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1 | /* | |
2 | * Copyright (c) 2000 Damien Miller. All rights reserved. | |
3 | * | |
4 | * Redistribution and use in source and binary forms, with or without | |
5 | * modification, are permitted provided that the following conditions | |
6 | * are met: | |
7 | * 1. Redistributions of source code must retain the above copyright | |
8 | * notice, this list of conditions and the following disclaimer. | |
9 | * 2. Redistributions in binary form must reproduce the above copyright | |
10 | * notice, this list of conditions and the following disclaimer in the | |
11 | * documentation and/or other materials provided with the distribution. | |
12 | * | |
13 | * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR | |
14 | * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES | |
15 | * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. | |
16 | * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT, | |
17 | * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT | |
18 | * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, | |
19 | * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY | |
20 | * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT | |
21 | * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF | |
22 | * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. | |
23 | */ | |
24 | ||
25 | #include "includes.h" | |
26 | ||
27 | #ifdef USE_PAM | |
28 | #include "ssh.h" | |
29 | #include "xmalloc.h" | |
30 | #include "log.h" | |
31 | #include "auth.h" | |
32 | #include "auth-pam.h" | |
33 | #include "servconf.h" | |
34 | #include "canohost.h" | |
35 | #include "readpass.h" | |
36 | ||
37 | extern char *__progname; | |
38 | ||
39 | RCSID("$Id$"); | |
40 | ||
41 | #define NEW_AUTHTOK_MSG \ | |
42 | "Warning: Your password has expired, please change it now" | |
43 | ||
44 | static int do_pam_conversation(int num_msg, const struct pam_message **msg, | |
45 | struct pam_response **resp, void *appdata_ptr); | |
46 | ||
47 | /* module-local variables */ | |
48 | static struct pam_conv conv = { | |
49 | do_pam_conversation, | |
50 | NULL | |
51 | }; | |
52 | static char *__pam_msg = NULL; | |
53 | static pam_handle_t *__pamh = NULL; | |
54 | static const char *__pampasswd = NULL; | |
55 | ||
56 | /* states for do_pam_conversation() */ | |
57 | enum { INITIAL_LOGIN, OTHER } pamstate = INITIAL_LOGIN; | |
58 | /* remember whether pam_acct_mgmt() returned PAM_NEWAUTHTOK_REQD */ | |
59 | static int password_change_required = 0; | |
60 | /* remember whether the last pam_authenticate() succeeded or not */ | |
61 | static int was_authenticated = 0; | |
62 | ||
63 | /* Remember what has been initialised */ | |
64 | static int session_opened = 0; | |
65 | static int creds_set = 0; | |
66 | ||
67 | /* accessor which allows us to switch conversation structs according to | |
68 | * the authentication method being used */ | |
69 | void do_pam_set_conv(struct pam_conv *conv) | |
70 | { | |
71 | pam_set_item(__pamh, PAM_CONV, conv); | |
72 | } | |
73 | ||
74 | /* start an authentication run */ | |
75 | int do_pam_authenticate(int flags) | |
76 | { | |
77 | int retval = pam_authenticate(__pamh, flags); | |
78 | was_authenticated = (retval == PAM_SUCCESS); | |
79 | return retval; | |
80 | } | |
81 | ||
82 | /* | |
83 | * PAM conversation function. | |
84 | * There are two states this can run in. | |
85 | * | |
86 | * INITIAL_LOGIN mode simply feeds the password from the client into | |
87 | * PAM in response to PAM_PROMPT_ECHO_OFF, and collects output | |
88 | * messages with into __pam_msg. This is used during initial | |
89 | * authentication to bypass the normal PAM password prompt. | |
90 | * | |
91 | * OTHER mode handles PAM_PROMPT_ECHO_OFF with read_passphrase() | |
92 | * and outputs messages to stderr. This mode is used if pam_chauthtok() | |
93 | * is called to update expired passwords. | |
94 | */ | |
95 | static int do_pam_conversation(int num_msg, const struct pam_message **msg, | |
96 | struct pam_response **resp, void *appdata_ptr) | |
97 | { | |
98 | struct pam_response *reply; | |
99 | int count; | |
100 | char buf[1024]; | |
101 | ||
102 | /* PAM will free this later */ | |
103 | reply = malloc(num_msg * sizeof(*reply)); | |
104 | if (reply == NULL) | |
105 | return PAM_CONV_ERR; | |
106 | ||
107 | for (count = 0; count < num_msg; count++) { | |
108 | if (pamstate == INITIAL_LOGIN) { | |
109 | /* | |
110 | * We can't use stdio yet, queue messages for | |
111 | * printing later | |
112 | */ | |
113 | switch(PAM_MSG_MEMBER(msg, count, msg_style)) { | |
114 | case PAM_PROMPT_ECHO_ON: | |
115 | free(reply); | |
116 | return PAM_CONV_ERR; | |
117 | case PAM_PROMPT_ECHO_OFF: | |
118 | if (__pampasswd == NULL) { | |
119 | free(reply); | |
120 | return PAM_CONV_ERR; | |
121 | } | |
122 | reply[count].resp = xstrdup(__pampasswd); | |
123 | reply[count].resp_retcode = PAM_SUCCESS; | |
124 | break; | |
125 | case PAM_ERROR_MSG: | |
126 | case PAM_TEXT_INFO: | |
127 | if ((*msg)[count].msg != NULL) { | |
128 | message_cat(&__pam_msg, | |
129 | PAM_MSG_MEMBER(msg, count, msg)); | |
130 | } | |
131 | reply[count].resp = xstrdup(""); | |
132 | reply[count].resp_retcode = PAM_SUCCESS; | |
133 | break; | |
134 | default: | |
135 | free(reply); | |
136 | return PAM_CONV_ERR; | |
137 | } | |
138 | } else { | |
139 | /* | |
140 | * stdio is connected, so interact directly | |
141 | */ | |
142 | switch(PAM_MSG_MEMBER(msg, count, msg_style)) { | |
143 | case PAM_PROMPT_ECHO_ON: | |
144 | fputs(PAM_MSG_MEMBER(msg, count, msg), stderr); | |
145 | fgets(buf, sizeof(buf), stdin); | |
146 | reply[count].resp = xstrdup(buf); | |
147 | reply[count].resp_retcode = PAM_SUCCESS; | |
148 | break; | |
149 | case PAM_PROMPT_ECHO_OFF: | |
150 | reply[count].resp = | |
151 | read_passphrase(PAM_MSG_MEMBER(msg, count, | |
152 | msg), RP_ALLOW_STDIN); | |
153 | reply[count].resp_retcode = PAM_SUCCESS; | |
154 | break; | |
155 | case PAM_ERROR_MSG: | |
156 | case PAM_TEXT_INFO: | |
157 | if ((*msg)[count].msg != NULL) | |
158 | fprintf(stderr, "%s\n", | |
159 | PAM_MSG_MEMBER(msg, count, msg)); | |
160 | reply[count].resp = xstrdup(""); | |
161 | reply[count].resp_retcode = PAM_SUCCESS; | |
162 | break; | |
163 | default: | |
164 | free(reply); | |
165 | return PAM_CONV_ERR; | |
166 | } | |
167 | } | |
168 | } | |
169 | ||
170 | *resp = reply; | |
171 | ||
172 | return PAM_SUCCESS; | |
173 | } | |
174 | ||
175 | /* Called at exit to cleanly shutdown PAM */ | |
176 | void do_pam_cleanup_proc(void *context) | |
177 | { | |
178 | int pam_retval = PAM_SUCCESS; | |
179 | ||
180 | if (__pamh && session_opened) { | |
181 | pam_retval = pam_close_session(__pamh, 0); | |
182 | if (pam_retval != PAM_SUCCESS) | |
183 | log("Cannot close PAM session[%d]: %.200s", | |
184 | pam_retval, PAM_STRERROR(__pamh, pam_retval)); | |
185 | } | |
186 | ||
187 | if (__pamh && creds_set) { | |
188 | pam_retval = pam_setcred(__pamh, PAM_DELETE_CRED); | |
189 | if (pam_retval != PAM_SUCCESS) | |
190 | debug("Cannot delete credentials[%d]: %.200s", | |
191 | pam_retval, PAM_STRERROR(__pamh, pam_retval)); | |
192 | } | |
193 | ||
194 | if (__pamh) { | |
195 | pam_retval = pam_end(__pamh, pam_retval); | |
196 | if (pam_retval != PAM_SUCCESS) | |
197 | log("Cannot release PAM authentication[%d]: %.200s", | |
198 | pam_retval, PAM_STRERROR(__pamh, pam_retval)); | |
199 | } | |
200 | } | |
201 | ||
202 | /* Attempt password authentation using PAM */ | |
203 | int auth_pam_password(Authctxt *authctxt, const char *password) | |
204 | { | |
205 | extern ServerOptions options; | |
206 | int pam_retval; | |
207 | struct passwd *pw = authctxt->pw; | |
208 | ||
209 | do_pam_set_conv(&conv); | |
210 | ||
211 | /* deny if no user. */ | |
212 | if (pw == NULL) | |
213 | return 0; | |
214 | if (pw->pw_uid == 0 && options.permit_root_login == PERMIT_NO_PASSWD) | |
215 | return 0; | |
216 | if (*password == '\0' && options.permit_empty_passwd == 0) | |
217 | return 0; | |
218 | ||
219 | __pampasswd = password; | |
220 | ||
221 | pamstate = INITIAL_LOGIN; | |
222 | pam_retval = do_pam_authenticate( | |
223 | options.permit_empty_passwd == 0 ? PAM_DISALLOW_NULL_AUTHTOK : 0); | |
224 | if (pam_retval == PAM_SUCCESS) { | |
225 | debug("PAM Password authentication accepted for " | |
226 | "user \"%.100s\"", pw->pw_name); | |
227 | return 1; | |
228 | } else { | |
229 | debug("PAM Password authentication for \"%.100s\" " | |
230 | "failed[%d]: %s", pw->pw_name, pam_retval, | |
231 | PAM_STRERROR(__pamh, pam_retval)); | |
232 | return 0; | |
233 | } | |
234 | } | |
235 | ||
236 | /* Do account management using PAM */ | |
237 | int do_pam_account(char *username, char *remote_user) | |
238 | { | |
239 | int pam_retval; | |
240 | ||
241 | do_pam_set_conv(&conv); | |
242 | ||
243 | if (remote_user) { | |
244 | debug("PAM setting ruser to \"%.200s\"", remote_user); | |
245 | pam_retval = pam_set_item(__pamh, PAM_RUSER, remote_user); | |
246 | if (pam_retval != PAM_SUCCESS) | |
247 | fatal("PAM set ruser failed[%d]: %.200s", pam_retval, | |
248 | PAM_STRERROR(__pamh, pam_retval)); | |
249 | } | |
250 | ||
251 | pam_retval = pam_acct_mgmt(__pamh, 0); | |
252 | debug2("pam_acct_mgmt() = %d", pam_retval); | |
253 | switch (pam_retval) { | |
254 | case PAM_SUCCESS: | |
255 | /* This is what we want */ | |
256 | break; | |
257 | #if 0 | |
258 | case PAM_NEW_AUTHTOK_REQD: | |
259 | message_cat(&__pam_msg, NEW_AUTHTOK_MSG); | |
260 | /* flag that password change is necessary */ | |
261 | password_change_required = 1; | |
262 | break; | |
263 | #endif | |
264 | default: | |
265 | log("PAM rejected by account configuration[%d]: " | |
266 | "%.200s", pam_retval, PAM_STRERROR(__pamh, | |
267 | pam_retval)); | |
268 | return(0); | |
269 | } | |
270 | ||
271 | return(1); | |
272 | } | |
273 | ||
274 | /* Do PAM-specific session initialisation */ | |
275 | void do_pam_session(char *username, const char *ttyname) | |
276 | { | |
277 | int pam_retval; | |
278 | ||
279 | do_pam_set_conv(&conv); | |
280 | ||
281 | if (ttyname != NULL) { | |
282 | debug("PAM setting tty to \"%.200s\"", ttyname); | |
283 | pam_retval = pam_set_item(__pamh, PAM_TTY, ttyname); | |
284 | if (pam_retval != PAM_SUCCESS) | |
285 | fatal("PAM set tty failed[%d]: %.200s", | |
286 | pam_retval, PAM_STRERROR(__pamh, pam_retval)); | |
287 | } | |
288 | ||
289 | pam_retval = pam_open_session(__pamh, 0); | |
290 | if (pam_retval != PAM_SUCCESS) | |
291 | fatal("PAM session setup failed[%d]: %.200s", | |
292 | pam_retval, PAM_STRERROR(__pamh, pam_retval)); | |
293 | ||
294 | session_opened = 1; | |
295 | } | |
296 | ||
297 | /* Set PAM credentials */ | |
298 | void do_pam_setcred(int init) | |
299 | { | |
300 | int pam_retval; | |
301 | ||
302 | do_pam_set_conv(&conv); | |
303 | ||
304 | debug("PAM establishing creds"); | |
305 | pam_retval = pam_setcred(__pamh, | |
306 | init ? PAM_ESTABLISH_CRED : PAM_REINITIALIZE_CRED); | |
307 | if (pam_retval != PAM_SUCCESS) { | |
308 | if (was_authenticated) | |
309 | fatal("PAM setcred failed[%d]: %.200s", | |
310 | pam_retval, PAM_STRERROR(__pamh, pam_retval)); | |
311 | else | |
312 | debug("PAM setcred failed[%d]: %.200s", | |
313 | pam_retval, PAM_STRERROR(__pamh, pam_retval)); | |
314 | } else | |
315 | creds_set = 1; | |
316 | } | |
317 | ||
318 | /* accessor function for file scope static variable */ | |
319 | int is_pam_password_change_required(void) | |
320 | { | |
321 | return password_change_required; | |
322 | } | |
323 | ||
324 | /* | |
325 | * Have user change authentication token if pam_acct_mgmt() indicated | |
326 | * it was expired. This needs to be called after an interactive | |
327 | * session is established and the user's pty is connected to | |
328 | * stdin/stout/stderr. | |
329 | */ | |
330 | void do_pam_chauthtok(void) | |
331 | { | |
332 | int pam_retval; | |
333 | ||
334 | do_pam_set_conv(&conv); | |
335 | ||
336 | if (password_change_required) { | |
337 | pamstate = OTHER; | |
338 | pam_retval = pam_chauthtok(__pamh, PAM_CHANGE_EXPIRED_AUTHTOK); | |
339 | if (pam_retval != PAM_SUCCESS) | |
340 | fatal("PAM pam_chauthtok failed[%d]: %.200s", | |
341 | pam_retval, PAM_STRERROR(__pamh, pam_retval)); | |
342 | } | |
343 | } | |
344 | ||
345 | /* Cleanly shutdown PAM */ | |
346 | void finish_pam(void) | |
347 | { | |
348 | do_pam_cleanup_proc(NULL); | |
349 | fatal_remove_cleanup(&do_pam_cleanup_proc, NULL); | |
350 | } | |
351 | ||
352 | /* Start PAM authentication for specified account */ | |
353 | void start_pam(const char *user) | |
354 | { | |
355 | int pam_retval; | |
356 | extern ServerOptions options; | |
357 | extern u_int utmp_len; | |
358 | const char *rhost; | |
359 | ||
360 | debug("Starting up PAM with username \"%.200s\"", user); | |
361 | ||
362 | pam_retval = pam_start(SSHD_PAM_SERVICE, user, &conv, &__pamh); | |
363 | ||
364 | if (pam_retval != PAM_SUCCESS) | |
365 | fatal("PAM initialisation failed[%d]: %.200s", | |
366 | pam_retval, PAM_STRERROR(__pamh, pam_retval)); | |
367 | ||
368 | rhost = get_remote_name_or_ip(utmp_len, options.verify_reverse_mapping); | |
369 | debug("PAM setting rhost to \"%.200s\"", rhost); | |
370 | ||
371 | pam_retval = pam_set_item(__pamh, PAM_RHOST, rhost); | |
372 | if (pam_retval != PAM_SUCCESS) | |
373 | fatal("PAM set rhost failed[%d]: %.200s", pam_retval, | |
374 | PAM_STRERROR(__pamh, pam_retval)); | |
375 | #ifdef PAM_TTY_KLUDGE | |
376 | /* | |
377 | * Some PAM modules (e.g. pam_time) require a TTY to operate, | |
378 | * and will fail in various stupid ways if they don't get one. | |
379 | * sshd doesn't set the tty until too late in the auth process and may | |
380 | * not even need one (for tty-less connections) | |
381 | * Kludge: Set a fake PAM_TTY | |
382 | */ | |
383 | pam_retval = pam_set_item(__pamh, PAM_TTY, "NODEVssh"); | |
384 | if (pam_retval != PAM_SUCCESS) | |
385 | fatal("PAM set tty failed[%d]: %.200s", | |
386 | pam_retval, PAM_STRERROR(__pamh, pam_retval)); | |
387 | #endif /* PAM_TTY_KLUDGE */ | |
388 | ||
389 | fatal_add_cleanup(&do_pam_cleanup_proc, NULL); | |
390 | } | |
391 | ||
392 | /* Return list of PAM enviornment strings */ | |
393 | char **fetch_pam_environment(void) | |
394 | { | |
395 | #ifdef HAVE_PAM_GETENVLIST | |
396 | return(pam_getenvlist(__pamh)); | |
397 | #else /* HAVE_PAM_GETENVLIST */ | |
398 | return(NULL); | |
399 | #endif /* HAVE_PAM_GETENVLIST */ | |
400 | } | |
401 | ||
402 | /* Print any messages that have been generated during authentication */ | |
403 | /* or account checking to stderr */ | |
404 | void print_pam_messages(void) | |
405 | { | |
406 | if (__pam_msg != NULL) | |
407 | fputs(__pam_msg, stderr); | |
408 | } | |
409 | ||
410 | /* Append a message to buffer */ | |
411 | void message_cat(char **p, const char *a) | |
412 | { | |
413 | char *cp; | |
414 | size_t new_len; | |
415 | ||
416 | new_len = strlen(a); | |
417 | ||
418 | if (*p) { | |
419 | size_t len = strlen(*p); | |
420 | ||
421 | *p = xrealloc(*p, new_len + len + 2); | |
422 | cp = *p + len; | |
423 | } else | |
424 | *p = cp = xmalloc(new_len + 2); | |
425 | ||
426 | memcpy(cp, a, new_len); | |
427 | cp[new_len] = '\n'; | |
428 | cp[new_len + 1] = '\0'; | |
429 | } | |
430 | ||
431 | #endif /* USE_PAM */ |