azblob: use UUIDs as block IDs

Signed-off-by: Nicola Murino <nicola.murino@gmail.com>

vfs/azblobfs.go

@@ -38,6 +38,7 @@ import (
 	"github.com/Azure/azure-sdk-for-go/sdk/azcore/policy"
 	"github.com/Azure/azure-sdk-for-go/sdk/storage/azblob"
 	"github.com/eikenb/pipeat"
+	"github.com/google/uuid"
 	"github.com/pkg/sftp"
 
 	"github.com/drakkan/sftpgo/v2/logger"
@@ -985,7 +986,6 @@ func (fs *AzureBlobFs) handleMultipartUpload(ctx context.Context, reader io.Read
 	// we only need to recycle few byte slices
 	pool := newBufferAllocator(int(partSize))
 	finished := false
-	binaryBlockID := make([]byte, 8)
 	var blocks []string
 	var wg sync.WaitGroup
 	var errOnce sync.Once
@@ -1012,8 +1012,15 @@ func (fs *AzureBlobFs) handleMultipartUpload(ctx context.Context, reader io.Read
 			return err
 		}
 
-		fs.incrementBlockID(binaryBlockID)
-		blockID := base64.StdEncoding.EncodeToString(binaryBlockID)
+		// Block IDs are unique values to avoid issue if 2+ clients are uploading blocks
+		// at the same time causing CommitBlockList to get a mix of blocks from all the clients.
+		generatedUUID, err := uuid.NewRandom()
+		if err != nil {
+			pool.releaseBuffer(buf)
+			pool.free()
+			return fmt.Errorf("unable to generate block ID: %w", err)
+		}
+		blockID := base64.StdEncoding.EncodeToString([]byte(generatedUUID.String()))
 		blocks = append(blocks, blockID)
 
 		guard <- struct{}{}
@@ -1090,18 +1097,6 @@ func (*AzureBlobFs) readFill(r io.Reader, buf []byte) (n int, err error) {
 	return n, err
 }
 
-// copied from rclone
-func (*AzureBlobFs) incrementBlockID(blockID []byte) {
-	for i, digit := range blockID {
-		newDigit := digit + 1
-		blockID[i] = newDigit
-		if newDigit >= digit {
-			// exit if no carry
-			break
-		}
-	}
-}
-
 func (fs *AzureBlobFs) preserveModificationTime(source, target string, fi os.FileInfo) {
 	if plugin.Handler.HasMetadater() {
 		if !fi.IsDir() {