connections: close the ssh channel before the network connection

This way if pkg/sftp is stuck in Serve() method should be unlocked.

sftpd/scp.go

@@ -35,7 +35,6 @@ type exitStatusMsg struct {
 type scpCommand struct {
 	connection Connection
 	args       []string
-	channel    ssh.Channel
 }
 
 func (c *scpCommand) handle() error {
@@ -160,7 +159,7 @@ func (c *scpCommand) getUploadFileData(sizeToRead int64, transfer *Transfer) err
 		remaining := sizeToRead
 		buf := make([]byte, int64(math.Min(32768, float64(sizeToRead))))
 		for {
-			n, err := c.channel.Read(buf)
+			n, err := c.connection.channel.Read(buf)
 			if err != nil {
 				c.sendErrorMessage(err.Error())
 				transfer.TransferError(err)
@@ -403,7 +402,7 @@ func (c *scpCommand) sendDownloadFileData(filePath string, stat os.FileInfo, tra
 		n, err := transfer.ReadAt(buf, readed)
 		if err == nil || err == io.EOF {
 			if n > 0 {
-				_, err = c.channel.Write(buf[:n])
+				_, err = c.connection.channel.Write(buf[:n])
 			}
 		}
 		readed += int64(n)
@@ -517,15 +516,15 @@ func (c *scpCommand) isRecursive() bool {
 func (c *scpCommand) readConfirmationMessage() error {
 	var msg strings.Builder
 	buf := make([]byte, 1)
-	n, err := c.channel.Read(buf)
+	n, err := c.connection.channel.Read(buf)
 	if err != nil {
-		c.channel.Close()
+		c.connection.channel.Close()
 		return err
 	}
 	if n == 1 && (buf[0] == warnMsg[0] || buf[0] == errMsg[0]) {
 		isError := buf[0] == errMsg[0]
 		for {
-			n, err = c.channel.Read(buf)
+			n, err = c.connection.channel.Read(buf)
 			readed := buf[:n]
 			if err != nil || (n == 1 && readed[0] == newLine[0]) {
 				break
@@ -536,7 +535,7 @@ func (c *scpCommand) readConfirmationMessage() error {
 		}
 		c.connection.Log(logger.LevelInfo, logSenderSCP, "scp error message received: %v is error: %v", msg.String(), isError)
 		err = fmt.Errorf("%v", msg.String())
-		c.channel.Close()
+		c.connection.channel.Close()
 	}
 	return err
 }
@@ -548,7 +547,7 @@ func (c *scpCommand) readProtocolMessage() (string, error) {
 	buf := make([]byte, 1)
 	for {
 		var n int
-		n, err = c.channel.Read(buf)
+		n, err = c.connection.channel.Read(buf)
 		if err != nil {
 			break
 		}
@@ -561,34 +560,34 @@ func (c *scpCommand) readProtocolMessage() (string, error) {
 		}
 	}
 	if err != nil {
-		c.channel.Close()
+		c.connection.channel.Close()
 	}
 	return command.String(), err
 }
 
 // send an error message and close the channel
 func (c *scpCommand) sendErrorMessage(error string) {
-	c.channel.Write(errMsg)
-	c.channel.Write([]byte(error))
-	c.channel.Write(newLine)
-	c.channel.Close()
+	c.connection.channel.Write(errMsg)
+	c.connection.channel.Write([]byte(error))
+	c.connection.channel.Write(newLine)
+	c.connection.channel.Close()
 }
 
 // send scp confirmation message and close the channel if an error happen
 func (c *scpCommand) sendConfirmationMessage() error {
-	_, err := c.channel.Write(okMsg)
+	_, err := c.connection.channel.Write(okMsg)
 	if err != nil {
-		c.channel.Close()
+		c.connection.channel.Close()
 	}
 	return err
 }
 
 // sends a protocol message and close the channel on error
 func (c *scpCommand) sendProtocolMessage(message string) error {
-	_, err := c.channel.Write([]byte(message))
+	_, err := c.connection.channel.Write([]byte(message))
 	if err != nil {
 		c.connection.Log(logger.LevelWarn, logSenderSCP, "error sending protocol message: %v, err: %v", message, err)
-		c.channel.Close()
+		c.connection.channel.Close()
 	}
 	return err
 }
@@ -604,8 +603,8 @@ func (c *scpCommand) sendExitStatus(err error) {
 	}
 	c.connection.Log(logger.LevelDebug, logSenderSCP, "send exit status for command with args: %v user: %v err: %v",
 		c.args, c.connection.User.Username, err)
-	c.channel.SendRequest("exit-status", false, ssh.Marshal(&ex))
-	c.channel.Close()
+	c.connection.channel.SendRequest("exit-status", false, ssh.Marshal(&ex))
+	c.connection.channel.Close()
 }
 
 // get the next upload protocol message ignoring T command if any