初始提交: Gitea 项目代码
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// Copyright 2021 The Gitea Authors. All rights reserved.
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// SPDX-License-Identifier: MIT
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package asymkey
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import (
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"bufio"
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"context"
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"fmt"
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"io"
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"os"
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"path/filepath"
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"regexp"
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"strings"
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"sync"
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"gitea.dev/models/db"
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"gitea.dev/modules/log"
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"gitea.dev/modules/setting"
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"gitea.dev/modules/util"
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"golang.org/x/crypto/ssh"
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)
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// AuthorizedStringCommentPrefix is a magic tag
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// some functions like RegeneratePublicKeys needs this tag to skip the keys generated by Gitea, while keep other keys
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const AuthorizedStringCommentPrefix = `# gitea public key`
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var sshOpLocker sync.Mutex
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func WithSSHOpLocker(f func() error) error {
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sshOpLocker.Lock()
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defer sshOpLocker.Unlock()
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return f()
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}
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// AuthorizedStringForKey creates the authorized keys string appropriate for the provided key
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func AuthorizedStringForKey(key *PublicKey) (string, error) {
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sb := &strings.Builder{}
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_, err := writeAuthorizedStringForKey(key, sb)
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return sb.String(), err
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}
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// WriteAuthorizedStringForValidKey writes the authorized key for the provided key. If the key is invalid, it does nothing.
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func WriteAuthorizedStringForValidKey(key *PublicKey, w io.Writer) error {
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validKey, err := writeAuthorizedStringForKey(key, w)
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if !validKey {
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log.Debug("WriteAuthorizedStringForValidKey: key %s is not valid: %v", key, err)
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return nil
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}
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return err
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}
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var globalVars = sync.OnceValue(func() (ret struct {
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principalRegexp *regexp.Regexp
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},
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) {
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// principalRegexp expresses whether a principal is considered valid.
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// This reverse engineers how sshd parses the authorized keys file,
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// see e.g. https://github.com/openssh/openssh-portable/blob/32deb00b38b4ee2b3302f261ea1e68c04e020a08/auth2-pubkeyfile.c#L221-L256
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// Any newline or # comment will be stripped when parsing, so don't allow
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// those. Also, if any space or tab is present in the principal, the part
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// proceeding this would be parsed as an option, so just avoid any whitespace
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// altogether.
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ret.principalRegexp = regexp.MustCompile(`^[^\s#]+$`)
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return ret
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})
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func writeAuthorizedStringForKey(key *PublicKey, w io.Writer) (keyValid bool, err error) {
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const tpl = AuthorizedStringCommentPrefix + "\n" + `command=%s,no-port-forwarding,no-X11-forwarding,no-agent-forwarding,no-pty,no-user-rc,restrict %s` + "\n"
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var sshKey string
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if key.Type == KeyTypePrincipal {
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// TODO: actually using PublicKey to store "principal" is an abuse
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if !globalVars().principalRegexp.MatchString(key.Content) {
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return false, fmt.Errorf("invalid principal key: %s", key.Content)
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}
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sshKey = fmt.Sprintf("%s # user-%d", key.Content, key.OwnerID)
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} else {
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pubKey, _, _, _, err := ssh.ParseAuthorizedKey([]byte(key.Content))
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if err != nil {
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return false, err
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}
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sshKeyMarshalled := strings.TrimSpace(string(ssh.MarshalAuthorizedKey(pubKey)))
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sshKey = fmt.Sprintf("%s user-%d", sshKeyMarshalled, key.OwnerID)
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}
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// now the key is valid, the code below could only return template/IO related errors
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sbCmd := &strings.Builder{}
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err = setting.SSH.AuthorizedKeysCommandTemplateTemplate.Execute(sbCmd, map[string]any{
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"AppPath": util.ShellEscape(setting.AppPath),
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"AppWorkPath": util.ShellEscape(setting.AppWorkPath),
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"CustomConf": util.ShellEscape(setting.CustomConf),
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"CustomPath": util.ShellEscape(setting.CustomPath),
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"Key": key,
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})
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if err != nil {
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return true, err
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}
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sshCommandEscaped := util.ShellEscape(sbCmd.String())
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_, err = fmt.Fprintf(w, tpl, sshCommandEscaped, sshKey)
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return true, err
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}
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// appendAuthorizedKeysToFile appends new SSH keys' content to authorized_keys file.
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func appendAuthorizedKeysToFile(keys ...*PublicKey) error {
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// Don't need to rewrite this file if builtin SSH server is enabled.
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if setting.SSH.StartBuiltinServer || !setting.SSH.CreateAuthorizedKeysFile {
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return nil
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}
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sshOpLocker.Lock()
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defer sshOpLocker.Unlock()
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if setting.SSH.RootPath != "" {
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// First of ensure that the RootPath is present, and if not make it with 0700 permissions
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// This of course doesn't guarantee that this is the right directory for authorized_keys
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// but at least if it's supposed to be this directory and it doesn't exist and we're the
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// right user it will at least be created properly.
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err := os.MkdirAll(setting.SSH.RootPath, 0o700)
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if err != nil {
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log.Error("Unable to MkdirAll(%s): %v", setting.SSH.RootPath, err)
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return err
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}
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}
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fPath := filepath.Join(setting.SSH.RootPath, "authorized_keys")
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f, err := os.OpenFile(fPath, os.O_CREATE|os.O_WRONLY|os.O_APPEND, 0o600)
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if err != nil {
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return err
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}
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defer f.Close()
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// Note: chmod command does not support in Windows.
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if !setting.IsWindows {
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fi, err := f.Stat()
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if err != nil {
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return err
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}
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// .ssh directory should have mode 700, and authorized_keys file should have mode 600.
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if fi.Mode().Perm() > 0o600 {
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log.Error("authorized_keys file has unusual permission flags: %s - setting to -rw-------", fi.Mode().Perm().String())
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if err = f.Chmod(0o600); err != nil {
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return err
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}
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}
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}
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for _, key := range keys {
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if key.Type == KeyTypePrincipal {
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continue
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}
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if err = WriteAuthorizedStringForValidKey(key, f); err != nil {
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return err
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}
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}
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return nil
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}
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// RegeneratePublicKeys regenerates the authorized_keys file
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func RegeneratePublicKeys(ctx context.Context, t io.Writer) error {
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if err := db.GetEngine(ctx).Where("type != ?", KeyTypePrincipal).Iterate(new(PublicKey), func(idx int, bean any) (err error) {
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return WriteAuthorizedStringForValidKey(bean.(*PublicKey), t)
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}); err != nil {
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return err
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}
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fPath := filepath.Join(setting.SSH.RootPath, "authorized_keys")
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isExist, err := util.IsExist(fPath)
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if err != nil {
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log.Error("Unable to check if %s exists. Error: %v", fPath, err)
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return err
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}
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if isExist {
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f, err := os.Open(fPath)
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if err != nil {
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return err
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}
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defer f.Close()
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scanner := bufio.NewScanner(f)
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for scanner.Scan() {
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line := scanner.Text()
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if strings.HasPrefix(line, AuthorizedStringCommentPrefix) {
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scanner.Scan()
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continue
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}
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_, err = io.WriteString(t, line+"\n")
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if err != nil {
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return err
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}
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}
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if err = scanner.Err(); err != nil {
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return fmt.Errorf("RegeneratePublicKeys scan: %w", err)
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}
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}
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return nil
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}
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