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gitea/modules/ssh/ssh.go

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Go

// Copyright 2014 The Gogs Authors. All rights reserved.
// Copyright 2017 The Gitea Authors. All rights reserved.
// Use of this source code is governed by a MIT-style
// license that can be found in the LICENSE file.
package ssh
import (
"crypto/rand"
"crypto/rsa"
"crypto/x509"
"encoding/pem"
"io"
"io/ioutil"
"net"
"os"
"os/exec"
"path/filepath"
"strings"
"github.com/Unknwon/com"
"golang.org/x/crypto/ssh"
"code.gitea.io/gitea/models"
"code.gitea.io/gitea/modules/log"
"code.gitea.io/gitea/modules/setting"
)
func cleanCommand(cmd string) string {
i := strings.Index(cmd, "git")
if i == -1 {
return cmd
}
return cmd[i:]
}
func handleServerConn(keyID string, chans <-chan ssh.NewChannel) {
for newChan := range chans {
if newChan.ChannelType() != "session" {
err := newChan.Reject(ssh.UnknownChannelType, "unknown channel type")
if err != nil {
log.Error("Error rejecting channel: %v", err)
}
continue
}
ch, reqs, err := newChan.Accept()
if err != nil {
log.Error("Error accepting channel: %v", err)
continue
}
go func(in <-chan *ssh.Request) {
defer func() {
if err = ch.Close(); err != nil {
log.Error("Close: %v", err)
}
}()
for req := range in {
payload := cleanCommand(string(req.Payload))
switch req.Type {
case "exec":
cmdName := strings.TrimLeft(payload, "'()")
log.Trace("SSH: Payload: %v", cmdName)
args := []string{"serv", "key-" + keyID, "--config=" + setting.CustomConf}
log.Trace("SSH: Arguments: %v", args)
cmd := exec.Command(setting.AppPath, args...)
cmd.Env = append(
os.Environ(),
"SSH_ORIGINAL_COMMAND="+cmdName,
"SKIP_MINWINSVC=1",
)
stdout, err := cmd.StdoutPipe()
if err != nil {
log.Error("SSH: StdoutPipe: %v", err)
return
}
stderr, err := cmd.StderrPipe()
if err != nil {
log.Error("SSH: StderrPipe: %v", err)
return
}
input, err := cmd.StdinPipe()
if err != nil {
log.Error("SSH: StdinPipe: %v", err)
return
}
// FIXME: check timeout
if err = cmd.Start(); err != nil {
log.Error("SSH: Start: %v", err)
return
}
err = req.Reply(true, nil)
if err != nil {
log.Error("SSH: Reply: %v", err)
}
go func() {
_, err = io.Copy(input, ch)
if err != nil {
log.Error("SSH: Copy: %v", err)
}
}()
_, err = io.Copy(ch, stdout)
if err != nil {
log.Error("SSH: Copy: %v", err)
}
_, err = io.Copy(ch.Stderr(), stderr)
if err != nil {
log.Error("SSH: Copy: %v", err)
}
if err = cmd.Wait(); err != nil {
log.Error("SSH: Wait: %v", err)
return
}
_, err = ch.SendRequest("exit-status", false, []byte{0, 0, 0, 0})
if err != nil {
log.Error("SSH: SendRequest: %v", err)
}
return
default:
}
}
}(reqs)
}
}
func listen(config *ssh.ServerConfig, host string, port int) {
listener, err := net.Listen("tcp", host+":"+com.ToStr(port))
if err != nil {
log.Fatal("Failed to start SSH server: %v", err)
}
for {
// Once a ServerConfig has been configured, connections can be accepted.
conn, err := listener.Accept()
if err != nil {
log.Error("SSH: Error accepting incoming connection: %v", err)
continue
}
// Before use, a handshake must be performed on the incoming net.Conn.
// It must be handled in a separate goroutine,
// otherwise one user could easily block entire loop.
// For example, user could be asked to trust server key fingerprint and hangs.
go func() {
log.Trace("SSH: Handshaking for %s", conn.RemoteAddr())
sConn, chans, reqs, err := ssh.NewServerConn(conn, config)
if err != nil {
if err == io.EOF {
log.Warn("SSH: Handshaking with %s was terminated: %v", conn.RemoteAddr(), err)
} else {
log.Error("SSH: Error on handshaking with %s: %v", conn.RemoteAddr(), err)
}
return
}
log.Trace("SSH: Connection from %s (%s)", sConn.RemoteAddr(), sConn.ClientVersion())
// The incoming Request channel must be serviced.
go ssh.DiscardRequests(reqs)
go handleServerConn(sConn.Permissions.Extensions["key-id"], chans)
}()
}
}
// Listen starts a SSH server listens on given port.
func Listen(host string, port int, ciphers []string, keyExchanges []string, macs []string) {
config := &ssh.ServerConfig{
Config: ssh.Config{
Ciphers: ciphers,
KeyExchanges: keyExchanges,
MACs: macs,
},
PublicKeyCallback: func(conn ssh.ConnMetadata, key ssh.PublicKey) (*ssh.Permissions, error) {
pkey, err := models.SearchPublicKeyByContent(strings.TrimSpace(string(ssh.MarshalAuthorizedKey(key))))
if err != nil {
log.Error("SearchPublicKeyByContent: %v", err)
return nil, err
}
return &ssh.Permissions{Extensions: map[string]string{"key-id": com.ToStr(pkey.ID)}}, nil
},
}
keyPath := filepath.Join(setting.AppDataPath, "ssh/gogs.rsa")
if !com.IsExist(keyPath) {
filePath := filepath.Dir(keyPath)
if err := os.MkdirAll(filePath, os.ModePerm); err != nil {
log.Error("Failed to create dir %s: %v", filePath, err)
}
err := GenKeyPair(keyPath)
if err != nil {
log.Fatal("Failed to generate private key: %v", err)
}
log.Trace("SSH: New private key is generateed: %s", keyPath)
}
privateBytes, err := ioutil.ReadFile(keyPath)
if err != nil {
log.Fatal("SSH: Failed to load private key")
}
private, err := ssh.ParsePrivateKey(privateBytes)
if err != nil {
log.Fatal("SSH: Failed to parse private key")
}
config.AddHostKey(private)
go listen(config, host, port)
}
// GenKeyPair make a pair of public and private keys for SSH access.
// Public key is encoded in the format for inclusion in an OpenSSH authorized_keys file.
// Private Key generated is PEM encoded
func GenKeyPair(keyPath string) error {
privateKey, err := rsa.GenerateKey(rand.Reader, 2048)
if err != nil {
return err
}
privateKeyPEM := &pem.Block{Type: "RSA PRIVATE KEY", Bytes: x509.MarshalPKCS1PrivateKey(privateKey)}
f, err := os.OpenFile(keyPath, os.O_RDWR|os.O_CREATE|os.O_TRUNC, 0600)
if err != nil {
return err
}
defer func() {
if err = f.Close(); err != nil {
log.Error("Close: %v", err)
}
}()
if err := pem.Encode(f, privateKeyPEM); err != nil {
return err
}
// generate public key
pub, err := ssh.NewPublicKey(&privateKey.PublicKey)
if err != nil {
return err
}
public := ssh.MarshalAuthorizedKey(pub)
p, err := os.OpenFile(keyPath+".pub", os.O_RDWR|os.O_CREATE|os.O_TRUNC, 0600)
if err != nil {
return err
}
defer func() {
if err = p.Close(); err != nil {
log.Error("Close: %v", err)
}
}()
_, err = p.Write(public)
return err
}