openpam_borrow_cred.c revision 174832 
1/*-
2 * Copyright (c) 2002-2003 Networks Associates Technology, Inc.
3 * Copyright (c) 2004-2007 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 * $Id: openpam_borrow_cred.c 408 2007-12-21 11:36:24Z des $
36 */
37
38#include <sys/param.h>
39
40#include <grp.h>
41#include <limits.h>
42#include <pwd.h>
43#include <stdlib.h>
44#include <unistd.h>
45
46#include <security/pam_appl.h>
47
48#include "openpam_impl.h"
49
50/*
51 * OpenPAM extension
52 *
53 * Temporarily borrow user credentials
54 */
55
56int
57openpam_borrow_cred(pam_handle_t *pamh,
58	const struct passwd *pwd)
59{
60	struct pam_saved_cred *scred;
61	const void *scredp;
62	int r;
63
64	ENTERI(pwd->pw_uid);
65	r = pam_get_data(pamh, PAM_SAVED_CRED, &scredp);
66	if (r == PAM_SUCCESS && scredp != NULL) {
67		openpam_log(PAM_LOG_DEBUG,
68		    "already operating under borrowed credentials");
69		RETURNC(PAM_SYSTEM_ERR);
70	}
71	if (geteuid() != 0 && geteuid() != pwd->pw_uid) {
72		openpam_log(PAM_LOG_DEBUG, "called with non-zero euid: %d",
73		    (int)geteuid());
74		RETURNC(PAM_PERM_DENIED);
75	}
76	scred = calloc(1, sizeof *scred);
77	if (scred == NULL)
78		RETURNC(PAM_BUF_ERR);
79	scred->euid = geteuid();
80	scred->egid = getegid();
81	r = getgroups(NGROUPS_MAX, scred->groups);
82	if (r < 0) {
83		FREE(scred);
84		RETURNC(PAM_SYSTEM_ERR);
85	}
86	scred->ngroups = r;
87	r = pam_set_data(pamh, PAM_SAVED_CRED, scred, &openpam_free_data);
88	if (r != PAM_SUCCESS) {
89		FREE(scred);
90		RETURNC(r);
91	}
92	if (geteuid() == pwd->pw_uid)
93		RETURNC(PAM_SUCCESS);
94	if (initgroups(pwd->pw_name, pwd->pw_gid) < 0 ||
95	      setegid(pwd->pw_gid) < 0 || seteuid(pwd->pw_uid) < 0) {
96		openpam_restore_cred(pamh);
97		RETURNC(PAM_SYSTEM_ERR);
98	}
99	RETURNC(PAM_SUCCESS);
100}
101
102/*
103 * Error codes:
104 *
105 *	=pam_set_data
106 *	PAM_SYSTEM_ERR
107 *	PAM_BUF_ERR
108 *	PAM_PERM_DENIED
109 */
110
111/**
112 * The =openpam_borrow_cred function saves the current credentials and
113 * switches to those of the user specified by its =pwd argument.
114 * The affected credentials are the effective UID, the effective GID, and
115 * the group access list.
116 * The original credentials can be restored using =openpam_restore_cred.
117 *
118 * >setegid 2
119 * >seteuid 2
120 * >setgroups 2
121 */
122