forked from aws/session-manager-plugin
/
basicportforwarding.go
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/
basicportforwarding.go
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// Copyright 2020 Amazon.com, Inc. or its affiliates. All Rights Reserved.
//
// Licensed under the Apache License, Version 2.0 (the "License"). You may not
// use this file except in compliance with the License. A copy of the
// License is located at
//
// http://aws.amazon.com/apache2.0/
//
// or in the "license" file accompanying this file. This file is distributed
// on an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND,
// either express or implied. See the License for the specific language governing
// permissions and limitations under the License.
// Package portsession starts port session.
package portsession
import (
"fmt"
"net"
"os"
"os/signal"
"strconv"
"time"
"github.com/aws/session-manager-plugin/src/config"
"github.com/aws/session-manager-plugin/src/log"
"github.com/aws/session-manager-plugin/src/message"
"github.com/aws/session-manager-plugin/src/sessionmanagerplugin/session"
"github.com/aws/session-manager-plugin/src/sessionmanagerplugin/session/sessionutil"
"github.com/aws/session-manager-plugin/src/version"
)
// BasicPortForwarding is type of port session
// accepts one client connection at a time
type BasicPortForwarding struct {
port IPortSession
stream *net.Conn
listener *net.Listener
sessionId string
portParameters PortParameters
session session.Session
}
// getNewListener returns a new listener to given address and type like tcp, unix etc.
var getNewListener = func(listenerType string, listenerAddress string) (listener net.Listener, err error) {
return net.Listen(listenerType, listenerAddress)
}
// acceptConnection returns connection to the listener
var acceptConnection = func(log log.T, listener net.Listener) (tcpConn net.Conn, err error) {
return listener.Accept()
}
// IsStreamNotSet checks if stream is not set
func (p *BasicPortForwarding) IsStreamNotSet() (status bool) {
return p.stream == nil
}
// Stop closes the stream
func (p *BasicPortForwarding) Stop() {
if p.stream != nil {
(*p.stream).Close()
}
os.Exit(0)
}
// InitializeStreams establishes connection and initializes the stream
func (p *BasicPortForwarding) InitializeStreams(log log.T, agentVersion string) (err error) {
p.handleControlSignals(log)
if err = p.startLocalConn(log); err != nil {
return
}
return
}
// ReadStream reads data from the stream
func (p *BasicPortForwarding) ReadStream(log log.T) (err error) {
msg := make([]byte, config.StreamDataPayloadSize)
for {
numBytes, err := (*p.stream).Read(msg)
if err != nil {
log.Debugf("Reading from port %s failed with error: %v. Close this connection, listen and accept new one.",
p.portParameters.PortNumber, err)
// Send DisconnectToPort flag to agent when client tcp connection drops to ensure agent closes tcp connection too with server port
if err = p.session.DataChannel.SendFlag(log, message.DisconnectToPort); err != nil {
log.Errorf("Failed to send packet: %v", err)
return err
}
if err = p.reconnect(log); err != nil {
return err
}
// continue to read from connection as it has been re-established
continue
}
log.Tracef("Received message of size %d from stdin.", numBytes)
if err = p.session.DataChannel.SendInputDataMessage(log, message.Output, msg[:numBytes]); err != nil {
log.Errorf("Failed to send packet: %v", err)
return err
}
// Sleep to process more data
time.Sleep(time.Millisecond)
}
}
// WriteStream writes data to stream
func (p *BasicPortForwarding) WriteStream(outputMessage message.ClientMessage) error {
_, err := (*p.stream).Write(outputMessage.Payload)
return err
}
// startLocalConn establishes a new local connection to forward remote server packets to
func (p *BasicPortForwarding) startLocalConn(log log.T) (err error) {
// When localPortNumber is not specified, set port number to 0 to let net.conn choose an open port at random
localPortNumber := p.portParameters.LocalPortNumber
if p.portParameters.LocalPortNumber == "" {
localPortNumber = "0"
}
var listener net.Listener
if listener, err = p.startLocalListener(log, localPortNumber); err != nil {
log.Errorf("Unable to open tcp connection to port. %v", err)
return err
}
var tcpConn net.Conn
if tcpConn, err = acceptConnection(log, listener); err != nil {
log.Errorf("Failed to accept connection with error. %v", err)
return err
}
log.Infof("Connection accepted for session %s.", p.sessionId)
fmt.Printf("Connection accepted for session %s.\n", p.sessionId)
p.listener = &listener
p.stream = &tcpConn
return
}
// startLocalListener starts a local listener to given address
func (p *BasicPortForwarding) startLocalListener(log log.T, portNumber string) (listener net.Listener, err error) {
var displayMessage string
switch p.portParameters.LocalConnectionType {
case "unix":
if listener, err = getNewListener(p.portParameters.LocalConnectionType, p.portParameters.LocalUnixSocket); err != nil {
return
}
displayMessage = fmt.Sprintf("Unix socket %s opened for sessionId %s.", p.portParameters.LocalUnixSocket, p.sessionId)
default:
if listener, err = getNewListener("tcp", "localhost:"+portNumber); err != nil {
return
}
// get port number the TCP listener opened
p.portParameters.LocalPortNumber = strconv.Itoa(listener.Addr().(*net.TCPAddr).Port)
displayMessage = fmt.Sprintf("Port %s opened for sessionId %s.", p.portParameters.LocalPortNumber, p.sessionId)
}
log.Info(displayMessage)
fmt.Println(displayMessage)
return
}
// handleControlSignals handles terminate signals
func (p *BasicPortForwarding) handleControlSignals(log log.T) {
c := make(chan os.Signal, 1)
signal.Notify(c, sessionutil.ControlSignals...)
go func() {
<-c
fmt.Println("Terminate signal received, exiting.")
if version.DoesAgentSupportTerminateSessionFlag(log, p.session.DataChannel.GetAgentVersion()) {
if err := p.session.DataChannel.SendFlag(log, message.TerminateSession); err != nil {
log.Errorf("Failed to send TerminateSession flag: %v", err)
}
p.Stop()
} else {
p.session.TerminateSession(log)
}
}()
}
// reconnect closes existing connection, listens to new connection and accept it
func (p *BasicPortForwarding) reconnect(log log.T) (err error) {
// close existing connection as it is in a state from which data cannot be read
(*p.stream).Close()
// wait for new connection on listener and accept it
var conn net.Conn
if conn, err = acceptConnection(log, *p.listener); err != nil {
return log.Errorf("Failed to accept connection with error. %v", err)
}
p.stream = &conn
return
}