summaryrefslogtreecommitdiff
path: root/auth-pam.c
blob: 99b03f45b19767b73da357e53dc852fa80f674e4 (plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
403
404
405
406
407
408
409
410
411
412
413
414
415
416
417
418
419
420
421
422
423
424
425
426
427
428
429
430
431
432
433
434
435
436
437
438
439
440
441
442
443
444
445
446
447
448
449
450
451
452
453
454
455
456
457
458
459
460
461
462
463
/*
 * Copyright (c) 2000 Damien Miller.  All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in the
 *    documentation and/or other materials provided with the distribution.
 *
 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
 * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
 * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
 * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
 * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
 * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
 * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
 * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
 * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 */

#include "includes.h"

#ifdef USE_PAM
#include "xmalloc.h"
#include "log.h"
#include "auth.h"
#include "auth-options.h"
#include "auth-pam.h"
#include "servconf.h"
#include "canohost.h"
#include "readpass.h"

extern char *__progname;

extern int use_privsep;

RCSID("$Id: auth-pam.c,v 1.54 2002/07/28 20:24:08 stevesk Exp $");

#define NEW_AUTHTOK_MSG \
	"Warning: Your password has expired, please change it now."
#define NEW_AUTHTOK_MSG_PRIVSEP \
	"Your password has expired, the session cannot proceed."

static int do_pam_conversation(int num_msg, const struct pam_message **msg,
	struct pam_response **resp, void *appdata_ptr);

/* module-local variables */
static struct pam_conv conv = {
	(int (*)())do_pam_conversation,
	NULL
};
static char *__pam_msg = NULL;
static pam_handle_t *__pamh = NULL;
static const char *__pampasswd = NULL;

/* states for do_pam_conversation() */
enum { INITIAL_LOGIN, OTHER } pamstate = INITIAL_LOGIN;
/* remember whether pam_acct_mgmt() returned PAM_NEW_AUTHTOK_REQD */
static int password_change_required = 0;
/* remember whether the last pam_authenticate() succeeded or not */
static int was_authenticated = 0;

/* Remember what has been initialised */
static int session_opened = 0;
static int creds_set = 0;

/* accessor which allows us to switch conversation structs according to
 * the authentication method being used */
void do_pam_set_conv(struct pam_conv *conv)
{
	pam_set_item(__pamh, PAM_CONV, conv);
}

/* start an authentication run */
int do_pam_authenticate(int flags)
{
	int retval = pam_authenticate(__pamh, flags);
	was_authenticated = (retval == PAM_SUCCESS);
	return retval;
}

/*
 * PAM conversation function.
 * There are two states this can run in.
 *
 * INITIAL_LOGIN mode simply feeds the password from the client into
 * PAM in response to PAM_PROMPT_ECHO_OFF, and collects output
 * messages with into __pam_msg.  This is used during initial
 * authentication to bypass the normal PAM password prompt.
 *
 * OTHER mode handles PAM_PROMPT_ECHO_OFF with read_passphrase()
 * and outputs messages to stderr. This mode is used if pam_chauthtok()
 * is called to update expired passwords.
 */
static int do_pam_conversation(int num_msg, const struct pam_message **msg,
	struct pam_response **resp, void *appdata_ptr)
{
	struct pam_response *reply;
	int count;
	char buf[1024];

	/* PAM will free this later */
	reply = xmalloc(num_msg * sizeof(*reply));

	for (count = 0; count < num_msg; count++) {
		if (pamstate == INITIAL_LOGIN) {
			/*
			 * We can't use stdio yet, queue messages for 
			 * printing later
			 */
			switch(PAM_MSG_MEMBER(msg, count, msg_style)) {
			case PAM_PROMPT_ECHO_ON:
				xfree(reply);
				return PAM_CONV_ERR;
			case PAM_PROMPT_ECHO_OFF:
				if (__pampasswd == NULL) {
					xfree(reply);
					return PAM_CONV_ERR;
				}
				reply[count].resp = xstrdup(__pampasswd);
				reply[count].resp_retcode = PAM_SUCCESS;
				break;
			case PAM_ERROR_MSG:
			case PAM_TEXT_INFO:
				if (PAM_MSG_MEMBER(msg, count, msg) != NULL) {
					message_cat(&__pam_msg, 
					    PAM_MSG_MEMBER(msg, count, msg));
				}
				reply[count].resp = xstrdup("");
				reply[count].resp_retcode = PAM_SUCCESS;
				break;
			default:
				xfree(reply);
				return PAM_CONV_ERR;
			}
		} else {
			/*
			 * stdio is connected, so interact directly
			 */
			switch(PAM_MSG_MEMBER(msg, count, msg_style)) {
			case PAM_PROMPT_ECHO_ON:
				fputs(PAM_MSG_MEMBER(msg, count, msg), stderr);
				fgets(buf, sizeof(buf), stdin);
				reply[count].resp = xstrdup(buf);
				reply[count].resp_retcode = PAM_SUCCESS;
				break;
			case PAM_PROMPT_ECHO_OFF:
				reply[count].resp = 
				    read_passphrase(PAM_MSG_MEMBER(msg, count,
					msg), RP_ALLOW_STDIN);
				reply[count].resp_retcode = PAM_SUCCESS;
				break;
			case PAM_ERROR_MSG:
			case PAM_TEXT_INFO:
				if (PAM_MSG_MEMBER(msg, count, msg) != NULL)
					fprintf(stderr, "%s\n", 
					    PAM_MSG_MEMBER(msg, count, msg));
				reply[count].resp = xstrdup("");
				reply[count].resp_retcode = PAM_SUCCESS;
				break;
			default:
				xfree(reply);
				return PAM_CONV_ERR;
			}
		}
	}

	*resp = reply;

	return PAM_SUCCESS;
}

/* Called at exit to cleanly shutdown PAM */
void do_pam_cleanup_proc(void *context)
{
	int pam_retval = PAM_SUCCESS;

	if (__pamh && session_opened) {
		pam_retval = pam_close_session(__pamh, 0);
		if (pam_retval != PAM_SUCCESS)
			log("Cannot close PAM session[%d]: %.200s",
			    pam_retval, PAM_STRERROR(__pamh, pam_retval));
	}

	if (__pamh && creds_set) {
		pam_retval = pam_setcred(__pamh, PAM_DELETE_CRED);
		if (pam_retval != PAM_SUCCESS)
			debug("Cannot delete credentials[%d]: %.200s", 
			    pam_retval, PAM_STRERROR(__pamh, pam_retval));
	}

	if (__pamh) {
		pam_retval = pam_end(__pamh, pam_retval);
		if (pam_retval != PAM_SUCCESS)
			log("Cannot release PAM authentication[%d]: %.200s",
			    pam_retval, PAM_STRERROR(__pamh, pam_retval));
	}
}

/* Attempt password authentation using PAM */
int auth_pam_password(Authctxt *authctxt, const char *password)
{
	extern ServerOptions options;
	int pam_retval;
	struct passwd *pw = authctxt->pw;

	do_pam_set_conv(&conv);

	/* deny if no user. */
	if (pw == NULL)
		return 0;
	if (pw->pw_uid == 0 && options.permit_root_login == PERMIT_NO_PASSWD)
		return 0;
	if (*password == '\0' && options.permit_empty_passwd == 0)
		return 0;

	__pampasswd = password;

	pamstate = INITIAL_LOGIN;
	pam_retval = do_pam_authenticate(
	    options.permit_empty_passwd == 0 ? PAM_DISALLOW_NULL_AUTHTOK : 0);
	if (pam_retval == PAM_SUCCESS) {
		debug("PAM Password authentication accepted for "
		    "user \"%.100s\"", pw->pw_name);
		return 1;
	} else {
		debug("PAM Password authentication for \"%.100s\" "
		    "failed[%d]: %s", pw->pw_name, pam_retval, 
		    PAM_STRERROR(__pamh, pam_retval));
		return 0;
	}
}

/* Do account management using PAM */
int do_pam_account(char *username, char *remote_user)
{
	int pam_retval;

	do_pam_set_conv(&conv);

	if (remote_user) {
		debug("PAM setting ruser to \"%.200s\"", remote_user);
		pam_retval = pam_set_item(__pamh, PAM_RUSER, remote_user);
		if (pam_retval != PAM_SUCCESS)
			fatal("PAM set ruser failed[%d]: %.200s", pam_retval, 
			    PAM_STRERROR(__pamh, pam_retval));
	}

	pam_retval = pam_acct_mgmt(__pamh, 0);
	debug2("pam_acct_mgmt() = %d", pam_retval);
	switch (pam_retval) {
		case PAM_SUCCESS:
			/* This is what we want */
			break;
#if 0
		case PAM_NEW_AUTHTOK_REQD:
			message_cat(&__pam_msg, use_privsep ?
			    NEW_AUTHTOK_MSG_PRIVSEP : NEW_AUTHTOK_MSG);
			/* flag that password change is necessary */
			password_change_required = 1;
			/* disallow other functionality for now */
			no_port_forwarding_flag |= 2;
			no_agent_forwarding_flag |= 2;
			no_x11_forwarding_flag |= 2;
			break;
#endif
		default:
			log("PAM rejected by account configuration[%d]: "
			    "%.200s", pam_retval, PAM_STRERROR(__pamh, 
			    pam_retval));
			return(0);
	}

	return(1);
}

/* Do PAM-specific session initialisation */
void do_pam_session(char *username, const char *ttyname)
{
	int pam_retval;

	do_pam_set_conv(&conv);

	if (ttyname != NULL) {
		debug("PAM setting tty to \"%.200s\"", ttyname);
		pam_retval = pam_set_item(__pamh, PAM_TTY, ttyname);
		if (pam_retval != PAM_SUCCESS)
			fatal("PAM set tty failed[%d]: %.200s",
			    pam_retval, PAM_STRERROR(__pamh, pam_retval));
	}

	pam_retval = pam_open_session(__pamh, 0);
	if (pam_retval != PAM_SUCCESS)
		fatal("PAM session setup failed[%d]: %.200s",
		    pam_retval, PAM_STRERROR(__pamh, pam_retval));

	session_opened = 1;
}

/* Set PAM credentials */
void do_pam_setcred(int init)
{
	int pam_retval;

	if (__pamh == NULL)
		return;

	do_pam_set_conv(&conv);

	debug("PAM establishing creds");
	pam_retval = pam_setcred(__pamh, 
	    init ? PAM_ESTABLISH_CRED : PAM_REINITIALIZE_CRED);
	if (pam_retval != PAM_SUCCESS) {
		if (was_authenticated)
			fatal("PAM setcred failed[%d]: %.200s",
			    pam_retval, PAM_STRERROR(__pamh, pam_retval));
		else
			debug("PAM setcred failed[%d]: %.200s",
			    pam_retval, PAM_STRERROR(__pamh, pam_retval));
	} else
		creds_set = 1;
}

/* accessor function for file scope static variable */
int is_pam_password_change_required(void)
{
	return password_change_required;
}

/*
 * Have user change authentication token if pam_acct_mgmt() indicated
 * it was expired.  This needs to be called after an interactive
 * session is established and the user's pty is connected to
 * stdin/stdout/stderr.
 */
void do_pam_chauthtok(void)
{
	int pam_retval;

	do_pam_set_conv(&conv);

	if (password_change_required) {
		if (use_privsep)
			fatal("Password changing is currently unsupported"
			    " with privilege separation");
		pamstate = OTHER;
		pam_retval = pam_chauthtok(__pamh, PAM_CHANGE_EXPIRED_AUTHTOK);
		if (pam_retval != PAM_SUCCESS)
			fatal("PAM pam_chauthtok failed[%d]: %.200s",
			    pam_retval, PAM_STRERROR(__pamh, pam_retval));
#if 0
		/* XXX: This would need to be done in the parent process,
		 * but there's currently no way to pass such request. */
		no_port_forwarding_flag &= ~2;
		no_agent_forwarding_flag &= ~2;
		no_x11_forwarding_flag &= ~2;
		if (!no_port_forwarding_flag && options.allow_tcp_forwarding)
			channel_permit_all_opens();
#endif
	}
}

/* Cleanly shutdown PAM */
void finish_pam(void)
{
	do_pam_cleanup_proc(NULL);
	fatal_remove_cleanup(&do_pam_cleanup_proc, NULL);
}

/* Start PAM authentication for specified account */
void start_pam(const char *user)
{
	int pam_retval;
	extern ServerOptions options;
	extern u_int utmp_len;
	const char *rhost;

	debug("Starting up PAM with username \"%.200s\"", user);

	pam_retval = pam_start(SSHD_PAM_SERVICE, user, &conv, &__pamh);

	if (pam_retval != PAM_SUCCESS)
		fatal("PAM initialisation failed[%d]: %.200s",
		    pam_retval, PAM_STRERROR(__pamh, pam_retval));

	rhost = get_remote_name_or_ip(utmp_len, options.verify_reverse_mapping);
	debug("PAM setting rhost to \"%.200s\"", rhost);

	pam_retval = pam_set_item(__pamh, PAM_RHOST, rhost);
	if (pam_retval != PAM_SUCCESS)
		fatal("PAM set rhost failed[%d]: %.200s", pam_retval,
		    PAM_STRERROR(__pamh, pam_retval));
#ifdef PAM_TTY_KLUDGE
	/*
	 * Some PAM modules (e.g. pam_time) require a TTY to operate,
	 * and will fail in various stupid ways if they don't get one.
	 * sshd doesn't set the tty until too late in the auth process and may
	 * not even need one (for tty-less connections)
	 * Kludge: Set a fake PAM_TTY
	 */
	pam_retval = pam_set_item(__pamh, PAM_TTY, "NODEVssh");
	if (pam_retval != PAM_SUCCESS)
		fatal("PAM set tty failed[%d]: %.200s",
		    pam_retval, PAM_STRERROR(__pamh, pam_retval));
#endif /* PAM_TTY_KLUDGE */

	fatal_add_cleanup(&do_pam_cleanup_proc, NULL);
}

/* Return list of PAM environment strings */
char **fetch_pam_environment(void)
{
#ifdef HAVE_PAM_GETENVLIST
	return(pam_getenvlist(__pamh));
#else /* HAVE_PAM_GETENVLIST */
	return(NULL);
#endif /* HAVE_PAM_GETENVLIST */
}

void free_pam_environment(char **env)
{
	int i;

	if (env != NULL) {
		for (i = 0; env[i] != NULL; i++)
			xfree(env[i]);
	}
}

/* Print any messages that have been generated during authentication */
/* or account checking to stderr */
void print_pam_messages(void)
{
	if (__pam_msg != NULL)
		fputs(__pam_msg, stderr);
}

/* Append a message to buffer */
void message_cat(char **p, const char *a)
{
	char *cp;
	size_t new_len;

	new_len = strlen(a);

	if (*p) {
		size_t len = strlen(*p);

		*p = xrealloc(*p, new_len + len + 2);
		cp = *p + len;
	} else
		*p = cp = xmalloc(new_len + 2);

	memcpy(cp, a, new_len);
	cp[new_len] = '\n';
	cp[new_len + 1] = '\0';
}

#endif /* USE_PAM */