components/webcrypto/algorithms/aes_ctr.cc - chromium/src - Git at Google

 // Copyright 2014 The Chromium Authors
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.

 #include <stddef.h>
 #include <stdint.h>
 #include <string.h>

 #include <array>
 #include <memory>

 #include "base/check_op.h"
 #include "base/containers/span.h"
 #include "base/numerics/safe_conversions.h"
 #include "base/numerics/safe_math.h"
 #include "base/strings/string_piece.h"
 #include "components/webcrypto/algorithms/aes.h"
 #include "components/webcrypto/algorithms/util.h"
 #include "components/webcrypto/blink_key_handle.h"
 #include "components/webcrypto/status.h"
 #include "crypto/openssl_util.h"
 #include "third_party/abseil-cpp/absl/numeric/int128.h"
 #include "third_party/blink/public/platform/web_crypto_algorithm_params.h"
 #include "third_party/boringssl/src/include/openssl/aes.h"
 #include "third_party/boringssl/src/include/openssl/cipher.h"

 namespace webcrypto {

 namespace {

 const EVP_CIPHER* GetAESCipherByKeyLength(size_t key_length_bytes) {
   // 192-bit AES is intentionally unsupported (http://crbug.com/533699).
   switch (key_length_bytes) {
     case 16:
       return EVP_aes_128_ctr();
     case 32:
       return EVP_aes_256_ctr();
     default:
       return nullptr;
   }
 }

 // Encrypts/decrypts given a 128-bit counter.
 //
 // |output| must have the same length as |input|.
 Status AesCtrEncrypt128BitCounter(const EVP_CIPHER* cipher,
                                   base::span<const uint8_t> raw_key,
                                   base::span<const uint8_t> input,
                                   base::span<const uint8_t, 16> counter,
                                   base::span<uint8_t> output) {
   DCHECK(cipher);
   DCHECK_EQ(input.size(), output.size());

   crypto::OpenSSLErrStackTracer err_tracer(FROM_HERE);
   bssl::ScopedEVP_CIPHER_CTX context;
   if (!EVP_CipherInit_ex(context.get(), cipher, nullptr, raw_key.data(),
                          counter.data(), ENCRYPT)) {
     return Status::OperationError();
   }

   int output_len = 0;
   if (!EVP_CipherUpdate(context.get(), output.data(), &output_len, input.data(),
                         base::checked_cast<int>(input.size()))) {
     return Status::OperationError();
   }
   int final_output_chunk_len = 0;
   if (!EVP_CipherFinal_ex(context.get(), output.data() + output_len,
                           &final_output_chunk_len)) {
     return Status::OperationError();
   }

   output_len += final_output_chunk_len;
   if (static_cast<size_t>(output_len) != input.size())
     return Status::ErrorUnexpected();

   return Status::Success();
 }

 // Returns ceil(a/b), where a and b are integers.
 template <typename T>
 T CeilDiv(T a, T b) {
   return a == 0 ? 0 : 1 + (a - 1) / b;
 }

 // Extracts the counter as a `absl::uint128`. The counter is the rightmost
 // `counter_length_bits` of the block, interpreted as a big-endian number.
 absl::uint128 GetCounter(base::span<const uint8_t, 16> counter_block,
                          unsigned int counter_length_bits) {
   unsigned int counter_length_remainder_bits = counter_length_bits % 8;
   unsigned int byte_length = CeilDiv(counter_length_bits, 8u);
   DCHECK_GT(byte_length, 0u);

   base::span<const uint8_t> suffix = counter_block.last(byte_length);
   absl::uint128 ret = suffix[0];
   // The first byte may be partial.
   if (counter_length_remainder_bits != 0) {
     ret &= ~(0xFF << counter_length_remainder_bits);
   }
   for (uint8_t b : suffix.subspan(1)) {
     ret = (ret << 8) | b;
   }
   return ret;
 }

 // Returns a counter block with the counter bits all set all zero.
 std::array<uint8_t, AES_BLOCK_SIZE> BlockWithZeroedCounter(
     base::span<const uint8_t, AES_BLOCK_SIZE> counter_block,
     unsigned int counter_length_bits) {
   unsigned int counter_length_bytes = counter_length_bits / 8;
   unsigned int counter_length_bits_remainder = counter_length_bits % 8;

   std::array<uint8_t, AES_BLOCK_SIZE> new_counter_block;
   memcpy(new_counter_block.data(), counter_block.data(), AES_BLOCK_SIZE);

   size_t index = new_counter_block.size() - counter_length_bytes;
   memset(&new_counter_block.front() + index, 0, counter_length_bytes);

   if (counter_length_bits_remainder) {
     new_counter_block[index - 1] &= 0xFF << counter_length_bits_remainder;
   }

   return new_counter_block;
 }

 // This function does encryption/decryption for AES-CTR (encryption and
 // decryption are the same).
 //
 // BoringSSL's interface for AES-CTR differs from that of WebCrypto. In
 // WebCrypto the caller specifies a 16-byte counter block and designates how
 // many of the right-most X bits to use as a big-endian counter. Whereas in
 // BoringSSL the entire counter block is interpreted as a 128-bit counter.
 //
 // In AES-CTR, the counter block MUST be unique across all messages that are
 // encrypted/decrypted. WebCrypto expects that the counter can start at any
 // value, and is therefore permitted to wrap around to zero on overflow.
 //
 // Some care is taken to fail if the counter wraps back to an earlier value.
 // However this protection is only enforced during a *single* call to
 // encrypt/decrypt.
 Status AesCtrEncryptDecrypt(const blink::WebCryptoAlgorithm& algorithm,
                             const blink::WebCryptoKey& key,
                             base::span<const uint8_t> data,
                             std::vector<uint8_t>* buffer) {
   const blink::WebCryptoAesCtrParams* params = algorithm.AesCtrParams();
   const std::vector<uint8_t>& raw_key = GetSymmetricKeyData(key);

   if (params->Counter().size() != AES_BLOCK_SIZE)
     return Status::ErrorIncorrectSizeAesCtrCounter();
   base::span<const uint8_t, AES_BLOCK_SIZE> counter_block(
       params->Counter().data(), params->Counter().size());

   unsigned int counter_length_bits = params->LengthBits();
   if (counter_length_bits < 1 || counter_length_bits > 128)
     return Status::ErrorInvalidAesCtrCounterLength();

   // The output of AES-CTR is the same size as the input. However BoringSSL
   // expects buffer sizes as an "int".
   base::CheckedNumeric<int> output_max_len = data.size();
   if (!output_max_len.IsValid())
     return Status::ErrorDataTooLarge();

   const EVP_CIPHER* const cipher = GetAESCipherByKeyLength(raw_key.size());
   if (!cipher)
     return Status::ErrorUnexpected();

   buffer->resize(base::ValueOrDieForType<size_t>(output_max_len));
   absl::uint128 current_counter =
       GetCounter(counter_block, counter_length_bits);

   if (counter_length_bits == 128) {
     return AesCtrEncrypt128BitCounter(cipher, raw_key, data, counter_block,
                                       *buffer);
   }

   // The total number of possible counter values is pow(2, counter_length_bits)
   absl::uint128 num_counter_values = absl::uint128(1) << counter_length_bits;

   // The number of AES blocks needed for encryption/decryption. The counter is
   // incremented this many times.
   size_t num_output_blocks = CeilDiv(buffer->size(), size_t{AES_BLOCK_SIZE});

   // If the counter is going to be incremented more times than there are counter
   // values, fail. (Repeating values of the counter block is bad).
   if (num_output_blocks > num_counter_values)
     return Status::ErrorAesCtrInputTooLongCounterRepeated();

   // This is the number of blocks that can be successfully encrypted without
   // overflowing the counter. Encrypting the subsequent block will need to
   // reset the counter to zero.
   absl::uint128 num_blocks_until_reset = num_counter_values - current_counter;

   // If the counter can be incremented for the entire input without
   // wrapping-around, do it as a single call into BoringSSL.
   if (num_blocks_until_reset >= num_output_blocks) {
     return AesCtrEncrypt128BitCounter(cipher, raw_key, data, counter_block,
                                       *buffer);
   }

   // Otherwise the encryption needs to be done in 2 parts. The first part using
   // the current counter_block, and the next part resetting the counter portion
   // of the block to zero.

   // This is guaranteed to fit in an `size_t` because it is bounded by the input
   // size.
   size_t input_size_part1 =
       static_cast<size_t>(num_blocks_until_reset * AES_BLOCK_SIZE);
   DCHECK_LT(input_size_part1, data.size());
   base::span<uint8_t> output_part1 =
       base::make_span(*buffer).first(input_size_part1);
   base::span<uint8_t> output_part2 =
       base::make_span(*buffer).subspan(input_size_part1);

   // Encrypt the first part (before wrap-around).
   Status status =
       AesCtrEncrypt128BitCounter(cipher, raw_key, data.first(input_size_part1),
                                  counter_block, output_part1);
   if (status.IsError())
     return status;

   // Encrypt the second part (after wrap-around).
   std::array<uint8_t, AES_BLOCK_SIZE> counter_block_part2 =
       BlockWithZeroedCounter(counter_block, counter_length_bits);

   return AesCtrEncrypt128BitCounter(cipher, raw_key,
                                     data.subspan(input_size_part1),
                                     counter_block_part2, output_part2);
 }

 class AesCtrImplementation : public AesAlgorithm {
  public:
   AesCtrImplementation() : AesAlgorithm("CTR") {}

   Status Encrypt(const blink::WebCryptoAlgorithm& algorithm,
                  const blink::WebCryptoKey& key,
                  base::span<const uint8_t> data,
                  std::vector<uint8_t>* buffer) const override {
     return AesCtrEncryptDecrypt(algorithm, key, data, buffer);
   }

   Status Decrypt(const blink::WebCryptoAlgorithm& algorithm,
                  const blink::WebCryptoKey& key,
                  base::span<const uint8_t> data,
                  std::vector<uint8_t>* buffer) const override {
     return AesCtrEncryptDecrypt(algorithm, key, data, buffer);
   }
 };

 }  // namespace

 std::unique_ptr<AlgorithmImplementation> CreateAesCtrImplementation() {
   return std::make_unique<AesCtrImplementation>();
 }

 }  // namespace webcrypto
	// Copyright 2014 The Chromium Authors
	// Use of this source code is governed by a BSD-style license that can be
	// found in the LICENSE file.

	#include <stddef.h>
	#include <stdint.h>
	#include <string.h>

	#include <array>
	#include <memory>

	#include "base/check_op.h"
	#include "base/containers/span.h"
	#include "base/numerics/safe_conversions.h"
	#include "base/numerics/safe_math.h"
	#include "base/strings/string_piece.h"
	#include "components/webcrypto/algorithms/aes.h"
	#include "components/webcrypto/algorithms/util.h"
	#include "components/webcrypto/blink_key_handle.h"
	#include "components/webcrypto/status.h"
	#include "crypto/openssl_util.h"
	#include "third_party/abseil-cpp/absl/numeric/int128.h"
	#include "third_party/blink/public/platform/web_crypto_algorithm_params.h"
	#include "third_party/boringssl/src/include/openssl/aes.h"
	#include "third_party/boringssl/src/include/openssl/cipher.h"

	namespace webcrypto {

	namespace {

	const EVP_CIPHER* GetAESCipherByKeyLength(size_t key_length_bytes) {
	// 192-bit AES is intentionally unsupported (http://crbug.com/533699).
	switch (key_length_bytes) {
	case 16:
	return EVP_aes_128_ctr();
	case 32:
	return EVP_aes_256_ctr();
	default:
	return nullptr;
	}
	}

	// Encrypts/decrypts given a 128-bit counter.
	//
	// \|output\| must have the same length as \|input\|.
	Status AesCtrEncrypt128BitCounter(const EVP_CIPHER* cipher,
	base::span<const uint8_t> raw_key,
	base::span<const uint8_t> input,
	base::span<const uint8_t, 16> counter,
	base::span<uint8_t> output) {
	DCHECK(cipher);
	DCHECK_EQ(input.size(), output.size());

	crypto::OpenSSLErrStackTracer err_tracer(FROM_HERE);
	bssl::ScopedEVP_CIPHER_CTX context;
	if (!EVP_CipherInit_ex(context.get(), cipher, nullptr, raw_key.data(),
	counter.data(), ENCRYPT)) {
	return Status::OperationError();
	}

	int output_len = 0;
	if (!EVP_CipherUpdate(context.get(), output.data(), &output_len, input.data(),
	base::checked_cast<int>(input.size()))) {
	return Status::OperationError();
	}
	int final_output_chunk_len = 0;
	if (!EVP_CipherFinal_ex(context.get(), output.data() + output_len,
	&final_output_chunk_len)) {
	return Status::OperationError();
	}

	output_len += final_output_chunk_len;
	if (static_cast<size_t>(output_len) != input.size())
	return Status::ErrorUnexpected();

	return Status::Success();
	}

	// Returns ceil(a/b), where a and b are integers.
	template <typename T>
	T CeilDiv(T a, T b) {
	return a == 0 ? 0 : 1 + (a - 1) / b;
	}

	// Extracts the counter as a `absl::uint128`. The counter is the rightmost
	// `counter_length_bits` of the block, interpreted as a big-endian number.
	absl::uint128 GetCounter(base::span<const uint8_t, 16> counter_block,
	unsigned int counter_length_bits) {
	unsigned int counter_length_remainder_bits = counter_length_bits % 8;
	unsigned int byte_length = CeilDiv(counter_length_bits, 8u);
	DCHECK_GT(byte_length, 0u);

	base::span<const uint8_t> suffix = counter_block.last(byte_length);
	absl::uint128 ret = suffix[0];
	// The first byte may be partial.
	if (counter_length_remainder_bits != 0) {
	ret &= ~(0xFF << counter_length_remainder_bits);
	}
	for (uint8_t b : suffix.subspan(1)) {
	ret = (ret << 8) \| b;
	}
	return ret;
	}

	// Returns a counter block with the counter bits all set all zero.
	std::array<uint8_t, AES_BLOCK_SIZE> BlockWithZeroedCounter(
	base::span<const uint8_t, AES_BLOCK_SIZE> counter_block,
	unsigned int counter_length_bits) {
	unsigned int counter_length_bytes = counter_length_bits / 8;
	unsigned int counter_length_bits_remainder = counter_length_bits % 8;

	std::array<uint8_t, AES_BLOCK_SIZE> new_counter_block;
	memcpy(new_counter_block.data(), counter_block.data(), AES_BLOCK_SIZE);

	size_t index = new_counter_block.size() - counter_length_bytes;
	memset(&new_counter_block.front() + index, 0, counter_length_bytes);

	if (counter_length_bits_remainder) {
	new_counter_block[index - 1] &= 0xFF << counter_length_bits_remainder;
	}

	return new_counter_block;
	}

	// This function does encryption/decryption for AES-CTR (encryption and
	// decryption are the same).
	//
	// BoringSSL's interface for AES-CTR differs from that of WebCrypto. In
	// WebCrypto the caller specifies a 16-byte counter block and designates how
	// many of the right-most X bits to use as a big-endian counter. Whereas in
	// BoringSSL the entire counter block is interpreted as a 128-bit counter.
	//
	// In AES-CTR, the counter block MUST be unique across all messages that are
	// encrypted/decrypted. WebCrypto expects that the counter can start at any
	// value, and is therefore permitted to wrap around to zero on overflow.
	//
	// Some care is taken to fail if the counter wraps back to an earlier value.
	// However this protection is only enforced during a single call to
	// encrypt/decrypt.
	Status AesCtrEncryptDecrypt(const blink::WebCryptoAlgorithm& algorithm,
	const blink::WebCryptoKey& key,
	base::span<const uint8_t> data,
	std::vector<uint8_t>* buffer) {
	const blink::WebCryptoAesCtrParams* params = algorithm.AesCtrParams();
	const std::vector<uint8_t>& raw_key = GetSymmetricKeyData(key);

	if (params->Counter().size() != AES_BLOCK_SIZE)
	return Status::ErrorIncorrectSizeAesCtrCounter();
	base::span<const uint8_t, AES_BLOCK_SIZE> counter_block(
	params->Counter().data(), params->Counter().size());

	unsigned int counter_length_bits = params->LengthBits();
	if (counter_length_bits < 1 \|\| counter_length_bits > 128)
	return Status::ErrorInvalidAesCtrCounterLength();

	// The output of AES-CTR is the same size as the input. However BoringSSL
	// expects buffer sizes as an "int".
	base::CheckedNumeric<int> output_max_len = data.size();
	if (!output_max_len.IsValid())
	return Status::ErrorDataTooLarge();

	const EVP_CIPHER* const cipher = GetAESCipherByKeyLength(raw_key.size());
	if (!cipher)
	return Status::ErrorUnexpected();

	buffer->resize(base::ValueOrDieForType<size_t>(output_max_len));
	absl::uint128 current_counter =
	GetCounter(counter_block, counter_length_bits);

	if (counter_length_bits == 128) {
	return AesCtrEncrypt128BitCounter(cipher, raw_key, data, counter_block,
	*buffer);
	}

	// The total number of possible counter values is pow(2, counter_length_bits)
	absl::uint128 num_counter_values = absl::uint128(1) << counter_length_bits;

	// The number of AES blocks needed for encryption/decryption. The counter is
	// incremented this many times.
	size_t num_output_blocks = CeilDiv(buffer->size(), size_t{AES_BLOCK_SIZE});

	// If the counter is going to be incremented more times than there are counter
	// values, fail. (Repeating values of the counter block is bad).
	if (num_output_blocks > num_counter_values)
	return Status::ErrorAesCtrInputTooLongCounterRepeated();

	// This is the number of blocks that can be successfully encrypted without
	// overflowing the counter. Encrypting the subsequent block will need to
	// reset the counter to zero.
	absl::uint128 num_blocks_until_reset = num_counter_values - current_counter;

	// If the counter can be incremented for the entire input without
	// wrapping-around, do it as a single call into BoringSSL.
	if (num_blocks_until_reset >= num_output_blocks) {
	return AesCtrEncrypt128BitCounter(cipher, raw_key, data, counter_block,
	*buffer);
	}

	// Otherwise the encryption needs to be done in 2 parts. The first part using
	// the current counter_block, and the next part resetting the counter portion
	// of the block to zero.

	// This is guaranteed to fit in an `size_t` because it is bounded by the input
	// size.
	size_t input_size_part1 =
	static_cast<size_t>(num_blocks_until_reset * AES_BLOCK_SIZE);
	DCHECK_LT(input_size_part1, data.size());
	base::span<uint8_t> output_part1 =
	base::make_span(*buffer).first(input_size_part1);
	base::span<uint8_t> output_part2 =
	base::make_span(*buffer).subspan(input_size_part1);

	// Encrypt the first part (before wrap-around).
	Status status =
	AesCtrEncrypt128BitCounter(cipher, raw_key, data.first(input_size_part1),
	counter_block, output_part1);
	if (status.IsError())
	return status;

	// Encrypt the second part (after wrap-around).
	std::array<uint8_t, AES_BLOCK_SIZE> counter_block_part2 =
	BlockWithZeroedCounter(counter_block, counter_length_bits);

	return AesCtrEncrypt128BitCounter(cipher, raw_key,
	data.subspan(input_size_part1),
	counter_block_part2, output_part2);
	}

	class AesCtrImplementation : public AesAlgorithm {
	public:
	AesCtrImplementation() : AesAlgorithm("CTR") {}

	Status Encrypt(const blink::WebCryptoAlgorithm& algorithm,
	const blink::WebCryptoKey& key,
	base::span<const uint8_t> data,
	std::vector<uint8_t>* buffer) const override {
	return AesCtrEncryptDecrypt(algorithm, key, data, buffer);
	}

	Status Decrypt(const blink::WebCryptoAlgorithm& algorithm,
	const blink::WebCryptoKey& key,
	base::span<const uint8_t> data,
	std::vector<uint8_t>* buffer) const override {
	return AesCtrEncryptDecrypt(algorithm, key, data, buffer);
	}
	};

	} // namespace

	std::unique_ptr<AlgorithmImplementation> CreateAesCtrImplementation() {
	return std::make_unique<AesCtrImplementation>();
	}

	} // namespace webcrypto