/***************************************************************************

 *                                  _   _ ____  _

 *  Project                     ___| | | |  _ \| |

 *                             / __| | | | |_) | |

 *                            | (__| |_| |  _ <| |___

 *                             \___|\___/|_| \_\_____|

 *

 * Copyright (C) Daniel Stenberg, <daniel@haxx.se>, et al.

 *

 * This software is licensed as described in the file COPYING, which

 * you should have received as part of this distribution. The terms

 * are also available at https://curl.se/docs/copyright.html.

 *

 * You may opt to use, copy, modify, merge, publish, distribute and/or sell

 * copies of the Software, and permit persons to whom the Software is

 * furnished to do so, under the terms of the COPYING file.

 *

 * This software is distributed on an "AS IS" basis, WITHOUT WARRANTY OF ANY

 * KIND, either express or implied.

 *

 * SPDX-License-Identifier: curl

 *

 ***************************************************************************/

#include "curl_setup.h"

#include <limits.h>

#ifdef HAVE_FCNTL_H

#include <fcntl.h>

#endif

#ifdef HAVE_ARPA_INET_H

#include <arpa/inet.h>

#endif

#include <curl/curl.h>

#include "urldata.h"

#include "vtls/vtls.h"

#include "sendf.h"

#include "timeval.h"

#include "rand.h"

#include "escape.h"

/* The last 3 #include files should be in this order */

#include "curl_printf.h"

#include "curl_memory.h"

#include "memdebug.h"

#ifdef _WIN32

#if defined(_WIN32_WINNT) && _WIN32_WINNT >= 0x600

#  define HAVE_WIN_BCRYPTGENRANDOM

#  include <bcrypt.h>

#  ifdef _MSC_VER

#    pragma comment(lib, "bcrypt.lib")

#  endif

#  ifndef BCRYPT_USE_SYSTEM_PREFERRED_RNG

#  define BCRYPT_USE_SYSTEM_PREFERRED_RNG 0x00000002

#  endif

#  ifndef STATUS_SUCCESS

#  define STATUS_SUCCESS ((NTSTATUS)0x00000000L)

#  endif

#elif defined(USE_WIN32_CRYPTO)

#  include <wincrypt.h>

#  ifdef _MSC_VER

#    pragma comment(lib, "advapi32.lib")

#  endif

#endif

CURLcode Curl_win32_random(unsigned char *entropy, size_t length)

{

  memset(entropy, 0, length);

#if defined(HAVE_WIN_BCRYPTGENRANDOM)

  if(BCryptGenRandom(NULL, entropy, (ULONG)length,

                     BCRYPT_USE_SYSTEM_PREFERRED_RNG) != STATUS_SUCCESS)

    return CURLE_FAILED_INIT;

  return CURLE_OK;

#elif defined(USE_WIN32_CRYPTO)

  {

    HCRYPTPROV hCryptProv = 0;

    if(!CryptAcquireContext(&hCryptProv, NULL, NULL, PROV_RSA_FULL,

                            CRYPT_VERIFYCONTEXT | CRYPT_SILENT))

      return CURLE_FAILED_INIT;

    if(!CryptGenRandom(hCryptProv, (DWORD)length, entropy)) {

      CryptReleaseContext(hCryptProv, 0UL);

      return CURLE_FAILED_INIT;

    }

    CryptReleaseContext(hCryptProv, 0UL);

  }

  return CURLE_OK;

#else

  return CURLE_NOT_BUILT_IN;

#endif

}

#endif

static CURLcode randit(struct Curl_easy *data, unsigned int *rnd)

{

  CURLcode result = CURLE_OK;

  static unsigned int randseed;

  static bool seeded = FALSE;

#ifdef CURLDEBUG

  char *force_entropy = getenv("CURL_ENTROPY");

  if(force_entropy) {

    if(!seeded) {

      unsigned int seed = 0;

      size_t elen = strlen(force_entropy);

      size_t clen = sizeof(seed);

      size_t min = elen < clen ? elen : clen;

      memcpy((char *)&seed, force_entropy, min);

      randseed = ntohl(seed);

      seeded = TRUE;

    }

    else

      randseed++;

    *rnd = randseed;

    return CURLE_OK;

  }

#endif

  /* data may be NULL! */

  result = Curl_ssl_random(data, (unsigned char *)rnd, sizeof(*rnd));

  if(result != CURLE_NOT_BUILT_IN)

    /* only if there is no random function in the TLS backend do the non crypto

       version, otherwise return result */

    return result;

  /* ---- non-cryptographic version following ---- */

#ifdef _WIN32

  if(!seeded) {

    result = Curl_win32_random((unsigned char *)rnd, sizeof(*rnd));

    if(result != CURLE_NOT_BUILT_IN)

      return result;

  }

#endif

#if defined(HAVE_ARC4RANDOM) && !defined(USE_OPENSSL)

  if(!seeded) {

    *rnd = (unsigned int)arc4random();

    return CURLE_OK;

  }

#endif

#if defined(RANDOM_FILE) && !defined(_WIN32)

  if(!seeded) {

    /* if there's a random file to read a seed from, use it */

    int fd = open(RANDOM_FILE, O_RDONLY);

    if(fd > -1) {

      /* read random data into the randseed variable */

      ssize_t nread = read(fd, &randseed, sizeof(randseed));

      if(nread == sizeof(randseed))

        seeded = TRUE;

      close(fd);

    }

  }

#endif

  if(!seeded) {

    struct curltime now = Curl_now();

    infof(data, "WARNING: using weak random seed");

    randseed += (unsigned int)now.tv_usec + (unsigned int)now.tv_sec;

    randseed = randseed * 1103515245 + 12345;

    randseed = randseed * 1103515245 + 12345;

    randseed = randseed * 1103515245 + 12345;

    seeded = TRUE;

  }

  {

    unsigned int r;

    /* Return an unsigned 32-bit pseudo-random number. */

    r = randseed = randseed * 1103515245 + 12345;

    *rnd = (r << 16) | ((r >> 16) & 0xFFFF);

  }

  return CURLE_OK;

}

/*

 * Curl_rand() stores 'num' number of random unsigned characters in the buffer

 * 'rnd' points to.

 *

 * If libcurl is built without TLS support or with a TLS backend that lacks a

 * proper random API (rustls or mbedTLS), this function will use "weak"

 * random.

 *

 * When built *with* TLS support and a backend that offers strong random, it

 * will return error if it cannot provide strong random values.

 *

 * NOTE: 'data' may be passed in as NULL when coming from external API without

 * easy handle!

 *

 */

CURLcode Curl_rand(struct Curl_easy *data, unsigned char *rnd, size_t num)

{

  CURLcode result = CURLE_BAD_FUNCTION_ARGUMENT;

  DEBUGASSERT(num);

  while(num) {

    unsigned int r;

    size_t left = num < sizeof(unsigned int) ? num : sizeof(unsigned int);

    result = randit(data, &r);

    if(result)

      return result;

    while(left) {

      *rnd++ = (unsigned char)(r & 0xFF);

      r >>= 8;

      --num;

      --left;

    }

  }

  return result;

}

/*

 * Curl_rand_hex() fills the 'rnd' buffer with a given 'num' size with random

 * hexadecimal digits PLUS a null-terminating byte. It must be an odd number

 * size.

 */

CURLcode Curl_rand_hex(struct Curl_easy *data, unsigned char *rnd,

                       size_t num)

{

  CURLcode result = CURLE_BAD_FUNCTION_ARGUMENT;

  unsigned char buffer[128];

  DEBUGASSERT(num > 1);

#ifdef __clang_analyzer__

  /* This silences a scan-build warning about accessing this buffer with

     uninitialized memory. */

  memset(buffer, 0, sizeof(buffer));

#endif

  if((num/2 >= sizeof(buffer)) || !(num&1)) {

    /* make sure it fits in the local buffer and that it is an odd number! */

    DEBUGF(infof(data, "invalid buffer size with Curl_rand_hex"));

    return CURLE_BAD_FUNCTION_ARGUMENT;

  }

  num--; /* save one for null-termination */

  result = Curl_rand(data, buffer, num/2);

  if(result)

    return result;

  Curl_hexencode(buffer, num/2, rnd, num + 1);

  return result;

}

/*

 * Curl_rand_alnum() fills the 'rnd' buffer with a given 'num' size with random

 * alphanumerical chars PLUS a null-terminating byte.

 */

static const char alnum[] =

  "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789";

CURLcode Curl_rand_alnum(struct Curl_easy *data, unsigned char *rnd,

                         size_t num)

{

  CURLcode result = CURLE_OK;

  const int alnumspace = sizeof(alnum) - 1;

  unsigned int r;

  DEBUGASSERT(num > 1);

  num--; /* save one for null-termination */

  while(num) {

    do {

      result = randit(data, &r);

      if(result)

        return result;

    } while(r >= (UINT_MAX - UINT_MAX % alnumspace));

    *rnd++ = alnum[r % alnumspace];

    num--;

  }

  *rnd = 0;

  return result;

}