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 #define ssh_add_identity(auth, key, comment) \
65 ssh_add_identity_constrained(auth, key, comment, 0, 0)
67 extern char **environ;
74 static const char *pam_ssh_prompt = "SSH passphrase: ";
75 static const char *pam_ssh_have_keys = "pam_ssh_have_keys";
77 static const char *pam_ssh_keyfiles[] = {
78 ".ssh/identity", /* SSH1 RSA key */
79 ".ssh/id_rsa", /* SSH2 RSA key */
80 ".ssh/id_dsa", /* SSH2 DSA key */
84 static const char *pam_ssh_agent = "/usr/bin/ssh-agent";
85 static char *const pam_ssh_agent_argv[] = { "ssh_agent", "-s", NULL };
86 static char *const pam_ssh_agent_envp[] = { NULL };
89 * Attempts to load a private key from the specified file in the specified
90 * directory, using the specified passphrase. If successful, returns a
91 * struct pam_ssh_key containing the key and its comment.
93 static struct pam_ssh_key *
94 pam_ssh_load_key(const char *dir, const char *kfn, const char *passphrase,
97 struct pam_ssh_key *psk;
102 if (snprintf(fn, sizeof(fn), "%s/%s", dir, kfn) > (int)sizeof(fn))
106 * If the key is unencrypted, OpenSSL ignores the passphrase, so
107 * it will seem like the user typed in the right one. This allows
108 * a user to circumvent nullok by providing a dummy passphrase.
109 * Verify that the key really *is* encrypted by trying to load it
110 * with an empty passphrase, and if the key is not encrypted,
111 * accept only an empty passphrase.
113 key = key_load_private(fn, NULL, &comment);
114 if (key != NULL && !(*passphrase == '\0' && nullok)) {
119 key = key_load_private(fn, passphrase, &comment);
121 openpam_log(PAM_LOG_DEBUG, "failed to load key from %s\n", fn);
125 openpam_log(PAM_LOG_DEBUG, "loaded '%s' from %s\n", comment, fn);
126 if ((psk = malloc(sizeof(*psk))) == NULL) {
132 psk->comment = comment;
137 * Wipes a private key and frees the associated resources.
140 pam_ssh_free_key(pam_handle_t *pamh __unused,
141 void *data, int pam_err __unused)
143 struct pam_ssh_key *psk;
152 pam_sm_authenticate(pam_handle_t *pamh, int flags __unused,
153 int argc __unused, const char *argv[] __unused)
155 const char **kfn, *passphrase, *user;
158 struct pam_ssh_key *psk;
159 int nkeys, nullok, pam_err, pass;
161 nullok = (openpam_get_option(pamh, "nullok") != NULL);
163 /* PEM is not loaded by default */
164 OpenSSL_add_all_algorithms();
166 /* get user name and home directory */
167 pam_err = pam_get_user(pamh, &user, NULL);
168 if (pam_err != PAM_SUCCESS)
170 pwd = getpwnam(user);
172 return (PAM_USER_UNKNOWN);
173 if (pwd->pw_dir == NULL)
174 return (PAM_AUTH_ERR);
177 pass = (pam_get_item(pamh, PAM_AUTHTOK, &item) == PAM_SUCCESS &&
181 pam_err = pam_get_authtok(pamh, PAM_AUTHTOK,
182 &passphrase, pam_ssh_prompt);
183 if (pam_err != PAM_SUCCESS)
186 /* switch to user credentials */
187 pam_err = openpam_borrow_cred(pamh, pwd);
188 if (pam_err != PAM_SUCCESS)
191 /* try to load keys from all keyfiles we know of */
192 for (kfn = pam_ssh_keyfiles; *kfn != NULL; ++kfn) {
193 psk = pam_ssh_load_key(pwd->pw_dir, *kfn, passphrase, nullok);
195 pam_set_data(pamh, *kfn, psk, pam_ssh_free_key);
200 /* switch back to arbitrator credentials */
201 openpam_restore_cred(pamh);
204 * If we tried an old token and didn't get anything, and
205 * try_first_pass was specified, try again after prompting the
206 * user for a new passphrase.
208 if (nkeys == 0 && pass == 1 &&
209 openpam_get_option(pamh, "try_first_pass") != NULL) {
210 pam_set_item(pamh, PAM_AUTHTOK, NULL);
217 return (PAM_AUTH_ERR);
219 pam_set_data(pamh, pam_ssh_have_keys, NULL, NULL);
220 return (PAM_SUCCESS);
224 pam_sm_setcred(pam_handle_t *pamh __unused, int flags __unused,
225 int argc __unused, const char *argv[] __unused)
228 return (PAM_SUCCESS);
232 * Parses a line from ssh-agent's output.
235 pam_ssh_process_agent_output(pam_handle_t *pamh, FILE *f)
237 char *line, *p, *key, *val;
240 while ((line = fgetln(f, &len)) != NULL) {
241 if (len < 4 || strncmp(line, "SSH_", 4) != 0)
244 /* find equal sign at end of key */
245 for (p = key = line; p < line + len; ++p)
248 if (p == line + len || *p != '=')
252 /* find semicolon at end of value */
253 for (val = ++p; p < line + len; ++p)
256 if (p == line + len || *p != ';')
260 /* store key-value pair in environment */
261 openpam_log(PAM_LOG_DEBUG, "got %s: %s", key, val);
262 pam_setenv(pamh, key, val, 1);
267 * Starts an ssh agent and stores the environment variables derived from
271 pam_ssh_start_agent(pam_handle_t *pamh)
277 /* get a pipe which we will use to read the agent's output */
278 if (pipe(agent_pipe) == -1)
279 return (PAM_SYSTEM_ERR);
281 /* start the agent */
282 openpam_log(PAM_LOG_DEBUG, "starting an ssh agent");
284 if (pid == (pid_t)-1) {
286 close(agent_pipe[0]);
287 close(agent_pipe[1]);
288 return (PAM_SYSTEM_ERR);
293 /* child: drop privs, close fds and start agent */
297 open(_PATH_DEVNULL, O_RDONLY);
298 dup2(agent_pipe[1], STDOUT_FILENO);
299 dup2(agent_pipe[1], STDERR_FILENO);
300 for (fd = 3; fd < getdtablesize(); ++fd)
302 execve(pam_ssh_agent, pam_ssh_agent_argv, pam_ssh_agent_envp);
307 close(agent_pipe[1]);
308 if ((f = fdopen(agent_pipe[0], "r")) == NULL)
309 return (PAM_SYSTEM_ERR);
310 pam_ssh_process_agent_output(pamh, f);
313 return (PAM_SUCCESS);
317 * Adds previously stored keys to a running agent.
320 pam_ssh_add_keys_to_agent(pam_handle_t *pamh)
322 AuthenticationConnection *ac;
323 const struct pam_ssh_key *psk;
326 char **envlist, **env;
329 /* switch to PAM environment */
331 if ((environ = pam_getenvlist(pamh)) == NULL) {
333 return (PAM_SYSTEM_ERR);
336 /* get a connection to the agent */
337 if ((ac = ssh_get_authentication_connection()) == NULL) {
338 pam_err = PAM_SYSTEM_ERR;
342 /* look for keys to add to it */
343 for (kfn = pam_ssh_keyfiles; *kfn != NULL; ++kfn) {
344 pam_err = pam_get_data(pamh, *kfn, &item);
345 if (pam_err == PAM_SUCCESS && item != NULL) {
347 if (ssh_add_identity(ac, psk->key, psk->comment))
348 openpam_log(PAM_LOG_DEBUG,
349 "added %s to ssh agent", psk->comment);
351 openpam_log(PAM_LOG_DEBUG, "failed "
352 "to add %s to ssh agent", psk->comment);
353 /* we won't need the key again, so wipe it */
354 pam_set_data(pamh, *kfn, NULL, NULL);
357 pam_err = PAM_SUCCESS;
359 /* disconnect from agent */
361 ssh_close_authentication_connection(ac);
363 /* switch back to original environment */
364 for (env = environ; *env != NULL; ++env)
373 pam_sm_open_session(pam_handle_t *pamh, int flags __unused,
374 int argc __unused, const char *argv[] __unused)
381 /* no keys, no work */
382 if (pam_get_data(pamh, pam_ssh_have_keys, &data) != PAM_SUCCESS &&
383 openpam_get_option(pamh, "want_agent") == NULL)
384 return (PAM_SUCCESS);
386 /* switch to user credentials */
387 pam_err = pam_get_user(pamh, &user, NULL);
388 if (pam_err != PAM_SUCCESS)
390 pwd = getpwnam(user);
392 return (PAM_USER_UNKNOWN);
393 pam_err = openpam_borrow_cred(pamh, pwd);
394 if (pam_err != PAM_SUCCESS)
397 /* start the agent */
398 pam_err = pam_ssh_start_agent(pamh);
399 if (pam_err != PAM_SUCCESS) {
400 openpam_restore_cred(pamh);
404 /* we have an agent, see if we can add any keys to it */
405 pam_err = pam_ssh_add_keys_to_agent(pamh);
406 if (pam_err != PAM_SUCCESS) {
407 /* XXX ignore failures */
410 openpam_restore_cred(pamh);
411 return (PAM_SUCCESS);
415 pam_sm_close_session(pam_handle_t *pamh, int flags __unused,
416 int argc __unused, const char *argv[] __unused)
418 const char *ssh_agent_pid;
423 if ((ssh_agent_pid = pam_getenv(pamh, "SSH_AGENT_PID")) == NULL) {
424 openpam_log(PAM_LOG_DEBUG, "no ssh agent");
425 return (PAM_SUCCESS);
427 pid = (pid_t)strtol(ssh_agent_pid, &end, 10);
428 if (*ssh_agent_pid == '\0' || *end != '\0') {
429 openpam_log(PAM_LOG_DEBUG, "invalid ssh agent pid");
430 return (PAM_SESSION_ERR);
432 openpam_log(PAM_LOG_DEBUG, "killing ssh agent %d", (int)pid);
433 if (kill(pid, SIGTERM) == -1 ||
434 (waitpid(pid, &status, 0) == -1 && errno != ECHILD))
435 return (PAM_SYSTEM_ERR);
436 return (PAM_SUCCESS);
439 PAM_MODULE_ENTRY("pam_ssh");