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// Copyright 2017 The Chromium Authors
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.
#include "components/gcm_driver/crypto/message_payload_parser.h"
#include <string_view>
#include "base/check_op.h"
#include "base/containers/span.h"
#include "base/numerics/byte_conversions.h"
#include "components/gcm_driver/crypto/gcm_decryption_result.h"
namespace gcm {
namespace {
// Size, in bytes, of the salt included in the message header.
constexpr size_t kSaltSize = 16;
// Size, in bytes, of the uncompressed point included in the message header.
constexpr size_t kUncompressedPointSize = 65;
// Size, in bytes, of the smallest allowable record_size value.
constexpr size_t kMinimumRecordSize = 18;
// Size, in bytes, of an empty message with the minimum amount of padding.
constexpr size_t kMinimumMessageSize =
kSaltSize + sizeof(uint32_t) + sizeof(uint8_t) + kUncompressedPointSize +
kMinimumRecordSize;
} // namespace
MessagePayloadParser::MessagePayloadParser(std::string_view message) {
if (message.size() < kMinimumMessageSize) {
failure_reason_ = GCMDecryptionResult::INVALID_BINARY_HEADER_PAYLOAD_LENGTH;
return;
}
salt_ = std::string(message.substr(0, kSaltSize));
message.remove_prefix(kSaltSize);
record_size_ = base::U32FromBigEndian(base::as_byte_span(message).first<4>());
message.remove_prefix(sizeof(record_size_));
if (record_size_ < kMinimumRecordSize) {
failure_reason_ = GCMDecryptionResult::INVALID_BINARY_HEADER_RECORD_SIZE;
return;
}
uint8_t public_key_length =
base::U8FromBigEndian(base::as_byte_span(message).first<1>());
message.remove_prefix(sizeof(public_key_length));
if (public_key_length != kUncompressedPointSize) {
failure_reason_ =
GCMDecryptionResult::INVALID_BINARY_HEADER_PUBLIC_KEY_LENGTH;
return;
}
if (message[0] != 0x04) {
failure_reason_ =
GCMDecryptionResult::INVALID_BINARY_HEADER_PUBLIC_KEY_FORMAT;
return;
}
public_key_ = std::string(message.substr(0, kUncompressedPointSize));
message.remove_prefix(kUncompressedPointSize);
ciphertext_ = std::string(message);
DCHECK_GE(ciphertext_.size(), kMinimumRecordSize);
is_valid_ = true;
}
MessagePayloadParser::~MessagePayloadParser() = default;
} // namespace gcm
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