upstream: add a SessionType directive to ssh_config, allowing the

configuration file to offer equivalent control to the -N (no session) and -s
(subsystem) command-line flags.

Part of GHPR#231 by Volker Diels-Grabsch with some minor tweaks;
feedback and ok dtucker@

OpenBSD-Commit-ID: 726ee931dd4c5cc7f1d7a187b26f41257f9a2d12

1 files changed, 19 insertions, 19 deletions

diff --git a/ssh.c b/ssh.c
index 0343cba32..710c4e9a7 100644
--- a/ssh.c
+++ b/ssh.c
@@ -1,4 +1,4 @@
-/* $OpenBSD: ssh.c,v 1.559 2021/06/08 07:07:15 djm Exp $ */
+/* $OpenBSD: ssh.c,v 1.560 2021/07/13 23:48:36 djm Exp $ */
 /*
  * Author: Tatu Ylonen <ylo@cs.hut.fi>
  * Copyright (c) 1995 Tatu Ylonen <ylo@cs.hut.fi>, Espoo, Finland
@@ -126,9 +126,6 @@ int debug_flag = 0;
 /* Flag indicating whether a tty should be requested */
 int tty_flag = 0;
 
-/* don't exec a shell */
-int no_shell_flag = 0;
-
 /*
  * Flag indicating that nothing should be read from stdin.  This can be set
  * on the command line.
@@ -142,7 +139,7 @@ int stdin_null_flag = 0;
 int need_controlpersist_detach = 0;
 
 /* Copies of flags for ControlPersist foreground mux-client */
-int ostdin_null_flag, ono_shell_flag, otty_flag, orequest_tty;
+int ostdin_null_flag, osession_type, otty_flag, orequest_tty;
 
 /*
  * Flag indicating that ssh should fork after authentication.  This is useful
@@ -182,9 +179,6 @@ Sensitive sensitive_data;
 /* command to be executed */
 struct sshbuf *command;
 
-/* Should we execute a command or invoke a subsystem? */
-int subsystem_flag = 0;
-
 /* # of replies received for global requests */
 static int forward_confirms_pending = -1;
 
@@ -921,7 +915,7 @@ main(int ac, char **av)
 				exit(255);
 			}
 			options.request_tty = REQUEST_TTY_NO;
-			no_shell_flag = 1;
+			options.session_type = SESSION_TYPE_NONE;
 			break;
 		case 'q':
 			options.log_level = SYSLOG_LEVEL_QUIET;
@@ -1024,7 +1018,10 @@ main(int ac, char **av)
 #endif
 			break;
 		case 'N':
-			no_shell_flag = 1;
+			if (options.session_type != -1 &&
+			    options.session_type != SESSION_TYPE_NONE)
+				fatal("Cannot specify -N with -s/SessionType");
+			options.session_type = SESSION_TYPE_NONE;
 			options.request_tty = REQUEST_TTY_NO;
 			break;
 		case 'T':
@@ -1039,7 +1036,10 @@ main(int ac, char **av)
 			free(line);
 			break;
 		case 's':
-			subsystem_flag = 1;
+			if (options.session_type != -1 &&
+			    options.session_type != SESSION_TYPE_SUBSYSTEM)
+				fatal("Cannot specify -s with -N/SessionType");
+			options.session_type = SESSION_TYPE_SUBSYSTEM;
 			break;
 		case 'S':
 			free(options.control_path);
@@ -1122,7 +1122,7 @@ main(int ac, char **av)
 	 */
 	if (!ac) {
 		/* No command specified - execute shell on a tty. */
-		if (subsystem_flag) {
+		if (options.session_type == SESSION_TYPE_SUBSYSTEM) {
 			fprintf(stderr,
 			    "You must specify a subsystem to invoke.\n");
 			usage();
@@ -1331,7 +1331,7 @@ main(int ac, char **av)
 
 	/* Cannot fork to background if no command. */
 	if (fork_after_authentication_flag && sshbuf_len(command) == 0 &&
-	    options.remote_command == NULL && !no_shell_flag)
+	    options.remote_command == NULL && options.session_type != SESSION_TYPE_NONE)
 		fatal("Cannot fork into background without a command "
 		    "to execute.");
 
@@ -2061,7 +2061,7 @@ ssh_session2_setup(struct ssh *ssh, int id, int success, void *arg)
 	if ((term = lookup_env_in_list("TERM", options.setenv,
 	    options.num_setenv)) == NULL || *term == '\0')
 		term = getenv("TERM");
-	client_session2_setup(ssh, id, tty_flag, subsystem_flag, term,
+	client_session2_setup(ssh, id, tty_flag, options.session_type == SESSION_TYPE_SUBSYSTEM, term,
 	    NULL, fileno(stdin), command, environ);
 }
 
@@ -2097,7 +2097,7 @@ ssh_session2_open(struct ssh *ssh)
 	debug3_f("channel_new: %d", c->self);
 
 	channel_send_open(ssh, c->self);
-	if (!no_shell_flag)
+	if (options.session_type != SESSION_TYPE_NONE)
 		channel_register_open_confirm(ssh, c->self,
 		    ssh_session2_setup, NULL);
 
@@ -2142,14 +2142,14 @@ ssh_session2(struct ssh *ssh, const struct ssh_conn_info *cinfo)
 	 */
 	if (options.control_persist && muxserver_sock != -1) {
 		ostdin_null_flag = stdin_null_flag;
-		ono_shell_flag = no_shell_flag;
+		osession_type = options.session_type;
 		orequest_tty = options.request_tty;
 		otty_flag = tty_flag;
 		stdin_null_flag = 1;
-		no_shell_flag = 1;
+		options.session_type = SESSION_TYPE_NONE;
 		tty_flag = 0;
 		if (!fork_after_authentication_flag &&
-		    (!ono_shell_flag || options.stdio_forward_host != NULL))
+		    (osession_type != SESSION_TYPE_NONE || options.stdio_forward_host != NULL))
 			need_controlpersist_detach = 1;
 		fork_after_authentication_flag = 1;
 	}
@@ -2160,7 +2160,7 @@ ssh_session2(struct ssh *ssh, const struct ssh_conn_info *cinfo)
 	if (options.control_persist && muxserver_sock == -1)
 		ssh_init_stdio_forwarding(ssh);
 
-	if (!no_shell_flag)
+	if (options.session_type != SESSION_TYPE_NONE)
 		id = ssh_session2_open(ssh);
 	else {
 		ssh_packet_set_interactive(ssh,