Add base64 encoded MD5 output for Hash Reader (#5315)

- Use it to send the Content-MD5 header correctly encoded to S3
  Gateway

- Fixes a bug in PutObject (including anonymous PutObject) and
  PutObjectPart with S3 Gateway found when testing with Mint.

cmd/gateway/s3/gateway-s3-anonymous.go

@@ -28,7 +28,7 @@ import (
 
 // AnonPutObject creates a new object anonymously with the incoming data,
 func (l *s3Objects) AnonPutObject(bucket string, object string, data *hash.Reader, metadata map[string]string) (objInfo minio.ObjectInfo, e error) {
-	oi, err := l.anonClient.PutObject(bucket, object, data, data.Size(), data.MD5HexString(), data.SHA256HexString(), minio.ToMinioClientMetadata(metadata))
+	oi, err := l.anonClient.PutObject(bucket, object, data, data.Size(), data.MD5Base64String(), data.SHA256HexString(), minio.ToMinioClientMetadata(metadata))
 	if err != nil {
 		return objInfo, minio.ErrorRespToObjectError(errors.Trace(err), bucket, object)
 	}

cmd/gateway/s3/gateway-s3.go

@@ -289,7 +289,7 @@ func (l *s3Objects) GetObjectInfo(bucket string, object string) (objInfo minio.O
 
 // PutObject creates a new object with the incoming data,
 func (l *s3Objects) PutObject(bucket string, object string, data *hash.Reader, metadata map[string]string) (objInfo minio.ObjectInfo, err error) {
-	oi, err := l.Client.PutObject(bucket, object, data, data.Size(), data.MD5HexString(), data.SHA256HexString(), minio.ToMinioClientMetadata(metadata))
+	oi, err := l.Client.PutObject(bucket, object, data, data.Size(), data.MD5Base64String(), data.SHA256HexString(), minio.ToMinioClientMetadata(metadata))
 	if err != nil {
 		return objInfo, minio.ErrorRespToObjectError(errors.Trace(err), bucket, object)
 	}
@@ -343,7 +343,7 @@ func (l *s3Objects) NewMultipartUpload(bucket string, object string, metadata ma
 
 // PutObjectPart puts a part of object in bucket
 func (l *s3Objects) PutObjectPart(bucket string, object string, uploadID string, partID int, data *hash.Reader) (pi minio.PartInfo, e error) {
-	info, err := l.Client.PutObjectPart(bucket, object, uploadID, partID, data, data.Size(), data.MD5HexString(), data.SHA256HexString())
+	info, err := l.Client.PutObjectPart(bucket, object, uploadID, partID, data, data.Size(), data.MD5Base64String(), data.SHA256HexString())
 	if err != nil {
 		return pi, minio.ErrorRespToObjectError(errors.Trace(err), bucket, object)
 	}

pkg/hash/reader.go

@@ -20,6 +20,7 @@ import (
 	"bytes"
 	"crypto/md5"
 	"crypto/sha256"
+	"encoding/base64"
 	"encoding/hex"
 	"errors"
 	"hash"
@@ -117,6 +118,11 @@ func (r *Reader) MD5HexString() string {
 	return hex.EncodeToString(r.md5sum)
 }
 
+// MD5Base64String returns base64 encoded MD5sum value.
+func (r *Reader) MD5Base64String() string {
+	return base64.StdEncoding.EncodeToString(r.md5sum)
+}
+
 // SHA256HexString returns hex sha256 value.
 func (r *Reader) SHA256HexString() string {
 	return hex.EncodeToString(r.sha256sum)

pkg/hash/reader_test.go

@@ -40,6 +40,9 @@ func TestHashReaderHelperMethods(t *testing.T) {
 	if r.SHA256HexString() != "88d4266fd4e6338d13b845fcf289579d209c897823b9217da3e161936f031589" {
 		t.Errorf("Expected sha256hex \"88d4266fd4e6338d13b845fcf289579d209c897823b9217da3e161936f031589\", got %s", r.SHA256HexString())
 	}
+	if r.MD5Base64String() != "4vxxTEcn7pOV8yTNLn8zHw==" {
+		t.Errorf("Expected md5base64 \"4vxxTEcn7pOV8yTNLn8zHw==\", got \"%s\"", r.MD5Base64String())
+	}
 	if r.Size() != 4 {
 		t.Errorf("Expected size 4, got %d", r.Size())
 	}