_secure_path.c

   1 /*-
   2  * Based on code copyright (c) 1995,1997 by
   3  * Berkeley Software Design, Inc.
   4  * All rights reserved.
   5  *
   6  * Redistribution and use in source and binary forms, with or without
   7  * modification, is permitted provided that the following conditions
   8  * are met:
   9  * 1. Redistributions of source code must retain the above copyright
  10  *    notice immediately at the beginning of the file, without modification,
  11  *    this list of conditions, and the following disclaimer.
  12  * 2. Redistributions in binary form must reproduce the above copyright
  13  *    notice, this list of conditions and the following disclaimer in the
  14  *    documentation and/or other materials provided with the distribution.
  15  * 3. This work was done expressly for inclusion into FreeBSD.  Other use
  16  *    is permitted provided this notation is included.
  17  * 4. Absolutely no warranty of function or purpose is made by the authors.
  18  * 5. Modifications may be freely made to this file providing the above
  19  *    conditions are met.
  20  */
  21
  22 #include <sys/cdefs.h>
  23
  24 #include <sys/types.h>
  25 #include <sys/stat.h>
  26
  27 #include <errno.h>
  28 #include <libutil.h>
  29 #include <stddef.h>
  30 #include <syslog.h>
  31
  32 /*
  33  * Check for common security problems on a given path
  34  * It must be:
  35  * 1. A regular file, and exists
  36  * 2. Owned and writable only by root (or given owner)
  37  * 3. Group ownership is given group or is non-group writable
  38  *
  39  * Returns:     -2 if file does not exist,
  40  *              -1 if security test failure
  41  *              0  otherwise
  42  */
  43
  44 int
  45 _secure_path(const char *path, uid_t uid, gid_t gid)
  46 {
  47     int         r = -1;
  48     struct stat sb;
  49     const char  *msg = NULL;
  50
  51     if (lstat(path, &sb) < 0) {
  52         if (errno == ENOENT) /* special case */
  53             r = -2;  /* if it is just missing, skip the log entry */
  54         else
  55             msg = "%s: cannot stat %s: %m";
  56     }
  57     else if (!S_ISREG(sb.st_mode))
  58         msg = "%s: %s is not a regular file";
  59     else if (sb.st_mode & S_IWOTH)
  60         msg = "%s: %s is world writable";
  61     else if ((int)uid != -1 && sb.st_uid != uid && sb.st_uid != 0) {
  62         if (uid == 0)
  63                 msg = "%s: %s is not owned by root";
  64         else
  65                 msg = "%s: %s is not owned by uid %d";
  66     } else if ((int)gid != -1 && sb.st_gid != gid && (sb.st_mode & S_IWGRP))
  67         msg = "%s: %s is group writeable by non-authorised groups";
  68     else
  69         r = 0;
  70     if (msg != NULL)
  71         syslog(LOG_ERR, msg, "_secure_path", path, uid);
  72     return r;
  73 }