Make internal SSH server host key path configurable (#14918)

* Make SSH server host key path configurable

* make it possible to have multiple keys

* Make gitea.rsa the default key

* Add some more logging

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

cmd/web.go

@@ -64,7 +64,7 @@ func runHTTPRedirector() {
 		http.Redirect(w, r, target, http.StatusTemporaryRedirect)
 	})
 
-	var err = runHTTP("tcp", source, context2.ClearHandler(handler))
+	var err = runHTTP("tcp", source, "HTTP Redirector", context2.ClearHandler(handler))
 
 	if err != nil {
 		log.Fatal("Failed to start port redirection: %v", err)
@@ -198,7 +198,7 @@ func listen(m http.Handler, handleRedirector bool) error {
 		if handleRedirector {
 			NoHTTPRedirector()
 		}
-		err = runHTTP("tcp", listenAddr, context2.ClearHandler(m))
+		err = runHTTP("tcp", listenAddr, "Web", context2.ClearHandler(m))
 	case setting.HTTPS:
 		if setting.EnableLetsEncrypt {
 			err = runLetsEncrypt(listenAddr, setting.Domain, setting.LetsEncryptDirectory, setting.LetsEncryptEmail, context2.ClearHandler(m))
@@ -211,22 +211,22 @@ func listen(m http.Handler, handleRedirector bool) error {
 				NoHTTPRedirector()
 			}
 		}
-		err = runHTTPS("tcp", listenAddr, setting.CertFile, setting.KeyFile, context2.ClearHandler(m))
+		err = runHTTPS("tcp", listenAddr, "Web", setting.CertFile, setting.KeyFile, context2.ClearHandler(m))
 	case setting.FCGI:
 		if handleRedirector {
 			NoHTTPRedirector()
 		}
-		err = runFCGI("tcp", listenAddr, context2.ClearHandler(m))
+		err = runFCGI("tcp", listenAddr, "FCGI Web", context2.ClearHandler(m))
 	case setting.UnixSocket:
 		if handleRedirector {
 			NoHTTPRedirector()
 		}
-		err = runHTTP("unix", listenAddr, context2.ClearHandler(m))
+		err = runHTTP("unix", listenAddr, "Web", context2.ClearHandler(m))
 	case setting.FCGIUnix:
 		if handleRedirector {
 			NoHTTPRedirector()
 		}
-		err = runFCGI("unix", listenAddr, context2.ClearHandler(m))
+		err = runFCGI("unix", listenAddr, "Web", context2.ClearHandler(m))
 	default:
 		log.Fatal("Invalid protocol: %s", setting.Protocol)
 	}

cmd/web_graceful.go

@@ -14,16 +14,16 @@ import (
 	"code.gitea.io/gitea/modules/log"
 )
 
-func runHTTP(network, listenAddr string, m http.Handler) error {
+func runHTTP(network, listenAddr, name string, m http.Handler) error {
-	return graceful.HTTPListenAndServe(network, listenAddr, m)
+	return graceful.HTTPListenAndServe(network, listenAddr, name, m)
 }
 
-func runHTTPS(network, listenAddr, certFile, keyFile string, m http.Handler) error {
+func runHTTPS(network, listenAddr, name, certFile, keyFile string, m http.Handler) error {
-	return graceful.HTTPListenAndServeTLS(network, listenAddr, certFile, keyFile, m)
+	return graceful.HTTPListenAndServeTLS(network, listenAddr, name, certFile, keyFile, m)
 }
 
-func runHTTPSWithTLSConfig(network, listenAddr string, tlsConfig *tls.Config, m http.Handler) error {
+func runHTTPSWithTLSConfig(network, listenAddr, name string, tlsConfig *tls.Config, m http.Handler) error {
-	return graceful.HTTPListenAndServeTLSConfig(network, listenAddr, tlsConfig, m)
+	return graceful.HTTPListenAndServeTLSConfig(network, listenAddr, name, tlsConfig, m)
 }
 
 // NoHTTPRedirector tells our cleanup routine that we will not be using a fallback http redirector
@@ -43,9 +43,9 @@ func NoInstallListener() {
 	graceful.GetManager().InformCleanup()
 }
 
-func runFCGI(network, listenAddr string, m http.Handler) error {
+func runFCGI(network, listenAddr, name string, m http.Handler) error {
 	// This needs to handle stdin as fcgi point
-	fcgiServer := graceful.NewServer(network, listenAddr)
+	fcgiServer := graceful.NewServer(network, listenAddr, name)
 
 	err := fcgiServer.ListenAndServe(func(listener net.Listener) error {
 		return fcgi.Serve(listener, m)

cmd/web_letsencrypt.go

@@ -46,14 +46,14 @@ func runLetsEncrypt(listenAddr, domain, directory, email string, m http.Handler)
 		go func() {
 			log.Info("Running Let's Encrypt handler on %s", setting.HTTPAddr+":"+setting.PortToRedirect)
 			// all traffic coming into HTTP will be redirect to HTTPS automatically (LE HTTP-01 validation happens here)
-			var err = runHTTP("tcp", setting.HTTPAddr+":"+setting.PortToRedirect, myACME.HTTPChallengeHandler(http.HandlerFunc(runLetsEncryptFallbackHandler)))
+			var err = runHTTP("tcp", setting.HTTPAddr+":"+setting.PortToRedirect, "Let's Encrypt HTTP Challenge", myACME.HTTPChallengeHandler(http.HandlerFunc(runLetsEncryptFallbackHandler)))
 			if err != nil {
 				log.Fatal("Failed to start the Let's Encrypt handler on port %s: %v", setting.PortToRedirect, err)
 			}
 		}()
 	}
 
-	return runHTTPSWithTLSConfig("tcp", listenAddr, tlsConfig, context2.ClearHandler(m))
+	return runHTTPSWithTLSConfig("tcp", listenAddr, "Web", tlsConfig, context2.ClearHandler(m))
 }
 
 func runLetsEncryptFallbackHandler(w http.ResponseWriter, r *http.Request) {

custom/conf/app.example.ini

@@ -319,6 +319,10 @@ SSH_SERVER_KEY_EXCHANGES = diffie-hellman-group1-sha1, diffie-hellman-group14-sh
 ; For the built-in SSH server, choose the MACs to support for SSH connections,
 ; for system SSH this setting has no effect
 SSH_SERVER_MACS = hmac-sha2-256-etm@openssh.com, hmac-sha2-256, hmac-sha1, hmac-sha1-96
+; For the built-in SSH server, choose the keypair to offer as the host key
+; The private key should be at SSH_SERVER_HOST_KEY and the public SSH_SERVER_HOST_KEY.pub
+; relative paths are made absolute relative to the APP_DATA_PATH
+SSH_SERVER_HOST_KEYS=ssh/gitea.rsa, ssh/gogs.rsa
 ; Directory to create temporary files in when testing public keys using ssh-keygen,
 ; default is the system temporary directory.
 SSH_KEY_TEST_PATH =

docs/content/doc/advanced/config-cheat-sheet.en-us.md

@@ -256,6 +256,7 @@ Values containing `#` or `;` must be quoted using `` ` `` or `"""`.
 - `SSH_SERVER_CIPHERS`: **aes128-ctr, aes192-ctr, aes256-ctr, aes128-gcm@openssh.com, arcfour256, arcfour128**: For the built-in SSH server, choose the ciphers to support for SSH connections, for system SSH this setting has no effect.
 - `SSH_SERVER_KEY_EXCHANGES`: **diffie-hellman-group1-sha1, diffie-hellman-group14-sha1, ecdh-sha2-nistp256, ecdh-sha2-nistp384, ecdh-sha2-nistp521, curve25519-sha256@libssh.org**: For the built-in SSH server, choose the key exchange algorithms to support for SSH connections, for system SSH this setting has no effect.
 - `SSH_SERVER_MACS`: **hmac-sha2-256-etm@openssh.com, hmac-sha2-256, hmac-sha1, hmac-sha1-96**: For the built-in SSH server, choose the MACs to support for SSH connections, for system SSH this setting has no effect
+- `SSH_SERVER_HOST_KEYS`: **ssh/gitea.rsa, ssh/gogs.rsa**: For the built-in SSH server, choose the keypairs to offer as the host key. The private key should be at `SSH_SERVER_HOST_KEY` and the public `SSH_SERVER_HOST_KEY.pub`. Relative paths are made absolute relative to the `APP_DATA_PATH`. If no key exists a 4096 bit RSA key will be created for you.
 - `SSH_KEY_TEST_PATH`: **/tmp**: Directory to create temporary files in when testing public keys using ssh-keygen, default is the system temporary directory.
 - `SSH_KEYGEN_PATH`: **ssh-keygen**: Path to ssh-keygen, default is 'ssh-keygen' which means the shell is responsible for finding out which one to call.
 - `SSH_EXPOSE_ANONYMOUS`: **false**: Enable exposure of SSH clone URL to anonymous visitors, default is false.

modules/graceful/server.go

@@ -48,11 +48,11 @@ type Server struct {
 }
 
 // NewServer creates a server on network at provided address
-func NewServer(network, address string) *Server {
+func NewServer(network, address, name string) *Server {
 	if GetManager().IsChild() {
-		log.Info("Restarting new server: %s:%s on PID: %d", network, address, os.Getpid())
+		log.Info("Restarting new %s server: %s:%s on PID: %d", name, network, address, os.Getpid())
 	} else {
-		log.Info("Starting new server: %s:%s on PID: %d", network, address, os.Getpid())
+		log.Info("Starting new %s server: %s:%s on PID: %d", name, network, address, os.Getpid())
 	}
 	srv := &Server{
 		wg:      sync.WaitGroup{},

modules/graceful/server_http.go

@@ -9,8 +9,8 @@ import (
 	"net/http"
 )
 
-func newHTTPServer(network, address string, handler http.Handler) (*Server, ServeFunction) {
+func newHTTPServer(network, address, name string, handler http.Handler) (*Server, ServeFunction) {
-	server := NewServer(network, address)
+	server := NewServer(network, address, name)
 	httpServer := http.Server{
 		ReadTimeout:    DefaultReadTimeOut,
 		WriteTimeout:   DefaultWriteTimeOut,
@@ -25,21 +25,21 @@ func newHTTPServer(network, address string, handler http.Handler) (*Server, Serv
 
 // HTTPListenAndServe listens on the provided network address and then calls Serve
 // to handle requests on incoming connections.
-func HTTPListenAndServe(network, address string, handler http.Handler) error {
+func HTTPListenAndServe(network, address, name string, handler http.Handler) error {
-	server, lHandler := newHTTPServer(network, address, handler)
+	server, lHandler := newHTTPServer(network, address, name, handler)
 	return server.ListenAndServe(lHandler)
 }
 
 // HTTPListenAndServeTLS listens on the provided network address and then calls Serve
 // to handle requests on incoming connections.
-func HTTPListenAndServeTLS(network, address, certFile, keyFile string, handler http.Handler) error {
+func HTTPListenAndServeTLS(network, address, name, certFile, keyFile string, handler http.Handler) error {
-	server, lHandler := newHTTPServer(network, address, handler)
+	server, lHandler := newHTTPServer(network, address, name, handler)
 	return server.ListenAndServeTLS(certFile, keyFile, lHandler)
 }
 
 // HTTPListenAndServeTLSConfig listens on the provided network address and then calls Serve
 // to handle requests on incoming connections.
-func HTTPListenAndServeTLSConfig(network, address string, tlsConfig *tls.Config, handler http.Handler) error {
+func HTTPListenAndServeTLSConfig(network, address, name string, tlsConfig *tls.Config, handler http.Handler) error {
-	server, lHandler := newHTTPServer(network, address, handler)
+	server, lHandler := newHTTPServer(network, address, name, handler)
 	return server.ListenAndServeTLSConfig(tlsConfig, lHandler)
 }

modules/setting/setting.go

@@ -132,6 +132,7 @@ var (
 		ServerCiphers                  []string          `ini:"SSH_SERVER_CIPHERS"`
 		ServerKeyExchanges             []string          `ini:"SSH_SERVER_KEY_EXCHANGES"`
 		ServerMACs                     []string          `ini:"SSH_SERVER_MACS"`
+		ServerHostKeys                 []string          `ini:"SSH_SERVER_HOST_KEYS"`
 		KeyTestPath                    string            `ini:"SSH_KEY_TEST_PATH"`
 		KeygenPath                     string            `ini:"SSH_KEYGEN_PATH"`
 		AuthorizedKeysBackup           bool              `ini:"SSH_AUTHORIZED_KEYS_BACKUP"`
@@ -157,6 +158,7 @@ var (
 		KeygenPath:          "ssh-keygen",
 		MinimumKeySizeCheck: true,
 		MinimumKeySizes:     map[string]int{"ed25519": 256, "ed25519-sk": 256, "ecdsa": 256, "ecdsa-sk": 256, "rsa": 2048},
+		ServerHostKeys:      []string{"ssh/gitea.rsa", "ssh/gogs.rsa"},
 	}
 
 	// Security settings
@@ -698,6 +700,11 @@ func NewContext() {
 	if err = Cfg.Section("server").MapTo(&SSH); err != nil {
 		log.Fatal("Failed to map SSH settings: %v", err)
 	}
+	for i, key := range SSH.ServerHostKeys {
+		if !filepath.IsAbs(key) {
+			SSH.ServerHostKeys[i] = filepath.Join(AppDataPath, key)
+		}
+	}
 
 	SSH.KeygenPath = sec.Key("SSH_KEYGEN_PATH").MustString("ssh-keygen")
 	SSH.Port = sec.Key("SSH_PORT").MustInt(22)

modules/ssh/ssh.go

@@ -259,29 +259,39 @@ func Listen(host string, port int, ciphers []string, keyExchanges []string, macs
 		},
 	}
 
-	keyPath := filepath.Join(setting.AppDataPath, "ssh/gogs.rsa")
+	keys := make([]string, 0, len(setting.SSH.ServerHostKeys))
-	isExist, err := util.IsExist(keyPath)
+	for _, key := range setting.SSH.ServerHostKeys {
+		isExist, err := util.IsExist(key)
 		if err != nil {
-		log.Fatal("Unable to check if %s exists. Error: %v", keyPath, err)
+			log.Fatal("Unable to check if %s exists. Error: %v", setting.SSH.ServerHostKeys, err)
 		}
-	if !isExist {
+		if isExist {
-		filePath := filepath.Dir(keyPath)
+			keys = append(keys, key)
+		}
+	}
+
+	if len(keys) == 0 {
+		filePath := filepath.Dir(setting.SSH.ServerHostKeys[0])
 
 		if err := os.MkdirAll(filePath, os.ModePerm); err != nil {
 			log.Error("Failed to create dir %s: %v", filePath, err)
 		}
 
-		err := GenKeyPair(keyPath)
+		err := GenKeyPair(setting.SSH.ServerHostKeys[0])
 		if err != nil {
 			log.Fatal("Failed to generate private key: %v", err)
 		}
-		log.Trace("New private key is generated: %s", keyPath)
+		log.Trace("New private key is generated: %s", setting.SSH.ServerHostKeys[0])
+		keys = append(keys, setting.SSH.ServerHostKeys[0])
 	}
 
-	err = srv.SetOption(ssh.HostKeyFile(keyPath))
+	for _, key := range keys {
+		log.Info("Adding SSH host key: %s", key)
+		err := srv.SetOption(ssh.HostKeyFile(key))
 		if err != nil {
 			log.Error("Failed to set Host Key. %s", err)
 		}
+	}
 
 	go listen(&srv)
 
@@ -291,7 +301,7 @@ func Listen(host string, port int, ciphers []string, keyExchanges []string, macs
 // 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)
+	privateKey, err := rsa.GenerateKey(rand.Reader, 4096)
 	if err != nil {
 		return err
 	}

modules/ssh/ssh_graceful.go

@@ -12,7 +12,7 @@ import (
 )
 
 func listen(server *ssh.Server) {
-	gracefulServer := graceful.NewServer("tcp", server.Addr)
+	gracefulServer := graceful.NewServer("tcp", server.Addr, "SSH")
 
 	err := gracefulServer.ListenAndServe(server.Serve)
 	if err != nil {