lokinet/crypto/csrng/randombytes.c

#include <assert.h>
#include <limits.h>
#include <stdint.h>
#include <stdlib.h>

#include <sys/types.h>

#ifdef __EMSCRIPTEN__
#include <emscripten.h>
#endif

#include <sodium/core.h>
#include <sodium/crypto_stream_xchacha20.h>
#include <sodium/randombytes.h>
#include <sodium/randombytes_salsa20_random.h>
#include <sodium/common.h>

/* C++Builder defines a "random" macro */
#undef random

static const randombytes_implementation *implementation = 0;

static void
randombytes_init_if_needed(void)
{
  if(implementation == NULL)
    implementation = &randombytes_salsa20_implementation;
}

int
randombytes_set_implementation(randombytes_implementation *impl)
{
  implementation = impl;

  return 0;
}

const char *
randombytes_implementation_name(void)
{
#ifndef __EMSCRIPTEN__
  randombytes_init_if_needed();
  return implementation->implementation_name();
#else
  return "js";
#endif
}

uint32_t
randombytes_random(void)
{
#ifndef __EMSCRIPTEN__
  randombytes_init_if_needed();
  return implementation->random();
#else
  return EM_ASM_INT_V({ return Module.getRandomValue(); });
#endif
}

void
randombytes_stir(void)
{
#ifndef __EMSCRIPTEN__
  randombytes_init_if_needed();
  if(implementation->stir != NULL)
  {
    implementation->stir();
  }
#else
  EM_ASM({
    if(Module.getRandomValue == = undefined)
    {
      try
      {
        var window_ = 'object' == = typeof window ? window : self;
        var crypto_               = typeof window_.crypto != =
            'undefined' ? window_.crypto : window_.msCrypto;
        var randomValuesStandard = function()
        {
          var buf = new Uint32Array(1);
          crypto_.getRandomValues(buf);
          return buf[0] >>> 0;
        };
        randomValuesStandard();
        Module.getRandomValue = randomValuesStandard;
      }
      catch(e)
      {
        try
        {
          var crypto            = require('crypto');
          var randomValueNodeJS = function()
          {
            var buf = crypto['randomBytes'](4);
            return (buf[0] << 24 | buf[1] << 16 | buf[2] << 8 | buf[3]) >>> 0;
          };
          randomValueNodeJS();
          Module.getRandomValue = randomValueNodeJS;
        }
        catch(e)
        {
          throw 'No secure random number generator found';
        }
      }
    }
  });
#endif
}

uint32_t
randombytes_uniform(const uint32_t upper_bound)
{
  uint32_t min;
  uint32_t r;

#ifndef __EMSCRIPTEN__
  randombytes_init_if_needed();
  if(implementation->uniform != NULL)
  {
    return implementation->uniform(upper_bound);
  }
#endif
  if(upper_bound < 2)
  {
    return 0;
  }
  min = (1U + ~upper_bound) % upper_bound; /* = 2**32 mod upper_bound */
  do
  {
    r = randombytes_random();
  } while(r < min);
  /* r is now clamped to a set whose size mod upper_bound == 0
   * the worst case (2**31+1) requires ~ 2 attempts */

  return r % upper_bound;
}

void
randombytes_buf(void *const buf, const size_t size)
{
  randombytes_init_if_needed();
  if(size > (size_t)0U)
  {
    implementation->buf(buf, size);
  }
}

void
randombytes_buf_deterministic(void *const buf, const size_t size,
                              const unsigned char seed[randombytes_SEEDBYTES])
{
  static const unsigned char nonce[crypto_stream_xchacha20_NONCEBYTES] = {
      'L', 'i', 'b', 's', 'o', 'd', 'i', 'u', 'm', 'D', 'R', 'G'};

  COMPILER_ASSERT(randombytes_SEEDBYTES == crypto_stream_xchacha20_KEYBYTES);
#if SIZE_MAX > 0x4000000000ULL
  COMPILER_ASSERT(randombytes_BYTES_MAX <= 0x4000000000ULL);
  if(size > 0x4000000000ULL)
  {
    sodium_misuse();
  }
#endif
  crypto_stream_xchacha20((unsigned char *)buf, (unsigned long long)size, nonce,
                          seed);
}

size_t
randombytes_seedbytes(void)
{
  return randombytes_SEEDBYTES;
}

int
randombytes_close(void)
{
  if(implementation != NULL && implementation->close != NULL)
  {
    return implementation->close();
  }
  return 0;
}

void
randombytes(unsigned char *const buf, const unsigned long long buf_len)
{
  assert(buf_len <= SIZE_MAX);
  randombytes_buf(buf, (size_t)buf_len);
}