fi.VersionID})
+				if err != nil {
+					t.Fatal(err)
+				}
+				if rec.Code != http.StatusForbidden {
+					t.Errorf("recovered upload bypassed existing UUID guard: status=%d", rec.Code)
+				}
+				retentionOverwriteUnchanged(t, before, after)
+			})
+		},
+	})
+}

cmd/replication-tagging-order_test.go

@@ -238,7 +238,7 @@ func r5APIOrdering(t *testing.T, encrypted bool) {
 						if err != nil {
 							t.Fatal(err)
 						}
-						original, err = obj.CompleteMultipartUpload(t.Context(), bucket, name, mp.UploadID, []CompletePart{{PartNumber: 1, ETag: part.ETag}}, ObjectOptions{Versioned: true})
+						original, err = obj.CompleteMultipartUpload(t.Context(), bucket, name, mp.UploadID, []CompletePart{{PartNumber: 1, ETag: part.ETag}}, ObjectOptions{Versioned: true, ReplicationRequest: true})
 						if err != nil {
 							t.Fatal(err)
 						}

cmd/storage-errors.go

@@ -70,6 +70,11 @@ var errDiskAccessDenied = StorageErr("drive access denied")
 // errFileNotFound - cannot find the file.
 var errFileNotFound = StorageErr("file not found")
 
+// errCommitMetaMissing - the staged xl.meta disappeared between the
+// data rename and the meta-file commit; a write-quorum failure, not
+// a missing object.
+var errCommitMetaMissing = StorageErr("commit metadata is missing")
+
 // errFileNotFound - cannot find requested file version.
 var errFileVersionNotFound = StorageErr("file version not found")
 

cmd/storage-rest-client.go

@@ -106,6 +106,8 @@ func toStorageErr(err error) error {
 		return errVolumeExists
 	case errFileNotFound.Error():
 		return errFileNotFound
+	case errCommitMetaMissing.Error():
+		return errCommitMetaMissing
 	case errFileVersionNotFound.Error():
 		return errFileVersionNotFound
 	case errFileNameTooLong.Error():

cmd/storage-rest-server.go

@@ -290,6 +290,9 @@ func (s *storageRESTServer) NSScannerHandler(ctx context.Context, params *nsScan
 		for update := range updates {
 			resp := storageNSScannerRPC.NewResponse()
 			resp.Update = &update
+			// Pooled responses may carry fields from a previous
+			// scan, always clear the fields not being set.
+			resp.Final = nil
 			out <- resp
 		}
 	}()
@@ -301,6 +304,7 @@ func (s *storageRESTServer) NSScannerHandler(ctx context.Context, params *nsScan
 	// Send final response.
 	resp := storageNSScannerRPC.NewResponse()
 	resp.Final = &ui
+	resp.Update = nil
 	out <- resp
 	return nil
 }

cmd/storage-rest-server_test.go

@@ -0,0 +1,94 @@
+// Copyright (c) 2026 Julien Laurenceau and Feng Ruohang
+//
+// This file is part of Silo Object Storage.
+//
+// This program is free software: you can redistribute it and/or modify
+// it under the terms of the GNU Affero General Public License as published by
+// the Free Software Foundation, either version 3 of the License, or
+// (at your option) any later version.
+//
+// This program is distributed in the hope that it will be useful
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+// GNU Affero General Public License for more details.
+//
+// You should have received a copy of the GNU Affero General Public License
+// along with this program.  If not, see <http://www.gnu.org/licenses/>.
+
+package cmd
+
+import (
+	"context"
+	"testing"
+
+	"github.com/minio/madmin-go/v3"
+	"github.com/minio/minio/internal/grid"
+)
+
+type scannerResponseTestDisk struct {
+	StorageAPI
+}
+
+func (scannerResponseTestDisk) NSScanner(_ context.Context, cache dataUsageCache, updates chan<- dataUsageEntry, _ madmin.HealScanMode, _ func() bool) (dataUsageCache, error) {
+	defer close(updates)
+	updates <- dataUsageEntry{Size: int64(cache.Info.NextCycle)}
+	cache.Info.NextCycle++
+	return cache, nil
+}
+
+func TestNSScannerHandlerClearsStaleResponses(t *testing.T) {
+	endpoint, err := NewEndpoint(t.TempDir())
+	if err != nil {
+		t.Fatal(err)
+	}
+	globalLocalDrivesMu.Lock()
+	oldDrives, oldSets := globalLocalDrivesMap, globalLocalSetDrives
+	globalLocalDrivesMap = map[string]StorageAPI{endpoint.String(): scannerResponseTestDisk{}}
+	globalLocalSetDrives = nil
+	globalLocalDrivesMu.Unlock()
+	t.Cleanup(func() {
+		globalLocalDrivesMu.Lock()
+		globalLocalDrivesMap, globalLocalSetDrives = oldDrives, oldSets
+		globalLocalDrivesMu.Unlock()
+	})
+
+	oldRPC := storageNSScannerRPC
+	t.Cleanup(func() { storageNSScannerRPC = oldRPC })
+	// Every new allocation is dirty too: the check must not depend on
+	// sync.Pool returning a previously used object.
+	storageNSScannerRPC = grid.NewStream[*nsScannerOptions, grid.NoPayload, *nsScannerResp](grid.HandlerNSScanner,
+		func() *nsScannerOptions { return &nsScannerOptions{} }, nil,
+		func() *nsScannerResp {
+			return &nsScannerResp{Update: &dataUsageEntry{Size: -1}, Final: &dataUsageCache{}}
+		})
+	server := storageRESTServer{endpoint: endpoint}
+	for cycle := uint32(1); cycle <= 3; cycle++ {
+		out := make(chan *nsScannerResp, 2)
+		params := &nsScannerOptions{Cache: &dataUsageCache{Info: dataUsageCacheInfo{Name: "bucket", NextCycle: cycle}}}
+		if err := server.NSScannerHandler(t.Context(), params, out); err != nil {
+			t.Fatal(err)
+		}
+		if len(out) != 2 {
+			t.Fatalf("cycle %d: got %d responses, want an update and a final cache", cycle, len(out))
+		}
+		for i := 0; i < 2; i++ {
+			resp := <-out
+			wire, err := resp.MarshalMsg(nil)
+			storageNSScannerRPC.PutResponse(resp)
+			if err != nil {
+				t.Fatal(err)
+			}
+			var decoded nsScannerResp
+			if _, err := decoded.UnmarshalMsg(wire); err != nil {
+				t.Fatal(err)
+			}
+			if i == 0 {
+				if decoded.Update == nil || decoded.Final != nil || decoded.Update.Size != int64(cycle) {
+					t.Errorf("cycle %d: invalid update response: %+v", cycle, decoded)
+				}
+			} else if decoded.Update != nil || decoded.Final == nil || decoded.Final.Info.NextCycle != cycle+1 {
+				t.Errorf("cycle %d: invalid final response: %+v", cycle, decoded)
+			}
+		}
+	}
+}

cmd/xl-storage-errors_test.go

@@ -18,10 +18,16 @@
 package cmd
 
 import (
+	"context"
+	"errors"
+	"net/http"
 	"os"
+	"path/filepath"
 	"runtime"
+	"sync"
 	"syscall"
 	"testing"
+	"time"
 )
 
 func TestSysErrors(t *testing.T) {
@@ -56,3 +62,120 @@ func TestSysErrors(t *testing.T) {
 		}
 	}
 }
+
+// TestCommitMetaMissingMapping verifies the RPC and object-layer mapping
+// of errCommitMetaMissing, returned when the staged xl.meta disappears
+// between the data rename and the meta-file commit in RenameData().
+func TestCommitMetaMissingMapping(t *testing.T) {
+	// The sentinel must survive a storage REST/grid round-trip; errors
+	// cross the wire as strings and are remapped by toStorageErr().
+	if got := toStorageErr(errors.New(errCommitMetaMissing.Error())); !errors.Is(got, errCommitMetaMissing) {
+		t.Fatalf("expected %s, got %s", errCommitMetaMissing, got)
+	}
+	if got := toStorageErr(errCommitMetaMissing); got != errCommitMetaMissing {
+		t.Fatalf("expected %s, got %s", errCommitMetaMissing, got)
+	}
+
+	// toObjectErr() must map the sentinel to InsufficientWriteQuorum
+	// (503), never to ObjectNotFound (404).
+	err := toObjectErr(errCommitMetaMissing, "bucket", "object")
+	qerr, ok := err.(InsufficientWriteQuorum)
+	if !ok {
+		t.Fatalf("expected InsufficientWriteQuorum, got %s (%T)", err, err)
+	}
+	if qerr.Bucket != "bucket" || qerr.Object != "object" {
+		t.Fatalf("unexpected bucket/object %s/%s", qerr.Bucket, qerr.Object)
+	}
+	apiErr := toAPIError(t.Context(), err)
+	if apiErr.Code != "SlowDownWrite" || apiErr.HTTPStatusCode != http.StatusServiceUnavailable {
+		t.Fatalf("expected SlowDownWrite/503, got %+v", apiErr)
+	}
+}
+
+// missingCommitMetaContext removes staged metadata at an existing cancellation
+// check, after WriteAll and (for non-inline objects) the data rename succeeded.
+// This deterministically models concurrent cleanup without changing production
+// code or relying on a filesystem race. The context itself remains live.
+type missingCommitMetaContext struct {
+	context.Context
+	mu             sync.Mutex
+	meta, dataDest string
+	removed        bool
+	removeErr      error
+}
+
+func (c *missingCommitMetaContext) Done() <-chan struct{} {
+	c.mu.Lock()
+	defer c.mu.Unlock()
+	if !c.removed {
+		if _, err := os.Stat(c.meta); err == nil {
+			dataMoved := c.dataDest == ""
+			if !dataMoved {
+				_, err = os.Stat(c.dataDest)
+				dataMoved = err == nil
+			}
+			if dataMoved {
+				c.removeErr = os.Remove(c.meta)
+				c.removed = c.removeErr == nil
+			}
+		}
+	}
+	return c.Context.Done()
+}
+
+func TestXLStorageRenameDataCommitMetaMissing(t *testing.T) {
+	for _, tc := range []struct {
+		name     string
+		dataFile bool
+	}{
+		{"empty_object", false},
+		{"data_directory", true},
+	} {
+		t.Run(tc.name, func(t *testing.T) {
+			disk, root, err := newXLStorageTestSetup(t)
+			if err != nil {
+				t.Fatal(err)
+			}
+			defer disk.Close()
+			s := disk.storage
+			if err := s.MakeVol(t.Context(), "bucket"); err != nil {
+				t.Fatal(err)
+			}
+			fi := newFileInfo("object", 2, 2)
+			fi.DataDir, fi.VersionID = mustGetUUID(), mustGetUUID()
+			fi.Erasure.Index = 1
+			fi.ModTime = time.Now().UTC()
+			fi.Fresh = true
+			ctx := &missingCommitMetaContext{
+				Context: t.Context(),
+				meta:    filepath.Join(root, minioMetaTmpBucket, "staged", xlStorageFormatFile),
+			}
+			if tc.dataFile {
+				fi.Size = 1
+				fi.AddObjectPart(1, "", 1, 1, fi.ModTime, nil, nil)
+				part := filepath.Join(root, minioMetaTmpBucket, "staged", fi.DataDir, "part.1")
+				if err := os.MkdirAll(filepath.Dir(part), 0o755); err != nil {
+					t.Fatal(err)
+				}
+				if err := os.WriteFile(part, []byte("a"), 0o644); err != nil {
+					t.Fatal(err)
+				}
+				ctx.dataDest = filepath.Join(root, "bucket", "object", fi.DataDir)
+			}
+			_, err = s.RenameData(ctx, minioMetaTmpBucket, "staged", fi, "bucket", "object", RenameOptions{})
+			if !ctx.removed {
+				t.Fatalf("metadata removal did not execute: removal error = %v, RenameData error = %v", ctx.removeErr, err)
+			}
+			if !errors.Is(err, errCommitMetaMissing) {
+				t.Fatalf("expected commit metadata missing, got %v", err)
+			}
+			apiErr := toAPIError(t.Context(), toObjectErr(err, "bucket", "object"))
+			if apiErr.Code != "SlowDownWrite" || apiErr.HTTPStatusCode != http.StatusServiceUnavailable {
+				t.Fatalf("expected SlowDownWrite/503, got %+v", apiErr)
+			}
+			if _, err := os.Stat(filepath.Join(root, "bucket", "object", xlStorageFormatFile)); !os.IsNotExist(err) {
+				t.Fatalf("failed commit must not produce destination metadata: %v", err)
+			}
+		})
+	}
+}

cmd/xl-storage-format-v2-legacy.go

@@ -40,6 +40,10 @@ func (x *xlMetaV2VersionHeader) unmarshalV(v uint8, bts []byte) (o []byte, err e
 
 // unmarshalV1 decodes version 1, never released.
 func (x *xlMetaV2VersionHeader) unmarshalV1(bts []byte) (o []byte, err error) {
+	// Fields absent from the V1 wire format must be reset since the
+	// header may be reused across decodes.
+	x.Signature = [4]byte{}
+	x.EcN, x.EcM = 0, 0
 	var zb0001 uint32
 	zb0001, bts, err = msgp.ReadArrayHeaderBytes(bts)
 	if err != nil {
@@ -134,7 +138,7 @@ type xlMetaV2VersionHeaderV2 struct {
 
 // UnmarshalMsg implements msgp.Unmarshaler
 func (z *xlMetaV2VersionHeaderV2) UnmarshalMsg(bts []byte) (o []byte, err error) {
-	z.EcN, z.EcN = 0, 0
+	z.EcN, z.EcM = 0, 0
 	var zb0001 uint32
 	zb0001, bts, err = msgp.ReadArrayHeaderBytes(bts)
 	if err != nil {
@@ -184,7 +188,7 @@ func (z *xlMetaV2VersionHeaderV2) UnmarshalMsg(bts []byte) (o []byte, err error)
 
 // DecodeMsg implements msgp.Decodable
 func (z *xlMetaV2VersionHeaderV2) DecodeMsg(dc *msgp.Reader) (err error) {
-	z.EcN, z.EcN = 0, 0
+	z.EcN, z.EcM = 0, 0
 	var zb0001 uint32
 	zb0001, err = dc.ReadArrayHeader()
 	if err != nil {

cmd/xl-storage-format-v2_test.go

@@ -38,6 +38,7 @@ import (
 	"github.com/klauspost/compress/zstd"
 	"github.com/minio/minio/internal/bucket/lifecycle"
 	xhttp "github.com/minio/minio/internal/http"
+	"github.com/tinylib/msgp/msgp"
 )
 
 func TestReadXLMetaNoData(t *testing.T) {
@@ -1190,3 +1191,92 @@ func BenchmarkToFileInfoNoParts(b *testing.B) {
 func BenchmarkToFileInfoWithParts(b *testing.B) {
 	benchmarkManyPartsOptionally(b, true)
 }
+
+// TestXLMetaV2HeaderLegacyUnmarshalResetsEc checks that decoding legacy
+// version headers, which carry no erasure metadata fields, cannot leak
+// stale EcN/EcM values from a previously decoded object into the same
+// structure.
+func TestXLMetaV2HeaderLegacyUnmarshalResetsEc(t *testing.T) {
+	base := xlMetaV2VersionHeader{
+		VersionID: [16]byte{1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16},
+		ModTime:   time.Now().Unix(),
+		Signature: [4]byte{1, 2, 3, 4},
+		Type:      ObjectType,
+		Flags:     xlFlagInlineData,
+	}
+
+	// Legacy V2 header wire format: 5 fields, no EcN/EcM.
+	var legacy []byte
+	legacy = msgp.AppendArrayHeader(legacy, 5)
+	legacy = msgp.AppendBytes(legacy, base.VersionID[:])
+	legacy = msgp.AppendInt64(legacy, base.ModTime)
+	legacy = msgp.AppendBytes(legacy, base.Signature[:])
+	legacy = msgp.AppendUint8(legacy, uint8(base.Type))
+	legacy = msgp.AppendUint8(legacy, uint8(base.Flags))
+
+	for _, decoder := range []string{"UnmarshalMsg", "DecodeMsg", "loadIndexed"} {
+		t.Run(decoder, func(t *testing.T) {
+			header := base
+			header.EcN, header.EcM = 4, 8
+			x2 := xlMetaV2VersionHeaderV2{xlMetaV2VersionHeader: &header}
+			var err error
+			switch decoder {
+			case "UnmarshalMsg":
+				_, err = x2.UnmarshalMsg(legacy)
+			case "DecodeMsg":
+				err = x2.DecodeMsg(msgp.NewReader(bytes.NewReader(legacy)))
+			case "loadIndexed":
+				indexed := msgp.AppendUint(nil, 2)
+				indexed = msgp.AppendUint(indexed, xlMetaVersion)
+				indexed = msgp.AppendInt(indexed, 1)
+				indexed = msgp.AppendBytes(indexed, legacy)
+				indexed = msgp.AppendBytes(indexed, nil)
+				xl := xlMetaV2{versions: []xlMetaV2ShallowVersion{{header: header}}}
+				err = xl.loadIndexed(indexed, nil)
+				header = xl.versions[0].header
+			}
+			if err != nil {
+				t.Fatal(err)
+			}
+			if header != base {
+				t.Fatalf("legacy header: got %+v, want %+v", header, base)
+			}
+		})
+	}
+
+	// V1 headers (4 fields, never released) must zero the fields too.
+	var v1 []byte
+	v1 = msgp.AppendArrayHeader(v1, 4)
+	v1 = msgp.AppendBytes(v1, base.VersionID[:])
+	v1 = msgp.AppendInt64(v1, base.ModTime)
+	v1 = msgp.AppendUint8(v1, uint8(base.Type))
+	v1 = msgp.AppendUint8(v1, uint8(base.Flags))
+
+	header := base
+	header.EcN, header.EcM = 4, 8
+	header.Signature = [4]byte{9, 9, 9, 9}
+	if _, err := header.unmarshalV1(v1); err != nil {
+		t.Fatalf("legacy V1 header unmarshal failed: %v", err)
+	}
+	if header.EcN != 0 || header.EcM != 0 {
+		t.Fatalf("stale erasure metadata leaked on V1 decode: EcN %d, EcM %d", header.EcN, header.EcM)
+	}
+	if header.Signature != ([4]byte{}) {
+		t.Fatalf("stale signature leaked on V1 decode: %v", header.Signature)
+	}
+
+	// Current headers must keep their erasure metadata.
+	current := base
+	current.EcN, current.EcM = 4, 8
+	wire, err := current.MarshalMsg(nil)
+	if err != nil {
+		t.Fatalf("header marshal failed: %v", err)
+	}
+	decoded := base
+	if _, err := decoded.UnmarshalMsg(wire); err != nil {
+		t.Fatalf("header unmarshal failed: %v", err)
+	}
+	if decoded.EcN != 4 || decoded.EcM != 8 {
+		t.Fatalf("erasure metadata lost on current decode: EcN %d, EcM %d", decoded.EcN, decoded.EcM)
+	}
+}

cmd/xl-storage.go

@@ -2925,7 +2925,15 @@ func (s *xlStorage) RenameData(ctx context.Context, srcVolume, srcPath string, f
 		// if its a partial rename() do not attempt to delete recursively.
 		// this can be healed since all parts are available.
 		s.deleteFile(dstVolumeDir, dstDataPath, false, false)
-		return res, osErrToFileErr(err)
+		err = osErrToFileErr(err)
+		if errors.Is(err, errFileNotFound) {
+			// The staged xl.meta disappeared between staging and commit.
+			// This is a write-quorum failure, not a missing object; use a
+			// dedicated error so the object layer returns 503 instead of
+			// mapping it to ObjectNotFound (404).
+			err = errCommitMetaMissing
+		}
+		return res, err
 	}
 
 	if srcVolume != minioMetaMultipartBucket {

go.mod

@@ -1,10 +1,10 @@
 module github.com/minio/minio
 
-go 1.27.1
+go 1.27.2
 
 // Console and MC retain their historical module paths for best-effort upstream
 // compatibility. Pin the maintained PGSTY implementations used by SILO.
-replace github.com/minio/console => github.com/pgsty/silo-console v0.0.0-20260916075814-1360e26d976d
+replace github.com/minio/console => github.com/pgsty/silo-console v0.0.0-20261015132217-e5b165e4c0ee
 
 replace github.com/minio/mc => github.com/pgsty/mc v0.0.0-20260916070421-e952aa78f10a
 
@@ -294,7 +294,7 @@ require (
 	go.opentelemetry.io/otel/trace v1.45.0 // indirect
 	go.uber.org/multierr v1.11.0 // indirect
 	golang.org/x/mod v0.41.0 // indirect
-	golang.org/x/net v0.59.0 // indirect
+	golang.org/x/net v0.60.0 // indirect
 	golang.org/x/text v0.42.0 // indirect
 	golang.org/x/tools v0.50.0 // indirect
 	google.golang.org/genproto v0.0.0-20260319201613-d00831a3d3e7 // indirect

go.sum

@@ -547,8 +547,8 @@ github.com/pborman/getopt v0.0.0-20170112200414-7148bc3a4c30/go.mod h1:85jBQOZwp
 github.com/pelletier/go-toml v1.2.0/go.mod h1:5z9KED0ma1S8pY6P1sdut58dfprrGBbd/94hg7ilaic=
 github.com/pgsty/mc v0.0.0-20260916070421-e952aa78f10a h1:FY1vcTQT67HGBe23ozlhOiQnWCzUCGmeSN5x6DT/kFs=
 github.com/pgsty/mc v0.0.0-20260916070421-e952aa78f10a/go.mod h1:6z9lX8kOvaWz2vLlP7BjjF3JWHnIH86XDA2HwcmpZH8=
-github.com/pgsty/silo-console v0.0.0-20260916075814-1360e26d976d h1:A9ou1GkUckGZd3BOgEXeZ393nbYST967SKcI4Lgr/Vs=
-github.com/pgsty/silo-console v0.0.0-20260916075814-1360e26d976d/go.mod h1:JS165CF2yoTBIx1X8k1IQ6vunJcZFG3pRZlWHJ8UT8o=
+github.com/pgsty/silo-console v0.0.0-20261015132217-e5b165e4c0ee h1:e51AnrGe0Zq+nHTYaGfv/GkehQMO9Mekuw/ew6zYwOM=
+github.com/pgsty/silo-console v0.0.0-20261015132217-e5b165e4c0ee/go.mod h1:jpt39bx4wjhXoFB+BTOa/bx/pmU3pXzp2cT7PnT21Lo=
 github.com/pgsty/silo-pkg/v3 v3.14.1 h1:8MONT3Hky9EOnsuPk29590pEBE6MILaOnJtaejPPi7M=
 github.com/pgsty/silo-pkg/v3 v3.14.1/go.mod h1:jxKWxi52jSsDaDhXXPqjOyPDYdxx2iqdBXyLfM/xSIw=
 github.com/philhofer/fwd v1.2.0 h1:e6DnBTl7vGY+Gz322/ASL4Gyp1FspeMvx1RNDoToZuM=
@@ -762,8 +762,8 @@ golang.org/x/net v0.0.0-20220722155237-a158d28d115b/go.mod h1:XRhObCWvk6IyKnWLug
 golang.org/x/net v0.5.0/go.mod h1:DivGGAXEgPSlEBzxGzZI+ZLohi+xUj054jfeKui00ws=
 golang.org/x/net v0.6.0/go.mod h1:2Tu9+aMcznHK/AK1HMvgo6xiTLG5rD5rZLDS+rp2Bjs=
 golang.org/x/net v0.7.0/go.mod h1:2Tu9+aMcznHK/AK1HMvgo6xiTLG5rD5rZLDS+rp2Bjs=
-golang.org/x/net v0.59.0 h1:5zfYln+w5XCxwrnMMJPufRgNoXEaGxl0wo5GqPXyues=
-golang.org/x/net v0.59.0/go.mod h1:2DA/G1UfVbCpQPeWTmMPGY7Cs2PkBkwu743bVX5PIVg=
+golang.org/x/net v0.60.0 h1:79p50tfZlm0J9YfoDsSi639qSXNGVwEzOPLCxM2FsYU=
+golang.org/x/net v0.60.0/go.mod h1:2DA/G1UfVbCpQPeWTmMPGY7Cs2PkBkwu743bVX5PIVg=
 golang.org/x/oauth2 v0.37.0 h1:JUlcxA8oAtauLfiH8FX2/FkAWHAdi0QtGCGc+hofE98=
 golang.org/x/oauth2 v0.37.0/go.mod h1:IxwZNxUULJmpBFf9K/9NTMSIfZZuvuTy1gGxhigP/58=
 golang.org/x/sync v0.0.0-20181108010431-42b317875d0f/go.mod h1:RxMgew5VJxzue5/jJTE5uejpjVlOe/izrB70Jof72aM=

internal/hash/checksum-errors_test.go

@@ -0,0 +1,73 @@
+// Copyright (c) 2026 PGSTY
+//
+// This file is part of SILO Object Storage.
+// SPDX-License-Identifier: AGPL-3.0-or-later
+//
+// This program is free software: you can redistribute it and/or modify
+// it under the terms of the GNU Affero General Public License as published by
+// the Free Software Foundation, either version 3 of the License, or
+// (at your option) any later version.
+//
+// This program is distributed in the hope that it will be useful
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+// GNU Affero General Public License for more details.
+//
+// You should have received a copy of the GNU Affero General Public License
+// along with this program. If not, see <http://www.gnu.org/licenses/>.
+
+package hash
+
+import (
+	"bytes"
+	"errors"
+	"io"
+	"net/http"
+	"net/http/httptest"
+	"testing"
+)
+
+func TestChecksumMismatchAlgorithm(t *testing.T) {
+	content := []byte("actual content")
+	for _, typ := range []ChecksumType{ChecksumCRC32, ChecksumCRC32C, ChecksumSHA1, ChecksumSHA256, ChecksumCRC64NVME} {
+		t.Run(typ.String(), func(t *testing.T) {
+			wrong := NewChecksumFromData(typ, []byte("wrong content"))
+			check := func(t *testing.T, err error) {
+				t.Helper()
+				var mismatch ChecksumMismatch
+				if !errors.As(err, &mismatch) || mismatch.Algorithm != typ.String() {
+					t.Fatalf("error=%+v, want %s checksum mismatch", err, typ)
+				}
+			}
+			check(t, wrong.Matches(content, 0))
+			parts := NewChecksumFromData(typ, content)
+			parts.WantParts = 2
+			check(t, parts.Matches(content, 1))
+			for _, mode := range []string{"header", "trailer", "malformed-trailer"} {
+				t.Run(mode, func(t *testing.T) {
+					reader, err := NewReader(t.Context(), bytes.NewReader(content), int64(len(content)), "", "", int64(len(content)))
+					if err != nil {
+						t.Fatal(err)
+					}
+					req := httptest.NewRequest(http.MethodPut, "http://localhost/bucket/object", nil)
+					if mode == "header" {
+						req.Header.Set(typ.Key(), wrong.Encoded)
+					} else {
+						req.Header.Set("x-amz-trailer", typ.Key())
+						req.Trailer = make(http.Header)
+						value := wrong.Encoded
+						if mode == "malformed-trailer" {
+							value = "!invalid-base64!"
+						}
+						req.Trailer.Set(typ.Key(), value)
+					}
+					if err = reader.AddChecksum(req, false); err != nil {
+						t.Fatal(err)
+					}
+					_, err = io.ReadAll(reader)
+					check(t, err)
+				})
+			}
+		})
+	}
+}

internal/hash/checksum.go

@@ -584,15 +584,17 @@ func (c Checksum) Matches(content []byte, parts int) error {
 	sum := hasher.Sum(nil)
 	if c.WantParts > 0 && c.WantParts != parts {
 		return ChecksumMismatch{
-			Want: fmt.Sprintf("%s-%d", c.Encoded, c.WantParts),
-			Got:  fmt.Sprintf("%s-%d", base64.StdEncoding.EncodeToString(sum), parts),
+			Algorithm: c.Type.String(),
+			Want:      fmt.Sprintf("%s-%d", c.Encoded, c.WantParts),
+			Got:       fmt.Sprintf("%s-%d", base64.StdEncoding.EncodeToString(sum), parts),
 		}
 	}
 
 	if !bytes.Equal(sum, c.Raw) {
 		return ChecksumMismatch{
-			Want: c.Encoded,
-			Got:  base64.StdEncoding.EncodeToString(sum),
+			Algorithm: c.Type.String(),
+			Want:      c.Encoded,
+			Got:       base64.StdEncoding.EncodeToString(sum),
 		}
 	}
 	return nil

internal/hash/errors.go

@@ -74,8 +74,11 @@ func (e SizeMismatch) Error() string {
 
 // ChecksumMismatch - when content checksum does not match with what was sent from client.
 type ChecksumMismatch struct {
-	Want string
-	Got  string
+	// Algorithm carries the requested checksum type (e.g. "CRC32") so API
+	// error rendering can name it, matching S3's wording.
+	Algorithm string
+	Want      string
+	Got       string
 }
 
 func (e ChecksumMismatch) Error() string {

internal/hash/reader.go

@@ -302,13 +302,14 @@ func (r *Reader) Read(p []byte) (int, error) {
 				r.contentHash.Encoded = r.trailer.Get(r.contentHash.Type.Key())
 				r.contentHash.Raw, err = base64.StdEncoding.DecodeString(r.contentHash.Encoded)
 				if err != nil || len(r.contentHash.Raw) == 0 {
-					return 0, ChecksumMismatch{Got: r.contentHash.Encoded}
+					return 0, ChecksumMismatch{Algorithm: r.contentHash.Type.String(), Got: r.contentHash.Encoded}
 				}
 			}
 			if sum := r.contentHasher.Sum(nil); !bytes.Equal(r.contentHash.Raw, sum) {
 				err := ChecksumMismatch{
-					Want: r.contentHash.Encoded,
-					Got:  base64.StdEncoding.EncodeToString(sum),
+					Algorithm: r.contentHash.Type.String(),
+					Want:      r.contentHash.Encoded,
+					Got:       base64.StdEncoding.EncodeToString(sum),
 				}
 				return n, err
 			}