fix: copy-object with replace metadata-directive

In copy-object, if the source and destination are the same then
X-Amz-Metadata-Directive must be set to "REPLACE" in order to use
this api call to update the metadata of the object in place.

The default X-Amz-Metadata-Directive is "COPY" if not specified.
"COPY" is only valid if source and destination are not the same
object.

When "REPLACE" selected, metadata does not have to differ for the
call to be successful. The "REPLACE" always sets the incoming
metadata (even if empty or the same as the source).

Fixes #734

s3api/controllers/base.go

@@ -1533,6 +1533,7 @@ func (c S3ApiController) PutActions(ctx *fiber.Ctx) error {
 	copySrcModifSince := ctx.Get("X-Amz-Copy-Source-If-Modified-Since")
 	copySrcUnmodifSince := ctx.Get("X-Amz-Copy-Source-If-Unmodified-Since")
 	copySrcRange := ctx.Get("X-Amz-Copy-Source-Range")
+	directive := ctx.Get("X-Amz-Metadata-Directive")
 
 	// Permission headers
 	acl := ctx.Get("X-Amz-Acl")
@@ -2054,6 +2055,22 @@ func (c S3ApiController) PutActions(ctx *fiber.Ctx) error {
 
 		metadata := utils.GetUserMetaData(&ctx.Request().Header)
 
+		if directive != "" && directive != "COPY" && directive != "REPLACE" {
+			return SendXMLResponse(ctx, nil,
+				s3err.GetAPIError(s3err.ErrInvalidMetadataDirective),
+				&MetaOpts{
+					Logger:      c.logger,
+					MetricsMng:  c.mm,
+					Action:      metrics.ActionCopyObject,
+					BucketOwner: parsedAcl.Owner,
+				})
+		}
+
+		metaDirective := types.MetadataDirectiveCopy
+		if directive == "REPLACE" {
+			metaDirective = types.MetadataDirectiveReplace
+		}
+
 		res, err := c.be.CopyObject(ctx.Context(),
 			&s3.CopyObjectInput{
 				Bucket:                      &bucket,
@@ -2065,6 +2082,7 @@ func (c S3ApiController) PutActions(ctx *fiber.Ctx) error {
 				CopySourceIfUnmodifiedSince: umtime,
 				ExpectedBucketOwner:         &acct.Access,
 				Metadata:                    metadata,
+				MetadataDirective:           metaDirective,
 				StorageClass:                types.StorageClass(storageClass),
 			})
 		if err == nil {