2 * Copyright (c) 2003 Networks Associates Technology, Inc.
5 * This software was developed for the FreeBSD Project by ThinkSec AS and
6 * NAI Labs, the Security Research Division of Network Associates, Inc.
7 * under DARPA/SPAWAR contract N66001-01-C-8035 ("CBOSS"), as part of the
8 * DARPA CHATS research program.
10 * Redistribution and use in source and binary forms, with or without
11 * modification, are permitted provided that the following conditions
13 * 1. Redistributions of source code must retain the above copyright
14 * notice, this list of conditions and the following disclaimer.
15 * 2. Redistributions in binary form must reproduce the above copyright
16 * notice, this list of conditions and the following disclaimer in the
17 * documentation and/or other materials provided with the distribution.
18 * 3. The name of the author may not be used to endorse or promote
19 * products derived from this software without specific prior written
22 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
23 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
24 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
25 * ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
26 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
27 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
28 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
29 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
30 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
31 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
35 #include <sys/cdefs.h>
36 __FBSDID("$FreeBSD$");
38 #include <sys/param.h>
51 #define PAM_SM_SESSION
53 #include <security/pam_appl.h>
54 #include <security/pam_modules.h>
55 #include <security/openpam.h>
57 #include <openssl/evp.h>
64 extern char **environ;
71 static const char *pam_ssh_prompt = "SSH passphrase: ";
72 static const char *pam_ssh_have_keys = "pam_ssh_have_keys";
74 static const char *pam_ssh_keyfiles[] = {
75 ".ssh/identity", /* SSH1 RSA key */
76 ".ssh/id_rsa", /* SSH2 RSA key */
77 ".ssh/id_dsa", /* SSH2 DSA key */
81 static const char *pam_ssh_agent = "/usr/bin/ssh-agent";
82 static char *const pam_ssh_agent_argv[] = { "ssh_agent", "-s", NULL };
83 static char *const pam_ssh_agent_envp[] = { NULL };
86 * Attempts to load a private key from the specified file in the specified
87 * directory, using the specified passphrase. If successful, returns a
88 * struct pam_ssh_key containing the key and its comment.
90 static struct pam_ssh_key *
91 pam_ssh_load_key(const char *dir, const char *kfn, const char *passphrase)
93 struct pam_ssh_key *psk;
98 if (snprintf(fn, sizeof(fn), "%s/%s", dir, kfn) > (int)sizeof(fn))
101 key = key_load_private(fn, passphrase, &comment);
103 openpam_log(PAM_LOG_DEBUG, "failed to load key from %s\n", fn);
107 openpam_log(PAM_LOG_DEBUG, "loaded '%s' from %s\n", comment, fn);
108 if ((psk = malloc(sizeof(*psk))) == NULL) {
114 psk->comment = comment;
119 * Wipes a private key and frees the associated resources.
122 pam_ssh_free_key(pam_handle_t *pamh __unused,
123 void *data, int pam_err __unused)
125 struct pam_ssh_key *psk;
134 pam_sm_authenticate(pam_handle_t *pamh, int flags __unused,
135 int argc __unused, const char *argv[] __unused)
137 const char **kfn, *passphrase, *user;
140 struct pam_ssh_key *psk;
141 int nkeys, nullok, pam_err, pass;
143 nullok = (openpam_get_option(pamh, "nullok") != NULL);
145 /* PEM is not loaded by default */
146 OpenSSL_add_all_algorithms();
148 /* get user name and home directory */
149 pam_err = pam_get_user(pamh, &user, NULL);
150 if (pam_err != PAM_SUCCESS)
152 pwd = getpwnam(user);
154 return (PAM_USER_UNKNOWN);
155 if (pwd->pw_dir == NULL)
156 return (PAM_AUTH_ERR);
159 pass = (pam_get_item(pamh, PAM_AUTHTOK, &item) == PAM_SUCCESS &&
163 pam_err = pam_get_authtok(pamh, PAM_AUTHTOK,
164 &passphrase, pam_ssh_prompt);
165 if (pam_err != PAM_SUCCESS)
168 if (*passphrase == '\0' && !nullok)
171 /* switch to user credentials */
172 pam_err = openpam_borrow_cred(pamh, pwd);
173 if (pam_err != PAM_SUCCESS)
176 /* try to load keys from all keyfiles we know of */
177 for (kfn = pam_ssh_keyfiles; *kfn != NULL; ++kfn) {
178 psk = pam_ssh_load_key(pwd->pw_dir, *kfn, passphrase);
180 pam_set_data(pamh, *kfn, psk, pam_ssh_free_key);
185 /* switch back to arbitrator credentials */
186 openpam_restore_cred(pamh);
190 * If we tried an old token and didn't get anything, and
191 * try_first_pass was specified, try again after prompting the
192 * user for a new passphrase.
194 if (nkeys == 0 && pass == 1 &&
195 openpam_get_option(pamh, "try_first_pass") != NULL) {
196 pam_set_item(pamh, PAM_AUTHTOK, NULL);
203 return (PAM_AUTH_ERR);
205 pam_set_data(pamh, pam_ssh_have_keys, NULL, NULL);
206 return (PAM_SUCCESS);
210 pam_sm_setcred(pam_handle_t *pamh __unused, int flags __unused,
211 int argc __unused, const char *argv[] __unused)
214 return (PAM_SUCCESS);
218 * Parses a line from ssh-agent's output.
221 pam_ssh_process_agent_output(pam_handle_t *pamh, FILE *f)
223 char *line, *p, *key, *val;
226 while ((line = fgetln(f, &len)) != NULL) {
227 if (len < 4 || strncmp(line, "SSH_", 4) != 0)
230 /* find equal sign at end of key */
231 for (p = key = line; p < line + len; ++p)
234 if (p == line + len || *p != '=')
238 /* find semicolon at end of value */
239 for (val = ++p; p < line + len; ++p)
242 if (p == line + len || *p != ';')
246 /* store key-value pair in environment */
247 openpam_log(PAM_LOG_DEBUG, "got %s: %s", key, val);
248 pam_setenv(pamh, key, val, 1);
253 * Starts an ssh agent and stores the environment variables derived from
257 pam_ssh_start_agent(pam_handle_t *pamh)
263 /* get a pipe which we will use to read the agent's output */
264 if (pipe(agent_pipe) == -1)
265 return (PAM_SYSTEM_ERR);
267 /* start the agent */
268 openpam_log(PAM_LOG_DEBUG, "starting an ssh agent");
270 if (pid == (pid_t)-1) {
272 close(agent_pipe[0]);
273 close(agent_pipe[1]);
274 return (PAM_SYSTEM_ERR);
279 /* child: drop privs, close fds and start agent */
283 open(_PATH_DEVNULL, O_RDONLY);
284 dup2(agent_pipe[1], STDOUT_FILENO);
285 dup2(agent_pipe[1], STDERR_FILENO);
286 for (fd = 3; fd < getdtablesize(); ++fd)
288 execve(pam_ssh_agent, pam_ssh_agent_argv, pam_ssh_agent_envp);
293 close(agent_pipe[1]);
294 if ((f = fdopen(agent_pipe[0], "r")) == NULL)
295 return (PAM_SYSTEM_ERR);
296 pam_ssh_process_agent_output(pamh, f);
299 return (PAM_SUCCESS);
303 * Adds previously stored keys to a running agent.
306 pam_ssh_add_keys_to_agent(pam_handle_t *pamh)
308 AuthenticationConnection *ac;
309 const struct pam_ssh_key *psk;
312 char **envlist, **env;
315 /* switch to PAM environment */
317 if ((environ = pam_getenvlist(pamh)) == NULL) {
319 return (PAM_SYSTEM_ERR);
322 /* get a connection to the agent */
323 if ((ac = ssh_get_authentication_connection()) == NULL) {
324 pam_err = PAM_SYSTEM_ERR;
328 /* look for keys to add to it */
329 for (kfn = pam_ssh_keyfiles; *kfn != NULL; ++kfn) {
330 pam_err = pam_get_data(pamh, *kfn, &item);
331 if (pam_err == PAM_SUCCESS && item != NULL) {
333 if (ssh_add_identity(ac, psk->key, psk->comment))
334 openpam_log(PAM_LOG_DEBUG,
335 "added %s to ssh agent", psk->comment);
337 openpam_log(PAM_LOG_DEBUG, "failed "
338 "to add %s to ssh agent", psk->comment);
339 /* we won't need the key again, so wipe it */
340 pam_set_data(pamh, *kfn, NULL, NULL);
343 pam_err = PAM_SUCCESS;
345 /* disconnect from agent */
347 ssh_close_authentication_connection(ac);
349 /* switch back to original environment */
350 for (env = environ; *env != NULL; ++env)
359 pam_sm_open_session(pam_handle_t *pamh, int flags __unused,
360 int argc __unused, const char *argv[] __unused)
367 /* no keys, no work */
368 if (pam_get_data(pamh, pam_ssh_have_keys, &data) != PAM_SUCCESS &&
369 openpam_get_option(pamh, "want_agent") == NULL)
370 return (PAM_SUCCESS);
372 /* switch to user credentials */
373 pam_err = pam_get_user(pamh, &user, NULL);
374 if (pam_err != PAM_SUCCESS)
376 pwd = getpwnam(user);
378 return (PAM_USER_UNKNOWN);
379 pam_err = openpam_borrow_cred(pamh, pwd);
380 if (pam_err != PAM_SUCCESS)
383 /* start the agent */
384 pam_err = pam_ssh_start_agent(pamh);
385 if (pam_err != PAM_SUCCESS) {
386 openpam_restore_cred(pamh);
390 /* we have an agent, see if we can add any keys to it */
391 pam_err = pam_ssh_add_keys_to_agent(pamh);
392 if (pam_err != PAM_SUCCESS) {
393 /* XXX ignore failures */
396 openpam_restore_cred(pamh);
397 return (PAM_SUCCESS);
401 pam_sm_close_session(pam_handle_t *pamh, int flags __unused,
402 int argc __unused, const char *argv[] __unused)
404 const char *ssh_agent_pid;
409 if ((ssh_agent_pid = pam_getenv(pamh, "SSH_AGENT_PID")) == NULL) {
410 openpam_log(PAM_LOG_DEBUG, "no ssh agent");
411 return (PAM_SUCCESS);
413 pid = (pid_t)strtol(ssh_agent_pid, &end, 10);
414 if (*ssh_agent_pid == '\0' || *end != '\0') {
415 openpam_log(PAM_LOG_DEBUG, "invalid ssh agent pid");
416 return (PAM_SESSION_ERR);
418 openpam_log(PAM_LOG_DEBUG, "killing ssh agent %d", (int)pid);
419 if (kill(pid, SIGTERM) == -1 ||
420 (waitpid(pid, &status, 0) == -1 && errno != ECHILD))
421 return (PAM_SYSTEM_ERR);
422 return (PAM_SUCCESS);
425 PAM_MODULE_ENTRY("pam_ssh");