contrib/openpam/lib/openpam_borrow_cred.c

   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#13 $
  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
  55 int
  56 openpam_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.
 113  * The affected credentials are the effective UID, the effective GID, and
 114  * the group access list.
 115  * The original credentials can be restored using =openpam_restore_cred.
 116  *
 117  * >setegid 2
 118  * >seteuid 2
 119  * >setgroups 2
 120  */