release/src/router/vsftpd/secutil.c

   1 /*
   2  * Part of Very Secure FTPd
   3  * Licence: GPL v2
   4  * Author: Chris Evans
   5  * secutil.c
   6  */
   7
   8 #include "secutil.h"
   9 #include "str.h"
  10 #include "sysutil.h"
  11 #include "sysstr.h"
  12 #include "utility.h"
  13 #include "sysdeputil.h"
  14
  15 void
  16 vsf_secutil_change_credentials(const struct mystr* p_user_str,
  17                                const struct mystr* p_dir_str,
  18                                const struct mystr* p_ext_dir_str,
  19                                unsigned int caps, unsigned int options)
  20 {
  21   struct vsf_sysutil_user* p_user;
  22   if (!vsf_sysutil_running_as_root())
  23   {
  24     bug("vsf_secutil_change_credentials: not running as root");
  25   }
  26   p_user = str_getpwnam(p_user_str);
  27   if (p_user == 0)
  28   {
  29     die2("cannot locate user entry:", str_getbuf(p_user_str));
  30   }
  31   {
  32     struct mystr dir_str = INIT_MYSTR;
  33     /* Work out where the chroot() jail is */
  34     if (p_dir_str == 0 || str_isempty(p_dir_str))
  35     {
  36       str_alloc_text(&dir_str, vsf_sysutil_user_get_homedir(p_user));
  37     }
  38     else
  39     {
  40       str_copy(&dir_str, p_dir_str);
  41     }
  42     /* Sort out supplementary groups before the chroot(). We need to access
  43      * /etc/groups
  44      */
  45     if (options & VSF_SECUTIL_OPTION_USE_GROUPS)
  46     {
  47       vsf_sysutil_initgroups(p_user);
  48     }
  49     else
  50     {
  51       vsf_sysutil_clear_supp_groups();
  52     }
  53     /* Always do the chdir() regardless of whether we are chroot()'ing */
  54     {
  55       /* Do chdir() with the target effective IDs to cater for NFS mounted
  56        * home directories.
  57        */
  58       int saved_euid = 0;
  59       int saved_egid = 0;
  60       int retval;
  61       if (options & VSF_SECUTIL_OPTION_CHANGE_EUID)
  62       {
  63         saved_euid = vsf_sysutil_geteuid();
  64         saved_egid = vsf_sysutil_getegid();
  65         vsf_sysutil_setegid(p_user);
  66         vsf_sysutil_seteuid(p_user);
  67       }
  68       retval = str_chdir(&dir_str);
  69       if (retval != 0)
  70       {
  71         die2("cannot change directory:", str_getbuf(&dir_str));
  72       }
  73       if (p_ext_dir_str && !str_isempty(p_ext_dir_str))
  74       {
  75         retval = str_chdir(p_ext_dir_str);
  76         /* Failure on the extra directory is OK as long as we're not in
  77          * chroot() mode
  78          */
  79         if (retval != 0 && !(options & VSF_SECUTIL_OPTION_CHROOT))
  80         {
  81           retval = 0;
  82         }
  83       }
  84       if (retval != 0)
  85       {
  86         die2("cannot change directory:", str_getbuf(p_ext_dir_str));
  87       }
  88       if (options & VSF_SECUTIL_OPTION_CHANGE_EUID)
  89       {
  90         vsf_sysutil_seteuid_numeric(saved_euid);
  91         vsf_sysutil_setegid_numeric(saved_egid);
  92       }
  93       /* Do the chroot() if required */
  94       if (options & VSF_SECUTIL_OPTION_CHROOT)
  95       {
  96         vsf_sysutil_chroot(".");
  97       }
  98     }
  99     str_free(&dir_str);
 100   }
 101   /* Handle capabilities */
 102   if (caps)
 103   {
 104     if (!vsf_sysdep_has_capabilities())
 105     {
 106       /* Need privilege but OS has no capabilities - have to keep root */
 107       return;
 108     }
 109     if (!vsf_sysdep_has_capabilities_as_non_root())
 110     {
 111       vsf_sysdep_adopt_capabilities(caps);
 112       return;
 113     }
 114     vsf_sysdep_keep_capabilities();
 115   }
 116   /* Set group id */
 117   vsf_sysutil_setgid(p_user);
 118   /* Finally set user id */
 119   vsf_sysutil_setuid(p_user);
 120   if (caps)
 121   {
 122     vsf_sysdep_adopt_capabilities(caps);
 123   }
 124 }
 125