source: trunk/third/openssh/auth-pam.c @ 17193

Revision 17193, 12.0 KB checked in by zacheiss, 22 years ago (diff)
GSSAPI support for v2 of the ssh protocol.
Line 
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-pam.h"
32#include "servconf.h"
33#include "canohost.h"
34#include "readpass.h"
35
36extern char *__progname;
37
38RCSID("$Id: auth-pam.c,v 1.2 2002-02-15 19:46:58 zacheiss Exp $");
39
40#define NEW_AUTHTOK_MSG \
41        "Warning: Your password has expired, please change it now"
42
43static int do_pam_conversation(int num_msg, const struct pam_message **msg,
44        struct pam_response **resp, void *appdata_ptr);
45
46/* module-local variables */
47static struct pam_conv conv = {
48        do_pam_conversation,
49        NULL
50};
51static char *__pam_msg = NULL;
52static pam_handle_t *__pamh = NULL;
53static const char *__pampasswd = NULL;
54
55/* states for do_pam_conversation() */
56enum { INITIAL_LOGIN, OTHER } pamstate = INITIAL_LOGIN;
57/* remember whether pam_acct_mgmt() returned PAM_NEWAUTHTOK_REQD */
58static int password_change_required = 0;
59/* remember whether the last pam_authenticate() succeeded or not */
60static int was_authenticated = 0;
61
62/* Remember what has been initialised */
63static int session_opened = 0;
64static int creds_set = 0;
65
66/* accessor which allows us to switch conversation structs according to
67 * the authentication method being used */
68void do_pam_set_conv(struct pam_conv *conv)
69{
70        pam_set_item(__pamh, PAM_CONV, conv);
71}
72
73/* start an authentication run */
74int do_pam_authenticate(int flags)
75{
76        int retval = pam_authenticate(__pamh, flags);
77        was_authenticated = (retval == PAM_SUCCESS);
78        return retval;
79}
80
81/*
82 * PAM conversation function.
83 * There are two states this can run in.
84 *
85 * INITIAL_LOGIN mode simply feeds the password from the client into
86 * PAM in response to PAM_PROMPT_ECHO_OFF, and collects output
87 * messages with into __pam_msg.  This is used during initial
88 * authentication to bypass the normal PAM password prompt.
89 *
90 * OTHER mode handles PAM_PROMPT_ECHO_OFF with read_passphrase()
91 * and outputs messages to stderr. This mode is used if pam_chauthtok()
92 * is called to update expired passwords.
93 */
94static int do_pam_conversation(int num_msg, const struct pam_message **msg,
95        struct pam_response **resp, void *appdata_ptr)
96{
97        struct pam_response *reply;
98        int count;
99        char buf[1024];
100
101        /* PAM will free this later */
102        reply = malloc(num_msg * sizeof(*reply));
103        if (reply == NULL)
104                return PAM_CONV_ERR;
105
106        for (count = 0; count < num_msg; count++) {
107                if (pamstate == INITIAL_LOGIN) {
108                        /*
109                         * We can't use stdio yet, queue messages for
110                         * printing later
111                         */
112                        switch(PAM_MSG_MEMBER(msg, count, msg_style)) {
113                        case PAM_PROMPT_ECHO_ON:
114                                free(reply);
115                                return PAM_CONV_ERR;
116                        case PAM_PROMPT_ECHO_OFF:
117                                if (__pampasswd == NULL) {
118                                        free(reply);
119                                        return PAM_CONV_ERR;
120                                }
121                                reply[count].resp = xstrdup(__pampasswd);
122                                reply[count].resp_retcode = PAM_SUCCESS;
123                                break;
124                        case PAM_ERROR_MSG:
125                        case PAM_TEXT_INFO:
126                                if ((*msg)[count].msg != NULL) {
127                                        message_cat(&__pam_msg,
128                                            PAM_MSG_MEMBER(msg, count, msg));
129                                }
130                                reply[count].resp = xstrdup("");
131                                reply[count].resp_retcode = PAM_SUCCESS;
132                                break;
133                        default:
134                                free(reply);
135                                return PAM_CONV_ERR;
136                        }
137                } else {
138                        /*
139                         * stdio is connected, so interact directly
140                         */
141                        switch(PAM_MSG_MEMBER(msg, count, msg_style)) {
142                        case PAM_PROMPT_ECHO_ON:
143                                fputs(PAM_MSG_MEMBER(msg, count, msg), stderr);
144                                fgets(buf, sizeof(buf), stdin);
145                                reply[count].resp = xstrdup(buf);
146                                reply[count].resp_retcode = PAM_SUCCESS;
147                                break;
148                        case PAM_PROMPT_ECHO_OFF:
149                                reply[count].resp =
150                                    read_passphrase(PAM_MSG_MEMBER(msg, count,
151                                        msg), RP_ALLOW_STDIN);
152                                reply[count].resp_retcode = PAM_SUCCESS;
153                                break;
154                        case PAM_ERROR_MSG:
155                        case PAM_TEXT_INFO:
156                                if ((*msg)[count].msg != NULL)
157                                        fprintf(stderr, "%s\n",
158                                            PAM_MSG_MEMBER(msg, count, msg));
159                                reply[count].resp = xstrdup("");
160                                reply[count].resp_retcode = PAM_SUCCESS;
161                                break;
162                        default:
163                                free(reply);
164                                return PAM_CONV_ERR;
165                        }
166                }
167        }
168
169        *resp = reply;
170
171        return PAM_SUCCESS;
172}
173
174/* Called at exit to cleanly shutdown PAM */
175void do_pam_cleanup_proc(void *context)
176{
177        int pam_retval = PAM_SUCCESS;
178
179        if (__pamh && session_opened) {
180                pam_retval = pam_close_session(__pamh, 0);
181                if (pam_retval != PAM_SUCCESS)
182                        log("Cannot close PAM session[%d]: %.200s",
183                            pam_retval, PAM_STRERROR(__pamh, pam_retval));
184        }
185
186        if (__pamh && creds_set) {
187                pam_retval = pam_setcred(__pamh, PAM_DELETE_CRED);
188                if (pam_retval != PAM_SUCCESS)
189                        debug("Cannot delete credentials[%d]: %.200s",
190                            pam_retval, PAM_STRERROR(__pamh, pam_retval));
191        }
192
193        if (__pamh) {
194                pam_retval = pam_end(__pamh, pam_retval);
195                if (pam_retval != PAM_SUCCESS)
196                        log("Cannot release PAM authentication[%d]: %.200s",
197                            pam_retval, PAM_STRERROR(__pamh, pam_retval));
198        }
199}
200
201/* Attempt password authentation using PAM */
202int auth_pam_password(struct passwd *pw, const char *password)
203{
204        extern ServerOptions options;
205        int pam_retval;
206
207        do_pam_set_conv(&conv);
208
209        /* deny if no user. */
210        if (pw == NULL)
211                return 0;
212        if (pw->pw_uid == 0 && options.permit_root_login == PERMIT_NO_PASSWD)
213                return 0;
214        if (*password == '\0' && options.permit_empty_passwd == 0)
215                return 0;
216
217        __pampasswd = password;
218
219        pamstate = INITIAL_LOGIN;
220        pam_retval = do_pam_authenticate(
221            options.permit_empty_passwd == 0 ? PAM_DISALLOW_NULL_AUTHTOK : 0);
222        if (pam_retval == PAM_SUCCESS) {
223                debug("PAM Password authentication accepted for "
224                    "user \"%.100s\"", pw->pw_name);
225                return 1;
226        } else {
227                debug("PAM Password authentication for \"%.100s\" "
228                    "failed[%d]: %s", pw->pw_name, pam_retval,
229                    PAM_STRERROR(__pamh, pam_retval));
230                return 0;
231        }
232}
233
234/* Do account management using PAM */
235int do_pam_account(char *username, char *remote_user)
236{
237        int pam_retval;
238
239        do_pam_set_conv(&conv);
240
241        if (remote_user) {
242                debug("PAM setting ruser to \"%.200s\"", remote_user);
243                pam_retval = pam_set_item(__pamh, PAM_RUSER, remote_user);
244                if (pam_retval != PAM_SUCCESS)
245                        fatal("PAM set ruser failed[%d]: %.200s", pam_retval,
246                            PAM_STRERROR(__pamh, pam_retval));
247        }
248
249        pam_retval = pam_acct_mgmt(__pamh, 0);
250        switch (pam_retval) {
251                case PAM_SUCCESS:
252                        /* This is what we want */
253                        break;
254                case PAM_NEW_AUTHTOK_REQD:
255                        message_cat(&__pam_msg, NEW_AUTHTOK_MSG);
256                        /* flag that password change is necessary */
257                        password_change_required = 1;
258                        break;
259                default:
260                        log("PAM rejected by account configuration[%d]: "
261                            "%.200s", pam_retval, PAM_STRERROR(__pamh,
262                            pam_retval));
263                        return(0);
264        }
265
266        return(1);
267}
268
269/* Do PAM-specific session initialisation */
270void do_pam_session(char *username, const char *ttyname)
271{
272        int pam_retval;
273
274        do_pam_set_conv(&conv);
275
276        if (ttyname != NULL) {
277                debug("PAM setting tty to \"%.200s\"", ttyname);
278                pam_retval = pam_set_item(__pamh, PAM_TTY, ttyname);
279                if (pam_retval != PAM_SUCCESS)
280                        fatal("PAM set tty failed[%d]: %.200s",
281                            pam_retval, PAM_STRERROR(__pamh, pam_retval));
282        }
283
284        pam_retval = pam_open_session(__pamh, 0);
285        if (pam_retval != PAM_SUCCESS)
286                fatal("PAM session setup failed[%d]: %.200s",
287                    pam_retval, PAM_STRERROR(__pamh, pam_retval));
288
289        session_opened = 1;
290}
291
292/* Set PAM credentials */
293void do_pam_setcred(int init)
294{
295        int pam_retval;
296
297        do_pam_set_conv(&conv);
298
299        debug("PAM establishing creds");
300        pam_retval = pam_setcred(__pamh,
301            init ? PAM_ESTABLISH_CRED : PAM_REINITIALIZE_CRED);
302        if (pam_retval != PAM_SUCCESS) {
303                if (was_authenticated)
304                        fatal("PAM setcred failed[%d]: %.200s",
305                            pam_retval, PAM_STRERROR(__pamh, pam_retval));
306                else
307                        debug("PAM setcred failed[%d]: %.200s",
308                            pam_retval, PAM_STRERROR(__pamh, pam_retval));
309        } else
310                creds_set = 1;
311}
312
313/* accessor function for file scope static variable */
314int is_pam_password_change_required(void)
315{
316        return password_change_required;
317}
318
319/*
320 * Have user change authentication token if pam_acct_mgmt() indicated
321 * it was expired.  This needs to be called after an interactive
322 * session is established and the user's pty is connected to
323 * stdin/stout/stderr.
324 */
325void do_pam_chauthtok(void)
326{
327        int pam_retval;
328
329        do_pam_set_conv(&conv);
330
331        if (password_change_required) {
332                pamstate = OTHER;
333                pam_retval = pam_chauthtok(__pamh, PAM_CHANGE_EXPIRED_AUTHTOK);
334                if (pam_retval != PAM_SUCCESS)
335                        fatal("PAM pam_chauthtok failed[%d]: %.200s",
336                            pam_retval, PAM_STRERROR(__pamh, pam_retval));
337        }
338}
339
340/* Cleanly shutdown PAM */
341void finish_pam(void)
342{
343        do_pam_cleanup_proc(NULL);
344        fatal_remove_cleanup(&do_pam_cleanup_proc, NULL);
345}
346
347/* Start PAM authentication for specified account */
348void start_pam(const char *user)
349{
350        int pam_retval;
351        extern ServerOptions options;
352        extern u_int utmp_len;
353        const char *rhost;
354
355        debug("Starting up PAM with username \"%.200s\"", user);
356
357        pam_retval = pam_start(SSHD_PAM_SERVICE, user, &conv, &__pamh);
358
359        if (pam_retval != PAM_SUCCESS)
360                fatal("PAM initialisation failed[%d]: %.200s",
361                    pam_retval, PAM_STRERROR(__pamh, pam_retval));
362
363        rhost = get_remote_name_or_ip(utmp_len, options.reverse_mapping_check);
364        debug("PAM setting rhost to \"%.200s\"", rhost);
365
366        pam_retval = pam_set_item(__pamh, PAM_RHOST, rhost);
367        if (pam_retval != PAM_SUCCESS)
368                fatal("PAM set rhost failed[%d]: %.200s", pam_retval,
369                    PAM_STRERROR(__pamh, pam_retval));
370#ifdef PAM_TTY_KLUDGE
371        /*
372         * Some PAM modules (e.g. pam_time) require a TTY to operate,
373         * and will fail in various stupid ways if they don't get one.
374         * sshd doesn't set the tty until too late in the auth process and may
375         * not even need one (for tty-less connections)
376         * Kludge: Set a fake PAM_TTY
377         */
378        pam_retval = pam_set_item(__pamh, PAM_TTY, "NODEVssh");
379        if (pam_retval != PAM_SUCCESS)
380                fatal("PAM set tty failed[%d]: %.200s",
381                    pam_retval, PAM_STRERROR(__pamh, pam_retval));
382#endif /* PAM_TTY_KLUDGE */
383
384        fatal_add_cleanup(&do_pam_cleanup_proc, NULL);
385}
386
387/* Return list of PAM enviornment strings */
388char **fetch_pam_environment(void)
389{
390#ifdef HAVE_PAM_GETENVLIST
391        return(pam_getenvlist(__pamh));
392#else /* HAVE_PAM_GETENVLIST */
393        return(NULL);
394#endif /* HAVE_PAM_GETENVLIST */
395}
396
397/* Set a PAM environment string. We need to do this so that the session
398 * modules can handle things like Kerberos/GSI credentials that appear
399 * during the ssh authentication process.
400 */
401
402int do_pam_putenv(char *name, char *value) {
403        char *compound;
404        int ret=1;
405       
406        compound=xmalloc(strlen(name)+strlen(value)+2);
407        if (compound) {
408                sprintf(compound,"%s=%s",name,value);
409                ret=pam_putenv(__pamh,compound);
410                xfree(compound);
411        }
412        return(ret);
413}
414
415/* Print any messages that have been generated during authentication */
416/* or account checking to stderr */
417void print_pam_messages(void)
418{
419        if (__pam_msg != NULL)
420                fputs(__pam_msg, stderr);
421}
422
423/* Append a message to buffer */
424void message_cat(char **p, const char *a)
425{
426        char *cp;
427        size_t new_len;
428
429        new_len = strlen(a);
430
431        if (*p) {
432                size_t len = strlen(*p);
433
434                *p = xrealloc(*p, new_len + len + 2);
435                cp = *p + len;
436        } else
437                *p = cp = xmalloc(new_len + 2);
438
439        memcpy(cp, a, new_len);
440        cp[new_len] = '\n';
441        cp[new_len + 1] = '\0';
442}
443
444#endif /* USE_PAM */
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