forward.go

Documentation: golang.org/x/crypto/ssh/agent

     1  // Copyright 2014 The Go Authors. All rights reserved.
     2  // Use of this source code is governed by a BSD-style
     3  // license that can be found in the LICENSE file.
     4  
     5  package agent
     6  
     7  import (
     8  	"errors"
     9  	"io"
    10  	"net"
    11  	"sync"
    12  
    13  	"golang.org/x/crypto/ssh"
    14  )
    15  
    16  // RequestAgentForwarding sets up agent forwarding for the session.
    17  // ForwardToAgent or ForwardToRemote should be called to route
    18  // the authentication requests.
    19  func RequestAgentForwarding(session *ssh.Session) error {
    20  	ok, err := session.SendRequest("auth-agent-req@openssh.com", true, nil)
    21  	if err != nil {
    22  		return err
    23  	}
    24  	if !ok {
    25  		return errors.New("forwarding request denied")
    26  	}
    27  	return nil
    28  }
    29  
    30  // ForwardToAgent routes authentication requests to the given keyring.
    31  func ForwardToAgent(client *ssh.Client, keyring Agent) error {
    32  	channels := client.HandleChannelOpen(channelType)
    33  	if channels == nil {
    34  		return errors.New("agent: already have handler for " + channelType)
    35  	}
    36  
    37  	go func() {
    38  		for ch := range channels {
    39  			channel, reqs, err := ch.Accept()
    40  			if err != nil {
    41  				continue
    42  			}
    43  			go ssh.DiscardRequests(reqs)
    44  			go func() {
    45  				ServeAgent(keyring, channel)
    46  				channel.Close()
    47  			}()
    48  		}
    49  	}()
    50  	return nil
    51  }
    52  
    53  const channelType = "auth-agent@openssh.com"
    54  
    55  // ForwardToRemote routes authentication requests to the ssh-agent
    56  // process serving on the given unix socket.
    57  func ForwardToRemote(client *ssh.Client, addr string) error {
    58  	channels := client.HandleChannelOpen(channelType)
    59  	if channels == nil {
    60  		return errors.New("agent: already have handler for " + channelType)
    61  	}
    62  	conn, err := net.Dial("unix", addr)
    63  	if err != nil {
    64  		return err
    65  	}
    66  	conn.Close()
    67  
    68  	go func() {
    69  		for ch := range channels {
    70  			channel, reqs, err := ch.Accept()
    71  			if err != nil {
    72  				continue
    73  			}
    74  			go ssh.DiscardRequests(reqs)
    75  			go forwardUnixSocket(channel, addr)
    76  		}
    77  	}()
    78  	return nil
    79  }
    80  
    81  func forwardUnixSocket(channel ssh.Channel, addr string) {
    82  	conn, err := net.Dial("unix", addr)
    83  	if err != nil {
    84  		return
    85  	}
    86  
    87  	var wg sync.WaitGroup
    88  	wg.Add(2)
    89  	go func() {
    90  		io.Copy(conn, channel)
    91  		conn.(*net.UnixConn).CloseWrite()
    92  		wg.Done()
    93  	}()
    94  	go func() {
    95  		io.Copy(channel, conn)
    96  		channel.CloseWrite()
    97  		wg.Done()
    98  	}()
    99  
   100  	wg.Wait()
   101  	conn.Close()
   102  	channel.Close()
   103  }
   104
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