mugit/internal/ssh/server.go(view raw)
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package ssh
import (
"fmt"
"log/slog"
"slices"
"strconv"
securejoin "github.com/cyphar/filepath-securejoin"
"github.com/gliderlabs/ssh"
"olexsmir.xyz/mugit/internal/config"
"olexsmir.xyz/mugit/internal/git"
"olexsmir.xyz/mugit/internal/git/gitservice"
gossh "golang.org/x/crypto/ssh"
)
type authorizedKeyType string
const authorizedKey authorizedKeyType = "authorized"
type Server struct {
c *config.Config
authKeys []gossh.PublicKey
}
func NewServer(cfg *config.Config) *Server {
return &Server{
c: cfg,
authKeys: []gossh.PublicKey{},
}
}
func (s *Server) Start() error {
if err := s.parseAuthKeys(); err != nil {
return err
}
srv := &ssh.Server{
Addr: ":" + strconv.Itoa(s.c.SSH.Port),
Handler: s.handler,
PublicKeyHandler: s.authhandler,
}
if err := srv.SetOption(ssh.HostKeyFile(s.c.SSH.HostKey)); err != nil {
// TODO: validate `gossh.ParsePrivateKey`
return err
}
return srv.ListenAndServe()
}
func (s *Server) authhandler(ctx ssh.Context, key ssh.PublicKey) bool {
fingerprint := gossh.FingerprintSHA256(key)
if ctx.User() != "git" {
slog.Info("non git ssh request", "user", ctx.User(), "fingerprint", fingerprint)
return false
}
slog.Info("ssh request", "fingerprint", fingerprint)
authorized := slices.ContainsFunc(s.authKeys, func(i gossh.PublicKey) bool {
return ssh.KeysEqual(key, i)
})
ctx.SetValue(authorizedKey, authorized)
return true
}
func (s *Server) handler(sess ssh.Session) {
authorized := sess.Context().Value(authorizedKey).(bool)
cmd := sess.Command()
if len(cmd) < 2 {
fmt.Fprintln(sess, "No command provided")
sess.Exit(1)
return
}
gitCmd := cmd[0]
repoPath := cmd[1]
repoPath, err := securejoin.SecureJoin(s.c.Repo.Dir, repoPath)
if err != nil {
slog.Error("ssh: invalid path", "err", err)
s.repoNotFound(sess)
return
}
repo, err := git.Open(repoPath, "")
if err != nil {
slog.Error("ssh: failed to open repo", "err", err)
s.repoNotFound(sess)
return
}
switch gitCmd {
case "git-upload-pack":
isPrivate, err := repo.IsPrivate()
if err != nil {
s.error(sess, err)
return
}
if isPrivate && !authorized {
s.repoNotFound(sess)
return
}
if err := gitservice.UploadPack(repoPath, false, sess, sess); err != nil {
s.error(sess, err)
return
}
sess.Exit(0)
case "git-receive-pack":
if !authorized {
s.unauthorized(sess)
return
}
if err := gitservice.ReceivePack(repoPath, sess, sess, sess.Stderr()); err != nil {
s.error(sess, err)
return
}
sess.Exit(0)
default:
slog.Error("ssh unsupported command", "cmd", cmd)
gitservice.PackError(sess, "Unsupported command.")
sess.Exit(1)
}
}
func (s *Server) parseAuthKeys() error {
parsedKeys := make([]gossh.PublicKey, len(s.c.SSH.Keys))
for i, key := range s.c.SSH.Keys {
pkey, _, _, _, err := gossh.ParseAuthorizedKey([]byte(key))
if err != nil {
return err
}
parsedKeys[i] = pkey
}
s.authKeys = parsedKeys
return nil
}
func (s *Server) repoNotFound(sess ssh.Session) {
gitservice.PackError(sess, "Repository not found.")
sess.Exit(1)
}
func (s *Server) unauthorized(sess ssh.Session) {
gitservice.PackError(sess, "You are not authorized to push to this repository.")
sess.Exit(1)
}
func (s *Server) error(sess ssh.Session, err error) {
slog.Error("error on ssh side", "err", err)
gitservice.PackError(sess, "Unexpected server error.")
sess.Exit(1)
}
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