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jumphost.go
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jumphost.go
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package handlers
import (
"fmt"
"io"
"net"
"github.com/NHAS/reverse_ssh/internal"
"github.com/NHAS/reverse_ssh/pkg/logger"
"golang.org/x/crypto/ssh"
)
func JumpHandler(sshPriv ssh.Signer) internal.ChannelHandler {
return func(_ *internal.User, newChannel ssh.NewChannel, log logger.Logger) {
connection, requests, err := newChannel.Accept()
if err != nil {
newChannel.Reject(ssh.ResourceShortage, err.Error())
return
}
go ssh.DiscardRequests(requests)
defer connection.Close()
config := &ssh.ServerConfig{
PublicKeyCallback: func(conn ssh.ConnMetadata, key ssh.PublicKey) (*ssh.Permissions, error) {
return &ssh.Permissions{
Extensions: map[string]string{
"pubkey-fp": internal.FingerprintSHA1Hex(key),
},
}, nil
},
}
config.AddHostKey(sshPriv)
p1, p2 := net.Pipe()
go io.Copy(connection, p2)
go func() {
io.Copy(p2, connection)
p2.Close()
p1.Close()
}()
conn, chans, reqs, err := ssh.NewServerConn(p1, config)
if err != nil {
log.Error("%s", err.Error())
return
}
defer conn.Close()
clientLog := logger.NewLog(conn.RemoteAddr().String())
clientLog.Info("New SSH connection, version %s", conn.ClientVersion())
user, err := internal.CreateUser(conn)
if err != nil {
log.Error("Unable to add user %s\n", err)
return
}
go func(in <-chan *ssh.Request) {
for r := range in {
switch r.Type {
case "tcpip-forward":
go StartRemoteForward(user, r, conn)
case "cancel-tcpip-forward":
var rf internal.RemoteForwardRequest
err := ssh.Unmarshal(r.Payload, &rf)
if err != nil {
r.Reply(false, []byte(fmt.Sprintf("Unable to unmarshal remote forward request in order to stop it: %s", err.Error())))
return
}
go func() {
err := StopRemoteForward(rf)
if err != nil {
r.Reply(false, []byte(err.Error()))
return
}
r.Reply(true, nil)
}()
default:
//Ignore any unspecified global requests
r.Reply(false, nil)
}
}
}(reqs)
err = internal.RegisterChannelCallbacks(user, chans, clientLog, map[string]internal.ChannelHandler{
"session": Session,
"direct-tcpip": LocalForward,
"tun@openssh.com": Tun,
})
for rf := range user.SupportedRemoteForwards {
go StopRemoteForward(rf)
}
return
}
}