1/*-
2 * Copyright (c) 2002-2003 Networks Associates Technology, Inc.
3 * Copyright (c) 2004-2011 Dag-Erling Sm��rgrav
4 * All rights reserved.
5 *
6 * This software was developed for the FreeBSD Project by ThinkSec AS and
7 * Network Associates Laboratories, the Security Research Division of
8 * Network Associates, Inc.  under DARPA/SPAWAR contract N66001-01-C-8035
9 * ("CBOSS"), as part of the DARPA CHATS research program.
10 *
11 * Redistribution and use in source and binary forms, with or without
12 * modification, are permitted provided that the following conditions
13 * are met:
14 * 1. Redistributions of source code must retain the above copyright
15 *    notice, this list of conditions and the following disclaimer.
16 * 2. Redistributions in binary form must reproduce the above copyright
17 *    notice, this list of conditions and the following disclaimer in the
18 *    documentation and/or other materials provided with the distribution.
19 * 3. The name of the author may not be used to endorse or promote
20 *    products derived from this software without specific prior written
21 *    permission.
22 *
23 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
24 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
25 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
26 * ARE DISCLAIMED.  IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
27 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
28 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
29 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
30 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
31 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
32 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
33 * SUCH DAMAGE.
34 *
35 * $OpenPAM: openpam_borrow_cred.c 938 2017-04-30 21:34:42Z des $
36 */
37
38#ifdef HAVE_CONFIG_H
39# include "config.h"
40#endif
41
42#include <sys/param.h>
43
44#include <grp.h>
45#include <limits.h>
46#include <pwd.h>
47#include <stdlib.h>
48#include <unistd.h>
49
50#include <security/pam_appl.h>
51
52#include "openpam_impl.h"
53#include "openpam_cred.h"
54
55/*
56 * OpenPAM extension
57 *
58 * Temporarily borrow user credentials
59 */
60
61int
62openpam_borrow_cred(pam_handle_t *pamh,
63	const struct passwd *pwd)
64{
65	struct pam_saved_cred *scred;
66	const void *scredp;
67	int r;
68
69	ENTERI(pwd->pw_uid);
70	r = pam_get_data(pamh, PAM_SAVED_CRED, &scredp);
71	if (r == PAM_SUCCESS && scredp != NULL) {
72		openpam_log(PAM_LOG_LIBDEBUG,
73		    "already operating under borrowed credentials");
74		RETURNC(PAM_SYSTEM_ERR);
75	}
76	if (geteuid() != 0 && geteuid() != pwd->pw_uid) {
77		openpam_log(PAM_LOG_LIBDEBUG, "called with non-zero euid: %d",
78		    (int)geteuid());
79		RETURNC(PAM_PERM_DENIED);
80	}
81	scred = calloc(1, sizeof *scred);
82	if (scred == NULL)
83		RETURNC(PAM_BUF_ERR);
84	scred->euid = geteuid();
85	scred->egid = getegid();
86	r = getgroups(NGROUPS_MAX, scred->groups);
87	if (r < 0) {
88		FREE(scred);
89		RETURNC(PAM_SYSTEM_ERR);
90	}
91	scred->ngroups = r;
92	r = pam_set_data(pamh, PAM_SAVED_CRED, scred, &openpam_free_data);
93	if (r != PAM_SUCCESS) {
94		FREE(scred);
95		RETURNC(r);
96	}
97	if (geteuid() == pwd->pw_uid)
98		RETURNC(PAM_SUCCESS);
99	if (initgroups(pwd->pw_name, pwd->pw_gid) < 0 ||
100	      setegid(pwd->pw_gid) < 0 || seteuid(pwd->pw_uid) < 0) {
101		openpam_restore_cred(pamh);
102		RETURNC(PAM_SYSTEM_ERR);
103	}
104	RETURNC(PAM_SUCCESS);
105}
106
107/*
108 * Error codes:
109 *
110 *	=pam_set_data
111 *	PAM_SYSTEM_ERR
112 *	PAM_BUF_ERR
113 *	PAM_PERM_DENIED
114 */
115
116/**
117 * The =openpam_borrow_cred function saves the current credentials and
118 * switches to those of the user specified by its =pwd argument.
119 * The affected credentials are the effective UID, the effective GID, and
120 * the group access list.
121 * The original credentials can be restored using =openpam_restore_cred.
122 *
123 * >setegid 2
124 * >seteuid 2
125 * >setgroups 2
126 */
127