/*
 *  OpenVPN -- An application to securely tunnel IP networks
 *             over a single TCP/UDP port, with support for SSL/TLS-based
 *             session authentication and key exchange,
 *             packet encryption, packet authentication, and
 *             packet compression.
 *
 *  Copyright (C) 2002-2010 OpenVPN Technologies, Inc. <sales@openvpn.net>
 *  Copyright (C) 2010 Fox Crypto B.V. <openvpn@fox-it.com>
 *
 *  This program is free software; you can redistribute it and/or modify
 *  it under the terms of the GNU General Public License version 2
 *  as published by the Free Software Foundation.
 *
 *  This program 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 (see the file COPYING included with this
 *  distribution); if not, write to the Free Software Foundation, Inc.,
 *  59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
 */

/**
 * @file Data Channel Cryptography mbed TLS-specific backend interface
 */

#ifdef HAVE_CONFIG_H
#include "config.h"
#elif defined(_MSC_VER)
#include "config-msvc.h"
#endif

#include "syshead.h"

#if defined(ENABLE_CRYPTO) && defined(ENABLE_CRYPTO_MBEDTLS)

#include "errlevel.h"
#include "basic.h"
#include "buffer.h"
#include "integer.h"
#include "crypto_backend.h"
#include "otime.h"
#include "misc.h"

#include <mbedtls/des.h>
#include <mbedtls/error.h>
#include <mbedtls/md5.h>
#include <mbedtls/cipher.h>
#include <mbedtls/havege.h>

#include <mbedtls/entropy.h>


/*
 *
 * Hardware engine support. Allows loading/unloading of engines.
 *
 */

void
crypto_init_lib_engine (const char *engine_name)
{
  msg (M_WARN, "Note: mbed TLS hardware crypto engine functionality is not "
      "available");
}

/*
 *
 * Functions related to the core crypto library
 *
 */

void
crypto_init_lib (void)
{
}

void
crypto_uninit_lib (void)
{
}

void
crypto_clear_error (void)
{
}

bool mbed_log_err(unsigned int flags, int errval, const char *prefix)
{
  if (0 != errval)
    {
      char errstr[256];
      mbedtls_strerror(errval, errstr, sizeof(errstr));

      if (NULL == prefix) prefix = "mbed TLS error";
      msg (flags, "%s: %s", prefix, errstr);
    }

  return 0 == errval;
}

bool mbed_log_func_line(unsigned int flags, int errval, const char *func,
    int line)
{
  char prefix[256];

  if (!openvpn_snprintf(prefix, sizeof(prefix), "%s:%d", func, line))
    return mbed_log_err(flags, errval, func);

  return mbed_log_err(flags, errval, prefix);
}


#ifdef DMALLOC
void
crypto_init_dmalloc (void)
{
  msg (M_ERR, "Error: dmalloc support is not available for mbed TLS.");
}
#endif /* DMALLOC */

const cipher_name_pair cipher_name_translation_table[] = {
    { "BF-CBC", "BLOWFISH-CBC" },
    { "BF-CFB", "BLOWFISH-CFB64" },
    { "CAMELLIA-128-CFB", "CAMELLIA-128-CFB128" },
    { "CAMELLIA-192-CFB", "CAMELLIA-192-CFB128" },
    { "CAMELLIA-256-CFB", "CAMELLIA-256-CFB128" }
};
const size_t cipher_name_translation_table_count =
    sizeof (cipher_name_translation_table) / sizeof (*cipher_name_translation_table);

static void print_cipher(const cipher_kt_t *info)
{
  if (info && (cipher_kt_mode_cbc(info)
#ifdef HAVE_AEAD_CIPHER_MODES
      || cipher_kt_mode_aead(info)
#endif
  ))
    {
      const char *ssl_only = cipher_kt_mode_cbc(info) ?
	  "" : ", TLS client/server mode only";
      const char *var_key_size = info->flags & MBEDTLS_CIPHER_VARIABLE_KEY_LEN ?
	  " by default" : "";

      printf ("%s  (%d bit key%s, %d bit block%s)\n",
	  cipher_kt_name(info), cipher_kt_key_size(info) * 8, var_key_size,
	  cipher_kt_block_size(info) * 8, ssl_only);
    }
}

void
show_available_ciphers ()
{
  const int *ciphers = mbedtls_cipher_list();

#ifndef ENABLE_SMALL
  printf ("The following ciphers and cipher modes are available for use\n"
	  "with " PACKAGE_NAME ".  Each cipher shown below may be used as a\n"
	  "parameter to the --cipher option.  Using a CBC or GCM mode is\n"
	  "recommended.  In static key mode only CBC mode is allowed.\n\n");
#endif

  while (*ciphers != 0)
    {
      const cipher_kt_t *info = mbedtls_cipher_info_from_type(*ciphers);
      if (info && cipher_kt_block_size(info) >= 128/8)
	{
	  print_cipher(info);
	}
      ciphers++;
    }

  printf ("\nThe following ciphers have a block size of less than 128 bits, \n"
	  "and are therefore deprecated.  Do not use unless you have to.\n\n");
  ciphers = mbedtls_cipher_list();
  while (*ciphers != 0)
    {
      const cipher_kt_t *info = mbedtls_cipher_info_from_type(*ciphers);
      if (info && cipher_kt_block_size(info) < 128/8)
	{
	  print_cipher(info);
	}
      ciphers++;
    }
  printf ("\n");
}

void
show_available_digests ()
{
  const int *digests = mbedtls_md_list();

#ifndef ENABLE_SMALL
  printf ("The following message digests are available for use with\n"
	  PACKAGE_NAME ".  A message digest is used in conjunction with\n"
	  "the HMAC function, to authenticate received packets.\n"
	  "You can specify a message digest as parameter to\n"
	  "the --auth option.\n\n");
#endif

  while (*digests != 0)
    {
      const mbedtls_md_info_t *info = mbedtls_md_info_from_type(*digests);

      if (info)
	printf ("%s %d bit default key\n", mbedtls_md_get_name(info),
	    mbedtls_md_get_size(info) * 8);
      digests++;
    }
  printf ("\n");
}

void
show_available_engines ()
{
  printf ("Sorry, mbed TLS hardware crypto engine functionality is not "
      "available\n");
}

/*
 *
 * Random number functions, used in cases where we want
 * reasonably strong cryptographic random number generation
 * without depleting our entropy pool.  Used for random
 * IV values and a number of other miscellaneous tasks.
 *
 */

/*
 * Initialise the given ctr_drbg context, using a personalisation string and an
 * entropy gathering function.
 */
mbedtls_ctr_drbg_context * rand_ctx_get()
{
  static mbedtls_entropy_context ec = {0};
  static mbedtls_ctr_drbg_context cd_ctx = {0};
  static bool rand_initialised = false;

  if (!rand_initialised)
    {
      struct gc_arena gc = gc_new();
      struct buffer pers_string = alloc_buf_gc(100, &gc);

      /*
       * Personalisation string, should be as unique as possible (see NIST
       * 800-90 section 8.7.1). We have very little information at this stage.
       * Include Program Name, memory address of the context and PID.
       */
      buf_printf(&pers_string, "OpenVPN %0u %p %s", platform_getpid(), &cd_ctx, time_string(0, 0, 0, &gc));

      /* Initialise mbed TLS RNG, and built-in entropy sources */
      mbedtls_entropy_init(&ec);

      mbedtls_ctr_drbg_init(&cd_ctx);
      if (!mbed_ok(mbedtls_ctr_drbg_seed(&cd_ctx, mbedtls_entropy_func, &ec,
		    BPTR(&pers_string), BLEN(&pers_string))))
        msg (M_FATAL, "Failed to initialize random generator");

      gc_free(&gc);
      rand_initialised = true;
  }

  return &cd_ctx;
}

#ifdef ENABLE_PREDICTION_RESISTANCE
void rand_ctx_enable_prediction_resistance()
{
  mbedtls_ctr_drbg_context *cd_ctx = rand_ctx_get();

  mbedtls_ctr_drbg_set_prediction_resistance(cd_ctx, 1);
}
#endif /* ENABLE_PREDICTION_RESISTANCE */

int
rand_bytes (uint8_t *output, int len)
{
  mbedtls_ctr_drbg_context *rng_ctx = rand_ctx_get();

  while (len > 0)
    {
      const size_t blen = min_int (len, MBEDTLS_CTR_DRBG_MAX_REQUEST);
      if (0 != mbedtls_ctr_drbg_random(rng_ctx, output, blen))
	return 0;

      output += blen;
      len -= blen;
    }

  return 1;
}

/*
 *
 * Key functions, allow manipulation of keys.
 *
 */


int
key_des_num_cblocks (const mbedtls_cipher_info_t *kt)
{
  int ret = 0;
  if (kt->type == MBEDTLS_CIPHER_DES_CBC)
    ret = 1;
  if (kt->type == MBEDTLS_CIPHER_DES_EDE_CBC)
    ret = 2;
  if (kt->type == MBEDTLS_CIPHER_DES_EDE3_CBC)
    ret = 3;

  dmsg (D_CRYPTO_DEBUG, "CRYPTO INFO: n_DES_cblocks=%d", ret);
  return ret;
}

bool
key_des_check (uint8_t *key, int key_len, int ndc)
{
  int i;
  struct buffer b;

  buf_set_read (&b, key, key_len);

  for (i = 0; i < ndc; ++i)
    {
      unsigned char *key = buf_read_alloc(&b, MBEDTLS_DES_KEY_SIZE);
      if (!key)
	{
	  msg (D_CRYPT_ERRORS, "CRYPTO INFO: check_key_DES: insufficient key material");
	  goto err;
	}
      if (0 != mbedtls_des_key_check_weak(key))
	{
	  msg (D_CRYPT_ERRORS, "CRYPTO INFO: check_key_DES: weak key detected");
	  goto err;
	}
      if (0 != mbedtls_des_key_check_key_parity(key))
	{
	  msg (D_CRYPT_ERRORS, "CRYPTO INFO: check_key_DES: bad parity detected");
	  goto err;
	}
    }
  return true;

 err:
  return false;
}

void
key_des_fixup (uint8_t *key, int key_len, int ndc)
{
  int i;
  struct buffer b;

  buf_set_read (&b, key, key_len);
  for (i = 0; i < ndc; ++i)
    {
      unsigned char *key = buf_read_alloc(&b, MBEDTLS_DES_KEY_SIZE);
      if (!key)
	{
	  msg (D_CRYPT_ERRORS, "CRYPTO INFO: fixup_key_DES: insufficient key material");
	  return;
	}
      mbedtls_des_key_set_parity(key);
    }
}

/*
 *
 * Generic cipher key type functions
 *
 */


const mbedtls_cipher_info_t *
cipher_kt_get (const char *ciphername)
{
  const mbedtls_cipher_info_t *cipher = NULL;

  ASSERT (ciphername);

  cipher = mbedtls_cipher_info_from_string(ciphername);

  if (NULL == cipher)
    {
      msg (D_LOW, "Cipher algorithm '%s' not found", ciphername);
      return NULL;
    }

  if (cipher->key_bitlen/8 > MAX_CIPHER_KEY_LENGTH)
    {
      msg (D_LOW, "Cipher algorithm '%s' uses a default key size (%d bytes) "
	  "which is larger than " PACKAGE_NAME "'s current maximum key size "
	  "(%d bytes)", ciphername, cipher->key_bitlen/8, MAX_CIPHER_KEY_LENGTH);
      return NULL;
    }

  return cipher;
}

const char *
cipher_kt_name (const mbedtls_cipher_info_t *cipher_kt)
{
  if (NULL == cipher_kt)
    return "[null-cipher]";

  return translate_cipher_name_to_openvpn(cipher_kt->name);
}

int
cipher_kt_key_size (const mbedtls_cipher_info_t *cipher_kt)
{
  if (NULL == cipher_kt)
    return 0;

  return cipher_kt->key_bitlen/8;
}

int
cipher_kt_iv_size (const mbedtls_cipher_info_t *cipher_kt)
{
  if (NULL == cipher_kt)
    return 0;
  return cipher_kt->iv_size;
}

int
cipher_kt_block_size (const mbedtls_cipher_info_t *cipher_kt)
{
  if (NULL == cipher_kt)
    return 0;
  return cipher_kt->block_size;
}

int
cipher_kt_tag_size (const mbedtls_cipher_info_t *cipher_kt)
{
#ifdef HAVE_AEAD_CIPHER_MODES
  if (cipher_kt && cipher_kt_mode_aead(cipher_kt))
    return OPENVPN_AEAD_TAG_LENGTH;
#endif
  return 0;
}

int
cipher_kt_mode (const mbedtls_cipher_info_t *cipher_kt)
{
  ASSERT(NULL != cipher_kt);
  return cipher_kt->mode;
}

bool
cipher_kt_mode_cbc(const cipher_kt_t *cipher)
{
  return cipher && cipher_kt_mode(cipher) == OPENVPN_MODE_CBC;
}

bool
cipher_kt_mode_ofb_cfb(const cipher_kt_t *cipher)
{
  return cipher && (cipher_kt_mode(cipher) == OPENVPN_MODE_OFB ||
      cipher_kt_mode(cipher) == OPENVPN_MODE_CFB);
}

bool
cipher_kt_mode_aead(const cipher_kt_t *cipher)
{
  return cipher && cipher_kt_mode(cipher) == OPENVPN_MODE_GCM;
}


/*
 *
 * Generic cipher context functions
 *
 */


void
cipher_ctx_init (mbedtls_cipher_context_t *ctx, uint8_t *key, int key_len,
    const mbedtls_cipher_info_t *kt, const mbedtls_operation_t operation)
{
  ASSERT(NULL != kt && NULL != ctx);

  CLEAR (*ctx);

  if (!mbed_ok(mbedtls_cipher_setup(ctx, kt)))
    msg (M_FATAL, "mbed TLS cipher context init #1");

  if (!mbed_ok(mbedtls_cipher_setkey(ctx, key, key_len*8, operation)))
    msg (M_FATAL, "mbed TLS cipher set key");

  /* make sure we used a big enough key */
  ASSERT (ctx->key_bitlen <= key_len*8);
}

void cipher_ctx_cleanup (mbedtls_cipher_context_t *ctx)
{
  mbedtls_cipher_free(ctx);
}

int cipher_ctx_iv_length (const mbedtls_cipher_context_t *ctx)
{
  return mbedtls_cipher_get_iv_size(ctx);
}

int cipher_ctx_get_tag (cipher_ctx_t *ctx, uint8_t* tag, int tag_len)
{
#ifdef HAVE_AEAD_CIPHER_MODES
  if (tag_len > SIZE_MAX)
    return 0;

  if (!mbed_ok (mbedtls_cipher_write_tag (ctx, (unsigned char *) tag, tag_len)))
    return 0;

  return 1;
#else
  ASSERT(0);
#endif /* HAVE_AEAD_CIPHER_MODES */
}

int cipher_ctx_block_size(const mbedtls_cipher_context_t *ctx)
{
  return mbedtls_cipher_get_block_size(ctx);
}

int cipher_ctx_mode (const mbedtls_cipher_context_t *ctx)
{
  ASSERT(NULL != ctx);

  return cipher_kt_mode(ctx->cipher_info);
}

const cipher_kt_t *
cipher_ctx_get_cipher_kt (const cipher_ctx_t *ctx)
{
  return ctx ? ctx->cipher_info : NULL;
}

int cipher_ctx_reset (mbedtls_cipher_context_t *ctx, uint8_t *iv_buf)
{
  if (!mbed_ok(mbedtls_cipher_reset(ctx)))
    return 0;

  if (!mbed_ok(mbedtls_cipher_set_iv(ctx, iv_buf, ctx->cipher_info->iv_size)))
    return 0;

  return 1;
}

int cipher_ctx_update_ad (cipher_ctx_t *ctx, const uint8_t *src, int src_len)
{
#ifdef HAVE_AEAD_CIPHER_MODES
  if (src_len > SIZE_MAX)
    return 0;

  if (!mbed_ok (mbedtls_cipher_update_ad (ctx, src, src_len)))
    return 0;

  return 1;
#else
  ASSERT(0);
#endif /* HAVE_AEAD_CIPHER_MODES */
}

int cipher_ctx_update (mbedtls_cipher_context_t *ctx, uint8_t *dst,
    int *dst_len, uint8_t *src, int src_len)
{
  size_t s_dst_len = *dst_len;

  if (!mbed_ok(mbedtls_cipher_update(ctx, src, (size_t) src_len, dst,
      &s_dst_len)))
    return 0;

  *dst_len = s_dst_len;

  return 1;
}

int cipher_ctx_final (mbedtls_cipher_context_t *ctx, uint8_t *dst, int *dst_len)
{
  size_t s_dst_len = *dst_len;

  if (!mbed_ok(mbedtls_cipher_finish(ctx, dst, &s_dst_len)))
    return 0;

  *dst_len = s_dst_len;

  return 1;
}

int cipher_ctx_final_check_tag (mbedtls_cipher_context_t *ctx, uint8_t *dst,
    int *dst_len, uint8_t *tag, size_t tag_len)
{
#ifdef HAVE_AEAD_CIPHER_MODES
  size_t olen = 0;

  if (MBEDTLS_DECRYPT != ctx->operation)
    return 0;

  if (tag_len > SIZE_MAX)
    return 0;

  if (!mbed_ok (mbedtls_cipher_finish (ctx, dst, &olen)))
    {
      msg (D_CRYPT_ERRORS, "%s: cipher_ctx_final() failed", __func__);
      return 0;
    }

  if (olen > INT_MAX)
    return 0;
  *dst_len = olen;

  if (!mbed_ok (mbedtls_cipher_check_tag (ctx, (const unsigned char *) tag,
      tag_len)))
    return 0;

  return 1;
#else
  ASSERT(0);
#endif /* HAVE_AEAD_CIPHER_MODES */
}

void
cipher_des_encrypt_ecb (const unsigned char key[DES_KEY_LENGTH],
    unsigned char *src,
    unsigned char *dst)
{
  mbedtls_des_context ctx;

  ASSERT (mbed_ok(mbedtls_des_setkey_enc(&ctx, key)));
  ASSERT (mbed_ok(mbedtls_des_crypt_ecb(&ctx, src, dst)));
}



/*
 *
 * Generic message digest information functions
 *
 */


const mbedtls_md_info_t *
md_kt_get (const char *digest)
{
  const mbedtls_md_info_t *md = NULL;
  ASSERT (digest);

  md = mbedtls_md_info_from_string(digest);
  if (!md)
    msg (M_FATAL, "Message hash algorithm '%s' not found", digest);
  if (mbedtls_md_get_size(md) > MAX_HMAC_KEY_LENGTH)
    msg (M_FATAL, "Message hash algorithm '%s' uses a default hash size (%d bytes) which is larger than " PACKAGE_NAME "'s current maximum hash size (%d bytes)",
	 digest,
	 mbedtls_md_get_size(md),
	 MAX_HMAC_KEY_LENGTH);
  return md;
}

const char *
md_kt_name (const mbedtls_md_info_t *kt)
{
  if (NULL == kt)
    return "[null-digest]";
  return mbedtls_md_get_name (kt);
}

int
md_kt_size (const mbedtls_md_info_t *kt)
{
  if (NULL == kt)
    return 0;
  return mbedtls_md_get_size(kt);
}

/*
 *
 * Generic message digest functions
 *
 */

int
md_full (const md_kt_t *kt, const uint8_t *src, int src_len, uint8_t *dst)
{
  return 0 == mbedtls_md(kt, src, src_len, dst);
}


void
md_ctx_init (mbedtls_md_context_t *ctx, const mbedtls_md_info_t *kt)
{
  ASSERT(NULL != ctx && NULL != kt);

  mbedtls_md_init(ctx);
  ASSERT(0 == mbedtls_md_setup(ctx, kt, 0));
  ASSERT(0 == mbedtls_md_starts(ctx));
}

void
md_ctx_cleanup(mbedtls_md_context_t *ctx)
{
}

int
md_ctx_size (const mbedtls_md_context_t *ctx)
{
  if (NULL == ctx)
    return 0;
  return mbedtls_md_get_size(ctx->md_info);
}

void
md_ctx_update (mbedtls_md_context_t *ctx, const uint8_t *src, int src_len)
{
  ASSERT(0 == mbedtls_md_update(ctx, src, src_len));
}

void
md_ctx_final (mbedtls_md_context_t *ctx, uint8_t *dst)
{
  ASSERT(0 == mbedtls_md_finish(ctx, dst));
  mbedtls_md_free(ctx);
}


/*
 *
 * Generic HMAC functions
 *
 */


/*
 * TODO: re-enable dmsg for crypto debug
 */
void
hmac_ctx_init (mbedtls_md_context_t *ctx, const uint8_t *key, int key_len,
    const mbedtls_md_info_t *kt)
{
  ASSERT(NULL != kt && NULL != ctx);

  mbedtls_md_init(ctx);
  ASSERT(0 == mbedtls_md_setup(ctx, kt, 1));
  ASSERT(0 == mbedtls_md_hmac_starts(ctx, key, key_len));

  /* make sure we used a big enough key */
  ASSERT (mbedtls_md_get_size(kt) <= key_len);
}

void
hmac_ctx_cleanup(mbedtls_md_context_t *ctx)
{
  mbedtls_md_free(ctx);
}

int
hmac_ctx_size (const mbedtls_md_context_t *ctx)
{
  if (NULL == ctx)
    return 0;
  return mbedtls_md_get_size(ctx->md_info);
}

void
hmac_ctx_reset (mbedtls_md_context_t *ctx)
{
  ASSERT(0 == mbedtls_md_hmac_reset(ctx));
}

void
hmac_ctx_update (mbedtls_md_context_t *ctx, const uint8_t *src, int src_len)
{
  ASSERT(0 == mbedtls_md_hmac_update(ctx, src, src_len));
}

void
hmac_ctx_final (mbedtls_md_context_t *ctx, uint8_t *dst)
{
  ASSERT(0 == mbedtls_md_hmac_finish(ctx, dst));
}

#endif /* ENABLE_CRYPTO && ENABLE_CRYPTO_MBEDTLS */
