/* Copyright (C) 2010-2018 Free Software Foundation, Inc.

   This file is part of the GNU C Library.

   The GNU C Library is free software; you can redistribute it and/or

   modify it under the terms of the GNU Lesser General Public

   License as published by the Free Software Foundation; either

   version 2.1 of the License, or (at your option) any later version.

   The GNU C Library is distributed in the hope that it will be useful,

   but WITHOUT ANY WARRANTY; without even the implied warranty of

   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU

   Lesser General Public License for more details.

   You should have received a copy of the GNU Lesser General Public

   License along with the GNU C Library; if not, see

   <http://www.gnu.org/licenses/>.  */

#include <pwd.h>

#include <unistd.h>

#include <not-cancel.h>

#include <scratch_buffer.h>

#define STATIC static

static int getlogin_r_fd0 (char *name, size_t namesize);

#define __getlogin_r getlogin_r_fd0

#include <sysdeps/unix/getlogin_r.c>

#undef __getlogin_r

/* Try to determine login name from /proc/self/loginuid and return 0

   if successful.  If /proc/self/loginuid cannot be read return -1.

   Otherwise return the error number.  */

int

attribute_hidden

__getlogin_r_loginuid (char *name, size_t namesize)

{

  int fd = __open_nocancel ("/proc/self/loginuid", O_RDONLY);

  if (fd == -1)

    return -1;

  /* We are reading a 32-bit number.  12 bytes are enough for the text

     representation.  If not, something is wrong.  */

  char uidbuf[12];

  ssize_t n = TEMP_FAILURE_RETRY (__read_nocancel (fd, uidbuf,

						   sizeof (uidbuf)));

  __close_nocancel_nostatus (fd);

  uid_t uid;

  char *endp;

  if (n <= 0

      || n == sizeof (uidbuf)

      || (uidbuf[n] = '\0',

	  uid = strtoul (uidbuf, &endp, 10),

	  endp == uidbuf || *endp != '\0'))

    return -1;

  /* If there is no login uid, linux sets /proc/self/loginid to the sentinel

     value of, (uid_t) -1, so check if that value is set and return early to

     avoid making unneeded nss lookups. */

  if (uid == (uid_t) -1)

    {

      __set_errno (ENXIO);

      return ENXIO;

    }

  struct passwd pwd;

  struct passwd *tpwd;

  int result = 0;

  int res;

  struct scratch_buffer tmpbuf;

  scratch_buffer_init (&tmpbuf);

  while ((res =  __getpwuid_r (uid, &pwd,

			       tmpbuf.data, tmpbuf.length, &tpwd)) == ERANGE)

    {

      if (!scratch_buffer_grow (&tmpbuf))

	{

	  result = ENOMEM;

	  goto out;

	}

    }

  if (res != 0 || tpwd == NULL)

    {

      result = -1;

      goto out;

    }

  size_t needed = strlen (pwd.pw_name) + 1;

  if (needed > namesize)

    {

      __set_errno (ERANGE);

      result = ERANGE;

      goto out;

    }

  memcpy (name, pwd.pw_name, needed);

 out:

  scratch_buffer_free (&tmpbuf);

  return result;

}

/* Return at most NAME_LEN characters of the login name of the user in NAME.

   If it cannot be determined or some other error occurred, return the error

   code.  Otherwise return 0.  */

int

__getlogin_r (char *name, size_t namesize)

{

  int res = __getlogin_r_loginuid (name, namesize);

  if (res >= 0)

    return res;

  return getlogin_r_fd0 (name, namesize);

}

libc_hidden_def (__getlogin_r)

weak_alias (__getlogin_r, getlogin_r)

libc_hidden_weak (getlogin_r)