Fix SSE-S3 copy: preserve encryption metadata and set chunk SSE type (#7598)

* Fix SSE-S3 copy: preserve encryption metadata and set chunk SSE type

Fixes GitHub #7562: Copying objects between encrypted buckets was failing.

Root causes:
1. processMetadataBytes was re-adding SSE headers from source entry, undoing
   the encryption header filtering. Now uses dstEntry.Extended which is
   already filtered.

2. SSE-S3 streaming copy returned nil metadata. Now properly generates and
   returns SSE-S3 destination metadata (SeaweedFSSSES3Key, AES256 header)
   via ExecuteStreamingCopyWithMetadata.

3. Chunks created during streaming copy didn't have SseType set. Now sets
   SseType and per-chunk SseMetadata with chunk-specific IVs for SSE-S3,
   enabling proper decryption on GetObject.

* Address review: make SSE-S3 metadata serialization failures fatal errors

- In executeEncryptCopy: return error instead of just logging if
  SerializeSSES3Metadata fails
- In createChunkFromData: return error if chunk SSE-S3 metadata
  serialization fails

This ensures objects/chunks are never created without proper encryption
metadata, preventing unreadable/corrupted data.

* fmt

* Refactor: reuse function names instead of creating WithMetadata variants

- Change ExecuteStreamingCopy to return (*EncryptionSpec, error) directly
- Remove ExecuteStreamingCopyWithMetadata wrapper
- Change executeStreamingReencryptCopy to return (*EncryptionSpec, error)
- Remove executeStreamingReencryptCopyWithMetadata wrapper
- Update callers to ignore encryption spec with _ where not needed

* Add TODO documenting large file SSE-S3 copy limitation

The streaming copy approach encrypts the entire stream with a single IV
but stores data in chunks with per-chunk IVs. This causes decryption
issues for large files. Small inline files work correctly.

This is a known architectural issue that needs separate work to fix.

* Use chunk-by-chunk encryption for SSE-S3 copy (consistent with SSE-C/SSE-KMS)

Instead of streaming encryption (which had IV mismatch issues for multi-chunk
files), SSE-S3 now uses the same chunk-by-chunk approach as SSE-C and SSE-KMS:

1. Extended copyMultipartCrossEncryption to handle SSE-S3:
   - Added SSE-S3 source decryption in copyCrossEncryptionChunk
   - Added SSE-S3 destination encryption with per-chunk IVs
   - Added object-level metadata generation for SSE-S3 destinations

2. Updated routing in executeEncryptCopy/executeDecryptCopy/executeReencryptCopy
   to use copyMultipartCrossEncryption for all SSE-S3 scenarios

3. Removed streaming copy functions (shouldUseStreamingCopy,
   executeStreamingReencryptCopy) as they're no longer used

4. Added large file (1MB) integration test to verify chunk-by-chunk copy works

This ensures consistent behavior across all SSE types and fixes data corruption
that occurred with large files in the streaming copy approach.

* fmt

* fmt

* Address review: fail explicitly if SSE-S3 metadata is missing

Instead of silently ignoring missing SSE-S3 metadata (which could create
unreadable objects), now explicitly fail the copy operation with a clear
error message if:
- First chunk is missing
- First chunk doesn't have SSE-S3 type
- First chunk has empty SSE metadata
- Deserialization fails

* Address review: improve comment to reflect full scope of chunk creation

* Address review: fail explicitly if baseIV is empty for SSE-S3 chunk encryption

If DestinationIV is not set when encrypting SSE-S3 chunks, the chunk would
be created without SseMetadata, causing GetObject decryption to fail later.
Now fails explicitly with a clear error message.

Note: calculateIVWithOffset returns ([]byte, int) not ([]byte, error) - the
int is a skip amount for intra-block alignment, not an error code.

* Address review: handle 0-byte files in SSE-S3 copy

For 0-byte files, there are no chunks to get metadata from. Generate an IV
for the object-level metadata to ensure even empty files are properly marked
as SSE-S3 encrypted.

Also validate that we don't have a non-empty file with no chunks (which
would indicate an internal error).

weed/s3api/s3api_streaming_copy.go

@@ -59,18 +59,19 @@ func NewStreamingCopyManager(s3a *S3ApiServer) *StreamingCopyManager {
 	}
 }
 
-// ExecuteStreamingCopy performs a streaming copy operation
-func (scm *StreamingCopyManager) ExecuteStreamingCopy(ctx context.Context, entry *filer_pb.Entry, r *http.Request, dstPath string, state *EncryptionState) ([]*filer_pb.FileChunk, error) {
+// ExecuteStreamingCopy performs a streaming copy operation and returns the encryption spec
+// The encryption spec is needed for SSE-S3 to properly set destination metadata (fixes GitHub #7562)
+func (scm *StreamingCopyManager) ExecuteStreamingCopy(ctx context.Context, entry *filer_pb.Entry, r *http.Request, dstPath string, state *EncryptionState) ([]*filer_pb.FileChunk, *EncryptionSpec, error) {
 	// Create streaming copy specification
 	spec, err := scm.createStreamingSpec(entry, r, state)
 	if err != nil {
-		return nil, fmt.Errorf("create streaming spec: %w", err)
+		return nil, nil, fmt.Errorf("create streaming spec: %w", err)
 	}
 
 	// Create source reader from entry
 	sourceReader, err := scm.createSourceReader(entry)
 	if err != nil {
-		return nil, fmt.Errorf("create source reader: %w", err)
+		return nil, nil, fmt.Errorf("create source reader: %w", err)
 	}
 	defer sourceReader.Close()
 
@@ -79,11 +80,16 @@ func (scm *StreamingCopyManager) ExecuteStreamingCopy(ctx context.Context, entry
 	// Create processing pipeline
 	processedReader, err := scm.createProcessingPipeline(spec)
 	if err != nil {
-		return nil, fmt.Errorf("create processing pipeline: %w", err)
+		return nil, nil, fmt.Errorf("create processing pipeline: %w", err)
 	}
 
 	// Stream to destination
-	return scm.streamToDestination(ctx, processedReader, spec, dstPath)
+	chunks, err := scm.streamToDestination(ctx, processedReader, spec, dstPath)
+	if err != nil {
+		return nil, nil, err
+	}
+
+	return chunks, spec.EncryptionSpec, nil
 }
 
 // createStreamingSpec creates a streaming specification based on copy parameters
@@ -453,8 +459,8 @@ func (scm *StreamingCopyManager) streamToChunks(ctx context.Context, reader io.R
 	for {
 		n, err := reader.Read(buffer)
 		if n > 0 {
-			// Create chunk for this data
-			chunk, chunkErr := scm.createChunkFromData(buffer[:n], offset, dstPath)
+		// Create chunk for this data, setting SSE type and per-chunk metadata (including chunk-specific IVs for SSE-S3)
+		chunk, chunkErr := scm.createChunkFromData(buffer[:n], offset, dstPath, spec.EncryptionSpec)
 			if chunkErr != nil {
 				return nil, fmt.Errorf("create chunk from data: %w", chunkErr)
 			}
@@ -474,7 +480,7 @@ func (scm *StreamingCopyManager) streamToChunks(ctx context.Context, reader io.R
 }
 
 // createChunkFromData creates a chunk from streaming data
-func (scm *StreamingCopyManager) createChunkFromData(data []byte, offset int64, dstPath string) (*filer_pb.FileChunk, error) {
+func (scm *StreamingCopyManager) createChunkFromData(data []byte, offset int64, dstPath string, encSpec *EncryptionSpec) (*filer_pb.FileChunk, error) {
 	// Assign new volume
 	assignResult, err := scm.s3a.assignNewVolume(dstPath)
 	if err != nil {
@@ -487,6 +493,42 @@ func (scm *StreamingCopyManager) createChunkFromData(data []byte, offset int64,
 		Size:   uint64(len(data)),
 	}
 
+	// Set SSE type and metadata on chunk if destination is encrypted
+	// This is critical for GetObject to know to decrypt the data - fixes GitHub #7562
+	if encSpec != nil && encSpec.NeedsEncryption {
+		switch encSpec.DestinationType {
+		case EncryptionTypeSSEC:
+			chunk.SseType = filer_pb.SSEType_SSE_C
+			// SSE-C metadata is handled at object level, not per-chunk for streaming copy
+		case EncryptionTypeSSEKMS:
+			chunk.SseType = filer_pb.SSEType_SSE_KMS
+			// SSE-KMS metadata is handled at object level, not per-chunk for streaming copy
+		case EncryptionTypeSSES3:
+			chunk.SseType = filer_pb.SSEType_SSE_S3
+			// Create per-chunk SSE-S3 metadata with chunk-specific IV
+			if sseKey, ok := encSpec.DestinationKey.(*SSES3Key); ok {
+				// Calculate chunk-specific IV using base IV and chunk offset
+				baseIV := encSpec.DestinationIV
+				if len(baseIV) == 0 {
+					return nil, fmt.Errorf("SSE-S3 encryption requires DestinationIV to be set for chunk at offset %d", offset)
+				}
+				chunkIV, _ := calculateIVWithOffset(baseIV, offset)
+				// Create chunk key with the chunk-specific IV
+				chunkSSEKey := &SSES3Key{
+					Key:       sseKey.Key,
+					KeyID:     sseKey.KeyID,
+					Algorithm: sseKey.Algorithm,
+					IV:        chunkIV,
+				}
+				chunkMetadata, serErr := SerializeSSES3Metadata(chunkSSEKey)
+				if serErr != nil {
+					return nil, fmt.Errorf("failed to serialize chunk SSE-S3 metadata: %w", serErr)
+				}
+				chunk.SseMetadata = chunkMetadata
+			}
+		}
+	}
+
 	// Set file ID
 	if err := scm.s3a.setChunkFileId(chunk, assignResult); err != nil {
 		return nil, err