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
34 * $FreeBSD: src/lib/libpam/modules/pam_ssh/pam_ssh.c,v 1.40 2004/02/10 10:13:21 des Exp $
35 * $DragonFly: src/lib/pam_module/pam_ssh/pam_ssh.c,v 1.1 2005/07/12 23:26:49 joerg Exp $
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>
63 extern char **environ;
70 static const char *pam_ssh_prompt = "SSH passphrase: ";
71 static const char *pam_ssh_have_keys = "pam_ssh_have_keys";
73 static const char *pam_ssh_keyfiles[] = {
74 ".ssh/identity", /* SSH1 RSA key */
75 ".ssh/id_rsa", /* SSH2 RSA key */
76 ".ssh/id_dsa", /* SSH2 DSA key */
80 static const char *pam_ssh_agent = "/usr/bin/ssh-agent";
81 static const char *pam_ssh_agent_argv[] = { "ssh_agent", "-s", NULL };
82 static char *const pam_ssh_agent_envp[] = { NULL };
85 * Attempts to load a private key from the specified file in the specified
86 * directory, using the specified passphrase. If successful, returns a
87 * struct pam_ssh_key containing the key and its comment.
89 static struct pam_ssh_key *
90 pam_ssh_load_key(const char *dir, const char *kfn, const char *passphrase)
92 struct pam_ssh_key *psk;
97 if (snprintf(fn, sizeof(fn), "%s/%s", dir, kfn) > (int)sizeof(fn))
100 key = key_load_private(fn, passphrase, &comment);
102 openpam_log(PAM_LOG_DEBUG, "failed to load key from %s\n", fn);
106 openpam_log(PAM_LOG_DEBUG, "loaded '%s' from %s\n", comment, fn);
107 if ((psk = malloc(sizeof(*psk))) == NULL) {
113 psk->comment = comment;
118 * Wipes a private key and frees the associated resources.
121 pam_ssh_free_key(pam_handle_t *pamh __unused,
122 void *data, int pam_err __unused)
124 struct pam_ssh_key *psk;
133 pam_sm_authenticate(pam_handle_t *pamh, int flags __unused,
134 int argc __unused, const char *argv[] __unused)
136 const char **kfn, *passphrase, *user;
138 struct pam_ssh_key *psk;
139 int nkeys, pam_err, pass;
141 /* PEM is not loaded by default */
142 OpenSSL_add_all_algorithms();
144 /* get user name and home directory */
145 pam_err = pam_get_user(pamh, &user, NULL);
146 if (pam_err != PAM_SUCCESS)
148 pwd = getpwnam(user);
150 return (PAM_USER_UNKNOWN);
151 if (pwd->pw_dir == NULL)
152 return (PAM_AUTH_ERR);
154 /* switch to user credentials */
155 pam_err = openpam_borrow_cred(pamh, pwd);
156 if (pam_err != PAM_SUCCESS)
159 pass = (pam_get_item(pamh, PAM_AUTHTOK,
160 (const void **)&passphrase) == PAM_SUCCESS);
163 pam_err = pam_get_authtok(pamh, PAM_AUTHTOK,
164 &passphrase, pam_ssh_prompt);
165 if (pam_err != PAM_SUCCESS) {
166 openpam_restore_cred(pamh);
170 /* try to load keys from all keyfiles we know of */
172 for (kfn = pam_ssh_keyfiles; *kfn != NULL; ++kfn) {
173 psk = pam_ssh_load_key(pwd->pw_dir, *kfn, passphrase);
175 pam_set_data(pamh, *kfn, psk, pam_ssh_free_key);
181 * If we tried an old token and didn't get anything, and
182 * try_first_pass was specified, try again after prompting the
183 * user for a new passphrase.
185 if (nkeys == 0 && pass == 1 &&
186 openpam_get_option(pamh, "try_first_pass") != NULL) {
187 pam_set_item(pamh, PAM_AUTHTOK, NULL);
192 /* switch back to arbitrator credentials before returning */
193 openpam_restore_cred(pamh);
197 return (PAM_AUTH_ERR);
199 pam_set_data(pamh, pam_ssh_have_keys, NULL, NULL);
200 return (PAM_SUCCESS);
204 pam_sm_setcred(pam_handle_t *pamh __unused, int flags __unused,
205 int argc __unused, const char *argv[] __unused)
208 return (PAM_SUCCESS);
212 * Parses a line from ssh-agent's output.
215 pam_ssh_process_agent_output(pam_handle_t *pamh, FILE *f)
217 char *line, *p, *key, *val;
220 while ((line = fgetln(f, &len)) != NULL) {
221 if (len < 4 || strncmp(line, "SSH_", 4) != 0)
224 /* find equal sign at end of key */
225 for (p = key = line; p < line + len; ++p)
228 if (p == line + len || *p != '=')
232 /* find semicolon at end of value */
233 for (val = ++p; p < line + len; ++p)
236 if (p == line + len || *p != ';')
240 /* store key-value pair in environment */
241 openpam_log(PAM_LOG_DEBUG, "got %s: %s", key, val);
242 pam_setenv(pamh, key, val, 1);
247 * Starts an ssh agent and stores the environment variables derived from
251 pam_ssh_start_agent(pam_handle_t *pamh)
257 /* get a pipe which we will use to read the agent's output */
258 if (pipe(agent_pipe) == -1) {
259 openpam_restore_cred(pamh);
260 return (PAM_SYSTEM_ERR);
263 /* start the agent */
264 openpam_log(PAM_LOG_DEBUG, "starting an ssh agent");
266 if (pid == (pid_t)-1) {
268 close(agent_pipe[0]);
269 close(agent_pipe[1]);
270 return (PAM_SYSTEM_ERR);
275 /* child: drop privs, close fds and start agent */
279 open(_PATH_DEVNULL, O_RDONLY);
280 dup2(agent_pipe[1], STDOUT_FILENO);
281 dup2(agent_pipe[1], STDERR_FILENO);
282 for (fd = 3; fd < getdtablesize(); ++fd)
284 execve(pam_ssh_agent,
285 __DECONST(char * const *, pam_ssh_agent_argv),
291 close(agent_pipe[1]);
292 if ((f = fdopen(agent_pipe[0], "r")) == NULL)
293 return (PAM_SYSTEM_ERR);
294 pam_ssh_process_agent_output(pamh, f);
297 return (PAM_SUCCESS);
301 * Adds previously stored keys to a running agent.
304 pam_ssh_add_keys_to_agent(pam_handle_t *pamh)
306 AuthenticationConnection *ac;
307 struct pam_ssh_key *psk;
309 char **envlist, **env;
312 /* switch to PAM environment */
314 if ((environ = pam_getenvlist(pamh)) == NULL) {
316 return (PAM_SYSTEM_ERR);
319 /* get a connection to the agent */
320 if ((ac = ssh_get_authentication_connection()) == NULL) {
321 pam_err = PAM_SYSTEM_ERR;
325 /* look for keys to add to it */
326 for (kfn = pam_ssh_keyfiles; *kfn != NULL; ++kfn) {
327 pam_err = pam_get_data(pamh, *kfn, (void **)&psk);
328 if (pam_err == PAM_SUCCESS && psk != NULL) {
329 if (ssh_add_identity(ac, psk->key, psk->comment))
330 openpam_log(PAM_LOG_DEBUG,
331 "added %s to ssh agent", psk->comment);
333 openpam_log(PAM_LOG_DEBUG, "failed "
334 "to add %s to ssh agent", psk->comment);
335 /* we won't need the key again, so wipe it */
336 pam_set_data(pamh, *kfn, NULL, NULL);
339 pam_err = PAM_SUCCESS;
341 /* disconnect from agent */
343 ssh_close_authentication_connection(ac);
345 /* switch back to original environment */
346 for (env = environ; *env != NULL; ++env)
355 pam_sm_open_session(pam_handle_t *pamh, int flags __unused,
356 int argc __unused, const char *argv[] __unused)
363 /* no keys, no work */
364 if (pam_get_data(pamh, pam_ssh_have_keys, &data) != PAM_SUCCESS &&
365 openpam_get_option(pamh, "want_agent") == NULL)
366 return (PAM_SUCCESS);
368 /* switch to user credentials */
369 pam_err = pam_get_user(pamh, &user, NULL);
370 if (pam_err != PAM_SUCCESS)
372 pwd = getpwnam(user);
374 return (PAM_USER_UNKNOWN);
375 pam_err = openpam_borrow_cred(pamh, pwd);
376 if (pam_err != PAM_SUCCESS)
379 /* start the agent */
380 pam_err = pam_ssh_start_agent(pamh);
381 if (pam_err != PAM_SUCCESS) {
382 openpam_restore_cred(pamh);
386 /* we have an agent, see if we can add any keys to it */
387 pam_err = pam_ssh_add_keys_to_agent(pamh);
388 if (pam_err != PAM_SUCCESS) {
389 /* XXX ignore failures */
392 openpam_restore_cred(pamh);
393 return (PAM_SUCCESS);
397 pam_sm_close_session(pam_handle_t *pamh, int flags __unused,
398 int argc __unused, const char *argv[] __unused)
400 const char *ssh_agent_pid;
405 if ((ssh_agent_pid = pam_getenv(pamh, "SSH_AGENT_PID")) == NULL) {
406 openpam_log(PAM_LOG_DEBUG, "no ssh agent");
407 return (PAM_SUCCESS);
409 pid = (pid_t)strtol(ssh_agent_pid, &end, 10);
410 if (*ssh_agent_pid == '\0' || *end != '\0') {
411 openpam_log(PAM_LOG_DEBUG, "invalid ssh agent pid");
412 return (PAM_SESSION_ERR);
414 openpam_log(PAM_LOG_DEBUG, "killing ssh agent %d", (int)pid);
415 if (kill(pid, SIGTERM) == -1 ||
416 (waitpid(pid, &status, 0) == -1 && errno != ECHILD))
417 return (PAM_SYSTEM_ERR);
418 return (PAM_SUCCESS);
421 PAM_MODULE_ENTRY("pam_ssh");