xref: /illumos-gate/usr/src/lib/gss_mechs/mech_krb5/krb5/krb/getuid.c (revision 4c87aefe8930bd07275b8dd2e96ea5f24d93a52e)
1 /*
2  * CDDL HEADER START
3  *
4  * The contents of this file are subject to the terms of the
5  * Common Development and Distribution License (the "License").
6  * You may not use this file except in compliance with the License.
7  *
8  * You can obtain a copy of the license at usr/src/OPENSOLARIS.LICENSE
9  * or http://www.opensolaris.org/os/licensing.
10  * See the License for the specific language governing permissions
11  * and limitations under the License.
12  *
13  * When distributing Covered Code, include this CDDL HEADER in each
14  * file and include the License file at usr/src/OPENSOLARIS.LICENSE.
15  * If applicable, add the following below this CDDL HEADER, with the
16  * fields enclosed by brackets "[]" replaced with your own identifying
17  * information: Portions Copyright [yyyy] [name of copyright owner]
18  *
19  * CDDL HEADER END
20  */
21 
22 /*
23  * Copyright 2007 Sun Microsystems, Inc.  All rights reserved.
24  * Use is subject to license terms.
25  */
26 
27 #pragma ident	"%Z%%M%	%I%	%E% SMI"
28 
29 #include	<sys/types.h>
30 #include	<unistd.h>
31 #include	<dlfcn.h>
32 #include	"k5-int.h"
33 
34 #define		KRB5_UID	"app_krb5_user_uid"
35 
36 /*
37  * mech_krb5 makes various calls to getuid().  When employed by gssd(1M) and
38  * ktkt_warnd(1M), app_krb5_user_uid() is used to select a given user's
39  * credential cache, rather than the id of the process.
40  */
41 uid_t
42 krb5_getuid()
43 {
44 	static uid_t	(*gptr)() = NULL;
45 	void		*handle;
46 
47 	if (gptr == NULL) {
48 		/*
49 		 * Specifically look for app_krb5_user_uid() in the application,
50 		 * and don't fall into an exhaustive search through all of the
51 		 * process dependencies.  This interface is suplied from
52 		 * gssd(1M) and ktkt_warnd(1M).
53 		 */
54 		if (((handle = dlopen(0, (RTLD_LAZY | RTLD_FIRST))) == NULL) ||
55 		    ((gptr = (uid_t (*)())dlsym(handle, KRB5_UID)) == NULL)) {
56 			/*
57 			 * Fall back to the default getuid(), which is probably
58 			 * libc.
59 			 */
60 			gptr = &getuid;
61 		}
62 	}
63 
64 	/*
65 	 * Return the appropriate uid.  Note, if a default getuid() couldn't
66 	 * be found, the getuid assignment would have failed to relocate, and
67 	 * hence this module would fail to load.
68 	 */
69 	return ((*gptr)());
70 }
71