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// 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 (
"bytes"
"crypto/rand"
"crypto/rsa"
"crypto/x509"
"encoding/pem"
"fmt"
"io"
"os"
"os/exec"
"path/filepath"
"strings"
"sync"
"syscall"
"code.gitea.io/gitea/models"
"code.gitea.io/gitea/modules/log"
"code.gitea.io/gitea/modules/setting"
"code.gitea.io/gitea/modules/util"
"github.com/gliderlabs/ssh"
"github.com/unknwon/com"
gossh "golang.org/x/crypto/ssh"
)
type contextKey string
const giteaKeyID = contextKey("gitea-key-id")
func getExitStatusFromError(err error) int {
if err == nil {
return 0
}
exitErr, ok := err.(*exec.ExitError)
if !ok {
return 1
}
waitStatus, ok := exitErr.Sys().(syscall.WaitStatus)
if !ok {
// This is a fallback and should at least let us return something useful
// when running on Windows, even if it isn't completely accurate.
if exitErr.Success() {
return 0
}
return 1
}
return waitStatus.ExitStatus()
}
func sessionHandler(session ssh.Session) {
keyID := session.Context().Value(giteaKeyID).(int64)
command := session.RawCommand()
log.Trace("SSH: Payload: %v", command)
args := []string{"serv", "key-" + com.ToStr(keyID), "--config=" + setting.CustomConf}
log.Trace("SSH: Arguments: %v", args)
cmd := exec.Command(setting.AppPath, args...)
cmd.Env = append(
os.Environ(),
"SSH_ORIGINAL_COMMAND="+command,
"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
}
stdin, err := cmd.StdinPipe()
if err != nil {
log.Error("SSH: StdinPipe: %v", err)
return
}
wg := &sync.WaitGroup{}
wg.Add(2)
if err = cmd.Start(); err != nil {
log.Error("SSH: Start: %v", err)
return
}
go func() {
defer stdin.Close()
if _, err := io.Copy(stdin, session); err != nil {
log.Error("Failed to write session to stdin. %s", err)
}
}()
go func() {
defer wg.Done()
if _, err := io.Copy(session, stdout); err != nil {
log.Error("Failed to write stdout to session. %s", err)
}
}()
go func() {
defer wg.Done()
if _, err := io.Copy(session.Stderr(), stderr); err != nil {
log.Error("Failed to write stderr to session. %s", err)
}
}()
// Ensure all the output has been written before we wait on the command
// to exit.
wg.Wait()
// Wait for the command to exit and log any errors we get
err = cmd.Wait()
if err != nil {
log.Error("SSH: Wait: %v", err)
}
if err := session.Exit(getExitStatusFromError(err)); err != nil {
log.Error("Session failed to exit. %s", err)
}
}
func publicKeyHandler(ctx ssh.Context, key ssh.PublicKey) bool {
if ctx.User() != setting.SSH.BuiltinServerUser {
return false
}
// check if we have a certificate
if cert, ok := key.(*gossh.Certificate); ok {
if len(setting.SSH.TrustedUserCAKeys) == 0 {
return false
}
// look for the exact principal
for _, principal := range cert.ValidPrincipals {
pkey, err := models.SearchPublicKeyByContentExact(principal)
if err != nil {
log.Error("SearchPublicKeyByContentExact: %v", err)
return false
}
if models.IsErrKeyNotExist(err) {
continue
}
c := &gossh.CertChecker{
IsUserAuthority: func(auth gossh.PublicKey) bool {
for _, k := range setting.SSH.TrustedUserCAKeysParsed {
if bytes.Equal(auth.Marshal(), k.Marshal()) {
return true
}
}
return false
},
}
// check the CA of the cert
if !c.IsUserAuthority(cert.SignatureKey) {
return false
}
// validate the cert for this principal
if err := c.CheckCert(principal, cert); err != nil {
return false
}
ctx.SetValue(giteaKeyID, pkey.ID)
return true
}
}
pkey, err := models.SearchPublicKeyByContent(strings.TrimSpace(string(gossh.MarshalAuthorizedKey(key))))
if err != nil {
log.Error("SearchPublicKeyByContent: %v", err)
return false
}
ctx.SetValue(giteaKeyID, pkey.ID)
return true
}
// Listen starts a SSH server listens on given port.
func Listen(host string, port int, ciphers []string, keyExchanges []string, macs []string) {
// TODO: Handle ciphers, keyExchanges, and macs
srv := ssh.Server{
Addr: fmt.Sprintf("%s:%d", host, port),
PublicKeyHandler: publicKeyHandler,
Handler: sessionHandler,
// We need to explicitly disable the PtyCallback so text displays
// properly.
PtyCallback: func(ctx ssh.Context, pty ssh.Pty) bool {
return false
},
}
keyPath := filepath.Join(setting.AppDataPath, "ssh/gogs.rsa")
isExist, err := util.IsExist(keyPath)
if err != nil {
log.Fatal("Unable to check if %s exists. Error: %v", keyPath, err)
}
if !isExist {
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("New private key is generated: %s", keyPath)
}
err = srv.SetOption(ssh.HostKeyFile(keyPath))
if err != nil {
log.Error("Failed to set Host Key. %s", err)
}
go listen(&srv)
}
// 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 := gossh.NewPublicKey(&privateKey.PublicKey)
if err != nil {
return err
}
public := gossh.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
}