sysdeps/unix/sysv/linux/getlogin_r.c

   1 /* Copyright (C) 2010-2015 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, see
  16    <http://www.gnu.org/licenses/>.  */
  17
  18 #include <pwd.h>
  19 #include <unistd.h>
  20 #include <not-cancel.h>
  21
  22 #define STATIC static
  23 static int getlogin_r_fd0 (char *name, size_t namesize);
  24 #define getlogin_r getlogin_r_fd0
  25 #include <sysdeps/unix/getlogin_r.c>
  26 #undef getlogin_r
  27
  28
  29 /* Try to determine login name from /proc/self/loginuid and return 0
  30    if successful.  If /proc/self/loginuid cannot be read return -1.
  31    Otherwise return the error number.  */
  32
  33 int
  34 attribute_hidden
  35 __getlogin_r_loginuid (name, namesize)
  36      char *name;
  37      size_t namesize;
  38 {
  39   int fd = open_not_cancel_2 ("/proc/self/loginuid", O_RDONLY);
  40   if (fd == -1)
  41     return -1;
  42
  43   /* We are reading a 32-bit number.  12 bytes are enough for the text
  44      representation.  If not, something is wrong.  */
  45   char uidbuf[12];
  46   ssize_t n = TEMP_FAILURE_RETRY (read_not_cancel (fd, uidbuf,
  47                                                    sizeof (uidbuf)));
  48   close_not_cancel_no_status (fd);
  49
  50   uid_t uid;
  51   char *endp;
  52   if (n <= 0
  53       || n == sizeof (uidbuf)
  54       || (uidbuf[n] = '\0',
  55           uid = strtoul (uidbuf, &endp, 10),
  56           endp == uidbuf || *endp != '\0'))
  57     return -1;
  58
  59   size_t buflen = 1024;
  60   char *buf = alloca (buflen);
  61   bool use_malloc = false;
  62   struct passwd pwd;
  63   struct passwd *tpwd;
  64   int result = 0;
  65   int res;
  66
  67   while ((res = __getpwuid_r (uid, &pwd, buf, buflen, &tpwd)) == ERANGE)
  68     if (__libc_use_alloca (2 * buflen))
  69       buf = extend_alloca (buf, buflen, 2 * buflen);
  70     else
  71       {
  72         buflen *= 2;
  73         char *newp = realloc (use_malloc ? buf : NULL, buflen);
  74         if (newp == NULL)
  75           {
  76             result = ENOMEM;
  77             goto out;
  78           }
  79         buf = newp;
  80         use_malloc = true;
  81       }
  82
  83   if (res != 0 || tpwd == NULL)
  84     {
  85       result = -1;
  86       goto out;
  87     }
  88
  89   size_t needed = strlen (pwd.pw_name) + 1;
  90   if (needed > namesize)
  91     {
  92       __set_errno (ERANGE);
  93       result = ERANGE;
  94       goto out;
  95     }
  96
  97   memcpy (name, pwd.pw_name, needed);
  98
  99  out:
 100   if (use_malloc)
 101     free (buf);
 102
 103   return result;
 104 }
 105
 106
 107 /* Return at most NAME_LEN characters of the login name of the user in NAME.
 108    If it cannot be determined or some other error occurred, return the error
 109    code.  Otherwise return 0.  */
 110
 111 int
 112 getlogin_r (name, namesize)
 113      char *name;
 114      size_t namesize;
 115 {
 116   int res = __getlogin_r_loginuid (name, namesize);
 117   if (res >= 0)
 118     return res;
 119
 120   return getlogin_r_fd0 (name, namesize);
 121 }
 122 libc_hidden_def (getlogin_r)