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forgejo/modules/ssh/ssh.go
Wim 9066d09c57
Add ssh certificate support (#12281)
* Add ssh certificate support

* Add ssh certificate support to builtin ssh

* Write trusted-user-ca-keys.pem based on configuration

* Update app.example.ini

* Update templates/user/settings/keys_principal.tmpl

Co-authored-by: silverwind <me@silverwind.io>

* Remove unused locale string

* Update options/locale/locale_en-US.ini

Co-authored-by: silverwind <me@silverwind.io>

* Update options/locale/locale_en-US.ini

Co-authored-by: silverwind <me@silverwind.io>

* Update models/ssh_key.go

Co-authored-by: silverwind <me@silverwind.io>

* Add missing creation of SSH.Rootpath

* Update cheatsheet, example and locale strings

* Update models/ssh_key.go

Co-authored-by: zeripath <art27@cantab.net>

* Update models/ssh_key.go

Co-authored-by: zeripath <art27@cantab.net>

* Update models/ssh_key.go

Co-authored-by: zeripath <art27@cantab.net>

* Update models/ssh_key.go

Co-authored-by: zeripath <art27@cantab.net>

* Update models/ssh_key.go

* Optimizations based on feedback

* Validate CA keys for external sshd

* Add filename option and change default filename

Add a SSH_TRUSTED_USER_CA_KEYS_FILENAME option which default is
RUN_USER/.ssh/gitea-trusted-user-ca-keys.pem

Do not write a file when SSH_TRUSTED_USER_CA_KEYS is empty.

Add some more documentation.

* Remove unneeded principalkey functions

* Add blank line

* Apply suggestions from code review

Co-authored-by: zeripath <art27@cantab.net>

* Add SSH_AUTHORIZED_PRINCIPALS_ALLOW option

This adds a SSH_AUTHORIZED_PRINCIPALS_ALLOW which is default
email,username this means that users only can add the principals
that match their email or username.

To allow anything the admin need to set the option anything.

This allows for a safe default in gitea which protects against malicious
users using other user's prinicipals. (before that user could set it).

This commit also has some small other fixes from the last code review.

* Rewrite principal keys file on user deletion

* Use correct rewrite method

* Set correct AuthorizedPrincipalsBackup default setting

* Rewrite principalsfile when adding principals

* Add update authorized_principals option to admin dashboard

* Handle non-primary emails

Signed-off-by: Andrew Thornton <art27@cantab.net>

* Add the command actually to the dashboard template

* Update models/ssh_key.go

Co-authored-by: silverwind <me@silverwind.io>

* By default do not show principal options unless there are CA keys set or they are explicitly set

Signed-off-by: Andrew Thornton <art27@cantab.net>

* allow settings when enabled

* Fix typos in TrustedUserCAKeys path

* Allow every CASignatureAlgorithms algorithm

As this depends on the content of TrustedUserCAKeys we should allow all
signature algorithms as admins can choose the specific algorithm on their
signing CA

* Update models/ssh_key.go

Co-authored-by: Lauris BH <lauris@nix.lv>

* Fix linting issue

Co-authored-by: silverwind <me@silverwind.io>
Co-authored-by: zeripath <art27@cantab.net>
Co-authored-by: Lauris BH <lauris@nix.lv>
Co-authored-by: techknowlogick <matti@mdranta.net>
Co-authored-by: techknowlogick <techknowlogick@gitea.io>
2020-10-10 20:38:09 -04:00

279 lines
6.1 KiB
Go

// 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"
"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")
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("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
}