webhandler - display encryption errors properly (#6339)

For encrypted objects, download errors need to be
displayed in web response format instead of xml format.

Fixes #6327

cmd/encryption-v1.go

@@ -43,6 +43,8 @@ var (
 	errKMSNotConfigured     = errors.New("KMS not configured for a server side encrypted object")
 	// Additional Minio errors for SSE-C requests.
 	errObjectTampered = errors.New("The requested object was modified and may be compromised")
+	// error returned when invalid encryption parameters are specified
+	errInvalidEncryptionParameters = errors.New("The encryption parameters are not applicable to this object")
 )
 
 const (
@@ -714,28 +716,25 @@ func DecryptCopyObjectInfo(info *ObjectInfo, headers http.Header) (apiErr APIErr
 // decryption succeeded.
 //
 // DecryptObjectInfo also returns whether the object is encrypted or not.
-func DecryptObjectInfo(info *ObjectInfo, headers http.Header) (apiErr APIErrorCode, encrypted bool) {
+func DecryptObjectInfo(info *ObjectInfo, headers http.Header) (encrypted bool, err error) {
 	// Directories are never encrypted.
 	if info.IsDir {
-		return ErrNone, false
+		return false, nil
 	}
 	// disallow X-Amz-Server-Side-Encryption header on HEAD and GET
 	if crypto.S3.IsRequested(headers) {
-		apiErr = ErrInvalidEncryptionParameters
+		err = errInvalidEncryptionParameters
 		return
 	}
-	if apiErr, encrypted = ErrNone, crypto.IsEncrypted(info.UserDefined); !encrypted && crypto.SSEC.IsRequested(headers) {
-		apiErr = ErrInvalidEncryptionParameters
+	if err, encrypted = nil, crypto.IsEncrypted(info.UserDefined); !encrypted && crypto.SSEC.IsRequested(headers) {
+		err = errInvalidEncryptionParameters
 	} else if encrypted {
 		if (crypto.SSEC.IsEncrypted(info.UserDefined) && !crypto.SSEC.IsRequested(headers)) ||
 			(crypto.S3.IsEncrypted(info.UserDefined) && crypto.SSEC.IsRequested(headers)) {
-			apiErr = ErrSSEEncryptedObject
+			err = errEncryptedObject
 			return
 		}
-		var err error
-		if info.Size, err = info.DecryptedSize(); err != nil {
-			apiErr = toAPIErrorCode(err)
-		}
+		info.Size, err = info.DecryptedSize()
 	}
 	return
 }

cmd/encryption-v1_test.go

@@ -521,43 +521,43 @@ func TestDecryptRequest(t *testing.T) {
 var decryptObjectInfoTests = []struct {
 	info    ObjectInfo
 	headers http.Header
-	expErr  APIErrorCode
+	expErr  error
 }{
 	{
 		info:    ObjectInfo{Size: 100},
 		headers: http.Header{},
-		expErr:  ErrNone,
+		expErr:  nil,
 	},
 	{
 		info:    ObjectInfo{Size: 100, UserDefined: map[string]string{crypto.SSESealAlgorithm: SSESealAlgorithmDareSha256}},
 		headers: http.Header{crypto.SSECAlgorithm: []string{crypto.SSEAlgorithmAES256}},
-		expErr:  ErrNone,
+		expErr:  nil,
 	},
 	{
 		info:    ObjectInfo{Size: 0, UserDefined: map[string]string{crypto.SSESealAlgorithm: SSESealAlgorithmDareSha256}},
 		headers: http.Header{crypto.SSECAlgorithm: []string{crypto.SSEAlgorithmAES256}},
-		expErr:  ErrNone,
+		expErr:  nil,
 	},
 	{
 		info:    ObjectInfo{Size: 100, UserDefined: map[string]string{crypto.SSECSealedKey: "EAAfAAAAAAD7v1hQq3PFRUHsItalxmrJqrOq6FwnbXNarxOOpb8jTWONPPKyM3Gfjkjyj6NCf+aB/VpHCLCTBA=="}},
 		headers: http.Header{},
-		expErr:  ErrSSEEncryptedObject,
+		expErr:  errEncryptedObject,
 	},
 	{
 		info:    ObjectInfo{Size: 100, UserDefined: map[string]string{}},
 		headers: http.Header{crypto.SSECAlgorithm: []string{crypto.SSEAlgorithmAES256}},
-		expErr:  ErrInvalidEncryptionParameters,
+		expErr:  errInvalidEncryptionParameters,
 	},
 	{
 		info:    ObjectInfo{Size: 31, UserDefined: map[string]string{crypto.SSESealAlgorithm: SSESealAlgorithmDareSha256}},
 		headers: http.Header{crypto.SSECAlgorithm: []string{crypto.SSEAlgorithmAES256}},
-		expErr:  ErrObjectTampered,
+		expErr:  errObjectTampered,
 	},
 }
 
 func TestDecryptObjectInfo(t *testing.T) {
 	for i, test := range decryptObjectInfoTests {
-		if err, encrypted := DecryptObjectInfo(&test.info, test.headers); err != test.expErr {
+		if encrypted, err := DecryptObjectInfo(&test.info, test.headers); err != test.expErr {
 			t.Errorf("Test %d: Decryption returned wrong error code: got %d , want %d", i, err, test.expErr)
 		} else if enc := crypto.IsEncrypted(test.info.UserDefined); encrypted && enc != encrypted {
 			t.Errorf("Test %d: Decryption thinks object is encrypted but it is not", i)

cmd/object-handlers.go

@@ -306,8 +306,8 @@ func (api objectAPIHandlers) GetObjectHandler(w http.ResponseWriter, r *http.Req
 	}
 
 	if objectAPI.IsEncryptionSupported() {
-		if apiErr, _ := DecryptObjectInfo(&objInfo, r.Header); apiErr != ErrNone {
-			writeErrorResponse(w, apiErr, r.URL)
+		if _, err = DecryptObjectInfo(&objInfo, r.Header); err != nil {
+			writeErrorResponse(w, toAPIErrorCode(err), r.URL)
 			return
 		}
 	}
@@ -468,10 +468,10 @@ func (api objectAPIHandlers) HeadObjectHandler(w http.ResponseWriter, r *http.Re
 		writeErrorResponseHeadersOnly(w, toAPIErrorCode(err))
 		return
 	}
-
+	var encrypted bool
 	if objectAPI.IsEncryptionSupported() {
-		if apiErr, encrypted := DecryptObjectInfo(&objInfo, r.Header); apiErr != ErrNone {
-			writeErrorResponse(w, apiErr, r.URL)
+		if encrypted, err = DecryptObjectInfo(&objInfo, r.Header); err != nil {
+			writeErrorResponse(w, toAPIErrorCode(err), r.URL)
 			return
 		} else if encrypted {
 			s3Encrypted := crypto.S3.IsEncrypted(objInfo.UserDefined)

cmd/web-handlers.go

@@ -715,8 +715,8 @@ func (web *webAPIHandlers) Download(w http.ResponseWriter, r *http.Request) {
 	}
 
 	if objectAPI.IsEncryptionSupported() {
-		if apiErr, _ := DecryptObjectInfo(&objInfo, r.Header); apiErr != ErrNone {
-			writeErrorResponse(w, apiErr, r.URL)
+		if _, err = DecryptObjectInfo(&objInfo, r.Header); err != nil {
+			writeWebErrorResponse(w, err)
 			return
 		}
 	}
@@ -818,8 +818,8 @@ func (web *webAPIHandlers) DownloadZip(w http.ResponseWriter, r *http.Request) {
 				return err
 			}
 			if objectAPI.IsEncryptionSupported() {
-				if apiErr, _ := DecryptObjectInfo(&info, r.Header); apiErr != ErrNone {
-					writeErrorResponse(w, apiErr, r.URL)
+				if _, err = DecryptObjectInfo(&info, r.Header); err != nil {
+					writeWebErrorResponse(w, err)
 					return err
 				}
 			}
@@ -1235,6 +1235,12 @@ func toWebAPIError(err error) APIError {
 			HTTPStatusCode: http.StatusBadRequest,
 			Description:    err.Error(),
 		}
+	} else if err == errEncryptedObject {
+		return getAPIError(ErrSSEEncryptedObject)
+	} else if err == errInvalidEncryptionParameters {
+		return getAPIError(ErrInvalidEncryptionParameters)
+	} else if err == errObjectTampered {
+		return getAPIError(ErrObjectTampered)
 	} else if err == errMethodNotAllowed {
 		return getAPIError(ErrMethodNotAllowed)
 	}