kes: remove unnecessary error conversion (#14459)

This commit removes some duplicate code that
converts KES API errors.

This code was added since KES `0.18.0` changed
some exported API errors. However, the KES SDK
handles this error conversion itself.
Therefore, it is not necessary to duplicate this
behavior in MinIO.

See: https://github.com/minio/kes/blob/21555fa624420def4aa4766686baa553b692010a/error.go#L94

Signed-off-by: Andreas Auernhammer <hi@aead.dev>

internal/kms/kes.go

@@ -22,7 +22,6 @@ import (
 	"crypto/tls"
 	"crypto/x509"
 	"errors"
-	"net/http"
 	"time"
 
 	"github.com/minio/kes"
@@ -141,10 +140,3 @@ func (c *kesClient) DecryptKey(keyID string, ciphertext []byte, ctx Context) ([]
 	}
 	return c.client.Decrypt(context.Background(), keyID, ciphertext, ctxBytes)
 }
-
-// KeyExists returns if key exists on KMS based on the provided error type
-func KeyExists(err error) bool {
-	// legacyKeyExists will be used to maintain compatibility with KES versions older than v0.18.0
-	legacyKeyExists := kes.NewError(http.StatusBadRequest, "key does already exist")
-	return errors.Is(err, kes.ErrKeyExists) || errors.Is(err, legacyKeyExists)
-}