contrib/openpam/lib/openpam_check_owner_perms.c

   1 /*-
   2  * Copyright (c) 2011 Dag-Erling Smørgrav
   3  * All rights reserved.
   4  *
   5  * Redistribution and use in source and binary forms, with or without
   6  * modification, are permitted provided that the following conditions
   7  * are met:
   8  * 1. Redistributions of source code must retain the above copyright
   9  *    notice, this list of conditions and the following disclaimer
  10  *    in this position and unchanged.
  11  * 2. Redistributions in binary form must reproduce the above copyright
  12  *    notice, this list of conditions and the following disclaimer in the
  13  *    documentation and/or other materials provided with the distribution.
  14  * 3. The name of the author may not be used to endorse or promote
  15  *    products derived from this software without specific prior written
  16  *    permission.
  17  *
  18  * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
  19  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
  20  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
  21  * ARE DISCLAIMED.  IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
  22  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
  23  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
  24  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
  25  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
  26  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
  27  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
  28  * SUCH DAMAGE.
  29  *
  30  * $Id: openpam_check_owner_perms.c 543 2012-03-31 22:11:34Z des $
  31  */
  32
  33 #ifdef HAVE_CONFIG_H
  34 # include "config.h"
  35 #endif
  36
  37 #include <sys/types.h>
  38 #include <sys/stat.h>
  39
  40 #include <errno.h>
  41 #include <limits.h>
  42 #include <stdlib.h>
  43 #include <string.h>
  44 #include <unistd.h>
  45
  46 #include <security/pam_appl.h>
  47
  48 #include "openpam_impl.h"
  49
  50 /*
  51  * OpenPAM internal
  52  *
  53  * Verify that the file or directory referenced by the given descriptor is
  54  * owned by either root or the arbitrator and that it is not writable by
  55  * group or other.
  56  */
  57
  58 int
  59 openpam_check_desc_owner_perms(const char *name, int fd)
  60 {
  61         uid_t root, arbitrator;
  62         struct stat sb;
  63         int serrno;
  64
  65         root = 0;
  66         arbitrator = geteuid();
  67         if (fstat(fd, &sb) != 0) {
  68                 serrno = errno;
  69                 openpam_log(PAM_LOG_ERROR, "%s: %m", name);
  70                 errno = serrno;
  71                 return (-1);
  72         }
  73         if (!S_ISREG(sb.st_mode)) {
  74                 openpam_log(PAM_LOG_ERROR,
  75                     "%s: not a regular file", name);
  76                 errno = EINVAL;
  77                 return (-1);
  78         }
  79         if ((sb.st_uid != root && sb.st_uid != arbitrator) ||
  80             (sb.st_mode & (S_IWGRP|S_IWOTH)) != 0) {
  81                 openpam_log(PAM_LOG_ERROR,
  82                     "%s: insecure ownership or permissions", name);
  83                 errno = EPERM;
  84                 return (-1);
  85         }
  86         return (0);
  87 }
  88
  89 /*
  90  * OpenPAM internal
  91  *
  92  * Verify that a file or directory and all components of the path leading
  93  * up to it are owned by either root or the arbitrator and that they are
  94  * not writable by group or other.
  95  *
  96  * Note that openpam_check_desc_owner_perms() should be used instead if
  97  * possible to avoid a race between the ownership / permission check and
  98  * the actual open().
  99  */
 100
 101 int
 102 openpam_check_path_owner_perms(const char *path)
 103 {
 104         uid_t root, arbitrator;
 105         char pathbuf[PATH_MAX];
 106         struct stat sb;
 107         int len, serrno, tip;
 108
 109         tip = 1;
 110         root = 0;
 111         arbitrator = geteuid();
 112         if (realpath(path, pathbuf) == NULL)
 113                 return (-1);
 114         len = strlen(pathbuf);
 115         while (len > 0) {
 116                 if (stat(pathbuf, &sb) != 0) {
 117                         if (errno != ENOENT) {
 118                                 serrno = errno;
 119                                 openpam_log(PAM_LOG_ERROR, "%s: %m", pathbuf);
 120                                 errno = serrno;
 121                         }
 122                         return (-1);
 123                 }
 124                 if (tip && !S_ISREG(sb.st_mode)) {
 125                         openpam_log(PAM_LOG_ERROR,
 126                             "%s: not a regular file", pathbuf);
 127                         errno = EINVAL;
 128                         return (-1);
 129                 }
 130                 if ((sb.st_uid != root && sb.st_uid != arbitrator) ||
 131                     (sb.st_mode & (S_IWGRP|S_IWOTH)) != 0) {
 132                         openpam_log(PAM_LOG_ERROR,
 133                             "%s: insecure ownership or permissions", pathbuf);
 134                         errno = EPERM;
 135                         return (-1);
 136                 }
 137                 while (--len > 0 && pathbuf[len] != '/')
 138                         pathbuf[len] = '\0';
 139                 tip = 0;
 140         }
 141         return (0);
 142 }
 143
 144 /*
 145  * NOPARSE
 146  */