upstream: let ssh_config(5)'s AddKeysToAgent keyword accept a time

limit for keys in addition to its current flag options. Time-limited keys
will automatically be removed from ssh-agent after their expiry time has
passed; ok markus@

OpenBSD-Commit-ID: 792e71cacbbc25faab5424cf80bee4a006119f94

4 files changed, 89 insertions, 27 deletions

diff --git a/readconf.c b/readconf.c
index a810736a4..94b67e1c6 100644
--- a/readconf.c
+++ b/readconf.c
@@ -1,4 +1,4 @@
-/* $OpenBSD: readconf.c,v 1.333 2020/07/17 07:09:24 dtucker Exp $ */
+/* $OpenBSD: readconf.c,v 1.334 2020/08/11 09:49:57 djm Exp $ */
 /*
  * Author: Tatu Ylonen <ylo@cs.hut.fi>
  * Copyright (c) 1995 Tatu Ylonen <ylo@cs.hut.fi>, Espoo, Finland
@@ -877,6 +877,21 @@ static const struct multistate multistate_compression[] = {
         { NULL, -1 }
 };
 
+static int
+parse_multistate_value(const char *arg, const char *filename, int linenum,
+    const struct multistate *multistate_ptr)
+{
+        int i;
+
+        if (!arg || *arg == '\0')
+                fatal("%s line %d: missing argument.", filename, linenum);
+        for (i = 0; multistate_ptr[i].key != NULL; i++) {
+                if (strcasecmp(arg, multistate_ptr[i].key) == 0)
+                        return multistate_ptr[i].value;
+        }
+        return -1;
+}
+
 /*
  * Processes a single option line as used in the configuration files. This
  * only sets those values that have not already been set.
@@ -1000,19 +1015,11 @@ parse_time:
                 multistate_ptr = multistate_flag;
  parse_multistate:
                 arg = strdelim(&s);
-                if (!arg || *arg == '\0')
-                        fatal("%s line %d: missing argument.",
-                            filename, linenum);
-                value = -1;
-                for (i = 0; multistate_ptr[i].key != NULL; i++) {
-                        if (strcasecmp(arg, multistate_ptr[i].key) == 0) {
-                                value = multistate_ptr[i].value;
-                                break;
-                        }
-                }
-                if (value == -1)
+                if ((value = parse_multistate_value(arg, filename, linenum,
+                     multistate_ptr)) == -1) {
                         fatal("%s line %d: unsupported option \"%s\".",
                             filename, linenum, arg);
+                }
                 if (*activep && *intptr == -1)
                         *intptr = value;
                 break;
@@ -1800,9 +1807,42 @@ parse_keytypes:
                 goto parse_keytypes;
 
         case oAddKeysToAgent:
-                intptr = &options->add_keys_to_agent;
-                multistate_ptr = multistate_yesnoaskconfirm;
-                goto parse_multistate;
+                arg = strdelim(&s);
+                arg2 = strdelim(&s);
+                value = parse_multistate_value(arg, filename, linenum,
+                     multistate_yesnoaskconfirm);
+                value2 = 0; /* unlimited lifespan by default */
+                if (value == 3 && arg2 != NULL) {
+                        /* allow "AddKeysToAgent confirm 5m" */
+                        if ((value2 = convtime(arg2)) == -1 || value2 > INT_MAX)
+                                fatal("%s line %d: invalid time value.",
+                                    filename, linenum);
+                } else if (value == -1 && arg2 == NULL) {
+                        if ((value2 = convtime(arg)) == -1 || value2 > INT_MAX)
+                                fatal("%s line %d: unsupported option",
+                                    filename, linenum);
+                        value = 1; /* yes */
+                } else if (value == -1 || arg2 != NULL) {
+                        fatal("%s line %d: unsupported option",
+                            filename, linenum);
+                }
+                if (*activep && options->add_keys_to_agent == -1) {
+                        options->add_keys_to_agent = value;
+                        options->add_keys_to_agent_lifespan = value2;
+                }
+                break;
+
+                arg = strdelim(&s);
+                if (!arg || *arg == '\0')
+                        fatal("%s line %d: missing time value.",
+                            filename, linenum);
+                if (strcmp(arg, "none") == 0)
+                        value = -1;
+                else if ((value = convtime(arg)) == -1 || value > INT_MAX)
+                        fatal("%s line %d: invalid time value.",
+                            filename, linenum);
+                if (*activep && *intptr == -1)
+                        *intptr = value;
 
         case oIdentityAgent:
                 charptr = &options->identity_agent;
@@ -2016,6 +2056,7 @@ initialize_options(Options * options)
         options->permit_local_command = -1;
         options->remote_command = NULL;
         options->add_keys_to_agent = -1;
+        options->add_keys_to_agent_lifespan = -1;
         options->identity_agent = NULL;
         options->visual_host_key = -1;
         options->ip_qos_interactive = -1;
@@ -2123,8 +2164,10 @@ fill_default_options(Options * options)
         if (options->number_of_password_prompts == -1)
                 options->number_of_password_prompts = 3;
         /* options->hostkeyalgorithms, default set in myproposals.h */
-        if (options->add_keys_to_agent == -1)
+        if (options->add_keys_to_agent == -1) {
                 options->add_keys_to_agent = 0;
+                options->add_keys_to_agent_lifespan = 0;
+        }
         if (options->num_identity_files == 0) {
                 add_identity_file(options, "~/", _PATH_SSH_CLIENT_ID_RSA, 0);
                 add_identity_file(options, "~/", _PATH_SSH_CLIENT_ID_DSA, 0);
@@ -2728,7 +2771,6 @@ dump_client_config(Options *o, const char *host)
         dump_cfg_int(oPort, o->port);
 
         /* Flag options */
-        dump_cfg_fmtint(oAddKeysToAgent, o->add_keys_to_agent);
         dump_cfg_fmtint(oAddressFamily, o->address_family);
         dump_cfg_fmtint(oBatchMode, o->batch_mode);
         dump_cfg_fmtint(oCanonicalizeFallbackLocal, o->canonicalize_fallback_local);
@@ -2816,6 +2858,15 @@ dump_client_config(Options *o, const char *host)
 
         /* Special cases */
 
+        /* AddKeysToAgent */
+        if (o->add_keys_to_agent_lifespan <= 0)
+                dump_cfg_fmtint(oAddKeysToAgent, o->add_keys_to_agent);
+        else {
+                printf("addkeystoagent%s %d\n",
+                    o->add_keys_to_agent == 3 ? " confirm" : "",
+                    o->add_keys_to_agent_lifespan);
+        }
+
         /* oForwardAgent */
         if (o->forward_agent_sock_path == NULL)
                 dump_cfg_fmtint(oForwardAgent, o->forward_agent);
diff --git a/readconf.h b/readconf.h
index e143a1082..d6a15550d 100644
--- a/readconf.h
+++ b/readconf.h
@@ -1,4 +1,4 @@
-/* $OpenBSD: readconf.h,v 1.133 2020/04/03 02:27:12 dtucker Exp $ */
+/* $OpenBSD: readconf.h,v 1.134 2020/08/11 09:49:57 djm Exp $ */
 
 /*
  * Author: Tatu Ylonen <ylo@cs.hut.fi>
@@ -97,6 +97,7 @@ typedef struct {
         struct sshkey *certificates[SSH_MAX_CERTIFICATE_FILES];
 
         int     add_keys_to_agent;
+        int     add_keys_to_agent_lifespan;
         char   *identity_agent;         /* Optional path to ssh-agent socket */
 
         /* Local TCP/IP forward requests. */
diff --git a/ssh_config.5 b/ssh_config.5
index 2b635410f..6be1f1aa2 100644
--- a/ssh_config.5
+++ b/ssh_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: ssh_config.5,v 1.331 2020/07/17 05:59:05 jmc Exp $
-.Dd $Mdocdate: July 17 2020 $
+.\" $OpenBSD: ssh_config.5,v 1.332 2020/08/11 09:49:57 djm Exp $
+.Dd $Mdocdate: August 11 2020 $
 .Dt SSH_CONFIG 5
 .Os
 .Sh NAME
@@ -245,13 +245,22 @@ option was specified to
 If this option is set to
 .Cm no ,
 no keys are added to the agent.
+Alternately, this option may be specified as a time interval
+using the format described in the
+.Sx TIME FORMATS
+section of
+.Xr sshd_config 5
+to specify the key's lifetime in
+.Xr ssh-agent 1 ,
+after which it will automatically be removed.
 The argument must be
-.Cm yes ,
-.Cm confirm ,
-.Cm ask ,
-or
 .Cm no
-(the default).
+(the default),
+.Cm yes ,
+.Cm confirm
+(optionally followed by a time interval),
+.Cm ask
+or a time interval.
 .It Cm AddressFamily
 Specifies which address family to use when connecting.
 Valid arguments are
diff --git a/sshconnect.c b/sshconnect.c
index f6d8a1bcf..63a97d039 100644
--- a/sshconnect.c
+++ b/sshconnect.c
@@ -1,4 +1,4 @@
-/* $OpenBSD: sshconnect.c,v 1.330 2020/07/17 03:43:42 dtucker Exp $ */
+/* $OpenBSD: sshconnect.c,v 1.331 2020/08/11 09:49:57 djm Exp $ */
 /*
  * Author: Tatu Ylonen <ylo@cs.hut.fi>
  * Copyright (c) 1995 Tatu Ylonen <ylo@cs.hut.fi>, Espoo, Finland
@@ -1433,7 +1433,8 @@ maybe_add_key_to_agent(const char *authfile, struct sshkey *private,
         if (sshkey_is_sk(private))
                 skprovider = options.sk_provider;
         if ((r = ssh_add_identity_constrained(auth_sock, private,
-            comment == NULL ? authfile : comment, 0,
+            comment == NULL ? authfile : comment,
+            options.add_keys_to_agent_lifespan,
             (options.add_keys_to_agent == 3), 0, skprovider)) == 0)
                 debug("identity added to agent: %s", authfile);
         else