fix: reject unsupported checksum assertions

Reject unimplemented x-amz-checksum value and trailer names instead of accepting uploads without verification. Apply the same contract to PutObject, multipart initiation and parts, CopyObject, and UploadPartCopy while preserving the five supported algorithms.

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

internal/hash/checksum.go

@@ -657,22 +657,55 @@ func AddChecksumHeader(w http.ResponseWriter, c map[string]string) {
 	}
 }
 
+func isSupportedChecksumHeader(name string) bool {
+	switch {
+	case strings.EqualFold(name, xhttp.AmzChecksumAlgo),
+		strings.EqualFold(name, xhttp.AmzChecksumType),
+		strings.EqualFold(name, xhttp.AmzChecksumMode):
+		return true
+	}
+	for _, checksumType := range BaseChecksumTypes {
+		if strings.EqualFold(name, checksumType.Key()) {
+			return true
+		}
+	}
+	return false
+}
+
+func hasUnsupportedChecksumHeader(h http.Header) bool {
+	for name := range h {
+		if strings.HasPrefix(strings.ToLower(name), "x-amz-checksum-") && !isSupportedChecksumHeader(name) {
+			return true
+		}
+	}
+	return false
+}
+
 // GetContentChecksum returns content checksum.
 // Returns ErrInvalidChecksum if so.
 // Returns nil, nil if no checksum.
 func GetContentChecksum(h http.Header) (*Checksum, error) {
+	if hasUnsupportedChecksumHeader(h) {
+		return nil, ErrInvalidChecksum
+	}
 	if trailing := h.Values(xhttp.AmzTrailer); len(trailing) > 0 {
 		var res *Checksum
-		for _, header := range trailing {
-			var duplicates bool
-			for _, t := range BaseChecksumTypes {
-				if strings.EqualFold(t.Key(), header) {
-					duplicates = res != nil
-					res = NewChecksumWithType(t|ChecksumTrailing, "")
+		for _, headers := range trailing {
+			for header := range strings.SplitSeq(headers, ",") {
+				header = strings.TrimSpace(header)
+				var duplicates bool
+				for _, t := range BaseChecksumTypes {
+					if strings.EqualFold(t.Key(), header) {
+						duplicates = res != nil
+						res = NewChecksumWithType(t|ChecksumTrailing, "")
+					}
+				}
+				if strings.HasPrefix(strings.ToLower(header), "x-amz-checksum-") && !isSupportedChecksumHeader(header) {
+					return nil, ErrInvalidChecksum
+				}
+				if duplicates {
+					return nil, ErrInvalidChecksum
 				}
-			}
-			if duplicates {
-				return nil, ErrInvalidChecksum
 			}
 		}
 		if res != nil {