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 /* Try to determine login name from /proc/self/loginuid and return 0
  31    if successful.  If /proc/self/loginuid cannot be read return -1.
  32    Otherwise return the error number.  */
  33
  34 int
  35 attribute_hidden
  36 __getlogin_r_loginuid (name, namesize)
  37      char *name;
  38      size_t namesize;
  39 {
  40   int fd = open_not_cancel_2 ("/proc/self/loginuid", O_RDONLY);
  41   if (fd == -1)
  42     return -1;
  43
  44   /* We are reading a 32-bit number.  12 bytes are enough for the text
  45      representation.  If not, something is wrong.  */
  46   char uidbuf[12];
  47   ssize_t n = TEMP_FAILURE_RETRY (read_not_cancel (fd, uidbuf,
  48                                                    sizeof (uidbuf)));
  49   close_not_cancel_no_status (fd);
  50
  51   uid_t uid;
  52   char *endp;
  53   if (n <= 0
  54       || n == sizeof (uidbuf)
  55       || (uidbuf[n] = '\0',
  56           uid = strtoul (uidbuf, &endp, 10),
  57           endp == uidbuf || *endp != '\0'))
  58     return -1;
  59
  60   size_t buflen = 1024;
  61   char *buf = alloca (buflen);
  62   bool use_malloc = false;
  63   struct passwd pwd;
  64   struct passwd *tpwd;
  65   int result = 0;
  66   int res;
  67
  68   while ((res = __getpwuid_r (uid, &pwd, buf, buflen, &tpwd)) == ERANGE)
  69     if (__libc_use_alloca (2 * buflen))
  70       buf = extend_alloca (buf, buflen, 2 * buflen);
  71     else
  72       {
  73         buflen *= 2;
  74         char *newp = realloc (use_malloc ? buf : NULL, buflen);
  75         if (newp == NULL)
  76           {
  77             result = ENOMEM;
  78             goto out;
  79           }
  80         buf = newp;
  81         use_malloc = true;
  82       }
  83
  84   if (res != 0 || tpwd == NULL)
  85     {
  86       result = -1;
  87       goto out;
  88     }
  89
  90   size_t needed = strlen (pwd.pw_name) + 1;
  91   if (needed > namesize)
  92     {
  93       __set_errno (ERANGE);
  94       result = ERANGE;
  95       goto out;
  96     }
  97
  98   memcpy (name, pwd.pw_name, needed);
  99
 100  out:
 101   if (use_malloc)
 102     free (buf);
 103
 104   return result;
 105 }
 106
 107
 108 /* Return at most NAME_LEN characters of the login name of the user in NAME.
 109    If it cannot be determined or some other error occurred, return the error
 110    code.  Otherwise return 0.  */
 111
 112 int
 113 getlogin_r (name, namesize)
 114      char *name;
 115      size_t namesize;
 116 {
 117   int res = __getlogin_r_loginuid (name, namesize);
 118   if (res >= 0)
 119     return res;
 120
 121   return getlogin_r_fd0 (name, namesize);
 122 }
 123 libc_hidden_def (getlogin_r)