/*
     This file is part of GNUnet.
     Copyright (C) 2012, 2013 GNUnet e.V.

     GNUnet is free software: you can redistribute it and/or modify it
     under the terms of the GNU Affero General Public License as published
     by the Free Software Foundation, either version 3 of the License,
     or (at your option) any later version.

     GNUnet 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
     Affero General Public License for more details.

     You should have received a copy of the GNU Affero General Public License
     along with this program.  If not, see <http://www.gnu.org/licenses/>.

     SPDX-License-Identifier: AGPL3.0-or-later
 */

/**
 * @file util/gnunet-ecc.c
 * @brief tool to manipulate EDDSA key files
 * @author Christian Grothoff
 */
#include "platform.h"
#include "gnunet_util_lib.h"
#include "gnunet_testing_lib.h"
#include <gcrypt.h>

/**
 * Number of characters a Base32-encoded public key requires.
 */
#define KEY_STR_LEN sizeof(struct GNUNET_CRYPTO_EddsaPublicKey) * 8 / 5 + 1

/**
 * Flag for listing public key.
 */
static int list_keys;

/**
 * Flag for listing public key.
 */
static unsigned int list_keys_count;

/**
 * Flag for printing public key.
 */
static int print_public_key;

/**
 * Flag for printing private key.
 */
static int print_private_key;

/**
 * Flag for printing public key in hex.
 */
static int print_public_key_hex;

/**
 * Flag for printing the output of random example operations.
 */
static int print_examples_flag;

/**
 * Option set to create a bunch of keys at once.
 */
static unsigned int make_keys;


/**
 * Create a flat file with a large number of key pairs for testing.
 *
 * @param fn File name to store the keys.
 * @param prefix Desired prefix for the public keys, NULL if any key is OK.
 */
static void
create_keys(const char *fn, const char *prefix)
{
  FILE *f;
  struct GNUNET_CRYPTO_EddsaPrivateKey *pk;
  struct GNUNET_CRYPTO_EddsaPublicKey target_pub;
  static char vanity[KEY_STR_LEN + 1];
  size_t len;
  size_t n;
  size_t rest;
  unsigned char mask;
  unsigned target_byte;
  char *s;

  if (NULL == (f = fopen(fn, "w+")))
    {
      fprintf(stderr, _("Failed to open `%s': %s\n"), fn, strerror(errno));
      return;
    }
  if (NULL != prefix)
    {
      len = GNUNET_strlcpy(vanity, prefix, sizeof(vanity));
      n = len * 5 / 8;
      rest = len * 5 % 8;

      memset(&vanity[len], '0', KEY_STR_LEN - len);
      vanity[KEY_STR_LEN] = '\0';
      GNUNET_assert(GNUNET_OK ==
                    GNUNET_CRYPTO_eddsa_public_key_from_string(vanity,
                                                               KEY_STR_LEN,
                                                               &target_pub));
      if (0 != rest)
        {
          /**
           * Documentation by example:
           * vanity = "A"
           * len = 1
           * n = 5/8 = 0 (bytes)
           * rest = 5%8 = 5 (bits)
           * mask = ~(2**(8 - 5) - 1) = ~(2**3 - 1) = ~(8 - 1) = ~b111 = b11111000
           */
          mask = ~((int)pow(2, 8 - rest) - 1);
          target_byte = ((unsigned char *)&target_pub)[n] & mask;
        }
      else
        {
          /* Just so old (debian) versions of GCC calm down with the warnings. */
          mask = target_byte = 0;
        }
      s = GNUNET_CRYPTO_eddsa_public_key_to_string(&target_pub);
      fprintf(stderr,
              _("Generating %u keys like %s, please wait"),
              make_keys,
              s);
      GNUNET_free(s);
      fprintf(stderr, "\nattempt %s [%u, %X]\n", vanity, (unsigned int)n, mask);
    }
  else
    {
      fprintf(stderr, _("Generating %u keys, please wait"), make_keys);
      /* Just so old (debian) versions of GCC calm down with the warnings. */
      n = rest = target_byte = mask = 0;
    }

  while (0 < make_keys--)
    {
      fprintf(stderr, ".");
      if (NULL == (pk = GNUNET_CRYPTO_eddsa_key_create()))
        {
          GNUNET_break(0);
          break;
        }
      if (NULL != prefix)
        {
          struct GNUNET_CRYPTO_EddsaPublicKey newkey;

          GNUNET_CRYPTO_eddsa_key_get_public(pk, &newkey);
          if (0 != memcmp(&target_pub, &newkey, n))
            {
              make_keys++;
              continue;
            }
          if (0 != rest)
            {
              unsigned char new_byte;

              new_byte = ((unsigned char *)&newkey)[n] & mask;
              if (target_byte != new_byte)
                {
                  make_keys++;
                  continue;
                }
            }
        }
      if (GNUNET_TESTING_HOSTKEYFILESIZE !=
          fwrite(pk, 1, GNUNET_TESTING_HOSTKEYFILESIZE, f))
        {
          fprintf(stderr,
                  _("\nFailed to write to `%s': %s\n"),
                  fn,
                  strerror(errno));
          GNUNET_free(pk);
          break;
        }
      GNUNET_free(pk);
    }
  if (UINT_MAX == make_keys)
    fprintf(stderr, _("\nFinished!\n"));
  else
    fprintf(stderr, _("\nError, %u keys not generated\n"), make_keys);
  fclose(f);
}


static void
print_hex(const char *msg, const void *buf, size_t size)
{
  printf("%s: ", msg);
  for (size_t i = 0; i < size; i++)
    {
      printf("%02hhx", ((const uint8_t *)buf)[i]);
    }
  printf("\n");
}


static void
print_examples_ecdh()
{
  struct GNUNET_CRYPTO_EcdhePrivateKey *dh_priv1;
  struct GNUNET_CRYPTO_EcdhePublicKey *dh_pub1;
  struct GNUNET_CRYPTO_EcdhePrivateKey *dh_priv2;
  struct GNUNET_CRYPTO_EcdhePublicKey *dh_pub2;
  struct GNUNET_HashCode hash;
  char buf[128];

  dh_pub1 = GNUNET_new(struct GNUNET_CRYPTO_EcdhePublicKey);
  dh_priv1 = GNUNET_CRYPTO_ecdhe_key_create();
  dh_pub2 = GNUNET_new(struct GNUNET_CRYPTO_EcdhePublicKey);
  dh_priv2 = GNUNET_CRYPTO_ecdhe_key_create();
  GNUNET_CRYPTO_ecdhe_key_get_public(dh_priv1, dh_pub1);
  GNUNET_CRYPTO_ecdhe_key_get_public(dh_priv2, dh_pub2);

  GNUNET_assert(NULL !=
                GNUNET_STRINGS_data_to_string(dh_priv1, 32, buf, 128));
  printf("ECDHE key 1:\n");
  printf("private: %s\n", buf);
  print_hex("private(hex)", dh_priv1, sizeof *dh_priv1);
  GNUNET_assert(NULL != GNUNET_STRINGS_data_to_string(dh_pub1, 32, buf, 128));
  printf("public: %s\n", buf);
  print_hex("public(hex)", dh_pub1, sizeof *dh_pub1);

  GNUNET_assert(NULL !=
                GNUNET_STRINGS_data_to_string(dh_priv2, 32, buf, 128));
  printf("ECDHE key 2:\n");
  printf("private: %s\n", buf);
  print_hex("private(hex)", dh_priv2, sizeof *dh_priv2);
  GNUNET_assert(NULL != GNUNET_STRINGS_data_to_string(dh_pub2, 32, buf, 128));
  printf("public: %s\n", buf);
  print_hex("public(hex)", dh_pub2, sizeof *dh_pub2);

  GNUNET_assert(GNUNET_OK ==
                GNUNET_CRYPTO_ecc_ecdh(dh_priv1, dh_pub2, &hash));
  GNUNET_assert(NULL != GNUNET_STRINGS_data_to_string(&hash, 64, buf, 128));
  printf("ECDH shared secret: %s\n", buf);

  GNUNET_free(dh_priv1);
  GNUNET_free(dh_priv2);
  GNUNET_free(dh_pub1);
  GNUNET_free(dh_pub2);
}


/**
 * Print some random example operations to stdout.
 */
static void
print_examples()
{
  print_examples_ecdh();
  // print_examples_ecdsa ();
  // print_examples_eddsa ();
}


static void
print_key(const char *filename)
{
  struct GNUNET_DISK_FileHandle *fd;
  struct GNUNET_CRYPTO_EddsaPrivateKey private_key;
  struct GNUNET_CRYPTO_EddsaPublicKey public_key;
  char *hostkeys_data;
  char *hostkey_str;
  uint64_t fs;
  unsigned int total_hostkeys;
  unsigned int c;
  ssize_t sret;

  if (GNUNET_YES != GNUNET_DISK_file_test(filename))
    {
      fprintf(stderr, _("Hostkeys file `%s' not found\n"), filename);
      return;
    }

  /* Check hostkey file size, read entire thing into memory */
  if (GNUNET_OK !=
      GNUNET_DISK_file_size(filename, &fs, GNUNET_YES, GNUNET_YES))
    fs = 0;
  if (0 == fs)
    {
      fprintf(stderr, _("Hostkeys file `%s' is empty\n"), filename);
      return; /* File is empty */
    }
  if (0 != (fs % GNUNET_TESTING_HOSTKEYFILESIZE))
    {
      fprintf(stderr, _("Incorrect hostkey file format: %s\n"), filename);
      return;
    }
  fd = GNUNET_DISK_file_open(filename,
                             GNUNET_DISK_OPEN_READ,
                             GNUNET_DISK_PERM_NONE);
  if (NULL == fd)
    {
      GNUNET_log_strerror_file(GNUNET_ERROR_TYPE_ERROR, "open", filename);
      return;
    }
  hostkeys_data = GNUNET_malloc(fs);
  sret = GNUNET_DISK_file_read(fd, hostkeys_data, fs);
  if ((sret < 0) || (fs != (size_t)sret))
    {
      fprintf(stderr, _("Could not read hostkey file: %s\n"), filename);
      GNUNET_free(hostkeys_data);
      GNUNET_DISK_file_close(fd);
      return;
    }
  GNUNET_DISK_file_close(fd);

  if (NULL == hostkeys_data)
    return;
  total_hostkeys = fs / GNUNET_TESTING_HOSTKEYFILESIZE;
  for (c = 0; (c < total_hostkeys) && (c < list_keys_count); c++)
    {
      GNUNET_memcpy(&private_key,
                    hostkeys_data + (c * GNUNET_TESTING_HOSTKEYFILESIZE),
                    GNUNET_TESTING_HOSTKEYFILESIZE);
      GNUNET_CRYPTO_eddsa_key_get_public(&private_key, &public_key);
      hostkey_str = GNUNET_CRYPTO_eddsa_public_key_to_string(&public_key);
      if (NULL != hostkey_str)
        {
          fprintf(stderr, "%4u: %s\n", c, hostkey_str);
          GNUNET_free(hostkey_str);
        }
      else
        fprintf(stderr, "%4u: %s\n", c, "invalid");
    }
  GNUNET_free(hostkeys_data);
}


/**
 * Main function that will be run by the scheduler.
 *
 * @param cls closure, NULL
 * @param args remaining command-line arguments
 * @param cfgfile name of the configuration file used (for saving, can be NULL!)
 * @param cfg configuration
 */
static void
run(void *cls,
    char *const *args,
    const char *cfgfile,
    const struct GNUNET_CONFIGURATION_Handle *cfg)
{
  (void)cls;
  (void)cfgfile;
  (void)cfg;

  if (print_examples_flag)
    {
      print_examples();
      return;
    }
  if (NULL == args[0])
    {
      fprintf(stderr, "%s", _("No hostkey file specified on command line\n"));
      return;
    }
  if (list_keys)
    {
      print_key(args[0]);
      return;
    }
  if (make_keys > 0)
    {
      create_keys(args[0], args[1]);
      return;
    }
  if (print_public_key || print_public_key_hex || print_private_key)
    {
      char *str;
      struct GNUNET_DISK_FileHandle *keyfile;
      struct GNUNET_CRYPTO_EddsaPrivateKey pk;
      struct GNUNET_CRYPTO_EddsaPublicKey pub;

      keyfile = GNUNET_DISK_file_open(args[0],
                                      GNUNET_DISK_OPEN_READ,
                                      GNUNET_DISK_PERM_NONE);
      if (NULL == keyfile)
        return;
      while (sizeof(pk) == GNUNET_DISK_file_read(keyfile, &pk, sizeof(pk)))
        {
          GNUNET_CRYPTO_eddsa_key_get_public(&pk, &pub);
          if (print_public_key_hex)
            {
              print_hex("HEX:", &pub, sizeof(pub));
            }
          else if (print_public_key)
            {
              str = GNUNET_CRYPTO_eddsa_public_key_to_string(&pub);
              fprintf(stdout, "%s\n", str);
              GNUNET_free(str);
            }
          else if (print_private_key)
            {
              str = GNUNET_CRYPTO_eddsa_private_key_to_string(&pk);
              fprintf(stdout, "%s\n", str);
              GNUNET_free(str);
            }
        }
      GNUNET_DISK_file_close(keyfile);
    }
}


/**
 * Program to manipulate ECC key files.
 *
 * @param argc number of arguments from the command line
 * @param argv command line arguments
 * @return 0 ok, 1 on error
 */
int
main(int argc, char *const *argv)
{
  struct GNUNET_GETOPT_CommandLineOption options[] =
  { GNUNET_GETOPT_option_flag('i',
                              "iterate",
                              gettext_noop(
                                "list keys included in a file (for testing)"),
                              &list_keys),
    GNUNET_GETOPT_option_uint(
      'e',
      "end=",
      "COUNT",
      gettext_noop("number of keys to list included in a file (for testing)"),
      &list_keys_count),
    GNUNET_GETOPT_option_uint(
      'g',
      "generate-keys",
      "COUNT",
      gettext_noop("create COUNT public-private key pairs (for testing)"),
      &make_keys),
    GNUNET_GETOPT_option_flag('p',
                              "print-public-key",
                              gettext_noop(
                                "print the public key in ASCII format"),
                              &print_public_key),
    GNUNET_GETOPT_option_flag('P',
                              "print-private-key",
                              gettext_noop(
                                "print the private key in ASCII format"),
                              &print_private_key),
    GNUNET_GETOPT_option_flag('x',
                              "print-hex",
                              gettext_noop(
                                "print the public key in HEX format"),
                              &print_public_key_hex),
    GNUNET_GETOPT_option_flag(
      'E',
      "examples",
      gettext_noop(
        "print examples of ECC operations (used for compatibility testing)"),
      &print_examples_flag),
    GNUNET_GETOPT_OPTION_END };
  int ret;

  list_keys_count = UINT32_MAX;
  if (GNUNET_OK != GNUNET_STRINGS_get_utf8_args(argc, argv, &argc, &argv))
    return 2;

  ret = (GNUNET_OK ==
         GNUNET_PROGRAM_run(argc,
                            argv,
                            "gnunet-ecc [OPTIONS] keyfile [VANITY_PREFIX]",
                            gettext_noop(
                              "Manipulate GNUnet private ECC key files"),
                            options,
                            &run,
                            NULL))
        ? 0
        : 1;
  GNUNET_free((void *)argv);
  return ret;
}

/* end of gnunet-ecc.c */