Add vttablet auth support for external Azure MySQL.

go/mysql/client.go

@@ -303,17 +303,23 @@ func (c *Conn) clientHandshake(characterSet uint8, params *ConnParams) error {
 	case AuthSwitchRequestPacket:
 		// Server is asking to use a different auth method. We
 		// only support cleartext plugin.
-		pluginName, _, err := parseAuthSwitchRequest(response)
+		pluginName, salt, err := parseAuthSwitchRequest(response)
 		if err != nil {
 			return NewSQLError(CRServerHandshakeErr, SSUnknownSQLState, "cannot parse auth switch request: %v", err)
 		}
-		if pluginName != MysqlClearPassword {
-			return NewSQLError(CRServerHandshakeErr, SSUnknownSQLState, "server asked for unsupported auth method: %v", pluginName)
-		}
 
-		// Write the password packet.
-		if err := c.writeClearTextPassword(params); err != nil {
-			return err
+		if pluginName == MysqlClearPassword {
+			// Write the cleartext password packet.
+			if err := c.writeClearTextPassword(params); err != nil {
+				return err
+			}
+		} else if pluginName == MysqlNativePassword {
+			// Write the mysql_native_password packet.
+			if err := c.writeMysqlNativePassword(params, salt); err != nil {
+				return err
+			}
+		} else {
+			return NewSQLError(CRServerHandshakeErr, SSUnknownSQLState, "server asked for unsupported auth method: %v", pluginName)
 		}
 
 		// Wait for OK packet.
@@ -649,7 +655,12 @@ func parseAuthSwitchRequest(data []byte) (string, []byte, error) {
 		return "", nil, vterrors.Errorf(vtrpc.Code_INTERNAL, "cannot get plugin name from AuthSwitchRequest: %v", data)
 	}
 
-	return pluginName, data[pos:], nil
+	// If this was a request with a salt in it, max 20 bytes
+	salt := data[pos:]
+	if len(salt) > 20 {
+		salt = salt[:20]
+	}
+	return pluginName, salt, nil
 }
 
 // writeClearTextPassword writes the clear text password.
@@ -665,3 +676,17 @@ func (c *Conn) writeClearTextPassword(params *ConnParams) error {
 	}
 	return c.writeEphemeralPacket()
 }
+
+// writeMysqlNativePassword writes the encrypted mysql_native_password format
+// Returns a SQLError.
+func (c *Conn) writeMysqlNativePassword(params *ConnParams, salt []byte) error {
+	scrambledPassword := ScramblePassword(salt, []byte(params.Pass))
+	data := c.startEphemeralPacket(len(scrambledPassword))
+	pos := 0
+	pos += copy(data[pos:], scrambledPassword)
+	// Sanity check.
+	if pos != len(data) {
+		return vterrors.Errorf(vtrpc.Code_INTERNAL, "error building MysqlNativePassword packet: got %v bytes expected %v", pos, len(data))
+	}
+	return c.writeEphemeralPacket()
+}