ssh: support multiple builtin SSH server listener

Adapted from https://github.com/go-gitea/gitea/pull/27969

docs/content/administration/config-cheat-sheet.en-us.md

@@ -334,7 +334,7 @@ The following configuration set `Content-Type: application/vnd.android.package-a
 - `SSH_USER`: **%(BUILTIN_SSH_SERVER_USER)s**: SSH username displayed in clone URLs. This is only for people who configure the SSH server themselves; in most cases, you want to leave this blank and modify the `BUILTIN_SSH_SERVER_USER`.
 - `SSH_DOMAIN`: **%(DOMAIN)s**: Domain name of this server, used for displayed clone URL.
 - `SSH_PORT`: **22**: SSH port displayed in clone URL.
-- `SSH_LISTEN_HOST`: **0.0.0.0**: Listen address for the built-in SSH server.
+- `SSH_LISTEN_HOST`: **0.0.0.0**: Listen address(es) for the built-in SSH server; multiple addresses can be separated by comma, addresses can include a port statement to override SSH_LISTEN_PORT.
 - `SSH_LISTEN_PORT`: **%(SSH\_PORT)s**: Port for the built-in SSH server.
 - `SSH_ROOT_PATH`: **~/.ssh**: Root path of SSH directory.
 - `SSH_CREATE_AUTHORIZED_KEYS_FILE`: **true**: Gitea will create a authorized_keys file by default when it is not using the internal ssh server. If you intend to use the AuthorizedKeysCommand functionality then you should turn this off.

modules/graceful/manager.go

@@ -239,6 +239,12 @@ func (g *Manager) InformCleanup() {
 	g.createServerCond.Signal()
 }
 
+// Should we need to create multile listener for one type (e.g. SSH built-in server),
+// the number of expected routines needs to be increased accordingly.
+func (g *Manager) IncreaseListenerCountBy(extraNumberOfServersToCreate int) {
+	g.createServerWaitGroup.Add(extraNumberOfServersToCreate)
+}
+
 // Done allows the manager to be viewed as a context.Context, it returns a channel that is closed when the server is finished terminating
 func (g *Manager) Done() <-chan struct{} {
 	return g.managerCtx.Done()

modules/setting/ssh.go

@@ -25,7 +25,7 @@ var SSH = struct {
 	Domain                                string             `ini:"SSH_DOMAIN"`
 	Port                                  int                `ini:"SSH_PORT"`
 	User                                  string             `ini:"SSH_USER"`
-	ListenHost                            string             `ini:"SSH_LISTEN_HOST"`
+	ListenHost                            []string             `ini:"SSH_LISTEN_HOST"`
 	ListenPort                            int                `ini:"SSH_LISTEN_PORT"`
 	RootPath                              string             `ini:"SSH_ROOT_PATH"`
 	ServerCiphers                         []string           `ini:"SSH_SERVER_CIPHERS"`
@@ -54,6 +54,7 @@ var SSH = struct {
 	Disabled:                      false,
 	StartBuiltinServer:            false,
 	Domain:                        "",
+	ListenHost:                    []string{"0.0.0.0"},
 	Port:                          22,
 	ServerCiphers:                 []string{"chacha20-poly1305@openssh.com", "aes128-ctr", "aes192-ctr", "aes256-ctr", "aes128-gcm@openssh.com", "aes256-gcm@openssh.com"},
 	ServerKeyExchanges:            []string{"curve25519-sha256", "ecdh-sha2-nistp256", "ecdh-sha2-nistp384", "ecdh-sha2-nistp521", "diffie-hellman-group14-sha256", "diffie-hellman-group14-sha1"},

modules/ssh/init.go

@@ -11,6 +11,7 @@ import (
 	"strconv"
 	"strings"
 
+	"code.gitea.io/gitea/modules/graceful"
 	"code.gitea.io/gitea/modules/log"
 	"code.gitea.io/gitea/modules/setting"
 )
@@ -22,12 +23,23 @@ func Init() error {
 	}
 
 	if setting.SSH.StartBuiltinServer {
-		Listen(setting.SSH.ListenHost, setting.SSH.ListenPort, setting.SSH.ServerCiphers, setting.SSH.ServerKeyExchanges, setting.SSH.ServerMACs)
-		log.Info("SSH server started on %s. Cipher list (%v), key exchange algorithms (%v), MACs (%v)",
-			net.JoinHostPort(setting.SSH.ListenHost, strconv.Itoa(setting.SSH.ListenPort)),
-			setting.SSH.ServerCiphers, setting.SSH.ServerKeyExchanges, setting.SSH.ServerMACs,
-		)
+		if len(setting.SSH.ListenHost) > 1 {
+			graceful.GetManager().IncreaseListenerCountBy(len(setting.SSH.ListenHost) - 1)
+		}
+		for _, listenHost := range setting.SSH.ListenHost {
+			var addr string
+			if _, _, err := net.SplitHostPort(listenHost); err == nil {
+				addr = listenHost
+			} else {
+				addr = net.JoinHostPort(listenHost, strconv.Itoa(setting.SSH.ListenPort))
+			}
+			Listen(addr, setting.SSH.ServerCiphers, setting.SSH.ServerKeyExchanges, setting.SSH.ServerMACs)
+			log.Info("SSH server started on %s. Cipher list (%v), key exchange algorithms (%v), MACs (%v)",
+				addr, setting.SSH.ServerCiphers, setting.SSH.ServerKeyExchanges, setting.SSH.ServerMACs,
+			)
+		}
 		return nil
+
 	}
 
 	builtinUnused()

modules/ssh/ssh.go

@@ -17,7 +17,7 @@ import (
 	"os"
 	"os/exec"
 	"path/filepath"
-	"strconv"
+	"reflect"
 	"strings"
 	"sync"
 	"syscall"
@@ -280,10 +280,10 @@ func sshConnectionFailed(conn net.Conn, err error) {
 	log.Warn("Failed authentication attempt from %s", conn.RemoteAddr())
 }
 
-// Listen starts a SSH server listens on given port.
-func Listen(host string, port int, ciphers, keyExchanges, macs []string) {
+// Listen starts a SSH server listens on given addr (host, port combination).
+func Listen(addr string, ciphers, keyExchanges, macs []string) {
 	srv := ssh.Server{
-		Addr:             net.JoinHostPort(host, strconv.Itoa(port)),
+		Addr:             addr,
 		PublicKeyHandler: publicKeyHandler,
 		Handler:          sessionHandler,
 		ServerConfigCallback: func(ctx ssh.Context) *gossh.ServerConfig {

tests/integration/git_helper_for_declarative_test.go

@@ -52,7 +52,7 @@ func createSSHUrl(gitPath string, u *url.URL) *url.URL {
 	u2 := *u
 	u2.Scheme = "ssh"
 	u2.User = url.User("git")
-	u2.Host = net.JoinHostPort(setting.SSH.ListenHost, strconv.Itoa(setting.SSH.ListenPort))
+	u2.Host = net.JoinHostPort(setting.SSH.ListenHost[0], strconv.Itoa(setting.SSH.ListenPort))
 	u2.Path = gitPath
 	return &u2
 }