| // Copyright (c) 2012 The Chromium Authors. All rights reserved. |
| // Use of this source code is governed by a BSD-style license that can be |
| // found in the LICENSE file. |
| |
| #include "net/websockets/websocket_frame.h" |
| |
| #include "base/basictypes.h" |
| #include "base/logging.h" |
| #include "base/rand_util.h" |
| #include "net/base/big_endian.h" |
| #include "net/base/io_buffer.h" |
| #include "net/base/net_errors.h" |
| |
| namespace { |
| |
| const uint8 kFinalBit = 0x80; |
| const uint8 kReserved1Bit = 0x40; |
| const uint8 kReserved2Bit = 0x20; |
| const uint8 kReserved3Bit = 0x10; |
| const uint8 kOpCodeMask = 0xF; |
| const uint8 kMaskBit = 0x80; |
| const uint64 kMaxPayloadLengthWithoutExtendedLengthField = 125; |
| const uint64 kPayloadLengthWithTwoByteExtendedLengthField = 126; |
| const uint64 kPayloadLengthWithEightByteExtendedLengthField = 127; |
| |
| inline void MaskWebSocketFramePayloadByBytes( |
| const net::WebSocketMaskingKey& masking_key, |
| size_t masking_key_offset, |
| char* const begin, |
| char* const end) { |
| for (char* masked = begin; masked != end; ++masked) { |
| *masked ^= masking_key.key[masking_key_offset++]; |
| if (masking_key_offset == net::WebSocketFrameHeader::kMaskingKeyLength) |
| masking_key_offset = 0; |
| } |
| } |
| |
| } // Unnamed namespace. |
| |
| namespace net { |
| |
| // Definitions for in-struct constants. |
| |
| WebSocketFrameChunk::WebSocketFrameChunk() : final_chunk(false) { |
| } |
| |
| WebSocketFrameChunk::~WebSocketFrameChunk() { |
| } |
| |
| int GetWebSocketFrameHeaderSize(const WebSocketFrameHeader& header) { |
| int extended_length_size = 0; |
| if (header.payload_length > kMaxPayloadLengthWithoutExtendedLengthField && |
| header.payload_length <= kuint16max) { |
| extended_length_size = 2; |
| } else if (header.payload_length > kuint16max) { |
| extended_length_size = 8; |
| } |
| |
| return (WebSocketFrameHeader::kBaseHeaderSize + |
| extended_length_size + |
| (header.masked ? WebSocketFrameHeader::kMaskingKeyLength : 0)); |
| } |
| |
| int WriteWebSocketFrameHeader(const WebSocketFrameHeader& header, |
| const WebSocketMaskingKey* masking_key, |
| char* buffer, |
| int buffer_size) { |
| DCHECK((header.opcode & kOpCodeMask) == header.opcode) |
| << "header.opcode must fit to kOpCodeMask."; |
| DCHECK(header.payload_length <= static_cast<uint64>(kint64max)) |
| << "WebSocket specification doesn't allow a frame longer than " |
| << "kint64max (0x7FFFFFFFFFFFFFFF) bytes."; |
| DCHECK_GE(buffer_size, 0); |
| |
| // WebSocket frame format is as follows: |
| // - Common header (2 bytes) |
| // - Optional extended payload length |
| // (2 or 8 bytes, present if actual payload length is more than 125 bytes) |
| // - Optional masking key (4 bytes, present if MASK bit is on) |
| // - Actual payload (XOR masked with masking key if MASK bit is on) |
| // |
| // This function constructs frame header (the first three in the list |
| // above). |
| |
| int header_size = GetWebSocketFrameHeaderSize(header); |
| if (header_size > buffer_size) |
| return ERR_INVALID_ARGUMENT; |
| |
| int buffer_index = 0; |
| |
| uint8 first_byte = 0u; |
| first_byte |= header.final ? kFinalBit : 0u; |
| first_byte |= header.reserved1 ? kReserved1Bit : 0u; |
| first_byte |= header.reserved2 ? kReserved2Bit : 0u; |
| first_byte |= header.reserved3 ? kReserved3Bit : 0u; |
| first_byte |= header.opcode & kOpCodeMask; |
| buffer[buffer_index++] = first_byte; |
| |
| int extended_length_size = 0; |
| uint8 second_byte = 0u; |
| second_byte |= header.masked ? kMaskBit : 0u; |
| if (header.payload_length <= |
| kMaxPayloadLengthWithoutExtendedLengthField) { |
| second_byte |= header.payload_length; |
| } else if (header.payload_length <= kuint16max) { |
| second_byte |= kPayloadLengthWithTwoByteExtendedLengthField; |
| extended_length_size = 2; |
| } else { |
| second_byte |= kPayloadLengthWithEightByteExtendedLengthField; |
| extended_length_size = 8; |
| } |
| buffer[buffer_index++] = second_byte; |
| |
| // Writes "extended payload length" field. |
| if (extended_length_size == 2) { |
| uint16 payload_length_16 = static_cast<uint16>(header.payload_length); |
| WriteBigEndian(buffer + buffer_index, payload_length_16); |
| buffer_index += sizeof(uint16); |
| } else if (extended_length_size == 8) { |
| WriteBigEndian(buffer + buffer_index, header.payload_length); |
| buffer_index += sizeof(uint64); |
| } |
| |
| // Writes "masking key" field, if needed. |
| if (header.masked) { |
| DCHECK(masking_key); |
| std::copy(masking_key->key, |
| masking_key->key + WebSocketFrameHeader::kMaskingKeyLength, |
| buffer + buffer_index); |
| buffer_index += WebSocketFrameHeader::kMaskingKeyLength; |
| } else { |
| DCHECK(!masking_key); |
| } |
| |
| DCHECK_EQ(header_size, buffer_index); |
| return header_size; |
| } |
| |
| WebSocketMaskingKey GenerateWebSocketMaskingKey() { |
| // Masking keys should be generated from a cryptographically secure random |
| // number generator, which means web application authors should not be able |
| // to guess the next value of masking key. |
| WebSocketMaskingKey masking_key; |
| base::RandBytes(masking_key.key, WebSocketFrameHeader::kMaskingKeyLength); |
| return masking_key; |
| } |
| |
| void MaskWebSocketFramePayload(const WebSocketMaskingKey& masking_key, |
| uint64 frame_offset, |
| char* const data, |
| int data_size) { |
| static const size_t kMaskingKeyLength = |
| WebSocketFrameHeader::kMaskingKeyLength; |
| |
| DCHECK_GE(data_size, 0); |
| |
| // Most of the masking is done one word at a time, except for the beginning |
| // and the end of the buffer which may be unaligned. We use size_t to get the |
| // word size for this architecture. We require it be a multiple of |
| // kMaskingKeyLength in size. |
| typedef size_t PackedMaskType; |
| PackedMaskType packed_mask_key = 0; |
| static const size_t kPackedMaskKeySize = sizeof(packed_mask_key); |
| COMPILE_ASSERT((kPackedMaskKeySize >= kMaskingKeyLength && |
| kPackedMaskKeySize % kMaskingKeyLength == 0), |
| word_size_is_not_multiple_of_mask_length); |
| char* const end = data + data_size; |
| // If the buffer is too small for the vectorised version to be useful, revert |
| // to the byte-at-a-time implementation early. |
| if (data_size <= static_cast<int>(kPackedMaskKeySize * 2)) { |
| MaskWebSocketFramePayloadByBytes(masking_key, |
| frame_offset % kMaskingKeyLength, |
| data, end); |
| return; |
| } |
| const size_t data_modulus = |
| reinterpret_cast<size_t>(data) % kPackedMaskKeySize; |
| char* const aligned_begin = data_modulus == 0 ? data : |
| (data + kPackedMaskKeySize - data_modulus); |
| // Guaranteed by the above check for small data_size. |
| DCHECK(aligned_begin < end); |
| MaskWebSocketFramePayloadByBytes(masking_key, |
| frame_offset % kMaskingKeyLength, |
| data, aligned_begin); |
| const size_t end_modulus = reinterpret_cast<size_t>(end) % kPackedMaskKeySize; |
| char* const aligned_end = end - end_modulus; |
| // Guaranteed by the above check for small data_size. |
| DCHECK(aligned_end > aligned_begin); |
| // Create a version of the mask which is rotated by the appropriate offset |
| // for our alignment. The "trick" here is that 0 XORed with the mask will |
| // give the value of the mask for the appropriate byte. |
| char realigned_mask[kMaskingKeyLength] = { 0 }; |
| MaskWebSocketFramePayloadByBytes(masking_key, |
| (frame_offset + aligned_begin - data) |
| % kMaskingKeyLength, |
| realigned_mask, |
| realigned_mask + kMaskingKeyLength); |
| |
| for (size_t i = 0; i < kPackedMaskKeySize; i += kMaskingKeyLength) { |
| // memcpy() is allegedly blessed by the C++ standard for type-punning. |
| memcpy(reinterpret_cast<char*>(&packed_mask_key) + i, |
| realigned_mask, kMaskingKeyLength); |
| } |
| |
| // The main loop. |
| for (char* merged = aligned_begin; |
| merged != aligned_end; |
| merged += kPackedMaskKeySize) { |
| // This is not quite standard-compliant C++. However, the standard-compliant |
| // equivalent (using memcpy()) compiles to slower code using g++. In |
| // practice, this will work for the compilers and architectures currently |
| // supported by Chromium, and the tests are extremely unlikely to pass if a |
| // future compiler/architecture breaks it. |
| *reinterpret_cast<PackedMaskType*>(merged) ^= packed_mask_key; |
| } |
| |
| MaskWebSocketFramePayloadByBytes(masking_key, |
| (frame_offset + (aligned_end - data)) |
| % kMaskingKeyLength, |
| aligned_end, end); |
| } |
| |
| } // namespace net |