seed_material.cc | Explore in Territory

// Copyright 2017 The Abseil Authors.
//
// 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
//
//      https://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 "absl/random/internal/seed_material.h"

#include <fcntl.h>

#ifndef _WIN32
#include <unistd.h>
#else
#include <io.h>
#endif

#include <algorithm>
#include <cerrno>
#include <cstdint>
#include <cstdlib>
#include <cstring>

#include "absl/base/dynamic_annotations.h"
#include "absl/base/internal/raw_logging.h"
#include "absl/strings/ascii.h"
#include "absl/strings/escaping.h"
#include "absl/strings/string_view.h"
#include "absl/strings/strip.h"

#if defined(__native_client__)

#include <nacl/nacl_random.h>
#define ABSL_RANDOM_USE_NACL_SECURE_RANDOM …

#elif defined(_WIN32)

#include <windows.h>
#define ABSL_RANDOM_USE_BCRYPT …
#pragma comment(lib, "bcrypt.lib")

#elif defined(__Fuchsia__)
#include <zircon/syscalls.h>

#endif

#if defined(__GLIBC__) && \
    (__GLIBC__ > 2 || (__GLIBC__ == 2 && __GLIBC_MINOR__ >= 25))
// glibc >= 2.25 has getentropy()
#define ABSL_RANDOM_USE_GET_ENTROPY …
#endif

#if defined(__EMSCRIPTEN__)
#include <sys/random.h>
// Emscripten has getentropy, but it resides in a different header.
#define ABSL_RANDOM_USE_GET_ENTROPY …
#endif

#if defined(ABSL_RANDOM_USE_BCRYPT)
#include <bcrypt.h>

#ifndef BCRYPT_SUCCESS
#define BCRYPT_SUCCESS …
#endif
// Also link bcrypt; this can be done via linker options or:
// #pragma comment(lib, "bcrypt.lib")
#endif

namespace absl {
ABSL_NAMESPACE_BEGIN
namespace random_internal {
namespace {

// Read OS Entropy for random number seeds.
// TODO(absl-team): Possibly place a cap on how much entropy may be read at a
// time.

#if defined(ABSL_RANDOM_USE_BCRYPT)

// On Windows potentially use the BCRYPT CNG API to read available entropy.
bool ReadSeedMaterialFromOSEntropyImpl(absl::Span<uint32_t> values) {
  BCRYPT_ALG_HANDLE hProvider;
  NTSTATUS ret;
  ret = BCryptOpenAlgorithmProvider(&hProvider, BCRYPT_RNG_ALGORITHM,
                                    MS_PRIMITIVE_PROVIDER, 0);
  if (!(BCRYPT_SUCCESS(ret))) {
    ABSL_RAW_LOG(ERROR, "Failed to open crypto provider.");
    return false;
  }
  ret = BCryptGenRandom(
      hProvider,                                             // provider
      reinterpret_cast<UCHAR*>(values.data()),               // buffer
      static_cast<ULONG>(sizeof(uint32_t) * values.size()),  // bytes
      0);                                                    // flags
  BCryptCloseAlgorithmProvider(hProvider, 0);
  return BCRYPT_SUCCESS(ret);
}

#elif defined(ABSL_RANDOM_USE_NACL_SECURE_RANDOM)

// On NaCL use nacl_secure_random to acquire bytes.
bool ReadSeedMaterialFromOSEntropyImpl(absl::Span<uint32_t> values) {
  auto buffer = reinterpret_cast<uint8_t*>(values.data());
  size_t buffer_size = sizeof(uint32_t) * values.size();

  uint8_t* output_ptr = buffer;
  while (buffer_size > 0) {
    size_t nread = 0;
    const int error = nacl_secure_random(output_ptr, buffer_size, &nread);
    if (error != 0 || nread > buffer_size) {
      ABSL_RAW_LOG(ERROR, "Failed to read secure_random seed data: %d", error);
      return false;
    }
    output_ptr += nread;
    buffer_size -= nread;
  }
  return true;
}

#elif defined(__Fuchsia__)

bool ReadSeedMaterialFromOSEntropyImpl(absl::Span<uint32_t> values) {
  auto buffer = reinterpret_cast<uint8_t*>(values.data());
  size_t buffer_size = sizeof(uint32_t) * values.size();
  zx_cprng_draw(buffer, buffer_size);
  return true;
}

#else

#if defined(ABSL_RANDOM_USE_GET_ENTROPY)
// On *nix, use getentropy() if supported. Note that libc may support
// getentropy(), but the kernel may not, in which case this function will return
// false.
bool ReadSeedMaterialFromGetEntropy(absl::Span<uint32_t> values) { … }
#endif  // defined(ABSL_RANDOM_GETENTROPY)

// On *nix, read entropy from /dev/urandom.
bool ReadSeedMaterialFromDevURandom(absl::Span<uint32_t> values) { … }

bool ReadSeedMaterialFromOSEntropyImpl(absl::Span<uint32_t> values) { … }

#endif

}  // namespace

bool ReadSeedMaterialFromOSEntropy(absl::Span<uint32_t> values) { … }

void MixIntoSeedMaterial(absl::Span<const uint32_t> sequence,
                         absl::Span<uint32_t> seed_material) { … }

absl::optional<uint32_t> GetSaltMaterial() { … }

}  // namespace random_internal
ABSL_NAMESPACE_END
}  // namespace absl
chromium/third_party/abseil-cpp/absl/random/internal/seed_material.cc
