/*
 * Copyright (C) 2001-2012 Free Software Foundation, Inc.
 *
 * This file is part of GnuTLS.
 *
 * GnuTLS is free software: you can redistribute it and/or modify it
 * under the terms of the GNU General Public License as published by
 * the Free Software Foundation, either version 3 of the License, or
 * (at your option) any later version.
 *
 * GnuTLS 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
 * General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program.  If not, see
 * <http://www.gnu.org/licenses/>.
 */

#include <config.h>

#include <stdio.h>
#include <string.h>
#include <stdlib.h>
#include <gnutls/gnutls.h>
#include <gnutls/crypto.h>      /* for random */

#include <sys/types.h>
#include <sys/stat.h>

#ifndef _WIN32
#include <pwd.h>
#include <unistd.h>
#else
#include <windows.h>
#endif

/* Gnulib portability files. */
#include <getpass.h>
#include <minmax.h>
#include <progname.h>
#include <version-etc.h>

#include <srptool-args.h>

/* This may need some rewrite. A lot of stuff which should be here
 * are in the library, which is not good.
 */

int crypt_int (const char *username, const char *passwd, int salt,
               const char *tpasswd_conf, const char *tpasswd, int uindex);
static int read_conf_values (gnutls_datum_t * g, gnutls_datum_t * n,
                             char *str);
static int _verify_passwd_int (const char *username, const char *passwd,
                               char *verifier, const char *salt,
                               const gnutls_datum_t * g,
                               const gnutls_datum_t * n);

static void
print_num (const char *msg, const gnutls_datum_t * num)
{
  unsigned int i;

  printf ("%s:\t", msg);

  for (i = 0; i < num->size; i++)
    {
      if (i != 0 && i % 12 == 0)
        printf ("\n\t");
      else if (i != 0 && i != num->size)
        printf (":");
      printf ("%.2x", num->data[i]);
    }
  printf ("\n\n");

}

static int
generate_create_conf (const char *tpasswd_conf)
{
  FILE *fd;
  char line[5 * 1024];
  int index = 1;
  gnutls_datum_t g, n;
  gnutls_datum_t str_g, str_n;

  fd = fopen (tpasswd_conf, "w");
  if (fd == NULL)
    {
      fprintf (stderr, "Cannot open file '%s'\n", tpasswd_conf);
      return -1;
    }

  for (index = 1; index <= 5; index++)
    {

      if (index == 1)
        {
          n = gnutls_srp_1024_group_prime;
          g = gnutls_srp_1024_group_generator;
        }
      else if (index == 2)
        {
          n = gnutls_srp_1536_group_prime;
          g = gnutls_srp_1536_group_generator;
        }
      else if (index == 3)
        {
          n = gnutls_srp_2048_group_prime;
          g = gnutls_srp_2048_group_generator;
        }
      else if (index == 4)
        {
          n = gnutls_srp_3072_group_prime;
          g = gnutls_srp_3072_group_generator;
        }
      else if (index == 5)
        {
          n = gnutls_srp_4096_group_prime;
          g = gnutls_srp_4096_group_generator;
        }
      else
        {
          fprintf(stderr, "Unknown index: %d\n", index);
          return -1;
        }

      printf ("\nGroup %d, of %d bits:\n", index, n.size * 8);
      print_num ("Generator", &g);
      print_num ("Prime", &n);

      if (gnutls_srp_base64_encode_alloc (&n, &str_n) < 0)
        {
          fprintf (stderr, "Could not encode\n");
          return -1;
        }

      if (gnutls_srp_base64_encode_alloc (&g, &str_g) < 0)
        {
          fprintf (stderr, "Could not encode\n");
          return -1;
        }

      sprintf (line, "%d:%s:%s\n", index, str_n.data, str_g.data);

      gnutls_free (str_n.data);
      gnutls_free (str_g.data);

      fwrite (line, 1, strlen (line), fd);

    }

  fclose (fd);

  return 0;

}

/* The format of a tpasswd file is:
 * username:verifier:salt:index
 *
 * index is the index of the prime-generator pair in tpasswd.conf
 */
static int
_verify_passwd_int (const char *username, const char *passwd,
                    char *verifier, const char *salt,
                    const gnutls_datum_t * g, const gnutls_datum_t * n)
{
  char _salt[1024];
  gnutls_datum_t tmp, raw_salt, new_verifier;
  size_t salt_size;
  char *pos;

  if (salt == NULL || verifier == NULL)
    return -1;

  if (strlen(salt) >= sizeof(_salt))
    {
      fprintf (stderr, "Too long salt.\n");
      return -1;
    }

  /* copy salt, and null terminate after the ':' */
  strcpy (_salt, salt);
  pos = strchr (_salt, ':');
  if (pos != NULL)
    *pos = 0;

  /* convert salt to binary. */
  tmp.data = (void*)_salt;
  tmp.size = strlen (_salt);

  if (gnutls_srp_base64_decode_alloc (&tmp, &raw_salt) < 0)
    {
      fprintf (stderr, "Could not decode salt.\n");
      return -1;
    }

  if (gnutls_srp_verifier
      (username, passwd, &raw_salt, g, n, &new_verifier) < 0)
    {
      fprintf (stderr, "Could not make the verifier\n");
      return -1;
    }

  free (raw_salt.data);

  /* encode the verifier into _salt */
  salt_size = sizeof (_salt);
  memset (_salt, 0, salt_size);
  if (gnutls_srp_base64_encode (&new_verifier, _salt, &salt_size) < 0)
    {
      fprintf (stderr, "Encoding error\n");
      return -1;
    }

  free (new_verifier.data);

  if (strncmp (verifier, _salt, strlen (_salt)) == 0)
    {
      fprintf (stderr, "Password verified\n");
      return 0;
    }
  else
    {
      fprintf (stderr, "Password does NOT match\n");
    }
  return -1;
}

static int
filecopy (const char *src, const char *dst)
{
  FILE *fd, *fd2;
  char line[5 * 1024];
  char *p;

  fd = fopen (dst, "w");
  if (fd == NULL)
    {
      fprintf (stderr, "Cannot open '%s' for write\n", dst);
      return -1;
    }

  fd2 = fopen (src, "r");
  if (fd2 == NULL)
    {
      /* empty file */
      fclose (fd);
      return 0;
    }

  line[sizeof (line) - 1] = 0;
  do
    {
      p = fgets (line, sizeof (line) - 1, fd2);
      if (p == NULL)
        break;

      fputs (line, fd);
    }
  while (1);

  fclose (fd);
  fclose (fd2);

  return 0;
}

/* accepts password file */
static int
find_strchr (const char *username, const char *file)
{
  FILE *fd;
  char *pos;
  char line[5 * 1024];
  unsigned int i;

  fd = fopen (file, "r");
  if (fd == NULL)
    {
      fprintf (stderr, "Cannot open file '%s'\n", file);
      return -1;
    }

  while (fgets (line, sizeof (line), fd) != NULL)
    {
      /* move to first ':' */
      i = 0;
      while ((line[i] != ':') && (line[i] != '\0') && (i < sizeof (line)))
        {
          i++;
        }
      if (strncmp (username, line, MAX (i, strlen (username))) == 0)
        {
          /* find the index */
          pos = strrchr (line, ':');
          pos++;
          fclose (fd);
          return atoi (pos);
        }
    }

  fclose (fd);
  return -1;
}

/* Parses the tpasswd files, in order to verify the given
 * username/password pair.
 */
static int
verify_passwd (const char *conffile, const char *tpasswd, 
               const char *username, const char *passwd)
{
  FILE *fd;
  char line[5 * 1024];
  unsigned int i;
  gnutls_datum_t g, n;
  int iindex;
  char *p, *pos;

  iindex = find_strchr (username, tpasswd);
  if (iindex == -1)
    {
      fprintf (stderr, "Cannot find '%s' in %s\n", username, tpasswd);
      return -1;
    }

  fd = fopen (conffile, "r");
  if (fd == NULL)
    {
      fprintf (stderr, "Cannot find %s\n", conffile);
      return -1;
    }

  do
    {
      p = fgets (line, sizeof (line) - 1, fd);
    }
  while (p != NULL && atoi (p) != iindex);

  if (p == NULL)
    {
      fprintf (stderr, "Cannot find entry in %s\n", conffile);
      return -1;
    }
  line[sizeof (line) - 1] = 0;

  fclose (fd);

  if ((iindex = read_conf_values (&g, &n, line)) < 0)
    {
      fprintf (stderr, "Cannot parse conf file '%s'\n", conffile);
      return -1;
    }

  fd = fopen (tpasswd, "r");
  if (fd == NULL)
    {
      fprintf (stderr, "Cannot open file '%s'\n", tpasswd);
      return -1;
    }

  while (fgets (line, sizeof (line), fd) != NULL)
    {
      /* move to first ':' 
       * This is the actual verifier.
       */
      i = 0;
      while ((line[i] != ':') && (line[i] != '\0') && (i < sizeof (line)))
        {
          i++;
        }
      if (strncmp (username, line, MAX (i, strlen (username))) == 0)
        {
          char *verifier_pos, *salt_pos;

          pos = strchr (line, ':');
          fclose (fd);
          if (pos == NULL)
            {
              fprintf (stderr, "Cannot parse conf file '%s'\n", conffile);
              return -1;
            }
          pos++;
          verifier_pos = pos;

          /* Move to the salt */
          pos = strchr (pos, ':');
          if (pos == NULL)
            {
              fprintf (stderr, "Cannot parse conf file '%s'\n", conffile);
              return -1;
            }
          pos++;
          salt_pos = pos;

          return _verify_passwd_int (username, passwd,
                                     verifier_pos, salt_pos, &g, &n);
        }
    }

  fclose (fd);
  return -1;

}

#define KPASSWD "/etc/tpasswd"
#define KPASSWD_CONF "/etc/tpasswd.conf"

static void
tls_log_func (int level, const char *str)
{
  fprintf (stderr, "|<%d>| %s", level, str);
}

int main (int argc, char **argv)
{
  const char *passwd;
  int salt_size, ret;
  int optct;
  const char* fpasswd, *fpasswd_conf;
  const char* username;
#ifndef _WIN32
   struct passwd *pwd;
#endif

  set_program_name (argv[0]);

  if ((ret = gnutls_global_init ()) < 0)
    {
      fprintf (stderr, "global_init: %s\n", gnutls_strerror (ret));
      exit (1);
    }

  umask (066);

  optct = optionProcess( &srptoolOptions, argc, argv);
  argc -= optct;
  argv += optct;

  gnutls_global_set_log_function (tls_log_func);
  gnutls_global_set_log_level (OPT_VALUE_DEBUG);

  if (HAVE_OPT(CREATE_CONF))
    {
      return generate_create_conf (OPT_ARG(CREATE_CONF));
    }

  if (HAVE_OPT(PASSWD))
    fpasswd = OPT_ARG(PASSWD);
  else
    fpasswd = (char *) KPASSWD;

  if (HAVE_OPT(PASSWD_CONF))
    fpasswd_conf = OPT_ARG(PASSWD_CONF);
  else
    fpasswd_conf = (char *) KPASSWD_CONF;

  if (HAVE_OPT(USERNAME))
    username = OPT_ARG(USERNAME);
  else
    {
#ifndef _WIN32
      pwd = getpwuid (getuid ());

      if (pwd == NULL)
        {
          fprintf (stderr, "No such user\n");
          return -1;
        }

      username = pwd->pw_name;
#else
      fprintf (stderr, "Please specify a user\n");
      return -1;
#endif
    }

  salt_size = 16;

  passwd = getpass ("Enter password: ");
  if (passwd == NULL)
    {
      fprintf (stderr, "Please specify a password\n");
      return -1;
    }

/* not ready yet */
  if (HAVE_OPT(VERIFY))
    {
      return verify_passwd (fpasswd_conf, fpasswd,
                            username, passwd);
    }


  return crypt_int (username, passwd, salt_size,
                    fpasswd_conf, fpasswd, VALUE_OPT_INDEX);

}

static char *
_srp_crypt (const char *username, const char *passwd, int salt_size,
            const gnutls_datum_t * g, const gnutls_datum_t * n)
{
  unsigned char salt[128];
  static char result[1024];
  gnutls_datum_t dat_salt, txt_salt;
  gnutls_datum_t verifier, txt_verifier;

  if ((unsigned) salt_size > sizeof (salt))
    return NULL;

  /* generate the salt
   */
  if (gnutls_rnd (GNUTLS_RND_NONCE, salt, salt_size) < 0)
    {
      fprintf (stderr, "Could not create nonce\n");
      return NULL;
    }

  dat_salt.data = salt;
  dat_salt.size = salt_size;

  if (gnutls_srp_verifier (username, passwd, &dat_salt, g, n, &verifier) < 0)
    {
      fprintf (stderr, "Error getting verifier\n");
      return NULL;
    }

  /* base64 encode the verifier */
  if (gnutls_srp_base64_encode_alloc (&verifier, &txt_verifier) < 0)
    {
      fprintf (stderr, "Error encoding\n");
      free (verifier.data);
      return NULL;
    }

  free (verifier.data);

  if (gnutls_srp_base64_encode_alloc (&dat_salt, &txt_salt) < 0)
    {
      fprintf (stderr, "Error encoding\n");
      return NULL;
    }

  sprintf (result, "%s:%s", txt_verifier.data, txt_salt.data);
  free (txt_salt.data);
  free (txt_verifier.data);

  return result;

}


int
crypt_int (const char *username, const char *passwd, int salt_size,
           const char *tpasswd_conf, const char *tpasswd, int uindex)
{
  FILE *fd;
  char *cr;
  gnutls_datum_t g, n;
  char line[5 * 1024];
  char *p, *pp;
  int iindex;
  char tmpname[1024];

  fd = fopen (tpasswd_conf, "r");
  if (fd == NULL)
    {
      fprintf (stderr, "Cannot find %s\n", tpasswd_conf);
      return -1;
    }

  do
    {                           /* find the specified uindex in file */
      p = fgets (line, sizeof (line) - 1, fd);
      iindex = atoi (p);
    }
  while (p != NULL && iindex != uindex);

  if (p == NULL)
    {
      fprintf (stderr, "Cannot find entry in %s\n", tpasswd_conf);
      return -1;
    }
  line[sizeof (line) - 1] = 0;

  fclose (fd);
  if ((iindex = read_conf_values (&g, &n, line)) < 0)
    {
      fprintf (stderr, "Cannot parse conf file '%s'\n", tpasswd_conf);
      return -1;
    }

  cr = _srp_crypt (username, passwd, salt_size, &g, &n);
  if (cr == NULL)
    {
      fprintf (stderr, "Cannot _srp_crypt()...\n");
      return -1;
    }
  else
    {
      /* delete previous entry */
      struct stat st;
      FILE *fd2;
      int put;

      if (strlen (tpasswd) > sizeof (tmpname) + 5)
        {
          fprintf (stderr, "file '%s' is tooooo long\n", tpasswd);
          return -1;
        }
      strcpy (tmpname, tpasswd);
      strcat (tmpname, ".tmp");

      if (stat (tmpname, &st) != -1)
        {
          fprintf (stderr, "file '%s' is locked\n", tpasswd);
          return -1;
        }

      if (filecopy (tpasswd, tmpname) != 0)
        {
          fprintf (stderr, "Cannot copy '%s' to '%s'\n", tpasswd, tmpname);
          return -1;
        }

      fd = fopen (tpasswd, "w");
      if (fd == NULL)
        {
          fprintf (stderr, "Cannot open '%s' for write\n", tpasswd);
          remove (tmpname);
          return -1;
        }

      fd2 = fopen (tmpname, "r");
      if (fd2 == NULL)
        {
          fprintf (stderr, "Cannot open '%s' for read\n", tmpname);
          remove (tmpname);
          return -1;
        }

      put = 0;
      do
        {
          p = fgets (line, sizeof (line) - 1, fd2);
          if (p == NULL)
            break;

          pp = strchr (line, ':');
          if (pp == NULL)
            continue;

          if (strncmp (p, username,
                       MAX (strlen (username), (unsigned int) (pp - p))) == 0)
            {
              put = 1;
              fprintf (fd, "%s:%s:%u\n", username, cr, iindex);
            }
          else
            {
              fputs (line, fd);
            }
        }
      while (1);

      if (put == 0)
        {
          fprintf (fd, "%s:%s:%u\n", username, cr, iindex);
        }

      fclose (fd);
      fclose (fd2);

      remove (tmpname);

    }


  return 0;
}



/* this function parses tpasswd.conf file. Format is:
 * int(index):base64(n):base64(g)
 */
static int
read_conf_values (gnutls_datum_t * g, gnutls_datum_t * n, char *str)
{
  char *p;
  int len;
  int index, ret;
  gnutls_datum_t dat;

  index = atoi (str);

  p = strrchr (str, ':');       /* we have g */
  if (p == NULL)
    {
      return -1;
    }

  *p = '\0';
  p++;

  /* read the generator */
  len = strlen (p);
  if (p[len - 1] == '\n')
    len--;

  dat.data = (void*)p;
  dat.size = len;
  ret = gnutls_srp_base64_decode_alloc (&dat, g);

  if (ret < 0)
    {
      fprintf (stderr, "Decoding error\n");
      return -1;
    }

  /* now go for n - modulo */
  p = strrchr (str, ':');       /* we have n */
  if (p == NULL)
    {
      return -1;
    }

  *p = '\0';
  p++;

  dat.data = (void*)p;
  dat.size = strlen (p);

  ret = gnutls_srp_base64_decode_alloc (&dat, n);

  if (ret < 0)
    {
      fprintf (stderr, "Decoding error\n");
      free (g->data);
      return -1;
    }

  return index;
}

extern void srptool_version (void);

void
srptool_version (void)
{
  const char *p = PACKAGE_NAME;
  if (strcmp (gnutls_check_version (NULL), PACKAGE_VERSION) != 0)
    p = PACKAGE_STRING;
  version_etc (stdout, "srptool", p, gnutls_check_version (NULL),
               "Nikos Mavrogiannopoulos", (char *) NULL);
}