source: openpam/trunk/lib/openpam_borrow_cred.c @ 201

Last change on this file since 201 was 201, checked in by Dag-Erling Smørgrav, 18 years ago

If a set of saved credentials already exists when we are called, log
a debugging message and fail.

If the effective uid is non-zero but identical to the target uid,
save the current credentials and return without doing anything else.

File size: 3.6 KB
Line 
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#4 $
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        ENTERI(pwd->pw_uid);
61        r = pam_get_data(pamh, PAM_SAVED_CRED, (const void **)&scred);
62        if (r == PAM_SUCCESS && scred != NULL) {
63                openpam_log(PAM_LOG_DEBUG,
64                    "already operating under borrowed credentials");
65                RETURNC(PAM_SYSTEM_ERR);
66        }
67        if (geteuid() != 0 && geteuid() != pwd->pw_uid) {
68                openpam_log(PAM_LOG_DEBUG, "called with non-zero euid: %d",
69                    (int)geteuid());
70                RETURNC(PAM_PERM_DENIED);
71        }
72        scred = calloc(1, sizeof *scred);
73        if (scred == NULL)
74                RETURNC(PAM_BUF_ERR);
75        scred->euid = geteuid();
76        scred->egid = getegid();
77        r = getgroups(NGROUPS_MAX, scred->groups);
78        if (r == -1) {
79                free(scred);
80                RETURNC(PAM_SYSTEM_ERR);
81        }
82        scred->ngroups = r;
83        r = pam_set_data(pamh, PAM_SAVED_CRED, scred, &openpam_free_data);
84        if (r != PAM_SUCCESS) {
85                free(scred);
86                RETURNC(r);
87        }
88        if (geteuid() == pwd->pw_uid)
89                RETURNC(PAM_SUCCESS);
90        if (initgroups(pwd->pw_name, pwd->pw_gid) == -1 ||
91              setegid(pwd->pw_gid) == -1 || seteuid(pwd->pw_uid) == -1) {
92                openpam_restore_cred(pamh);
93                RETURNC(PAM_SYSTEM_ERR);
94        }
95        RETURNC(PAM_SUCCESS);
96}
97
98/*
99 * Error codes:
100 *
101 *      =pam_set_data
102 *      PAM_SYSTEM_ERR
103 *      PAM_BUF_ERR
104 *      PAM_PERM_DENIED
105 */
106
107/**
108 * The =openpam_borrow_cred function saves the current credentials and
109 * switches to those of the user specified by its =pwd argument.  The
110 * affected credentials are the effective UID, the effective GID, and the
111 * group access list.  The original credentials can be restored using
112 * =openpam_restore_cred.
113 *
114 * >setegid
115 * >seteuid
116 * >setgroups
117 */
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