1/*	$NetBSD: pam_exec.c,v 1.8 2021/10/30 11:34:59 nia Exp $	*/
2
3/*-
4 * Copyright (c) 2001,2003 Networks Associates Technology, Inc.
5 * All rights reserved.
6 *
7 * This software was developed for the FreeBSD Project by ThinkSec AS and
8 * NAI Labs, the Security Research Division of Network Associates, Inc.
9 * under DARPA/SPAWAR contract N66001-01-C-8035 ("CBOSS"), as part of the
10 * DARPA CHATS research program.
11 *
12 * Redistribution and use in source and binary forms, with or without
13 * modification, are permitted provided that the following conditions
14 * are met:
15 * 1. Redistributions of source code must retain the above copyright
16 *    notice, this list of conditions and the following disclaimer.
17 * 2. Redistributions in binary form must reproduce the above copyright
18 *    notice, this list of conditions and the following disclaimer in the
19 *    documentation and/or other materials provided with the distribution.
20 * 3. The name of the author may not be used to endorse or promote
21 *    products derived from this software without specific prior written
22 *    permission.
23 *
24 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
25 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
26 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
27 * ARE DISCLAIMED.  IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
28 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
29 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
30 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
31 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
32 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
33 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
34 * SUCH DAMAGE.
35 */
36
37#include <sys/cdefs.h>
38#ifdef __FreeBSD__
39__FBSDID("$FreeBSD: src/lib/libpam/modules/pam_exec/pam_exec.c,v 1.4 2005/02/01 10:37:07 des Exp $");
40#else
41__RCSID("$NetBSD: pam_exec.c,v 1.8 2021/10/30 11:34:59 nia Exp $");
42#endif
43
44#include <sys/types.h>
45#include <sys/wait.h>
46
47#include <errno.h>
48#include <stdlib.h>
49#include <stdio.h>
50#include <string.h>
51#include <unistd.h>
52
53#include <security/pam_appl.h>
54#include <security/pam_modules.h>
55#include <security/openpam.h>
56
57#define ENV_ITEM(n) { (n), #n }
58static struct {
59	int item;
60	const char *name;
61} env_items[] = {
62	ENV_ITEM(PAM_SERVICE),
63	ENV_ITEM(PAM_USER),
64	ENV_ITEM(PAM_TTY),
65	ENV_ITEM(PAM_RHOST),
66	ENV_ITEM(PAM_RUSER),
67};
68
69static int
70_pam_exec(pam_handle_t *pamh __unused, int flags __unused,
71    int argc, const char *argv[])
72{
73	size_t envlen, i, nitems;
74	int pam_err, status;
75	char **envlist;
76	volatile int childerr;
77	pid_t pid;
78
79	if (argc < 1)
80		return (PAM_SERVICE_ERR);
81
82	/*
83	 * XXX For additional credit, divert child's stdin/stdout/stderr
84	 * to the conversation function.
85	 */
86
87	/*
88	 * Set up the child's environment list.  It consists of the PAM
89	 * environment, plus a few hand-picked PAM items.
90	 */
91	envlist = pam_getenvlist(pamh);
92	for (envlen = 0; envlist[envlen] != NULL; ++envlen)
93		/* nothing */ ;
94	nitems = sizeof(env_items) / sizeof(*env_items);
95	if (reallocarr(&envlist, envlen + nitems + 1, sizeof(*envlist)) != 0) {
96		openpam_free_envlist(envlist);
97		return (PAM_BUF_ERR);
98	}
99	for (i = 0; i < nitems; ++i) {
100		const void *item;
101		char *envstr;
102
103		pam_err = pam_get_item(pamh, env_items[i].item, &item);
104		if (pam_err != PAM_SUCCESS || item == NULL)
105			continue;
106		asprintf(&envstr, "%s=%s", env_items[i].name,
107		    (const char *)item);
108		if (envstr == NULL) {
109			openpam_free_envlist(envlist);
110			return (PAM_BUF_ERR);
111		}
112		envlist[envlen++] = envstr;
113		envlist[envlen] = NULL;
114	}
115
116	/*
117	 * Fork and run the command.  By using vfork() instead of fork(),
118	 * we can distinguish between an execve() failure and a non-zero
119	 * exit code from the command.
120	 */
121	childerr = 0;
122	if ((pid = vfork()) == 0) {
123		/*LINTED const cast*/
124		execve(argv[0], (char **)__UNCONST(argv), envlist);
125		childerr = errno;
126		_exit(1);
127	}
128	openpam_free_envlist(envlist);
129	if (pid == -1) {
130		openpam_log(PAM_LOG_ERROR, "vfork(): %s", strerror(errno));
131		return (PAM_SYSTEM_ERR);
132	}
133	if (waitpid(pid, &status, 0) == -1) {
134		openpam_log(PAM_LOG_ERROR, "waitpid(): %s", strerror(errno));
135		return (PAM_SYSTEM_ERR);
136	}
137	if (childerr != 0) {
138		openpam_log(PAM_LOG_ERROR, "execve(): %s", strerror(errno));
139		return (PAM_SYSTEM_ERR);
140	}
141	if (WIFSIGNALED(status)) {
142		openpam_log(PAM_LOG_ERROR, "%s caught signal %d%s",
143		    argv[0], WTERMSIG(status),
144		    WCOREDUMP(status) ? " (core dumped)" : "");
145		return (PAM_SYSTEM_ERR);
146	}
147	if (!WIFEXITED(status)) {
148		openpam_log(PAM_LOG_ERROR, "unknown status 0x%x", status);
149		return (PAM_SYSTEM_ERR);
150	}
151	if (WEXITSTATUS(status) != 0) {
152		openpam_log(PAM_LOG_ERROR, "%s returned code %d",
153		    argv[0], WEXITSTATUS(status));
154		return (PAM_SYSTEM_ERR);
155	}
156	return (PAM_SUCCESS);
157}
158
159PAM_EXTERN int
160pam_sm_authenticate(pam_handle_t *pamh, int flags,
161    int argc, const char *argv[])
162{
163
164	return (_pam_exec(pamh, flags, argc, argv));
165}
166
167PAM_EXTERN int
168pam_sm_setcred(pam_handle_t *pamh, int flags,
169    int argc, const char *argv[])
170{
171
172	return (_pam_exec(pamh, flags, argc, argv));
173}
174
175PAM_EXTERN int
176pam_sm_acct_mgmt(pam_handle_t *pamh, int flags,
177    int argc, const char *argv[])
178{
179
180	return (_pam_exec(pamh, flags, argc, argv));
181}
182
183PAM_EXTERN int
184pam_sm_open_session(pam_handle_t *pamh, int flags,
185    int argc, const char *argv[])
186{
187
188	return (_pam_exec(pamh, flags, argc, argv));
189}
190
191PAM_EXTERN int
192pam_sm_close_session(pam_handle_t *pamh, int flags,
193    int argc, const char *argv[])
194{
195
196	return (_pam_exec(pamh, flags, argc, argv));
197}
198
199PAM_EXTERN int
200pam_sm_chauthtok(pam_handle_t *pamh, int flags,
201    int argc, const char *argv[])
202{
203
204	return (_pam_exec(pamh, flags, argc, argv));
205}
206
207PAM_MODULE_ENTRY("pam_exec");
208