dist/openpam/lib/openpam_borrow_cred.c

   1 /*-
   2  * Copyright (c) 2002-2003 Networks Associates Technology, Inc.
   3  * Copyright (c) 2004-2007 Dag-Erling Smørgrav
   4  * All rights reserved.
   5  *
   6  * This software was developed for the FreeBSD Project by ThinkSec AS and
   7  * Network Associates Laboratories, the Security Research Division of
   8  * Network Associates, Inc.  under DARPA/SPAWAR contract N66001-01-C-8035
   9  * ("CBOSS"), as part of the DARPA CHATS research program.
  10  *
  11  * Redistribution and use in source and binary forms, with or without
  12  * modification, are permitted provided that the following conditions
  13  * are met:
  14  * 1. Redistributions of source code must retain the above copyright
  15  *    notice, this list of conditions and the following disclaimer.
  16  * 2. Redistributions in binary form must reproduce the above copyright
  17  *    notice, this list of conditions and the following disclaimer in the
  18  *    documentation and/or other materials provided with the distribution.
  19  * 3. The name of the author may not be used to endorse or promote
  20  *    products derived from this software without specific prior written
  21  *    permission.
  22  *
  23  * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
  24  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
  25  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
  26  * ARE DISCLAIMED.  IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
  27  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
  28  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
  29  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
  30  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
  31  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
  32  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
  33  * SUCH DAMAGE.
  34  *
  35  * $Id: openpam_borrow_cred.c,v 1.6 2008/01/27 01:22:58 christos Exp $
  36  */
  37
  38 #include <sys/param.h>
  39
  40 #include <grp.h>
  41 #include <limits.h>
  42 #include <pwd.h>
  43 #include <stdlib.h>
  44 #include <unistd.h>
  45
  46 #include <security/pam_appl.h>
  47
  48 #include "openpam_impl.h"
  49
  50 /*
  51  * OpenPAM extension
  52  *
  53  * Temporarily borrow user credentials
  54  */
  55
  56 int
  57 openpam_borrow_cred(pam_handle_t *pamh,
  58         const struct passwd *pwd)
  59 {
  60         struct pam_saved_cred *scred;
  61         const void *scredp;
  62         int r;
  63
  64         ENTERI(pwd->pw_uid);
  65         r = pam_get_data(pamh, PAM_SAVED_CRED, &scredp);
  66         if (r == PAM_SUCCESS && scredp != NULL) {
  67                 openpam_log(PAM_LOG_DEBUG,
  68                     "already operating under borrowed credentials");
  69                 RETURNC(PAM_SYSTEM_ERR);
  70         }
  71         if (geteuid() != 0 && geteuid() != pwd->pw_uid) {
  72                 openpam_log(PAM_LOG_DEBUG, "called with non-zero euid: %d",
  73                     (int)geteuid());
  74                 RETURNC(PAM_PERM_DENIED);
  75         }
  76         scred = calloc((size_t)1, sizeof *scred);
  77         if (scred == NULL)
  78                 RETURNC(PAM_BUF_ERR);
  79         scred->euid = geteuid();
  80         scred->egid = getegid();
  81         r = getgroups(NGROUPS_MAX, scred->groups);
  82         if (r < 0) {
  83                 FREE(scred);
  84                 RETURNC(PAM_SYSTEM_ERR);
  85         }
  86         scred->ngroups = r;
  87         r = pam_set_data(pamh, PAM_SAVED_CRED, scred, &openpam_free_data);
  88         if (r != PAM_SUCCESS) {
  89                 FREE(scred);
  90                 RETURNC(r);
  91         }
  92         if (geteuid() == pwd->pw_uid)
  93                 RETURNC(PAM_SUCCESS);
  94         if (initgroups(pwd->pw_name, pwd->pw_gid) < 0 ||
  95               setegid(pwd->pw_gid) < 0 || seteuid(pwd->pw_uid) < 0) {
  96                 openpam_restore_cred(pamh);
  97                 RETURNC(PAM_SYSTEM_ERR);
  98         }
  99         RETURNC(PAM_SUCCESS);
 100         /*NOTREACHED*/
 101 }
 102
 103 /*
 104  * Error codes:
 105  *
 106  *      =pam_set_data
 107  *      PAM_SYSTEM_ERR
 108  *      PAM_BUF_ERR
 109  *      PAM_PERM_DENIED
 110  */
 111
 112 /**
 113  * The =openpam_borrow_cred function saves the current credentials and
 114  * switches to those of the user specified by its =pwd argument.
 115  * The affected credentials are the effective UID, the effective GID, and
 116  * the group access list.
 117  * The original credentials can be restored using =openpam_restore_cred.
 118  *
 119  * >setegid 2
 120  * >seteuid 2
 121  * >setgroups 2
 122  */