s3: accept S3 parameter

registry/storage/driver/s3-aws/s3.go

@@ -84,6 +84,10 @@ var validObjectACLs = map[string]struct{}{}
 
 //DriverParameters A struct that encapsulates all of the driver parameters after all values have been set
 type DriverParameters struct {
+	// S3 is an optional parameter. If specified, it will use the existing session
+	// to construct the Driver.
+	S3 *s3.S3
+
 	AccessKey                   string
 	SecretKey                   string
 	Bucket                      string
@@ -342,6 +346,7 @@ func FromParameters(parameters map[string]interface{}) (*Driver, error) {
 	sessionToken := ""
 
 	params := DriverParameters{
+		nil,
 		fmt.Sprint(accessKey),
 		fmt.Sprint(secretKey),
 		fmt.Sprint(bucket),
@@ -398,6 +403,8 @@ func getParameterAsInt64(parameters map[string]interface{}, name string, default
 // New constructs a new Driver with the given AWS credentials, region, encryption flag, and
 // bucketName
 func New(params DriverParameters) (*Driver, error) {
+	s3obj := params.S3
+	if s3obj == nil {
 		if !params.V4Auth &&
 			(params.RegionEndpoint == "" ||
 				strings.Contains(params.RegionEndpoint, "s3.amazonaws.com")) {
@@ -453,12 +460,13 @@ func New(params DriverParameters) (*Driver, error) {
 		if err != nil {
 			return nil, fmt.Errorf("failed to create new session with aws config: %v", err)
 		}
-	s3obj := s3.New(sess)
+		s3obj = s3.New(sess)
 
 		// enable S3 compatible signature v2 signing instead
 		if !params.V4Auth {
 			setv2Handlers(s3obj)
 		}
+	}
 
 	// TODO Currently multipart uploads have no timestamps, so this would be unwise
 	// if you initiated a new s3driver while another one is running on the same bucket.

registry/storage/driver/s3-aws/s3_test.go

@@ -77,6 +77,7 @@ func init() {
 		}
 
 		parameters := DriverParameters{
+			nil,
 			accessKey,
 			secretKey,
 			bucket,