upstream commit

add a whitelist of paths from which ssh-agent will load
(via ssh-pkcs11-helper) a PKCS#11 module; ok markus@

Upstream-ID: fe79769469d9cd6d26fe0dc15751b83ef2a06e8f

2 files changed, 50 insertions, 10 deletions

diff --git a/ssh-agent.1 b/ssh-agent.1
index c4b50bbdf..372adbe7c 100644
--- a/ssh-agent.1
+++ b/ssh-agent.1
@@ -1,4 +1,4 @@
-.\" $OpenBSD: ssh-agent.1,v 1.62 2015/11/15 23:54:15 jmc Exp $
+.\" $OpenBSD: ssh-agent.1,v 1.63 2016/11/30 03:07:37 djm Exp $
 .\"
 .\" Author: Tatu Ylonen <ylo@cs.hut.fi>
 .\" Copyright (c) 1995 Tatu Ylonen <ylo@cs.hut.fi>, Espoo, Finland
@@ -34,7 +34,7 @@
 .\" (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
 .\" THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 .\"
-.Dd $Mdocdate: November 15 2015 $
+.Dd $Mdocdate: November 30 2016 $
 .Dt SSH-AGENT 1
 .Os
 .Sh NAME
@@ -47,6 +47,7 @@
 .Op Fl a Ar bind_address
 .Op Fl E Ar fingerprint_hash
 .Op Fl t Ar life
+.Op Fl P Ar pkcs11_whitelist
 .Op Ar command Op Ar arg ...
 .Nm ssh-agent
 .Op Fl c | s
@@ -121,6 +122,18 @@ The default is
 Kill the current agent (given by the
 .Ev SSH_AGENT_PID
 environment variable).
+.It Fl P
+Specify a pattern-list of acceptable paths for PKCS#11 shared libraries
+that may be added using the
+.Fl s
+option to
+.Xr ssh-add 1 .
+The default is to allow loading PKCS#11 libraries from
+.Dq /usr/lib/*,/usr/local/lib/* .
+PKCS#11 libraries that do not match the whitelist will be refused.
+See PATTERNS in
+.Xr ssh_config 5
+for a description of pattern-list syntax.
 .It Fl s
 Generate Bourne shell commands on
 .Dv stdout .
diff --git a/ssh-agent.c b/ssh-agent.c
index fd5f2b35d..395213553 100644
--- a/ssh-agent.c
+++ b/ssh-agent.c
@@ -1,4 +1,4 @@
-/* $OpenBSD: ssh-agent.c,v 1.214 2016/09/12 01:22:38 deraadt Exp $ */
+/* $OpenBSD: ssh-agent.c,v 1.215 2016/11/30 03:07:37 djm Exp $ */
 /*
  * Author: Tatu Ylonen <ylo@cs.hut.fi>
  * Copyright (c) 1995 Tatu Ylonen <ylo@cs.hut.fi>, Espoo, Finland
@@ -82,11 +82,16 @@
 #include "misc.h"
 #include "digest.h"
 #include "ssherr.h"
+#include "match.h"
 
 #ifdef ENABLE_PKCS11
 #include "ssh-pkcs11.h"
 #endif
 
+#ifndef DEFAULT_PKCS11_WHITELIST
+# define DEFAULT_PKCS11_WHITELIST "/usr/lib/*,/usr/local/lib/*"
+#endif
+
 typedef enum {
         AUTH_UNUSED,
         AUTH_SOCKET,
@@ -134,6 +139,9 @@ pid_t cleanup_pid = 0;
 char socket_name[PATH_MAX];
 char socket_dir[PATH_MAX];
 
+/* PKCS#11 path whitelist */
+static char *pkcs11_whitelist;
+
 /* locking */
 #define LOCK_SIZE       32
 #define LOCK_SALT_SIZE  16
@@ -737,7 +745,7 @@ no_identities(SocketEntry *e, u_int type)
 static void
 process_add_smartcard_key(SocketEntry *e)
 {
-        char *provider = NULL, *pin;
+        char *provider = NULL, *pin, canonical_provider[PATH_MAX];
         int r, i, version, count = 0, success = 0, confirm = 0;
         u_int seconds;
         time_t death = 0;
@@ -769,10 +777,21 @@ process_add_smartcard_key(SocketEntry *e)
                         goto send;
                 }
         }
+        if (realpath(provider, canonical_provider) == NULL) {
+                verbose("failed PKCS#11 add of \"%.100s\": realpath: %s",
+                    provider, strerror(errno));
+                goto send;
+        }
+        if (match_pattern_list(canonical_provider, pkcs11_whitelist, 0) != 1) {
+                verbose("refusing PKCS#11 add of \"%.100s\": "
+                    "provider not whitelisted", canonical_provider);
+                goto send;
+        }
+        debug("%s: add %.100s", __func__, canonical_provider);
         if (lifetime && !death)
                 death = monotime() + lifetime;
 
-        count = pkcs11_add_provider(provider, pin, &keys);
+        count = pkcs11_add_provider(canonical_provider, pin, &keys);
         for (i = 0; i < count; i++) {
                 k = keys[i];
                 version = k->type == KEY_RSA1 ? 1 : 2;
@@ -780,8 +799,8 @@ process_add_smartcard_key(SocketEntry *e)
                 if (lookup_identity(k, version) == NULL) {
                         id = xcalloc(1, sizeof(Identity));
                         id->key = k;
-                        id->provider = xstrdup(provider);
-                        id->comment = xstrdup(provider); /* XXX */
+                        id->provider = xstrdup(canonical_provider);
+                        id->comment = xstrdup(canonical_provider); /* XXX */
                         id->death = death;
                         id->confirm = confirm;
                         TAILQ_INSERT_TAIL(&tab->idlist, id, next);
@@ -1172,7 +1191,7 @@ usage(void)
 {
         fprintf(stderr,
             "usage: ssh-agent [-c | -s] [-Dd] [-a bind_address] [-E fingerprint_hash]\n"
-            "                 [-t life] [command [arg ...]]\n"
+            "                 [-P pkcs11_whitelist] [-t life] [command [arg ...]]\n"
             "       ssh-agent [-c | -s] -k\n");
         exit(1);
 }
@@ -1213,7 +1232,7 @@ main(int ac, char **av)
         __progname = ssh_get_progname(av[0]);
         seed_rng();
 
-        while ((ch = getopt(ac, av, "cDdksE:a:t:")) != -1) {
+        while ((ch = getopt(ac, av, "cDdksE:a:P:t:")) != -1) {
                 switch (ch) {
                 case 'E':
                         fingerprint_hash = ssh_digest_alg_by_name(optarg);
@@ -1228,6 +1247,11 @@ main(int ac, char **av)
                 case 'k':
                         k_flag++;
                         break;
+                case 'P':
+                        if (pkcs11_whitelist != NULL)
+                                fatal("-P option already specified");
+                        pkcs11_whitelist = xstrdup(optarg);
+                        break;
                 case 's':
                         if (c_flag)
                                 usage();
@@ -1262,6 +1286,9 @@ main(int ac, char **av)
         if (ac > 0 && (c_flag || k_flag || s_flag || d_flag || D_flag))
                 usage();
 
+        if (pkcs11_whitelist == NULL)
+                pkcs11_whitelist = xstrdup(DEFAULT_PKCS11_WHITELIST);
+
         if (ac == 0 && !c_flag && !s_flag) {
                 shell = getenv("SHELL");
                 if (shell != NULL && (len = strlen(shell)) > 2 &&
@@ -1409,7 +1436,7 @@ skip:
         signal(SIGTERM, cleanup_handler);
         nalloc = 0;
 
-        if (pledge("stdio cpath unix id proc exec", NULL) == -1)
+        if (pledge("stdio rpath cpath unix id proc exec", NULL) == -1)
                 fatal("%s: pledge: %s", __progname, strerror(errno));
         platform_pledge_agent();