openpam_borrow_cred.c revision 125647 
1/*-
2 * Copyright (c) 2002-2003 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#11 $
35 */
36
37#include <sys/param.h>
38
39#include <grp.h>
40#include <limits.h>
41#include <pwd.h>
42#include <stdlib.h>
43#include <unistd.h>
44
45#include <security/pam_appl.h>
46
47#include "openpam_impl.h"
48
49/*
50 * OpenPAM extension
51 *
52 * Temporarily borrow user credentials
53 */
54
55int
56openpam_borrow_cred(pam_handle_t *pamh,
57	const struct passwd *pwd)
58{
59	struct pam_saved_cred *scred;
60	void *scredp;
61	int r;
62
63	ENTERI(pwd->pw_uid);
64	r = pam_get_data(pamh, PAM_SAVED_CRED, &scredp);
65	if (r == PAM_SUCCESS && scredp != NULL) {
66		openpam_log(PAM_LOG_DEBUG,
67		    "already operating under borrowed credentials");
68		RETURNC(PAM_SYSTEM_ERR);
69	}
70	if (geteuid() != 0 && geteuid() != pwd->pw_uid) {
71		openpam_log(PAM_LOG_DEBUG, "called with non-zero euid: %d",
72		    (int)geteuid());
73		RETURNC(PAM_PERM_DENIED);
74	}
75	scred = calloc(1, sizeof *scred);
76	if (scred == NULL)
77		RETURNC(PAM_BUF_ERR);
78	scred->euid = geteuid();
79	scred->egid = getegid();
80	r = getgroups(NGROUPS_MAX, scred->groups);
81	if (r < 0) {
82		FREE(scred);
83		RETURNC(PAM_SYSTEM_ERR);
84	}
85	scred->ngroups = r;
86	r = pam_set_data(pamh, PAM_SAVED_CRED, scred, &openpam_free_data);
87	if (r != PAM_SUCCESS) {
88		FREE(scred);
89		RETURNC(r);
90	}
91	if (geteuid() == pwd->pw_uid)
92		RETURNC(PAM_SUCCESS);
93	if (initgroups(pwd->pw_name, pwd->pw_gid) < 0 ||
94	      setegid(pwd->pw_gid) < 0 || seteuid(pwd->pw_uid) < 0) {
95		openpam_restore_cred(pamh);
96		RETURNC(PAM_SYSTEM_ERR);
97	}
98	RETURNC(PAM_SUCCESS);
99}
100
101/*
102 * Error codes:
103 *
104 *	=pam_set_data
105 *	PAM_SYSTEM_ERR
106 *	PAM_BUF_ERR
107 *	PAM_PERM_DENIED
108 */
109
110/**
111 * The =openpam_borrow_cred function saves the current credentials and
112 * switches to those of the user specified by its =pwd argument.  The
113 * affected credentials are the effective UID, the effective GID, and the
114 * group access list.  The original credentials can be restored using
115 * =openpam_restore_cred.
116 *
117 * >setegid
118 * >seteuid
119 * >setgroups
120 */
121