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agent.go
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agent.go
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package ssh
import (
"io"
"io/ioutil"
"net"
"path"
"sync"
gossh "golang.org/x/crypto/ssh"
)
const (
agentRequestType = "auth-agent-req@openssh.com"
agentChannelType = "auth-agent@openssh.com"
agentTempDir = "auth-agent"
agentListenFile = "listener.sock"
)
// contextKeyAgentRequest is an internal context key for storing if the
// client requested agent forwarding
var contextKeyAgentRequest = &contextKey{"auth-agent-req"}
// SetAgentRequested sets up the session context so that AgentRequested
// returns true.
func SetAgentRequested(ctx Context) {
ctx.SetValue(contextKeyAgentRequest, true)
}
// AgentRequested returns true if the client requested agent forwarding.
func AgentRequested(sess Session) bool {
return sess.Context().Value(contextKeyAgentRequest) == true
}
// NewAgentListener sets up a temporary Unix socket that can be communicated
// to the session environment and used for forwarding connections.
func NewAgentListener() (net.Listener, error) {
dir, err := ioutil.TempDir("", agentTempDir)
if err != nil {
return nil, err
}
l, err := net.Listen("unix", path.Join(dir, agentListenFile))
if err != nil {
return nil, err
}
return l, nil
}
// ForwardAgentConnections takes connections from a listener to proxy into the
// session on the OpenSSH channel for agent connections. It blocks and services
// connections until the listener stop accepting.
func ForwardAgentConnections(l net.Listener, s Session) {
sshConn := s.Context().Value(ContextKeyConn).(gossh.Conn)
for {
conn, err := l.Accept()
if err != nil {
return
}
go func(conn net.Conn) {
defer conn.Close()
channel, reqs, err := sshConn.OpenChannel(agentChannelType, nil)
if err != nil {
return
}
defer channel.Close()
go gossh.DiscardRequests(reqs)
var wg sync.WaitGroup
wg.Add(2)
go func() {
io.Copy(conn, channel)
conn.(*net.UnixConn).CloseWrite()
wg.Done()
}()
go func() {
io.Copy(channel, conn)
channel.CloseWrite()
wg.Done()
}()
wg.Wait()
}(conn)
}
}