2 * Copyright (c) 2003 Networks Associates Technology, Inc.
3 * Copyright (c) 2004-2011 Dag-Erling Smørgrav
6 * This software was developed for the FreeBSD Project by ThinkSec AS and
7 * NAI Labs, the Security Research Division of Network Associates, Inc.
8 * under DARPA/SPAWAR contract N66001-01-C-8035 ("CBOSS"), as part of the
9 * DARPA CHATS research program.
11 * Redistribution and use in source and binary forms, with or without
12 * modification, are permitted provided that the following conditions
14 * 1. Redistributions of source code must retain the above copyright
15 * notice, this list of conditions and the following disclaimer.
16 * 2. Redistributions in binary form must reproduce the above copyright
17 * notice, this list of conditions and the following disclaimer in the
18 * documentation and/or other materials provided with the distribution.
19 * 3. The name of the author may not be used to endorse or promote
20 * products derived from this software without specific prior written
23 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
24 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
25 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
26 * ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
27 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
28 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
29 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
30 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
31 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
32 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
36 #include <sys/cdefs.h>
37 __FBSDID("$FreeBSD$");
39 #include <sys/param.h>
52 #define PAM_SM_SESSION
54 #include <security/pam_appl.h>
55 #include <security/pam_modules.h>
56 #include <security/openpam.h>
58 #include <openssl/evp.h>
65 #define ssh_add_identity(auth, key, comment) \
66 ssh_add_identity_constrained(auth, key, comment, 0, 0)
68 extern char **environ;
75 static const char *pam_ssh_prompt = "SSH passphrase: ";
76 static const char *pam_ssh_have_keys = "pam_ssh_have_keys";
78 static const char *pam_ssh_keyfiles[] = {
79 ".ssh/identity", /* SSH1 RSA key */
80 ".ssh/id_rsa", /* SSH2 RSA key */
81 ".ssh/id_dsa", /* SSH2 DSA key */
82 ".ssh/id_ecdsa", /* SSH2 ECDSA key */
86 static const char *pam_ssh_agent = "/usr/bin/ssh-agent";
87 static char *const pam_ssh_agent_argv[] = { "ssh_agent", "-s", NULL };
88 static char *const pam_ssh_agent_envp[] = { NULL };
91 * Attempts to load a private key from the specified file in the specified
92 * directory, using the specified passphrase. If successful, returns a
93 * struct pam_ssh_key containing the key and its comment.
95 static struct pam_ssh_key *
96 pam_ssh_load_key(const char *dir, const char *kfn, const char *passphrase,
99 struct pam_ssh_key *psk;
104 if (snprintf(fn, sizeof(fn), "%s/%s", dir, kfn) > (int)sizeof(fn))
108 * If the key is unencrypted, OpenSSL ignores the passphrase, so
109 * it will seem like the user typed in the right one. This allows
110 * a user to circumvent nullok by providing a dummy passphrase.
111 * Verify that the key really *is* encrypted by trying to load it
112 * with an empty passphrase, and if the key is not encrypted,
113 * accept only an empty passphrase.
115 key = key_load_private(fn, "", &comment);
116 if (key != NULL && !(*passphrase == '\0' && nullok)) {
121 key = key_load_private(fn, passphrase, &comment);
123 openpam_log(PAM_LOG_DEBUG, "failed to load key from %s", fn);
127 openpam_log(PAM_LOG_DEBUG, "loaded '%s' from %s", comment, fn);
128 if ((psk = malloc(sizeof(*psk))) == NULL) {
134 psk->comment = comment;
139 * Wipes a private key and frees the associated resources.
142 pam_ssh_free_key(pam_handle_t *pamh __unused,
143 void *data, int pam_err __unused)
145 struct pam_ssh_key *psk;
154 pam_sm_authenticate(pam_handle_t *pamh, int flags __unused,
155 int argc __unused, const char *argv[] __unused)
157 const char **kfn, *passphrase, *user;
160 struct pam_ssh_key *psk;
161 int nkeys, nullok, pam_err, pass;
163 nullok = (openpam_get_option(pamh, "nullok") != NULL);
165 /* PEM is not loaded by default */
166 OpenSSL_add_all_algorithms();
168 /* get user name and home directory */
169 pam_err = pam_get_user(pamh, &user, NULL);
170 if (pam_err != PAM_SUCCESS)
172 pwd = getpwnam(user);
174 return (PAM_USER_UNKNOWN);
175 if (pwd->pw_dir == NULL)
176 return (PAM_AUTH_ERR);
179 pass = (pam_get_item(pamh, PAM_AUTHTOK, &item) == PAM_SUCCESS &&
183 pam_err = pam_get_authtok(pamh, PAM_AUTHTOK,
184 &passphrase, pam_ssh_prompt);
185 if (pam_err != PAM_SUCCESS)
188 /* switch to user credentials */
189 pam_err = openpam_borrow_cred(pamh, pwd);
190 if (pam_err != PAM_SUCCESS)
193 /* try to load keys from all keyfiles we know of */
194 for (kfn = pam_ssh_keyfiles; *kfn != NULL; ++kfn) {
195 psk = pam_ssh_load_key(pwd->pw_dir, *kfn, passphrase, nullok);
197 pam_set_data(pamh, *kfn, psk, pam_ssh_free_key);
202 /* switch back to arbitrator credentials */
203 openpam_restore_cred(pamh);
206 * If we tried an old token and didn't get anything, and
207 * try_first_pass was specified, try again after prompting the
208 * user for a new passphrase.
210 if (nkeys == 0 && pass == 1 &&
211 openpam_get_option(pamh, "try_first_pass") != NULL) {
212 pam_set_item(pamh, PAM_AUTHTOK, NULL);
219 return (PAM_AUTH_ERR);
221 pam_set_data(pamh, pam_ssh_have_keys, NULL, NULL);
222 return (PAM_SUCCESS);
226 pam_sm_setcred(pam_handle_t *pamh __unused, int flags __unused,
227 int argc __unused, const char *argv[] __unused)
230 return (PAM_SUCCESS);
234 * Parses a line from ssh-agent's output.
237 pam_ssh_process_agent_output(pam_handle_t *pamh, FILE *f)
239 char *line, *p, *key, *val;
242 while ((line = fgetln(f, &len)) != NULL) {
243 if (len < 4 || strncmp(line, "SSH_", 4) != 0)
246 /* find equal sign at end of key */
247 for (p = key = line; p < line + len; ++p)
250 if (p == line + len || *p != '=')
254 /* find semicolon at end of value */
255 for (val = ++p; p < line + len; ++p)
258 if (p == line + len || *p != ';')
262 /* store key-value pair in environment */
263 openpam_log(PAM_LOG_DEBUG, "got %s: %s", key, val);
264 pam_setenv(pamh, key, val, 1);
269 * Starts an ssh agent and stores the environment variables derived from
273 pam_ssh_start_agent(pam_handle_t *pamh)
279 /* get a pipe which we will use to read the agent's output */
280 if (pipe(agent_pipe) == -1)
281 return (PAM_SYSTEM_ERR);
283 /* start the agent */
284 openpam_log(PAM_LOG_DEBUG, "starting an ssh agent");
286 if (pid == (pid_t)-1) {
288 close(agent_pipe[0]);
289 close(agent_pipe[1]);
290 return (PAM_SYSTEM_ERR);
295 /* child: drop privs, close fds and start agent */
299 open(_PATH_DEVNULL, O_RDONLY);
300 dup2(agent_pipe[1], STDOUT_FILENO);
301 dup2(agent_pipe[1], STDERR_FILENO);
302 for (fd = 3; fd < getdtablesize(); ++fd)
304 execve(pam_ssh_agent, pam_ssh_agent_argv, pam_ssh_agent_envp);
309 close(agent_pipe[1]);
310 if ((f = fdopen(agent_pipe[0], "r")) == NULL)
311 return (PAM_SYSTEM_ERR);
312 pam_ssh_process_agent_output(pamh, f);
315 return (PAM_SUCCESS);
319 * Adds previously stored keys to a running agent.
322 pam_ssh_add_keys_to_agent(pam_handle_t *pamh)
324 AuthenticationConnection *ac;
325 const struct pam_ssh_key *psk;
328 char **envlist, **env;
331 /* switch to PAM environment */
333 if ((environ = pam_getenvlist(pamh)) == NULL) {
335 return (PAM_SYSTEM_ERR);
338 /* get a connection to the agent */
339 if ((ac = ssh_get_authentication_connection()) == NULL) {
340 openpam_log(PAM_LOG_DEBUG, "failed to connect to the agent");
341 pam_err = PAM_SYSTEM_ERR;
345 /* look for keys to add to it */
346 for (kfn = pam_ssh_keyfiles; *kfn != NULL; ++kfn) {
347 pam_err = pam_get_data(pamh, *kfn, &item);
348 if (pam_err == PAM_SUCCESS && item != NULL) {
350 if (ssh_add_identity(ac, psk->key, psk->comment))
351 openpam_log(PAM_LOG_DEBUG,
352 "added %s to ssh agent", psk->comment);
354 openpam_log(PAM_LOG_DEBUG, "failed "
355 "to add %s to ssh agent", psk->comment);
356 /* we won't need the key again, so wipe it */
357 pam_set_data(pamh, *kfn, NULL, NULL);
360 pam_err = PAM_SUCCESS;
362 /* disconnect from agent */
364 ssh_close_authentication_connection(ac);
366 /* switch back to original environment */
367 for (env = environ; *env != NULL; ++env)
376 pam_sm_open_session(pam_handle_t *pamh, int flags __unused,
377 int argc __unused, const char *argv[] __unused)
384 /* no keys, no work */
385 if (pam_get_data(pamh, pam_ssh_have_keys, &data) != PAM_SUCCESS &&
386 openpam_get_option(pamh, "want_agent") == NULL)
387 return (PAM_SUCCESS);
389 /* switch to user credentials */
390 pam_err = pam_get_user(pamh, &user, NULL);
391 if (pam_err != PAM_SUCCESS)
393 pwd = getpwnam(user);
395 return (PAM_USER_UNKNOWN);
396 pam_err = openpam_borrow_cred(pamh, pwd);
397 if (pam_err != PAM_SUCCESS)
400 /* start the agent */
401 pam_err = pam_ssh_start_agent(pamh);
402 if (pam_err != PAM_SUCCESS) {
403 openpam_restore_cred(pamh);
407 /* we have an agent, see if we can add any keys to it */
408 pam_err = pam_ssh_add_keys_to_agent(pamh);
409 if (pam_err != PAM_SUCCESS) {
410 /* XXX ignore failures */
413 openpam_restore_cred(pamh);
414 return (PAM_SUCCESS);
418 pam_sm_close_session(pam_handle_t *pamh, int flags __unused,
419 int argc __unused, const char *argv[] __unused)
421 const char *ssh_agent_pid;
426 if ((ssh_agent_pid = pam_getenv(pamh, "SSH_AGENT_PID")) == NULL) {
427 openpam_log(PAM_LOG_DEBUG, "no ssh agent");
428 return (PAM_SUCCESS);
430 pid = (pid_t)strtol(ssh_agent_pid, &end, 10);
431 if (*ssh_agent_pid == '\0' || *end != '\0') {
432 openpam_log(PAM_LOG_DEBUG, "invalid ssh agent pid");
433 return (PAM_SESSION_ERR);
435 openpam_log(PAM_LOG_DEBUG, "killing ssh agent %d", (int)pid);
436 if (kill(pid, SIGTERM) == -1 ||
437 (waitpid(pid, &status, 0) == -1 && errno != ECHILD))
438 return (PAM_SYSTEM_ERR);
439 return (PAM_SUCCESS);
442 PAM_MODULE_ENTRY("pam_ssh");