upstream: implement loading resident keys in ssh-add

"ssh-add -O" will load resident keys from a FIDO2 token and add them
to a ssh-agent.

feedback and ok markus@

OpenBSD-Commit-ID: 608104ae957a7d65cb84e0a3a26c8f60e0df3290

1 files changed, 63 insertions, 5 deletions

diff --git a/ssh-add.c b/ssh-add.c
index 1d85e9d60..c25b57cc1 100644
--- a/ssh-add.c
+++ b/ssh-add.c
@@ -1,4 +1,4 @@
-/* $OpenBSD: ssh-add.c,v 1.147 2019/11/25 00:51:37 djm Exp $ */
+/* $OpenBSD: ssh-add.c,v 1.148 2019/12/30 09:22:49 djm Exp $ */
 /*
  * Author: Tatu Ylonen <ylo@cs.hut.fi>
  * Copyright (c) 1995 Tatu Ylonen <ylo@cs.hut.fi>, Espoo, Finland
@@ -66,6 +66,7 @@
 #include "misc.h"
 #include "ssherr.h"
 #include "digest.h"
+#include "ssh-sk.h"
 
 /* argv0 */
 extern char *__progname;
@@ -540,6 +541,54 @@ lock_agent(int agent_fd, int lock)
 }
 
 static int
+load_resident_keys(int agent_fd, const char *skprovider, int qflag)
+{
+        struct sshkey **keys;
+        size_t nkeys, i;
+        int r, ok = 0;
+        char *fp;
+
+        pass = read_passphrase("Enter PIN for security key: ", RP_ALLOW_STDIN);
+        if ((r = sshsk_load_resident(skprovider, pass, &keys, &nkeys)) != 0) {
+                error("Unable to load resident keys: %s", ssh_err(r));
+                return r;
+        }
+        for (i = 0; i < nkeys; i++) {
+                if ((fp = sshkey_fingerprint(keys[i],
+                    fingerprint_hash, SSH_FP_DEFAULT)) == NULL)
+                        fatal("%s: sshkey_fingerprint failed", __func__);
+                if ((r = ssh_add_identity_constrained(agent_fd, keys[i], "",
+                    lifetime, confirm, maxsign, skprovider)) != 0) {
+                        error("Unable to add key %s %s",
+                            sshkey_type(keys[i]), fp);
+                        free(fp);
+                        ok = r;
+                        continue;
+                }
+                if (ok == 0)
+                        ok = 1;
+                if (!qflag) {
+                        fprintf(stderr, "Resident identity added: %s %s\n",
+                            sshkey_type(keys[i]), fp);
+                        if (lifetime != 0) {
+                                fprintf(stderr,
+                                    "Lifetime set to %d seconds\n", lifetime);
+                        }
+                        if (confirm != 0) {
+                                fprintf(stderr, "The user must confirm "
+                                    "each use of the key\n");
+                        }
+                }
+                free(fp);
+                sshkey_free(keys[i]);
+        }
+        free(keys);
+        if (nkeys == 0)
+                return SSH_ERR_KEY_NOT_FOUND;
+        return ok == 1 ? 0 : ok;
+}
+
+static int
 do_file(int agent_fd, int deleting, int key_only, char *file, int qflag,
     const char *skprovider)
 {
@@ -585,7 +634,7 @@ main(int argc, char **argv)
         extern int optind;
         int agent_fd;
         char *pkcs11provider = NULL, *skprovider = NULL;
-        int r, i, ch, deleting = 0, ret = 0, key_only = 0;
+        int r, i, ch, deleting = 0, ret = 0, key_only = 0, do_download = 0;
         int xflag = 0, lflag = 0, Dflag = 0, qflag = 0, Tflag = 0;
         SyslogFacility log_facility = SYSLOG_FACILITY_AUTH;
         LogLevel log_level = SYSLOG_LEVEL_INFO;
@@ -615,7 +664,7 @@ main(int argc, char **argv)
 
         skprovider = getenv("SSH_SK_PROVIDER");
 
-        while ((ch = getopt(argc, argv, "vklLcdDTxXE:e:M:m:qs:S:t:")) != -1) {
+        while ((ch = getopt(argc, argv, "vklLcdDTxXE:e:M:m:Oqs:S:t:")) != -1) {
                 switch (ch) {
                 case 'v':
                         if (log_level == SYSLOG_LEVEL_INFO)
@@ -637,6 +686,9 @@ main(int argc, char **argv)
                                 fatal("-%c flag already specified", lflag);
                         lflag = ch;
                         break;
+                case 'O':
+                        do_download = 1;
+                        break;
                 case 'x':
                 case 'X':
                         if (xflag != 0)
@@ -736,6 +788,13 @@ main(int argc, char **argv)
                         ret = 1;
                 goto done;
         }
+        if (do_download) {
+                if (skprovider == NULL)
+                        fatal("Cannot download keys without provider");
+                if (load_resident_keys(agent_fd, skprovider, qflag) != 0)
+                        ret = 1;
+                goto done;
+        }
         if (argc == 0) {
                 char buf[PATH_MAX];
                 struct passwd *pw;
@@ -769,9 +828,8 @@ main(int argc, char **argv)
                                 ret = 1;
                 }
         }
-        clear_pass();
-
 done:
+        clear_pass();
         ssh_close_authentication_socket(agent_fd);
         return ret;
 }