From 176eca147b5f7d9ae650c7deec9dc67010c89882 Mon Sep 17 00:00:00 2001
From: djm <djm@openbsd.org>
Date: Wed, 6 Sep 2023 23:35:35 +0000
Subject: [PATCH] allow override of Sybsystem directives in sshd Match blocks

---
 usr.bin/ssh/servconf.c | 48 ++++++++++++++++++++++++++++++++++++++++--
 usr.bin/ssh/servconf.h | 14 ++++++------
 2 files changed, 54 insertions(+), 8 deletions(-)

diff --git a/usr.bin/ssh/servconf.c b/usr.bin/ssh/servconf.c
index f0d091097fd..fea3bdfbe9d 100644
--- a/usr.bin/ssh/servconf.c
+++ b/usr.bin/ssh/servconf.c
@@ -1,4 +1,4 @@
-/* $OpenBSD: servconf.c,v 1.400 2023/09/06 23:26:37 djm Exp $ */
+/* $OpenBSD: servconf.c,v 1.401 2023/09/06 23:35:35 djm Exp $ */
 /*
  * Copyright (c) 1995 Tatu Ylonen <ylo@cs.hut.fi>, Espoo, Finland
  *                    All rights reserved
@@ -599,7 +599,7 @@ static struct {
 	{ "macs", sMacs, SSHCFG_GLOBAL },
 	{ "protocol", sIgnore, SSHCFG_GLOBAL },
 	{ "gatewayports", sGatewayPorts, SSHCFG_ALL },
-	{ "subsystem", sSubsystem, SSHCFG_GLOBAL },
+	{ "subsystem", sSubsystem, SSHCFG_ALL },
 	{ "maxstartups", sMaxStartups, SSHCFG_GLOBAL },
 	{ "persourcemaxstartups", sPerSourceMaxStartups, SSHCFG_GLOBAL },
 	{ "persourcenetblocksize", sPerSourceNetBlockSize, SSHCFG_GLOBAL },
@@ -2633,6 +2633,47 @@ int parse_server_match_testspec(struct connection_info *ci, char *spec)
 	return 0;
 }
 
+void
+servconf_merge_subsystems(ServerOptions *dst, ServerOptions *src)
+{
+	u_int i, j, found;
+
+	for (i = 0; i < src->num_subsystems; i++) {
+		found = 0;
+		for (j = 0; j < dst->num_subsystems; j++) {
+			if (strcmp(src->subsystem_name[i],
+			    dst->subsystem_name[j]) == 0) {
+				found = 1;
+				break;
+			}
+		}
+		if (found) {
+			debug_f("override \"%s\"", dst->subsystem_name[j]);
+			free(dst->subsystem_command[j]);
+			free(dst->subsystem_args[j]);
+			dst->subsystem_command[j] =
+			    xstrdup(src->subsystem_command[i]);
+			dst->subsystem_args[j] =
+			    xstrdup(src->subsystem_args[i]);
+			continue;
+		}
+		debug_f("add \"%s\"", src->subsystem_name[i]);
+		dst->subsystem_name = xrecallocarray(
+		    dst->subsystem_name, dst->num_subsystems,
+		    dst->num_subsystems + 1, sizeof(dst->subsystem_name));
+		dst->subsystem_command = xrecallocarray(
+		    dst->subsystem_command, dst->num_subsystems,
+		    dst->num_subsystems + 1, sizeof(dst->subsystem_command));
+		dst->subsystem_args = xrecallocarray(
+		    dst->subsystem_args, dst->num_subsystems,
+		    dst->num_subsystems + 1, sizeof(dst->subsystem_args));
+		j = dst->num_subsystems++;
+		dst->subsystem_name[j] = xstrdup(src->subsystem_name[i]);
+		dst->subsystem_command[j] = xstrdup(src->subsystem_command[i]);
+		dst->subsystem_args[j] = xstrdup(src->subsystem_args[i]);
+	}
+}
+
 /*
  * Copy any supported values that are set.
  *
@@ -2739,6 +2780,9 @@ copy_set_server_options(ServerOptions *dst, ServerOptions *src, int preauth)
 		free(dst->chroot_directory);
 		dst->chroot_directory = NULL;
 	}
+
+	/* Subsystems require merging. */
+	servconf_merge_subsystems(dst, src);
 }
 
 #undef M_CP_INTOPT
diff --git a/usr.bin/ssh/servconf.h b/usr.bin/ssh/servconf.h
index 1a2411e1b39..bff6f268691 100644
--- a/usr.bin/ssh/servconf.h
+++ b/usr.bin/ssh/servconf.h
@@ -1,4 +1,4 @@
-/* $OpenBSD: servconf.h,v 1.159 2023/01/17 09:44:48 djm Exp $ */
+/* $OpenBSD: servconf.h,v 1.160 2023/09/06 23:35:35 djm Exp $ */
 
 /*
  * Author: Tatu Ylonen <ylo@cs.hut.fi>
@@ -20,8 +20,6 @@
 
 #define MAX_PORTS		256	/* Max # ports. */
 
-#define MAX_SUBSYSTEMS		256	/* Max # subsystems. */
-
 /* permit_root_login */
 #define	PERMIT_NOT_SET		-1
 #define	PERMIT_NO		0
@@ -165,9 +163,9 @@ typedef struct {
 	char   **deny_groups;
 
 	u_int num_subsystems;
-	char   *subsystem_name[MAX_SUBSYSTEMS];
-	char   *subsystem_command[MAX_SUBSYSTEMS];
-	char   *subsystem_args[MAX_SUBSYSTEMS];
+	char   **subsystem_name;
+	char   **subsystem_command;
+	char   **subsystem_args;
 
 	u_int num_accept_env;
 	char   **accept_env;
@@ -292,6 +290,9 @@ TAILQ_HEAD(include_list, include_item);
 		M_CP_STRARRAYOPT(permitted_listens, num_permitted_listens); \
 		M_CP_STRARRAYOPT(channel_timeouts, num_channel_timeouts); \
 		M_CP_STRARRAYOPT(log_verbose, num_log_verbose); \
+		M_CP_STRARRAYOPT(subsystem_name, num_subsystems); \
+		M_CP_STRARRAYOPT(subsystem_command, num_subsystems); \
+		M_CP_STRARRAYOPT(subsystem_args, num_subsystems); \
 	} while (0)
 
 struct connection_info *get_connection_info(struct ssh *, int, int);
@@ -308,6 +309,7 @@ void	 parse_server_match_config(ServerOptions *,
 	    struct include_list *includes, struct connection_info *);
 int	 parse_server_match_testspec(struct connection_info *, char *);
 int	 server_match_spec_complete(struct connection_info *);
+void	 servconf_merge_subsystems(ServerOptions *, ServerOptions *);
 void	 copy_set_server_options(ServerOptions *, ServerOptions *, int);
 void	 dump_config(ServerOptions *);
 char	*derelativise_path(const char *);
-- 
2.20.1