summaryrefslogtreecommitdiffstats
path: root/modules/pam_unix/unix_update.c
blob: 3559972bbf4877c6f960612ed29863fa9bfc5fbd (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
/*
 * This program is designed to run with sufficient privilege
 * to read and write all of the unix password databases.
 * Its purpose is to allow updating the databases when
 * SELinux confinement of the caller domain prevents them to
 * do that themselves.
 *
 * The password is read from the standard input. The exit status of
 * this program indicates whether the password was updated or not.
 *
 * Copyright information is located at the end of the file.
 *
 */

#include "config.h"

#include <stdarg.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <syslog.h>
#include <unistd.h>
#include <sys/types.h>
#include <sys/stat.h>
#include <pwd.h>
#include <shadow.h>
#include <signal.h>
#include <time.h>
#include <sys/time.h>

#include <security/_pam_types.h>
#include <security/_pam_macros.h>

#include "passverify.h"
#include "pam_inline.h"

static int
set_password(const char *forwho, const char *shadow, const char *remember)
{
    struct passwd *pwd = NULL;
    int retval;
    char pass[PAM_MAX_RESP_SIZE + 1];
    char towhat[PAM_MAX_RESP_SIZE + 1];
    int npass = 0;
    /* we don't care about number format errors because the helper
       should be called internally only */
    int doshadow = atoi(shadow);
    int nremember = atoi(remember);
    char *passwords[] = { pass, towhat };

    /* read the password from stdin (a pipe from the pam_unix module) */

    npass = pam_read_passwords(STDIN_FILENO, 2, passwords);

    if (npass != 2) {	/* is it a valid password? */
      if (npass == 1) {
        helper_log_err(LOG_DEBUG, "no new password supplied");
	memset(pass, '\0', PAM_MAX_RESP_SIZE);
      } else {
        helper_log_err(LOG_DEBUG, "no valid passwords supplied");
      }
      return PAM_AUTHTOK_ERR;
    }

    if (lock_pwdf() != PAM_SUCCESS)
	return PAM_AUTHTOK_LOCK_BUSY;

    pwd = getpwnam(forwho);

    if (pwd == NULL) {
        retval = PAM_USER_UNKNOWN;
        goto done;
    }

    /* If real caller uid is not root we must verify that
       received old pass agrees with the current one.
       We always allow change from null pass. */
    if (getuid()) {
	retval = helper_verify_password(forwho, pass, 1);
	if (retval != PAM_SUCCESS) {
	    goto done;
	}
    }

    /* first, save old password */
    if (save_old_password(forwho, pass, nremember)) {
	retval = PAM_AUTHTOK_ERR;
	goto done;
    }

    if (doshadow || is_pwd_shadowed(pwd)) {
	retval = unix_update_shadow(forwho, towhat);
	if (retval == PAM_SUCCESS)
	    if (!is_pwd_shadowed(pwd))
		retval = unix_update_passwd(forwho, "x");
    } else {
	retval = unix_update_passwd(forwho, towhat);
    }

done:
    memset(pass, '\0', PAM_MAX_RESP_SIZE);
    memset(towhat, '\0', PAM_MAX_RESP_SIZE);

    unlock_pwdf();

    if (retval == PAM_SUCCESS) {
	return PAM_SUCCESS;
    } else {
	return PAM_AUTHTOK_ERR;
    }
}

int main(int argc, char *argv[])
{
	char *option;

	/*
	 * Catch or ignore as many signal as possible.
	 */
	setup_signals();

	/*
	 * we establish that this program is running with non-tty stdin.
	 * this is to discourage casual use. It does *NOT* prevent an
	 * intruder from repeatadly running this program to determine the
	 * password of the current user (brute force attack, but one for
	 * which the attacker must already have gained access to the user's
	 * account).
	 */

	if (isatty(STDIN_FILENO) || argc != 5 ) {
		helper_log_err(LOG_NOTICE
		      ,"inappropriate use of Unix helper binary [UID=%d]"
			 ,getuid());
		fprintf(stderr
		 ,"This binary is not designed for running in this way\n"
		      "-- the system administrator has been informed\n");
		sleep(10);	/* this should discourage/annoy the user */
		return PAM_SYSTEM_ERR;
	}

	/* We must be root to read/update shadow.
	 */
	if (geteuid() != 0) {
	    return PAM_CRED_INSUFFICIENT;
	}

	option = argv[2];

	if (strcmp(option, "update") == 0) {
	    /* Attempting to change the password */
	    return set_password(argv[1], argv[3], argv[4]);
	}

	return PAM_SYSTEM_ERR;
}

/*
 * Copyright (c) Andrew G. Morgan, 1996. All rights reserved
 * Copyright (c) Red Hat, Inc., 2007, 2008. 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, 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 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.
 */