sysdeps/unix/sysv/linux/getlogin_r.c

   1 /* Copyright (C) 2010 Free Software Foundation, Inc.
   2    This file is part of the GNU C Library.
   3
   4    The GNU C Library is free software; you can redistribute it and/or
   5    modify it under the terms of the GNU Lesser General Public
   6    License as published by the Free Software Foundation; either
   7    version 2.1 of the License, or (at your option) any later version.
   8
   9    The GNU C Library is distributed in the hope that it will be useful,
  10    but WITHOUT ANY WARRANTY; without even the implied warranty of
  11    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  12    Lesser General Public License for more details.
  13
  14    You should have received a copy of the GNU Lesser General Public
  15    License along with the GNU C Library; if not, write to the Free
  16    Software Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA
  17    02111-1307 USA.  */
  18
  19 #include <pwd.h>
  20 #include <unistd.h>
  21 #include <not-cancel.h>
  22
  23 #define STATIC static
  24 static int getlogin_r_fd0 (char *name, size_t namesize);
  25 #define getlogin_r getlogin_r_fd0
  26 #include <sysdeps/unix/getlogin_r.c>
  27 #undef getlogin_r
  28
  29
  30 int
  31 attribute_hidden
  32 __getlogin_r_loginuid (name, namesize)
  33      char *name;
  34      size_t namesize;
  35 {
  36   int fd = open_not_cancel_2 ("/proc/self/loginuid", O_RDONLY);
  37   if (fd == -1)
  38     return 1;
  39
  40   ssize_t n = TEMP_FAILURE_RETRY (read_not_cancel (fd, name, namesize));
  41   close_not_cancel_no_status (fd);
  42
  43   uid_t uid;
  44   char *endp;
  45   if (n <= 0
  46       || (uid = strtoul (name, &endp, 10), endp == name || *endp != '\0'))
  47     return 1;
  48
  49   size_t buflen = 1024;
  50   char *buf = alloca (buflen);
  51   bool use_malloc = false;
  52   struct passwd pwd;
  53   struct passwd *tpwd;
  54   int res;
  55
  56   while ((res = __getpwuid_r (uid, &pwd, buf, buflen, &tpwd)) != 0)
  57     if (__libc_use_alloca (2 * buflen))
  58       extend_alloca (buf, buflen, 2 * buflen);
  59     else
  60       {
  61         buflen *= 2;
  62         char *newp = realloc (use_malloc ? buf : NULL, buflen);
  63         if (newp == NULL)
  64           {
  65           fail:
  66             if (use_malloc)
  67               free (buf);
  68             return 1;
  69           }
  70         buf = newp;
  71         use_malloc = true;
  72       }
  73
  74   if (tpwd == NULL)
  75     goto fail;
  76
  77   strncpy (name, pwd.pw_name, namesize - 1);
  78   name[namesize - 1] = '\0';
  79
  80   if (use_malloc)
  81     free (buf);
  82
  83   return 0;
  84 }
  85
  86
  87 /* Return the login name of the user, or NULL if it can't be determined.
  88    The returned pointer, if not NULL, is good only until the next call.  */
  89
  90 int
  91 getlogin_r (name, namesize)
  92      char *name;
  93      size_t namesize;
  94 {
  95   if (__getlogin_r_loginuid (name, namesize) == 0)
  96     return 0;
  97
  98   return getlogin_r_fd0 (name, namesize);
  99 }
 100 libc_hidden_def (getlogin_r)