allow sshd_config PermitUserEnvironment to accept a pattern-list of

whitelisted environment variable names in addition to yes|no.

bz#1800, feedback and ok markus@

4 files changed, 62 insertions, 11 deletions

diff --git a/usr.bin/ssh/servconf.c b/usr.bin/ssh/servconf.c
index 4e973d06277..e2534c676ba 100644
--- a/usr.bin/ssh/servconf.c
+++ b/usr.bin/ssh/servconf.c
@@ -1,5 +1,5 @@
 
-/* $OpenBSD: servconf.c,v 1.333 2018/06/19 02:59:41 djm Exp $ */
+/* $OpenBSD: servconf.c,v 1.334 2018/07/03 10:59:35 djm Exp $ */
 /*
  * Copyright (c) 1995 Tatu Ylonen <ylo@cs.hut.fi>, Espoo, Finland
  *                    All rights reserved
@@ -116,6 +116,7 @@ initialize_server_options(ServerOptions *options)
 	options->challenge_response_authentication = -1;
 	options->permit_empty_passwd = -1;
 	options->permit_user_env = -1;
+	options->permit_user_env_whitelist = NULL;
 	options->compression = -1;
 	options->rekey_limit = -1;
 	options->rekey_interval = -1;
@@ -308,8 +309,10 @@ fill_default_server_options(ServerOptions *options)
 		options->challenge_response_authentication = 1;
 	if (options->permit_empty_passwd == -1)
 		options->permit_empty_passwd = 0;
-	if (options->permit_user_env == -1)
+	if (options->permit_user_env == -1) {
 		options->permit_user_env = 0;
+		options->permit_user_env_whitelist = NULL;
+	}
 	if (options->compression == -1)
 		options->compression = COMP_DELAYED;
 	if (options->rekey_limit == -1)
@@ -1451,7 +1454,29 @@ process_server_config_line(ServerOptions *options, char *line,
 
 	case sPermitUserEnvironment:
 		intptr = &options->permit_user_env;
-		goto parse_flag;
+		charptr = &options->permit_user_env_whitelist;
+		arg = strdelim(&cp);
+		if (!arg || *arg == '\0')
+			fatal("%s line %d: missing argument.",
+			    filename, linenum);
+		value = 0;
+		p = NULL;
+		if (strcmp(arg, "yes") == 0)
+			value = 1;
+		else if (strcmp(arg, "no") == 0)
+			value = 0;
+		else {
+			/* Pattern-list specified */
+			value = 1;
+			p = xstrdup(arg);
+		}
+		if (*activep && *intptr == -1) {
+			*intptr = value;
+			*charptr = p;
+			p = NULL;
+		}
+		free(p);
+		break;
 
 	case sCompression:
 		intptr = &options->compression;
@@ -2458,7 +2483,6 @@ dump_config(ServerOptions *o)
 	dump_cfg_fmtint(sStrictModes, o->strict_modes);
 	dump_cfg_fmtint(sTCPKeepAlive, o->tcp_keep_alive);
 	dump_cfg_fmtint(sEmptyPasswd, o->permit_empty_passwd);
-	dump_cfg_fmtint(sPermitUserEnvironment, o->permit_user_env);
 	dump_cfg_fmtint(sCompression, o->compression);
 	dump_cfg_fmtint(sGatewayPorts, o->fwd_opts.gateway_ports);
 	dump_cfg_fmtint(sUseDNS, o->use_dns);
@@ -2558,4 +2582,12 @@ dump_config(ServerOptions *o)
 			printf(" %s", o->permitted_listens[i]);
 	}
 	printf("\n");
+
+	if (o->permit_user_env_whitelist == NULL) {
+		dump_cfg_fmtint(sPermitUserEnvironment, o->permit_user_env);
+	} else {
+		printf("permituserenvironment %s\n",
+		    o->permit_user_env_whitelist);
+	}
+
 }
diff --git a/usr.bin/ssh/servconf.h b/usr.bin/ssh/servconf.h
index e8a108ce779..97561874194 100644
--- a/usr.bin/ssh/servconf.h
+++ b/usr.bin/ssh/servconf.h
@@ -1,4 +1,4 @@
-/* $OpenBSD: servconf.h,v 1.134 2018/06/09 03:03:10 djm Exp $ */
+/* $OpenBSD: servconf.h,v 1.135 2018/07/03 10:59:35 djm Exp $ */
 
 /*
  * Author: Tatu Ylonen <ylo@cs.hut.fi>
@@ -133,6 +133,7 @@ typedef struct {
 	int     permit_empty_passwd;	/* If false, do not permit empty
 					 * passwords. */
 	int     permit_user_env;	/* If true, read ~/.ssh/environment */
+	char   *permit_user_env_whitelist; /* pattern-list whitelist */
 	int     compression;	/* If true, compression is allowed */
 	int	allow_tcp_forwarding; /* One of FORWARD_* */
 	int	allow_streamlocal_forwarding; /* One of FORWARD_* */
@@ -240,6 +241,7 @@ struct connection_info {
 		M_CP_STROPT(hostbased_key_types); \
 		M_CP_STROPT(pubkey_key_types); \
 		M_CP_STROPT(routing_domain); \
+		M_CP_STROPT(permit_user_env_whitelist); \
 		M_CP_STRARRAYOPT(authorized_keys_files, num_authkeys_files); \
 		M_CP_STRARRAYOPT(allow_users, num_allow_users); \
 		M_CP_STRARRAYOPT(deny_users, num_deny_users); \
diff --git a/usr.bin/ssh/session.c b/usr.bin/ssh/session.c
index d245368dbea..6fb5b43d8ba 100644
--- a/usr.bin/ssh/session.c
+++ b/usr.bin/ssh/session.c
@@ -1,4 +1,4 @@
-/* $OpenBSD: session.c,v 1.300 2018/06/09 03:03:10 djm Exp $ */
+/* $OpenBSD: session.c,v 1.301 2018/07/03 10:59:35 djm Exp $ */
 /*
  * Copyright (c) 1995 Tatu Ylonen <ylo@cs.hut.fi>, Espoo, Finland
  *                    All rights reserved
@@ -778,10 +778,12 @@ check_quietlogin(Session *s, const char *command)
  * into the environment.  If the file does not exist, this does nothing.
  * Otherwise, it must consist of empty lines, comments (line starts with '#')
  * and assignments of the form name=value.  No other forms are allowed.
+ * If whitelist is not NULL, then it is interpreted as a pattern list and
+ * only variable names that match it will be accepted.
  */
 static void
 read_environment_file(char ***env, u_int *envsize,
-	const char *filename)
+	const char *filename, const char *whitelist)
 {
 	FILE *f;
 	char *line = NULL, *cp, *value;
@@ -814,6 +816,9 @@ read_environment_file(char ***env, u_int *envsize,
 		 */
 		*value = '\0';
 		value++;
+		if (whitelist != NULL &&
+		    match_pattern_list(cp, whitelist, 0) != 1)
+			continue;
 		child_set_env(env, envsize, cp, value);
 	}
 	free(line);
@@ -882,7 +887,12 @@ do_setup_env(struct ssh *ssh, Session *s, const char *shell)
 			cp = strchr(ocp, '=');
 			if (*cp == '=') {
 				*cp = '\0';
-				child_set_env(&env, &envsize, ocp, cp + 1);
+				/* Apply PermitUserEnvironment whitelist */
+				if (options.permit_user_env_whitelist == NULL ||
+				    match_pattern_list(ocp,
+				    options.permit_user_env_whitelist, 0) == 1)
+					child_set_env(&env, &envsize,
+					    ocp, cp + 1);
 			}
 			free(ocp);
 		}
@@ -892,7 +902,8 @@ do_setup_env(struct ssh *ssh, Session *s, const char *shell)
 	if (options.permit_user_env) {
 		snprintf(buf, sizeof buf, "%.200s/.ssh/environment",
 		    pw->pw_dir);
-		read_environment_file(&env, &envsize, buf);
+		read_environment_file(&env, &envsize, buf,
+		    options.permit_user_env_whitelist);
 	}
 
 	/* Environment specified by admin */
diff --git a/usr.bin/ssh/sshd_config.5 b/usr.bin/ssh/sshd_config.5
index 994f241cfcf..4b5cd188179 100644
--- a/usr.bin/ssh/sshd_config.5
+++ b/usr.bin/ssh/sshd_config.5
@@ -33,8 +33,8 @@
 .\" (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
 .\" THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 .\"
-.\" $OpenBSD: sshd_config.5,v 1.277 2018/06/19 05:36:57 jmc Exp $
-.Dd $Mdocdate: June 19 2018 $
+.\" $OpenBSD: sshd_config.5,v 1.278 2018/07/03 10:59:35 djm Exp $
+.Dd $Mdocdate: July 3 2018 $
 .Dt SSHD_CONFIG 5
 .Os
 .Sh NAME
@@ -1333,6 +1333,12 @@ options in
 .Pa ~/.ssh/authorized_keys
 are processed by
 .Xr sshd 8 .
+Valid options are
+.Cm yes ,
+.Cm no
+or a pattern-list specifying which environment variable names to accept
+(for example
+.Qq LANG,LC_* ) .
 The default is
 .Cm no .
 Enabling environment processing may enable users to bypass access