openpam_borrow_cred.c revision 107937 
1/*-
2 * Copyright (c) 2002 Networks Associates Technology, Inc.
3 * All rights reserved.
4 *
5 * This software was developed for the FreeBSD Project by ThinkSec AS and
6 * Network Associates Laboratories, the Security Research Division of
7 * Network Associates, Inc.  under DARPA/SPAWAR contract N66001-01-C-8035
8 * ("CBOSS"), as part of the DARPA CHATS research program.
9 *
10 * Redistribution and use in source and binary forms, with or without
11 * modification, are permitted provided that the following conditions
12 * are met:
13 * 1. Redistributions of source code must retain the above copyright
14 *    notice, this list of conditions and the following disclaimer.
15 * 2. Redistributions in binary form must reproduce the above copyright
16 *    notice, this list of conditions and the following disclaimer in the
17 *    documentation and/or other materials provided with the distribution.
18 * 3. The name of the author may not be used to endorse or promote
19 *    products derived from this software without specific prior written
20 *    permission.
21 *
22 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
23 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
24 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
25 * ARE DISCLAIMED.  IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
26 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
27 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
28 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
29 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
30 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
31 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
32 * SUCH DAMAGE.
33 *
34 * $P4: //depot/projects/openpam/lib/openpam_borrow_cred.c#3 $
35 */
36
37#include <sys/param.h>
38
39#include <pwd.h>
40#include <stdlib.h>
41#include <unistd.h>
42
43#include <security/pam_appl.h>
44
45#include "openpam_impl.h"
46
47/*
48 * OpenPAM extension
49 *
50 * Temporarily borrow user credentials
51 */
52
53int
54openpam_borrow_cred(pam_handle_t *pamh,
55	const struct passwd *pwd)
56{
57	struct pam_saved_cred *scred;
58	int r;
59
60	ENTER();
61	if (geteuid() != 0)
62		RETURNC(PAM_PERM_DENIED);
63	scred = calloc(1, sizeof *scred);
64	if (scred == NULL)
65		RETURNC(PAM_BUF_ERR);
66	scred->euid = geteuid();
67	scred->egid = getegid();
68	r = getgroups(NGROUPS_MAX, scred->groups);
69	if (r == -1) {
70		free(scred);
71		RETURNC(PAM_SYSTEM_ERR);
72	}
73	scred->ngroups = r;
74	r = pam_set_data(pamh, PAM_SAVED_CRED, scred, &openpam_free_data);
75	if (r != PAM_SUCCESS) {
76		free(scred);
77		RETURNC(r);
78	}
79	if (initgroups(pwd->pw_name, pwd->pw_gid) == -1 ||
80	      setegid(pwd->pw_gid) == -1 || seteuid(pwd->pw_uid) == -1) {
81		openpam_restore_cred(pamh);
82		RETURNC(PAM_SYSTEM_ERR);
83	}
84	RETURNC(PAM_SUCCESS);
85}
86
87/*
88 * Error codes:
89 *
90 *	=pam_set_data
91 *	PAM_SYSTEM_ERR
92 *	PAM_BUF_ERR
93 *	PAM_PERM_DENIED
94 */
95
96/**
97 * The =openpam_borrow_cred function saves the current credentials and
98 * switches to those of the user specified by its =pwd argument.  The
99 * affected credentials are the effective UID, the effective GID, and the
100 * group access list.  The original credentials can be restored using
101 * =openpam_restore_cred.
102 *
103 * >setegid
104 * >seteuid
105 * >setgroups
106 */
107