/**

 * FreeRDP: A Remote Desktop Protocol Implementation

 * Cryptographic Abstraction Layer

 *

 * Copyright 2011-2012 Marc-Andre Moreau <marcandre.moreau@gmail.com>

 * Copyright 2023 Armin Novak <anovak@thincast.com>

 * Copyright 2023 Thincast Technologies GmbH

 *

 * Licensed under the Apache License, Version 2.0 (the "License");

 * you may not use this file except in compliance with the License.

 * You may obtain a copy of the License at

 *

 *   http://www.apache.org/licenses/LICENSE-2.0

 *

 * Unless required by applicable law or agreed to in writing, software

 * distributed under the License is distributed on an "AS IS" BASIS,

 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.

 * See the License for the specific language governing permissions and

 * limitations under the License.

 */

#include <errno.h>

#include <openssl/objects.h>

#include <openssl/bn.h>

#include <freerdp/config.h>

#include <winpr/crt.h>

#include <winpr/assert.h>

#include <freerdp/log.h>

#include <freerdp/crypto/crypto.h>

#include "crypto.h"

#include "privatekey.h"

#if !defined(_WIN32)

#include <sys/stat.h>

#endif

#define TAG FREERDP_TAG("crypto")

static SSIZE_T crypto_rsa_common(const BYTE* input, size_t length, UINT32 key_length,

                                 const BYTE* modulus, const BYTE* exponent, size_t exponent_size,

                                 BYTE* output, size_t out_length)

{

  BN_CTX* ctx = nullptr;

  int output_length = -1;

  BYTE* input_reverse = nullptr;

  BYTE* modulus_reverse = nullptr;

  BYTE* exponent_reverse = nullptr;

  BIGNUM* mod = nullptr;

  BIGNUM* exp = nullptr;

  BIGNUM* x = nullptr;

  BIGNUM* y = nullptr;

  size_t bufferSize = 0;

  if (!input || !modulus || !exponent || !output)

    return -1;

  if (exponent_size > INT_MAX / 2)

    return -1;

  if (key_length >= INT_MAX / 2 - exponent_size)

    return -1;

  bufferSize = 2ULL * key_length + exponent_size;

  if (length > bufferSize)

    bufferSize = length;

  input_reverse = (BYTE*)calloc(bufferSize, 1);

  if (!input_reverse)

    return -1;

  modulus_reverse = input_reverse + key_length;

  exponent_reverse = modulus_reverse + key_length;

  memmove(modulus_reverse, modulus, key_length);

  crypto_reverse(modulus_reverse, key_length);

  memmove(exponent_reverse, exponent, exponent_size);

  crypto_reverse(exponent_reverse, exponent_size);

  memmove(input_reverse, input, length);

  crypto_reverse(input_reverse, length);

  if (!(ctx = BN_CTX_new()))

    goto fail;

  if (!(mod = BN_new()))

    goto fail;

  if (!(exp = BN_new()))

    goto fail;

  if (!(x = BN_new()))

    goto fail;

  if (!(y = BN_new()))

    goto fail;

  if (!BN_bin2bn(modulus_reverse, (int)key_length, mod))

    goto fail;

  if (!BN_bin2bn(exponent_reverse, (int)exponent_size, exp))

    goto fail;

  if (!BN_bin2bn(input_reverse, (int)length, x))

    goto fail;

  if (BN_mod_exp(y, x, exp, mod, ctx) != 1)

    goto fail;

  {

    const int len = BN_num_bytes(y);

    if ((len < 0) || (WINPR_ASSERTING_INT_CAST(size_t, len) > out_length))

      goto fail;

    output_length = BN_bn2bin(y, output);

  }

  if (output_length < 0)

    goto fail;

  crypto_reverse(output, WINPR_ASSERTING_INT_CAST(size_t, output_length));

  if ((size_t)output_length < key_length)

  {

    size_t diff = key_length - WINPR_ASSERTING_INT_CAST(size_t, output_length);

    if ((size_t)output_length + diff > out_length)

      diff = out_length - (size_t)output_length;

    memset(output + output_length, 0, diff);

  }

fail:

  BN_free(y);

  BN_clear_free(x);

  BN_free(exp);

  BN_free(mod);

  BN_CTX_free(ctx);

  free(input_reverse);

  return output_length;

}

static SSIZE_T crypto_rsa_public(const BYTE* input, size_t length, const rdpCertInfo* cert,

                                 BYTE* output, size_t output_length)

{

  WINPR_ASSERT(cert);

  return crypto_rsa_common(input, length, cert->ModulusLength, cert->Modulus, cert->exponent,

                           sizeof(cert->exponent), output, output_length);

}

static SSIZE_T crypto_rsa_private(const BYTE* input, size_t length, const rdpPrivateKey* key,

                                  BYTE* output, size_t output_length)

{

  WINPR_ASSERT(key);

  const rdpCertInfo* info = freerdp_key_get_info(key);

  WINPR_ASSERT(info);

  size_t PrivateExponentLength = 0;

  const BYTE* PrivateExponent = freerdp_key_get_exponent(key, &PrivateExponentLength);

  return crypto_rsa_common(input, length, info->ModulusLength, info->Modulus, PrivateExponent,

                           PrivateExponentLength, output, output_length);

}

SSIZE_T crypto_rsa_public_encrypt(const BYTE* input, size_t length, const rdpCertInfo* cert,

                                  BYTE* output, size_t output_length)

{

  return crypto_rsa_public(input, length, cert, output, output_length);

}

SSIZE_T crypto_rsa_public_decrypt(const BYTE* input, size_t length, const rdpCertInfo* cert,

                                  BYTE* output, size_t output_length)

{

  return crypto_rsa_public(input, length, cert, output, output_length);

}

SSIZE_T crypto_rsa_private_encrypt(const BYTE* input, size_t length, const rdpPrivateKey* key,

                                   BYTE* output, size_t output_length)

{

  return crypto_rsa_private(input, length, key, output, output_length);

}

SSIZE_T crypto_rsa_private_decrypt(const BYTE* input, size_t length, const rdpPrivateKey* key,

                                   BYTE* output, size_t output_length)

{

  return crypto_rsa_private(input, length, key, output, output_length);

}

void crypto_reverse(BYTE* data, size_t length)

{

  if (length < 1)

    return;

  for (size_t i = 0, j = length - 1; i < j; i++, j--)

  {

    const BYTE temp = data[i];

    data[i] = data[j];

    data[j] = temp;

  }

}

char* crypto_read_pem(const char* WINPR_RESTRICT filename, size_t* WINPR_RESTRICT plength)

{

  char* pem = nullptr;

  FILE* fp = nullptr;

  WINPR_ASSERT(filename);

  if (plength)

    *plength = 0;

  /* Binary mode: the size is taken from SEEK_END and then demanded in a single fread().

   * In text mode on Windows CRLF collapses to LF, fewer than size bytes come back and the

   * read fails, which makes every CRLF-terminated PEM unreadable -- and that is what the

   * Windows tooling writes. */

  fp = winpr_fopen(filename, "rb");

  if (!fp)

    goto fail;

  {

    const int rs = _fseeki64(fp, 0, SEEK_END);

    if (rs < 0)

      goto fail;

  }

  {

    const int64_t size = _ftelli64(fp);

    if (size < 0)

      goto fail;

    {

      const int rc = _fseeki64(fp, 0, SEEK_SET);

      if (rc < 0)

        goto fail;

    }

    pem = calloc(WINPR_ASSERTING_INT_CAST(size_t, size) + 1, sizeof(char));

    if (!pem)

      goto fail;

    {

      const size_t fr = fread(pem, (size_t)size, 1, fp);

      if (fr != 1)

        goto fail;

    }

    if (plength)

      *plength = strnlen(pem, WINPR_ASSERTING_INT_CAST(size_t, size));

  }

  (void)fclose(fp);

  return pem;

fail:

{

  char buffer[8192] = WINPR_C_ARRAY_INIT;

  WLog_WARN(TAG, "Failed to read PEM from file '%s' [%s]", filename,

            winpr_strerror(errno, buffer, sizeof(buffer)));

}

  if (fp)

    (void)fclose(fp);

  free(pem);

  return nullptr;

}

BOOL crypto_write_pem(const char* WINPR_RESTRICT filename, const char* WINPR_RESTRICT pem,

                      size_t length)

{

  WINPR_ASSERT(filename);

  WINPR_ASSERT(pem || (length == 0));

  WINPR_ASSERT(filename);

  WINPR_ASSERT(pem);

  const size_t size = strnlen(pem, length) + 1;

  size_t rc = 0;

  FILE* fp = winpr_fopen(filename, "w");

  if (!fp)

    goto fail;

#if !defined(_WIN32)

  const int res = fchmod(fileno(fp), S_IRUSR | S_IWUSR);

  if (res != 0)

  {

    char buffer[128] = WINPR_C_ARRAY_INIT;

    WLog_WARN(TAG, "Failed to chmod %s: %s", filename,

              winpr_strerror(errno, buffer, sizeof(buffer)));

    const int fres = fclose(fp);

    if (fres != 0)

    {

      char buffer2[128] = WINPR_C_ARRAY_INIT;

      WLog_WARN(TAG, "Failed to close PEM [%" PRIuz "] to file '%s' [%s]", length, filename,

                winpr_strerror(errno, buffer2, sizeof(buffer2)));

    }

    goto fail;

  }

#endif

  rc = fwrite(pem, 1, size, fp);

  const int fres = fclose(fp);

  if (fres != 0)

  {

    char buffer[128] = WINPR_C_ARRAY_INIT;

    WLog_WARN(TAG, "Failed to close PEM [%" PRIuz "] to file '%s' [%s]", length, filename,

              winpr_strerror(errno, buffer, sizeof(buffer)));

  }

fail:

  if (rc == 0)

  {

    char buffer[128] = WINPR_C_ARRAY_INIT;

    WLog_WARN(TAG, "Failed to write PEM [%" PRIuz "] to file '%s' [%s]", length, filename,

              winpr_strerror(errno, buffer, sizeof(buffer)));

  }

  return rc == size;

}