usr/src/lib/gss_mechs/mech_krb5/krb5/krb/getuid.c

   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 }