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>
60 #define __bounded__(x, y, z)
66 #define ssh_add_identity(auth, key, comment) \
67 ssh_add_identity_constrained(auth, key, comment, 0, 0)
69 extern char **environ;
76 static const char *pam_ssh_prompt = "SSH passphrase: ";
77 static const char *pam_ssh_have_keys = "pam_ssh_have_keys";
79 static const char *pam_ssh_keyfiles[] = {
80 ".ssh/id_rsa", /* SSH2 RSA key */
81 ".ssh/id_dsa", /* SSH2 DSA key */
82 ".ssh/id_ecdsa", /* SSH2 ECDSA key */
83 ".ssh/id_ed25519", /* SSH2 Ed25519 key */
87 static const char *pam_ssh_agent = "/usr/bin/ssh-agent";
88 static char str_ssh_agent[] = "ssh-agent";
89 static char str_dash_s[] = "-s";
90 static char *const pam_ssh_agent_argv[] = { str_ssh_agent, str_dash_s, NULL };
91 static char *const pam_ssh_agent_envp[] = { NULL };
94 * Attempts to load a private key from the specified file in the specified
95 * directory, using the specified passphrase. If successful, returns a
96 * struct pam_ssh_key containing the key and its comment.
98 static struct pam_ssh_key *
99 pam_ssh_load_key(const char *dir, const char *kfn, const char *passphrase,
102 struct pam_ssh_key *psk;
107 if (snprintf(fn, sizeof(fn), "%s/%s", dir, kfn) > (int)sizeof(fn))
111 * If the key is unencrypted, OpenSSL ignores the passphrase, so
112 * it will seem like the user typed in the right one. This allows
113 * a user to circumvent nullok by providing a dummy passphrase.
114 * Verify that the key really *is* encrypted by trying to load it
115 * with an empty passphrase, and if the key is not encrypted,
116 * accept only an empty passphrase.
118 key = key_load_private(fn, "", &comment);
119 if (key != NULL && !(*passphrase == '\0' && nullok)) {
124 key = key_load_private(fn, passphrase, &comment);
126 openpam_log(PAM_LOG_DEBUG, "failed to load key from %s", fn);
130 openpam_log(PAM_LOG_DEBUG, "loaded '%s' from %s", comment, fn);
131 if ((psk = malloc(sizeof(*psk))) == NULL) {
137 psk->comment = comment;
142 * Wipes a private key and frees the associated resources.
145 pam_ssh_free_key(pam_handle_t *pamh __unused,
146 void *data, int pam_err __unused)
148 struct pam_ssh_key *psk;
157 pam_sm_authenticate(pam_handle_t *pamh, int flags __unused,
158 int argc __unused, const char *argv[] __unused)
160 const char **kfn, *passphrase, *user;
163 struct pam_ssh_key *psk;
164 int nkeys, nullok, pam_err, pass;
166 nullok = (openpam_get_option(pamh, "nullok") != NULL);
168 /* PEM is not loaded by default */
169 OpenSSL_add_all_algorithms();
171 /* get user name and home directory */
172 pam_err = pam_get_user(pamh, &user, NULL);
173 if (pam_err != PAM_SUCCESS)
175 pwd = getpwnam(user);
177 return (PAM_USER_UNKNOWN);
178 if (pwd->pw_dir == NULL)
179 return (PAM_AUTH_ERR);
182 pass = (pam_get_item(pamh, PAM_AUTHTOK, &item) == PAM_SUCCESS &&
186 pam_err = pam_get_authtok(pamh, PAM_AUTHTOK,
187 &passphrase, pam_ssh_prompt);
188 if (pam_err != PAM_SUCCESS)
191 /* switch to user credentials */
192 pam_err = openpam_borrow_cred(pamh, pwd);
193 if (pam_err != PAM_SUCCESS)
196 /* try to load keys from all keyfiles we know of */
197 for (kfn = pam_ssh_keyfiles; *kfn != NULL; ++kfn) {
198 psk = pam_ssh_load_key(pwd->pw_dir, *kfn, passphrase, nullok);
200 pam_set_data(pamh, *kfn, psk, pam_ssh_free_key);
205 /* switch back to arbitrator credentials */
206 openpam_restore_cred(pamh);
209 * If we tried an old token and didn't get anything, and
210 * try_first_pass was specified, try again after prompting the
211 * user for a new passphrase.
213 if (nkeys == 0 && pass == 1 &&
214 openpam_get_option(pamh, "try_first_pass") != NULL) {
215 pam_set_item(pamh, PAM_AUTHTOK, NULL);
222 return (PAM_AUTH_ERR);
224 pam_set_data(pamh, pam_ssh_have_keys, NULL, NULL);
225 return (PAM_SUCCESS);
229 pam_sm_setcred(pam_handle_t *pamh __unused, int flags __unused,
230 int argc __unused, const char *argv[] __unused)
233 return (PAM_SUCCESS);
237 * Parses a line from ssh-agent's output.
240 pam_ssh_process_agent_output(pam_handle_t *pamh, FILE *f)
242 char *line, *p, *key, *val;
245 while ((line = fgetln(f, &len)) != NULL) {
246 if (len < 4 || strncmp(line, "SSH_", 4) != 0)
249 /* find equal sign at end of key */
250 for (p = key = line; p < line + len; ++p)
253 if (p == line + len || *p != '=')
257 /* find semicolon at end of value */
258 for (val = ++p; p < line + len; ++p)
261 if (p == line + len || *p != ';')
265 /* store key-value pair in environment */
266 openpam_log(PAM_LOG_DEBUG, "got %s: %s", key, val);
267 pam_setenv(pamh, key, val, 1);
272 * Starts an ssh agent and stores the environment variables derived from
276 pam_ssh_start_agent(pam_handle_t *pamh)
282 /* get a pipe which we will use to read the agent's output */
283 if (pipe(agent_pipe) == -1)
284 return (PAM_SYSTEM_ERR);
286 /* start the agent */
287 openpam_log(PAM_LOG_DEBUG, "starting an ssh agent");
289 if (pid == (pid_t)-1) {
291 close(agent_pipe[0]);
292 close(agent_pipe[1]);
293 return (PAM_SYSTEM_ERR);
298 /* child: drop privs, close fds and start agent */
302 open(_PATH_DEVNULL, O_RDONLY);
303 dup2(agent_pipe[1], STDOUT_FILENO);
304 dup2(agent_pipe[1], STDERR_FILENO);
305 for (fd = 3; fd < getdtablesize(); ++fd)
307 execve(pam_ssh_agent, pam_ssh_agent_argv, pam_ssh_agent_envp);
312 close(agent_pipe[1]);
313 if ((f = fdopen(agent_pipe[0], "r")) == NULL)
314 return (PAM_SYSTEM_ERR);
315 pam_ssh_process_agent_output(pamh, f);
318 return (PAM_SUCCESS);
322 * Adds previously stored keys to a running agent.
325 pam_ssh_add_keys_to_agent(pam_handle_t *pamh)
327 const struct pam_ssh_key *psk;
330 char **envlist, **env;
333 /* switch to PAM environment */
335 if ((environ = pam_getenvlist(pamh)) == NULL) {
337 return (PAM_SYSTEM_ERR);
340 /* get a connection to the agent */
341 if (ssh_get_authentication_socket(&fd) != 0) {
342 openpam_log(PAM_LOG_DEBUG, "failed to connect to the agent");
343 pam_err = PAM_SYSTEM_ERR;
347 /* look for keys to add to it */
348 for (kfn = pam_ssh_keyfiles; *kfn != NULL; ++kfn) {
349 pam_err = pam_get_data(pamh, *kfn, &item);
350 if (pam_err == PAM_SUCCESS && item != NULL) {
352 if (ssh_add_identity(fd, psk->key, psk->comment) == 0)
353 openpam_log(PAM_LOG_DEBUG,
354 "added %s to ssh agent", psk->comment);
356 openpam_log(PAM_LOG_DEBUG, "failed "
357 "to add %s to ssh agent", psk->comment);
358 /* we won't need the key again, so wipe it */
359 pam_set_data(pamh, *kfn, NULL, NULL);
362 pam_err = PAM_SUCCESS;
364 /* disconnect from agent */
365 ssh_close_authentication_socket(fd);
368 /* switch back to original environment */
369 for (env = environ; *env != NULL; ++env)
378 pam_sm_open_session(pam_handle_t *pamh, int flags __unused,
379 int argc __unused, const char *argv[] __unused)
386 /* no keys, no work */
387 if (pam_get_data(pamh, pam_ssh_have_keys, &data) != PAM_SUCCESS &&
388 openpam_get_option(pamh, "want_agent") == NULL)
389 return (PAM_SUCCESS);
391 /* switch to user credentials */
392 pam_err = pam_get_user(pamh, &user, NULL);
393 if (pam_err != PAM_SUCCESS)
395 pwd = getpwnam(user);
397 return (PAM_USER_UNKNOWN);
398 pam_err = openpam_borrow_cred(pamh, pwd);
399 if (pam_err != PAM_SUCCESS)
402 /* start the agent */
403 pam_err = pam_ssh_start_agent(pamh);
404 if (pam_err != PAM_SUCCESS) {
405 openpam_restore_cred(pamh);
409 /* we have an agent, see if we can add any keys to it */
410 pam_err = pam_ssh_add_keys_to_agent(pamh);
411 if (pam_err != PAM_SUCCESS) {
412 /* XXX ignore failures */
415 openpam_restore_cred(pamh);
416 return (PAM_SUCCESS);
420 pam_sm_close_session(pam_handle_t *pamh, int flags __unused,
421 int argc __unused, const char *argv[] __unused)
423 const char *ssh_agent_pid;
428 if ((ssh_agent_pid = pam_getenv(pamh, "SSH_AGENT_PID")) == NULL) {
429 openpam_log(PAM_LOG_DEBUG, "no ssh agent");
430 return (PAM_SUCCESS);
432 pid = (pid_t)strtol(ssh_agent_pid, &end, 10);
433 if (*ssh_agent_pid == '\0' || *end != '\0') {
434 openpam_log(PAM_LOG_DEBUG, "invalid ssh agent pid");
435 return (PAM_SESSION_ERR);
437 openpam_log(PAM_LOG_DEBUG, "killing ssh agent %d", (int)pid);
438 if (kill(pid, SIGTERM) == -1 ||
439 (waitpid(pid, &status, 0) == -1 && errno != ECHILD))
440 return (PAM_SYSTEM_ERR);
441 return (PAM_SUCCESS);
444 PAM_MODULE_ENTRY("pam_ssh");