summaryrefslogtreecommitdiff
path: root/pam_pwdfile.c
blob: bebbeeadcc7ddee320a97a8b51ce877e7c93caa5 (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
/* 
 * pam authentication module that can be pointed at any username/crypted
 * text file so that pam using application can use an alternate set of
 * passwords than specified in system password database
 * 
 * Copyright (c) 1999-2003 Charl P. Botha <cpbotha@cpbotha.net>
 * Copyright (c) 2012-2013 Timo Weingärtner <timo@tiwe.de>
 * 
 * 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, and the entire permission notice in its entirety,
 *    including the disclaimer of warranties.
 * 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.
 * 3. The name of the author may not be used to endorse or promote
 *    products derived from this software without specific prior
 *    written permission.
 * 
 * ALTERNATIVELY, this product may be distributed under the terms of the
 * GNU General Public License, in which case the provisions of the GPL are
 * required INSTEAD OF the above restrictions.  (This clause is
 * necessary due to a potential bad interaction between the GPL and
 * the restrictions contained in a BSD-style copyright.)
 * 
 * THIS SOFTWARE IS PROVIDED ``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.
 */

#ifdef USE_CRYPT_R
#define _GNU_SOURCE
#include <crypt.h>
#else
#ifndef _XOPEN_SOURCE
#define _XOPEN_SOURCE 700
#endif
#ifndef _BSD_SOURCE
#define _BSD_SOURCE
#endif
#endif

#include <syslog.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <errno.h>
#include <sys/types.h>
#include <sys/stat.h>
#include <sys/wait.h>
#include <sys/file.h>
#include <unistd.h>
#include <syslog.h>

#include <security/pam_appl.h>

#define PAM_SM_AUTH
#include <security/pam_modules.h>
#include <security/pam_ext.h>

#include "md5.h"
#include "bigcrypt.h"

static int lock_fd(int fd) {
    int delay;
    
    for (delay = 5; delay <= 40; delay *= 2) {
	if (flock(fd, LOCK_SH | LOCK_NB) == -1) {
	    /* failed */
	    if (errno != EWOULDBLOCK) goto failed;
	    sleep(delay);
	}else{
	    return 0;
	}
    }
    if (flock(fd, LOCK_SH | LOCK_NB) != -1) return 0;
    failed:
    return -1;
}

/* expected hook for auth service */
__attribute__((visibility("default")))
PAM_EXTERN int pam_sm_authenticate(pam_handle_t *pamh, int flags,
				   int argc, const char **argv) {
    int i;
    const char *name;
    char const * password;
    char const * pwdfilename = NULL;
    char const * stored_crypted_password = NULL;
    char const * crypted_password;
    FILE *pwdfile;
    int use_flock = 0;
    int use_delay = 1;
    int legacy_crypt = 0;
    int debug = 0;
    char * linebuf = NULL;
    size_t linebuflen;
#ifdef USE_CRYPT_R
    struct crypt_data crypt_buf;
#endif
    
    /* we require the pwdfile switch and argument to be present, else we don't work */
    for (i = 0; i < argc; ++i) {
	if (!strcmp(argv[i], "pwdfile") && i + 1 < argc)
	    pwdfilename = argv[++i];
	else if (!strncmp(argv[i], "pwdfile=", strlen("pwdfile=")))
	    pwdfilename = argv[i] + strlen("pwdfile=");
	else if (!strcmp(argv[i], "flock"))
	    use_flock = 1;
	else if (!strcmp(argv[i], "noflock"))
	    use_flock = 0;
	else if (!strcmp(argv[i], "nodelay"))
	    use_delay = 0;
	else if (!strcmp(argv[i], "debug"))
	    debug = 1;
	else if (!strcmp(argv[i], "legacy_crypt"))
	    legacy_crypt = 1;
    }
    
#ifdef HAVE_PAM_FAIL_DELAY
    if (use_delay) {
	if (debug) pam_syslog(pamh, LOG_DEBUG, "setting fail delay");
	(void) pam_fail_delay(pamh, 2000000);   /* 2 sec */
    }
#endif
    
    if (!pwdfilename) {
	pam_syslog(pamh, LOG_ERR, "password file name not specified");
	return PAM_AUTHINFO_UNAVAIL;
    }
    
    if (pam_get_user(pamh, &name, NULL) != PAM_SUCCESS) {
	pam_syslog(pamh, LOG_ERR, "couldn't get username from PAM stack");
	return PAM_AUTH_ERR;
    }
    if (debug) pam_syslog(pamh, LOG_DEBUG, "username is %s", name);
    
    if (!(pwdfile = fopen(pwdfilename, "r"))) {
	pam_syslog(pamh, LOG_ALERT, "couldn't open password file %s", pwdfilename);
	return PAM_AUTHINFO_UNAVAIL;
    }
    
    if (use_flock && lock_fd(fileno(pwdfile)) == -1) {
	pam_syslog(pamh, LOG_ALERT, "couldn't lock password file %s", pwdfilename);
	fclose(pwdfile);
	return PAM_AUTHINFO_UNAVAIL;
    }
    
    /* get the crypted password corresponding to this user out of pwdfile */
    while (getline(&linebuf, &linebuflen, pwdfile) > 0) {
	/* strsep changes its argument, make a copy */
	char * nexttok = linebuf;
	
	/* first field: username */
	char * curtok = strsep(&nexttok, ":");
	
	/* skip non-matching usernames */
	if (strcmp(curtok, name))
	    continue;
	
	/* second field: password (until next colon or newline) */
	if ((curtok = strsep(&nexttok, ":\n"))) {
	    stored_crypted_password = curtok;
	    break;
	}
    }
    fclose(pwdfile);
    /* we keep linebuf (allocated by getline), stored_crypted_password is pointing into it */

    if (!stored_crypted_password)
	if (debug) pam_syslog(pamh, LOG_ERR, "user not found in password database");
    
    if (stored_crypted_password && !strlen(stored_crypted_password)) {
	if (debug) pam_syslog(pamh, LOG_DEBUG, "user has empty password field");
	free(linebuf);
	return flags & PAM_DISALLOW_NULL_AUTHTOK ? PAM_AUTH_ERR : PAM_SUCCESS;
    }
    
    if (pam_get_authtok(pamh, PAM_AUTHTOK, &password, NULL) != PAM_SUCCESS) {
	pam_syslog(pamh, LOG_ERR, "couldn't get password from PAM stack");
	free(linebuf);
	return PAM_AUTH_ERR;
    }
    
    if (!stored_crypted_password) {
	free(linebuf);
	return PAM_USER_UNKNOWN;
    }
    
    if (debug) pam_syslog(pamh, LOG_DEBUG, "got crypted password == '%s'", stored_crypted_password);
    
#ifdef USE_CRYPT_R
    crypt_buf.initialized = 0;
    if (!(crypted_password = crypt_r(password, stored_crypted_password, &crypt_buf)))
#else
    if (!(crypted_password = crypt(password, stored_crypted_password)))
#endif
    {
	pam_syslog(pamh, LOG_ERR, "crypt() failed");
	free(linebuf);
	return PAM_AUTH_ERR;
    }
    
    if (legacy_crypt && strcmp(crypted_password, stored_crypted_password)) {
	if (!strncmp(stored_crypted_password, "$1$", 3))
	    crypted_password = Brokencrypt_md5(password, stored_crypted_password);
	else
	    crypted_password = bigcrypt(password, stored_crypted_password);
    }

    if (strcmp(crypted_password, stored_crypted_password)) {
	pam_syslog(pamh, LOG_NOTICE, "wrong password for user %s", name);
	free(linebuf);
	return PAM_AUTH_ERR;
    }
    
    if (debug) pam_syslog(pamh, LOG_DEBUG, "passwords match");
    free(linebuf);
    return PAM_SUCCESS;
}

/* another expected hook */
__attribute__((visibility("default")))
PAM_EXTERN int pam_sm_setcred(pam_handle_t *pamh, int flags, 
			      int argc, const char **argv)
{
    return PAM_SUCCESS;
}

#ifdef PAM_STATIC
struct pam_module _pam_listfile_modstruct = {
    "pam_pwdfile",
	pam_sm_authenticate,
	pam_sm_setcred,
	NULL,
	NULL,
	NULL,
	NULL,
};
#endif
/* vim:set ts=8 sw=4: */