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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 "servconf.h" | |
31 | ||
32 | RCSID("$Id$"); | |
33 | ||
34 | #define NEW_AUTHTOK_MSG \ | |
35 | "Warning: Your password has expired, please change it now" | |
36 | ||
37 | /* Callbacks */ | |
38 | static int pamconv(int num_msg, const struct pam_message **msg, | |
39 | struct pam_response **resp, void *appdata_ptr); | |
40 | void pam_cleanup_proc(void *context); | |
41 | void pam_msg_cat(const char *msg); | |
42 | ||
43 | /* module-local variables */ | |
44 | static struct pam_conv conv = { | |
45 | pamconv, | |
46 | NULL | |
47 | }; | |
48 | static pam_handle_t *pamh = NULL; | |
49 | static const char *pampasswd = NULL; | |
50 | static char *pam_msg = NULL; | |
51 | ||
52 | /* states for pamconv() */ | |
53 | enum { INITIAL_LOGIN, OTHER } pamstate = INITIAL_LOGIN; | |
54 | /* remember whether pam_acct_mgmt() returned PAM_NEWAUTHTOK_REQD */ | |
55 | static int password_change_required = 0; | |
56 | /* remember whether the last pam_authenticate() succeeded or not */ | |
57 | static int was_authenticated = 0; | |
58 | ||
59 | /* accessor which allows us to switch conversation structs according to | |
60 | * the authentication method being used */ | |
61 | void pam_set_conv(struct pam_conv *conv) | |
62 | { | |
63 | pam_set_item(pamh, PAM_CONV, conv); | |
64 | } | |
65 | ||
66 | /* start an authentication run */ | |
67 | int do_pam_authenticate(int flags) | |
68 | { | |
69 | int retval = pam_authenticate(pamh, flags); | |
70 | was_authenticated = (retval == PAM_SUCCESS); | |
71 | return retval; | |
72 | } | |
73 | ||
74 | /* | |
75 | * PAM conversation function. | |
76 | * There are two states this can run in. | |
77 | * | |
78 | * INITIAL_LOGIN mode simply feeds the password from the client into | |
79 | * PAM in response to PAM_PROMPT_ECHO_OFF, and collects output | |
80 | * messages with pam_msg_cat(). This is used during initial | |
81 | * authentication to bypass the normal PAM password prompt. | |
82 | * | |
83 | * OTHER mode handles PAM_PROMPT_ECHO_OFF with read_passphrase(prompt, 1) | |
84 | * and outputs messages to stderr. This mode is used if pam_chauthtok() | |
85 | * is called to update expired passwords. | |
86 | */ | |
87 | static int pamconv(int num_msg, const struct pam_message **msg, | |
88 | struct pam_response **resp, void *appdata_ptr) | |
89 | { | |
90 | struct pam_response *reply; | |
91 | int count; | |
92 | char buf[1024]; | |
93 | ||
94 | /* PAM will free this later */ | |
95 | reply = malloc(num_msg * sizeof(*reply)); | |
96 | if (reply == NULL) | |
97 | return PAM_CONV_ERR; | |
98 | ||
99 | for (count = 0; count < num_msg; count++) { | |
100 | switch(PAM_MSG_MEMBER(msg, count, msg_style)) { | |
101 | case PAM_PROMPT_ECHO_ON: | |
102 | if (pamstate == INITIAL_LOGIN) { | |
103 | free(reply); | |
104 | return PAM_CONV_ERR; | |
105 | } else { | |
106 | fputs(PAM_MSG_MEMBER(msg, count, msg), stderr); | |
107 | fgets(buf, sizeof(buf), stdin); | |
108 | reply[count].resp = xstrdup(buf); | |
109 | reply[count].resp_retcode = PAM_SUCCESS; | |
110 | break; | |
111 | } | |
112 | case PAM_PROMPT_ECHO_OFF: | |
113 | if (pamstate == INITIAL_LOGIN) { | |
114 | if (pampasswd == NULL) { | |
115 | free(reply); | |
116 | return PAM_CONV_ERR; | |
117 | } | |
118 | reply[count].resp = xstrdup(pampasswd); | |
119 | } else { | |
120 | reply[count].resp = | |
121 | xstrdup(read_passphrase(PAM_MSG_MEMBER(msg, count, msg), 1)); | |
122 | } | |
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 | if (pamstate == INITIAL_LOGIN) | |
129 | pam_msg_cat(PAM_MSG_MEMBER(msg, count, msg)); | |
130 | else { | |
131 | fputs(PAM_MSG_MEMBER(msg, count, msg), stderr); | |
132 | fputs("\n", stderr); | |
133 | } | |
134 | } | |
135 | reply[count].resp = xstrdup(""); | |
136 | reply[count].resp_retcode = PAM_SUCCESS; | |
137 | break; | |
138 | default: | |
139 | free(reply); | |
140 | return PAM_CONV_ERR; | |
141 | } | |
142 | } | |
143 | ||
144 | *resp = reply; | |
145 | ||
146 | return PAM_SUCCESS; | |
147 | } | |
148 | ||
149 | /* Called at exit to cleanly shutdown PAM */ | |
150 | void pam_cleanup_proc(void *context) | |
151 | { | |
152 | int pam_retval; | |
153 | ||
154 | if (pamh != NULL) | |
155 | { | |
156 | pam_retval = pam_close_session(pamh, 0); | |
157 | if (pam_retval != PAM_SUCCESS) { | |
158 | log("Cannot close PAM session[%d]: %.200s", | |
159 | pam_retval, PAM_STRERROR(pamh, pam_retval)); | |
160 | } | |
161 | ||
162 | pam_retval = pam_setcred(pamh, PAM_DELETE_CRED); | |
163 | if (pam_retval != PAM_SUCCESS) { | |
164 | debug("Cannot delete credentials[%d]: %.200s", | |
165 | pam_retval, PAM_STRERROR(pamh, pam_retval)); | |
166 | } | |
167 | ||
168 | pam_retval = pam_end(pamh, pam_retval); | |
169 | if (pam_retval != PAM_SUCCESS) { | |
170 | log("Cannot release PAM authentication[%d]: %.200s", | |
171 | pam_retval, PAM_STRERROR(pamh, pam_retval)); | |
172 | } | |
173 | } | |
174 | } | |
175 | ||
176 | /* Attempt password authentation using PAM */ | |
177 | int auth_pam_password(struct passwd *pw, const char *password) | |
178 | { | |
179 | extern ServerOptions options; | |
180 | int pam_retval; | |
181 | ||
182 | pam_set_conv(&conv); | |
183 | ||
184 | /* deny if no user. */ | |
185 | if (pw == NULL) | |
186 | return 0; | |
187 | if (pw->pw_uid == 0 && options.permit_root_login == 2) | |
188 | return 0; | |
189 | if (*password == '\0' && options.permit_empty_passwd == 0) | |
190 | return 0; | |
191 | ||
192 | pampasswd = password; | |
193 | ||
194 | pamstate = INITIAL_LOGIN; | |
195 | pam_retval = do_pam_authenticate(0); | |
196 | if (pam_retval == PAM_SUCCESS) { | |
197 | debug("PAM Password authentication accepted for user \"%.100s\"", | |
198 | pw->pw_name); | |
199 | return 1; | |
200 | } else { | |
201 | debug("PAM Password authentication for \"%.100s\" failed[%d]: %s", | |
202 | pw->pw_name, pam_retval, PAM_STRERROR(pamh, pam_retval)); | |
203 | return 0; | |
204 | } | |
205 | } | |
206 | ||
207 | /* Do account management using PAM */ | |
208 | int do_pam_account(char *username, char *remote_user) | |
209 | { | |
210 | int pam_retval; | |
211 | ||
212 | debug("PAM setting rhost to \"%.200s\"", get_canonical_hostname()); | |
213 | pam_retval = pam_set_item(pamh, PAM_RHOST, | |
214 | get_canonical_hostname()); | |
215 | if (pam_retval != PAM_SUCCESS) { | |
216 | fatal("PAM set rhost failed[%d]: %.200s", | |
217 | pam_retval, PAM_STRERROR(pamh, pam_retval)); | |
218 | } | |
219 | ||
220 | if (remote_user != NULL) { | |
221 | debug("PAM setting ruser to \"%.200s\"", remote_user); | |
222 | pam_retval = pam_set_item(pamh, PAM_RUSER, remote_user); | |
223 | if (pam_retval != PAM_SUCCESS) { | |
224 | fatal("PAM set ruser failed[%d]: %.200s", | |
225 | pam_retval, PAM_STRERROR(pamh, pam_retval)); | |
226 | } | |
227 | } | |
228 | ||
229 | pam_retval = pam_acct_mgmt(pamh, 0); | |
230 | switch (pam_retval) { | |
231 | case PAM_SUCCESS: | |
232 | /* This is what we want */ | |
233 | break; | |
234 | case PAM_NEW_AUTHTOK_REQD: | |
235 | pam_msg_cat(NEW_AUTHTOK_MSG); | |
236 | /* flag that password change is necessary */ | |
237 | password_change_required = 1; | |
238 | break; | |
239 | default: | |
240 | log("PAM rejected by account configuration[%d]: %.200s", | |
241 | pam_retval, PAM_STRERROR(pamh, pam_retval)); | |
242 | return(0); | |
243 | } | |
244 | ||
245 | return(1); | |
246 | } | |
247 | ||
248 | /* Do PAM-specific session initialisation */ | |
249 | void do_pam_session(char *username, const char *ttyname) | |
250 | { | |
251 | int pam_retval; | |
252 | ||
253 | if (ttyname != NULL) { | |
254 | debug("PAM setting tty to \"%.200s\"", ttyname); | |
255 | pam_retval = pam_set_item(pamh, PAM_TTY, ttyname); | |
256 | if (pam_retval != PAM_SUCCESS) { | |
257 | fatal("PAM set tty failed[%d]: %.200s", | |
258 | pam_retval, PAM_STRERROR(pamh, pam_retval)); | |
259 | } | |
260 | } | |
261 | ||
262 | pam_retval = pam_open_session(pamh, 0); | |
263 | if (pam_retval != PAM_SUCCESS) { | |
264 | fatal("PAM session setup failed[%d]: %.200s", | |
265 | pam_retval, PAM_STRERROR(pamh, pam_retval)); | |
266 | } | |
267 | } | |
268 | ||
269 | /* Set PAM credentials */ | |
270 | void do_pam_setcred(void) | |
271 | { | |
272 | int pam_retval; | |
273 | ||
274 | debug("PAM establishing creds"); | |
275 | pam_retval = pam_setcred(pamh, PAM_ESTABLISH_CRED); | |
276 | if (pam_retval != PAM_SUCCESS) { | |
277 | if(was_authenticated) { | |
278 | fatal("PAM setcred failed[%d]: %.200s", | |
279 | pam_retval, PAM_STRERROR(pamh, pam_retval)); | |
280 | } else { | |
281 | debug("PAM setcred failed[%d]: %.200s", | |
282 | pam_retval, PAM_STRERROR(pamh, pam_retval)); | |
283 | } | |
284 | } | |
285 | } | |
286 | ||
287 | /* accessor function for file scope static variable */ | |
288 | int pam_password_change_required(void) | |
289 | { | |
290 | return password_change_required; | |
291 | } | |
292 | ||
293 | /* | |
294 | * Have user change authentication token if pam_acct_mgmt() indicated | |
295 | * it was expired. This needs to be called after an interactive | |
296 | * session is established and the user's pty is connected to | |
297 | * stdin/stout/stderr. | |
298 | */ | |
299 | void do_pam_chauthtok(void) | |
300 | { | |
301 | int pam_retval; | |
302 | ||
303 | if (password_change_required) { | |
304 | pamstate = OTHER; | |
305 | /* | |
306 | * XXX: should we really loop forever? | |
307 | */ | |
308 | do { | |
309 | pam_retval = pam_chauthtok(pamh, PAM_CHANGE_EXPIRED_AUTHTOK); | |
310 | if (pam_retval != PAM_SUCCESS) { | |
311 | log("PAM pam_chauthtok failed[%d]: %.200s", | |
312 | pam_retval, PAM_STRERROR(pamh, pam_retval)); | |
313 | } | |
314 | } while (pam_retval != PAM_SUCCESS); | |
315 | } | |
316 | } | |
317 | ||
318 | /* Cleanly shutdown PAM */ | |
319 | void finish_pam(void) | |
320 | { | |
321 | pam_cleanup_proc(NULL); | |
322 | fatal_remove_cleanup(&pam_cleanup_proc, NULL); | |
323 | } | |
324 | ||
325 | /* Start PAM authentication for specified account */ | |
326 | void start_pam(const char *user) | |
327 | { | |
328 | int pam_retval; | |
329 | ||
330 | debug("Starting up PAM with username \"%.200s\"", user); | |
331 | ||
332 | pam_retval = pam_start(SSHD_PAM_SERVICE, user, &conv, &pamh); | |
333 | ||
334 | if (pam_retval != PAM_SUCCESS) { | |
335 | fatal("PAM initialisation failed[%d]: %.200s", | |
336 | pam_retval, PAM_STRERROR(pamh, pam_retval)); | |
337 | } | |
338 | ||
339 | #ifdef PAM_TTY_KLUDGE | |
340 | /* | |
341 | * Some PAM modules (e.g. pam_time) require a TTY to operate, | |
342 | * and will fail in various stupid ways if they don't get one. | |
343 | * sshd doesn't set the tty until too late in the auth process and may | |
344 | * not even need one (for tty-less connections) | |
345 | * Kludge: Set a fake PAM_TTY | |
346 | */ | |
347 | pam_retval = pam_set_item(pamh, PAM_TTY, "ssh"); | |
348 | if (pam_retval != PAM_SUCCESS) { | |
349 | fatal("PAM set tty failed[%d]: %.200s", | |
350 | pam_retval, PAM_STRERROR(pamh, pam_retval)); | |
351 | } | |
352 | #endif /* PAM_TTY_KLUDGE */ | |
353 | ||
354 | fatal_add_cleanup(&pam_cleanup_proc, NULL); | |
355 | } | |
356 | ||
357 | /* Return list of PAM enviornment strings */ | |
358 | char **fetch_pam_environment(void) | |
359 | { | |
360 | #ifdef HAVE_PAM_GETENVLIST | |
361 | return(pam_getenvlist(pamh)); | |
362 | #else /* HAVE_PAM_GETENVLIST */ | |
363 | return(NULL); | |
364 | #endif /* HAVE_PAM_GETENVLIST */ | |
365 | } | |
366 | ||
367 | /* Print any messages that have been generated during authentication */ | |
368 | /* or account checking to stderr */ | |
369 | void print_pam_messages(void) | |
370 | { | |
371 | if (pam_msg != NULL) | |
372 | fputs(pam_msg, stderr); | |
373 | } | |
374 | ||
375 | /* Append a message to the PAM message buffer */ | |
376 | void pam_msg_cat(const char *msg) | |
377 | { | |
378 | char *p; | |
379 | size_t new_msg_len; | |
380 | size_t pam_msg_len; | |
381 | ||
382 | new_msg_len = strlen(msg); | |
383 | ||
384 | if (pam_msg) { | |
385 | pam_msg_len = strlen(pam_msg); | |
386 | pam_msg = xrealloc(pam_msg, new_msg_len + pam_msg_len + 2); | |
387 | p = pam_msg + pam_msg_len; | |
388 | } else { | |
389 | pam_msg = p = xmalloc(new_msg_len + 2); | |
390 | } | |
391 | ||
392 | memcpy(p, msg, new_msg_len); | |
393 | p[new_msg_len] = '\n'; | |
394 | p[new_msg_len + 1] = '\0'; | |
395 | } | |
396 | ||
397 | #endif /* USE_PAM */ |