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   /* We are reading a 32-bit number.  12 bytes are enough for the text
  41      representation.  If not, something is wrong.  */
  42   char uidbuf[12];
  43   ssize_t n = TEMP_FAILURE_RETRY (read_not_cancel (fd, uidbuf,
  44                                                    sizeof (uidbuf)));
  45   close_not_cancel_no_status (fd);
  46
  47   uid_t uid;
  48   char *endp;
  49   if (n <= 0
  50       || n == sizeof (uidbuf)
  51       || (uidbuf[n] = '\0',
  52           uid = strtoul (uidbuf, &endp, 10),
  53           endp == uidbuf || *endp != '\0'))
  54     return 1;
  55
  56   size_t buflen = 1024;
  57   char *buf = alloca (buflen);
  58   bool use_malloc = false;
  59   struct passwd pwd;
  60   struct passwd *tpwd;
  61   int res;
  62
  63   while ((res = __getpwuid_r (uid, &pwd, buf, buflen, &tpwd)) != 0)
  64     if (__libc_use_alloca (2 * buflen))
  65       extend_alloca (buf, buflen, 2 * buflen);
  66     else
  67       {
  68         buflen *= 2;
  69         char *newp = realloc (use_malloc ? buf : NULL, buflen);
  70         if (newp == NULL)
  71           {
  72           fail:
  73             if (use_malloc)
  74               free (buf);
  75             return 1;
  76           }
  77         buf = newp;
  78         use_malloc = true;
  79       }
  80
  81   if (tpwd == NULL)
  82     goto fail;
  83
  84   strncpy (name, pwd.pw_name, namesize - 1);
  85   name[namesize - 1] = '\0';
  86
  87   if (use_malloc)
  88     free (buf);
  89
  90   return 0;
  91 }
  92
  93
  94 /* Return at most NAME_LEN characters of the login name of the user in NAME.
  95    If it cannot be determined or some other error occurred, return the error
  96    code.  Otherwise return 0.  */
  97
  98 int
  99 getlogin_r (name, namesize)
 100      char *name;
 101      size_t namesize;
 102 {
 103   if (__getlogin_r_loginuid (name, namesize) == 0)
 104     return 0;
 105
 106   return getlogin_r_fd0 (name, namesize);
 107 }
 108 libc_hidden_def (getlogin_r)