allow ssh_config SetEnv to override $TERM, which is otherwise handled

specially by the protocol. Useful in ~/.ssh/config to set TERM to
something generic (e.g. "xterm" instead of "xterm-256color") for
destinations that lack terminfo entries. feedback and ok dtucker@

4 files changed, 32 insertions, 10 deletions

diff --git a/usr.bin/ssh/misc.c b/usr.bin/ssh/misc.c
index 2f54d6305ab..94a1ea8266c 100644
--- a/usr.bin/ssh/misc.c
+++ b/usr.bin/ssh/misc.c
@@ -1,4 +1,4 @@
-/* $OpenBSD: misc.c,v 1.164 2021/04/03 06:18:40 djm Exp $ */
+/* $OpenBSD: misc.c,v 1.165 2021/06/04 05:02:40 djm Exp $ */
 /*
  * Copyright (c) 2000 Markus Friedl.  All rights reserved.
  * Copyright (c) 2005-2020 Damien Miller.  All rights reserved.
@@ -2570,3 +2570,18 @@ subprocess(const char *tag, const char *command,
 		*child = f;
 	return pid;
 }
+
+const char *
+lookup_env_in_list(const char *env, char * const *envs, size_t nenvs)
+{
+	size_t i, envlen;
+
+	envlen = strlen(env);
+	for (i = 0; i < nenvs; i++) {
+		if (strncmp(envs[i], env, envlen) == 0 &&
+		    envs[i][envlen] == '=') {
+			return envs[i] + envlen + 1;
+		}
+	}
+	return NULL;
+}
diff --git a/usr.bin/ssh/misc.h b/usr.bin/ssh/misc.h
index 70cd7787e86..eba125c88c6 100644
--- a/usr.bin/ssh/misc.h
+++ b/usr.bin/ssh/misc.h
@@ -1,4 +1,4 @@
-/* $OpenBSD: misc.h,v 1.95 2021/04/03 06:18:40 djm Exp $ */
+/* $OpenBSD: misc.h,v 1.96 2021/06/04 05:02:40 djm Exp $ */
 
 /*
  * Author: Tatu Ylonen <ylo@cs.hut.fi>
@@ -173,6 +173,8 @@ void mktemp_proto(char *, size_t);
 
 void	 child_set_env(char ***envp, u_int *envsizep, const char *name,
 	    const char *value);
+const char *lookup_env_in_list(const char *env,
+	    char * const *envs, size_t nenvs);
 
 int	 argv_split(const char *, int *, char ***);
 char	*argv_assemble(int, char **argv);
diff --git a/usr.bin/ssh/mux.c b/usr.bin/ssh/mux.c
index d37101ae20f..fbb346ef3ef 100644
--- a/usr.bin/ssh/mux.c
+++ b/usr.bin/ssh/mux.c
@@ -1,4 +1,4 @@
-/* $OpenBSD: mux.c,v 1.88 2021/05/19 01:24:05 djm Exp $ */
+/* $OpenBSD: mux.c,v 1.89 2021/06/04 05:02:40 djm Exp $ */
 /*
  * Copyright (c) 2002-2008 Damien Miller <djm@openbsd.org>
  *
@@ -1847,7 +1847,7 @@ mux_client_request_session(int fd)
 {
 	struct sshbuf *m;
 	char *e;
-	const char *term;
+	const char *term = NULL;
 	u_int echar, rid, sid, esid, exitval, type, exitval_seen;
 	extern char **environ;
 	int r, i, rawmode;
@@ -1864,8 +1864,10 @@ mux_client_request_session(int fd)
 	if (stdin_null_flag && stdfd_devnull(1, 0, 0) == -1)
 		fatal_f("stdfd_devnull failed");
 
-	if ((term = getenv("TERM")) == NULL)
-		term = "";
+	if ((term = lookup_env_in_list("TERM", options.setenv,
+	    options.num_setenv)) == NULL || *term == '\0')
+		term = getenv("TERM");
+
 	echar = 0xffffffff;
 	if (options.escape_char != SSH_ESCAPECHAR_NONE)
 	    echar = (u_int)options.escape_char;
@@ -1880,7 +1882,7 @@ mux_client_request_session(int fd)
 	    (r = sshbuf_put_u32(m, options.forward_agent)) != 0 ||
 	    (r = sshbuf_put_u32(m, subsystem_flag)) != 0 ||
 	    (r = sshbuf_put_u32(m, echar)) != 0 ||
-	    (r = sshbuf_put_cstring(m, term)) != 0 ||
+	    (r = sshbuf_put_cstring(m, term == NULL ? "" : term)) != 0 ||
 	    (r = sshbuf_put_stringb(m, command)) != 0)
 		fatal_fr(r, "request");
 
diff --git a/usr.bin/ssh/ssh.c b/usr.bin/ssh/ssh.c
index 9cbb93d5d94..35c03270310 100644
--- a/usr.bin/ssh/ssh.c
+++ b/usr.bin/ssh/ssh.c
@@ -1,4 +1,4 @@
-/* $OpenBSD: ssh.c,v 1.557 2021/05/19 01:24:05 djm Exp $ */
+/* $OpenBSD: ssh.c,v 1.558 2021/06/04 05:02:40 djm Exp $ */
 /*
  * Author: Tatu Ylonen <ylo@cs.hut.fi>
  * Copyright (c) 1995 Tatu Ylonen <ylo@cs.hut.fi>, Espoo, Finland
@@ -1997,7 +1997,7 @@ static void
 ssh_session2_setup(struct ssh *ssh, int id, int success, void *arg)
 {
 	extern char **environ;
-	const char *display;
+	const char *display, *term;
 	int r, interactive = tty_flag;
 	char *proto = NULL, *data = NULL;
 
@@ -2032,7 +2032,10 @@ ssh_session2_setup(struct ssh *ssh, int id, int success, void *arg)
 	ssh_packet_set_interactive(ssh, interactive,
 	    options.ip_qos_interactive, options.ip_qos_bulk);
 
-	client_session2_setup(ssh, id, tty_flag, subsystem_flag, getenv("TERM"),
+	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,
 	    NULL, fileno(stdin), command, environ);
 }