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// The framer consists of two [Transform Stream][1] subclasses that operate in [object mode][2]:
// the Serializer and the Deserializer
var assert = require('assert');
var Transform = require('stream').Transform;
exports.Serializer = Serializer;
exports.Deserializer = Deserializer;
var logData = Boolean(process.env.HTTP2_LOG_DATA);
var MAX_PAYLOAD_SIZE = 16384;
var WINDOW_UPDATE_PAYLOAD_SIZE = 4;
// Serializer
// ----------
//
// Frame Objects
// * * * * * * * --+---------------------------
// | |
// v v Buffers
// [] -----> Payload Ser. --[buffers]--> Header Ser. --> * * * *
// empty adds payload adds header
// array buffers buffer
function Serializer(log) {
this._log = log.child({ component: 'serializer' });
Transform.call(this, { objectMode: true });
}
Serializer.prototype = Object.create(Transform.prototype, { constructor: { value: Serializer } });
// When there's an incoming frame object, it first generates the frame type specific part of the
// frame (payload), and then then adds the header part which holds fields that are common to all
// frame types (like the length of the payload).
Serializer.prototype._transform = function _transform(frame, encoding, done) {
this._log.trace({ frame: frame }, 'Outgoing frame');
assert(frame.type in Serializer, 'Unknown frame type: ' + frame.type);
var buffers = [];
Serializer[frame.type](frame, buffers);
var length = Serializer.commonHeader(frame, buffers);
assert(length <= MAX_PAYLOAD_SIZE, 'Frame too large!');
for (var i = 0; i < buffers.length; i++) {
if (logData) {
this._log.trace({ data: buffers[i] }, 'Outgoing data');
}
this.push(buffers[i]);
}
done();
};
// Deserializer
// ------------
//
// Buffers
// * * * * --------+-------------------------
// | |
// v v Frame Objects
// {} -----> Header Des. --{frame}--> Payload Des. --> * * * * * * *
// empty adds parsed adds parsed
// object header properties payload properties
function Deserializer(log, role) {
this._role = role;
this._log = log.child({ component: 'deserializer' });
Transform.call(this, { objectMode: true });
this._next(COMMON_HEADER_SIZE);
}
Deserializer.prototype = Object.create(Transform.prototype, { constructor: { value: Deserializer } });
// The Deserializer is stateful, and it's two main alternating states are: *waiting for header* and
// *waiting for payload*. The state is stored in the boolean property `_waitingForHeader`.
//
// When entering a new state, a `_buffer` is created that will hold the accumulated data (header or
// payload). The `_cursor` is used to track the progress.
Deserializer.prototype._next = function(size) {
this._cursor = 0;
this._buffer = Buffer.alloc(size);
this._waitingForHeader = !this._waitingForHeader;
if (this._waitingForHeader) {
this._frame = {};
}
};
// Parsing an incoming buffer is an iterative process because it can hold multiple frames if it's
// large enough. A `cursor` is used to track the progress in parsing the incoming `chunk`.
Deserializer.prototype._transform = function _transform(chunk, encoding, done) {
var cursor = 0;
if (logData) {
this._log.trace({ data: chunk }, 'Incoming data');
}
while(cursor < chunk.length) {
// The content of an incoming buffer is first copied to `_buffer`. If it can't hold the full
// chunk, then only a part of it is copied.
var toCopy = Math.min(chunk.length - cursor, this._buffer.length - this._cursor);
chunk.copy(this._buffer, this._cursor, cursor, cursor + toCopy);
this._cursor += toCopy;
cursor += toCopy;
// When `_buffer` is full, it's content gets parsed either as header or payload depending on
// the actual state.
// If it's header then the parsed data is stored in a temporary variable and then the
// deserializer waits for the specified length payload.
if ((this._cursor === this._buffer.length) && this._waitingForHeader) {
var payloadSize = Deserializer.commonHeader(this._buffer, this._frame);
if (payloadSize <= MAX_PAYLOAD_SIZE) {
this._next(payloadSize);
} else {
this.emit('error', 'FRAME_SIZE_ERROR');
return;
}
}
// If it's payload then the the frame object is finalized and then gets pushed out.
// Unknown frame types are ignored.
//
// Note: If we just finished the parsing of a header and the payload length is 0, this branch
// will also run.
if ((this._cursor === this._buffer.length) && !this._waitingForHeader) {
if (this._frame.type) {
var error = Deserializer[this._frame.type](this._buffer, this._frame, this._role);
if (error) {
this._log.error('Incoming frame parsing error: ' + error);
this.emit('error', error);
} else {
this._log.trace({ frame: this._frame }, 'Incoming frame');
this.push(this._frame);
}
} else {
this._log.error('Unknown type incoming frame');
// Ignore it other than logging
}
this._next(COMMON_HEADER_SIZE);
}
}
done();
};
// --------------------------------------------------------------
//
// HTTP/2 frames share a common base format consisting of a 9-byte header followed by 0 to 2^24 - 1
// bytes of data.
//
// Additional size limits can be set by specific application uses. HTTP limits the frame size to
// 16,384 octets by default, though this can be increased by a receiver.
//
// 0 1 2 3
// 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
// +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
// | Length (24) |
// +---------------+---------------+---------------+
// | Type (8) | Flags (8) |
// +-+-----------------------------+---------------+---------------+
// |R| Stream Identifier (31) |
// +-+-------------------------------------------------------------+
// | Frame Data (0...) ...
// +---------------------------------------------------------------+
//
// The fields of the frame header are defined as:
//
// * Length:
// The length of the frame data expressed as an unsigned 24-bit integer. The 9 bytes of the frame
// header are not included in this value.
//
// * Type:
// The 8-bit type of the frame. The frame type determines how the remainder of the frame header
// and data are interpreted. Implementations MUST ignore unsupported and unrecognized frame types.
//
// * Flags:
// An 8-bit field reserved for frame-type specific boolean flags.
//
// Flags are assigned semantics specific to the indicated frame type. Flags that have no defined
// semantics for a particular frame type MUST be ignored, and MUST be left unset (0) when sending.
//
// * R:
// A reserved 1-bit field. The semantics of this bit are undefined and the bit MUST remain unset
// (0) when sending and MUST be ignored when receiving.
//
// * Stream Identifier:
// A 31-bit stream identifier. The value 0 is reserved for frames that are associated with the
// connection as a whole as opposed to an individual stream.
//
// The structure and content of the remaining frame data is dependent entirely on the frame type.
var COMMON_HEADER_SIZE = 9;
var frameTypes = [];
var frameFlags = {};
var genericAttributes = ['type', 'flags', 'stream'];
var typeSpecificAttributes = {};
Serializer.commonHeader = function writeCommonHeader(frame, buffers) {
var headerBuffer = Buffer.alloc(COMMON_HEADER_SIZE);
var size = 0;
for (var i = 0; i < buffers.length; i++) {
size += buffers[i].length;
}
headerBuffer.writeUInt8(0, 0);
headerBuffer.writeUInt16BE(size, 1);
var typeId = frameTypes.indexOf(frame.type); // If we are here then the type is valid for sure
headerBuffer.writeUInt8(typeId, 3);
var flagByte = 0;
for (var flag in frame.flags) {
var position = frameFlags[frame.type].indexOf(flag);
assert(position !== -1, 'Unknown flag for frame type ' + frame.type + ': ' + flag);
if (frame.flags[flag]) {
flagByte |= (1 << position);
}
}
headerBuffer.writeUInt8(flagByte, 4);
assert((0 <= frame.stream) && (frame.stream < 0x7fffffff), frame.stream);
headerBuffer.writeUInt32BE(frame.stream || 0, 5);
buffers.unshift(headerBuffer);
return size;
};
Deserializer.commonHeader = function readCommonHeader(buffer, frame) {
if (buffer.length < 9) {
return 'FRAME_SIZE_ERROR';
}
var totallyWastedByte = buffer.readUInt8(0);
var length = buffer.readUInt16BE(1);
// We do this just for sanity checking later on, to make sure no one sent us a
// frame that's super large.
length += totallyWastedByte << 16;
frame.type = frameTypes[buffer.readUInt8(3)];
if (!frame.type) {
// We are required to ignore unknown frame types
return length;
}
frame.flags = {};
var flagByte = buffer.readUInt8(4);
var definedFlags = frameFlags[frame.type];
for (var i = 0; i < definedFlags.length; i++) {
frame.flags[definedFlags[i]] = Boolean(flagByte & (1 << i));
}
frame.stream = buffer.readUInt32BE(5) & 0x7fffffff;
return length;
};
// Frame types
// ===========
// Every frame type is registered in the following places:
//
// * `frameTypes`: a register of frame type codes (used by `commonHeader()`)
// * `frameFlags`: a register of valid flags for frame types (used by `commonHeader()`)
// * `typeSpecificAttributes`: a register of frame specific frame object attributes (used by
// logging code and also serves as documentation for frame objects)
// ------------------------------------------------------------
//
// DATA frames (type=0x0) convey arbitrary, variable-length sequences of octets associated with a
// stream.
//
// The DATA frame defines the following flags:
//
// * END_STREAM (0x1):
// Bit 1 being set indicates that this frame is the last that the endpoint will send for the
// identified stream.
// * PADDED (0x08):
// Bit 4 being set indicates that the Pad Length field is present.
frameTypes[0x0] = 'DATA';
frameFlags.DATA = ['END_STREAM', 'RESERVED2', 'RESERVED4', 'PADDED'];
typeSpecificAttributes.DATA = ['data'];
Serializer.DATA = function writeData(frame, buffers) {
buffers.push(frame.data);
};
Deserializer.DATA = function readData(buffer, frame) {
var dataOffset = 0;
var paddingLength = 0;
if (frame.flags.PADDED) {
if (buffer.length < 1) {
// We must have at least one byte for padding control, but we don't. Bad peer!
return 'FRAME_SIZE_ERROR';
}
paddingLength = (buffer.readUInt8(dataOffset) & 0xff);
dataOffset = 1;
}
if (paddingLength) {
if (paddingLength >= (buffer.length - 1)) {
// We don't have enough room for the padding advertised - bad peer!
return 'FRAME_SIZE_ERROR';
}
frame.data = buffer.slice(dataOffset, -1 * paddingLength);
} else {
frame.data = buffer.slice(dataOffset);
}
};
// --------------------------------------------------------------
//
// The HEADERS frame (type=0x1) allows the sender to create a stream.
//
// The HEADERS frame defines the following flags:
//
// * END_STREAM (0x1):
// Bit 1 being set indicates that this frame is the last that the endpoint will send for the
// identified stream.
// * END_HEADERS (0x4):
// The END_HEADERS bit indicates that this frame contains the entire payload necessary to provide
// a complete set of headers.
// * PADDED (0x08):
// Bit 4 being set indicates that the Pad Length field is present.
// * PRIORITY (0x20):
// Bit 6 being set indicates that the Exlusive Flag (E), Stream Dependency, and Weight fields are
// present.
frameTypes[0x1] = 'HEADERS';
frameFlags.HEADERS = ['END_STREAM', 'RESERVED2', 'END_HEADERS', 'PADDED', 'RESERVED5', 'PRIORITY'];
typeSpecificAttributes.HEADERS = ['priorityDependency', 'priorityWeight', 'exclusiveDependency', 'headers', 'data'];
// 0 1 2 3
// 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
// +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
// |Pad Length? (8)|
// +-+-------------+---------------+-------------------------------+
// |E| Stream Dependency? (31) |
// +-+-------------+-----------------------------------------------+
// | Weight? (8) |
// +-+-------------+-----------------------------------------------+
// | Header Block Fragment (*) ...
// +---------------------------------------------------------------+
// | Padding (*) ...
// +---------------------------------------------------------------+
//
// The payload of a HEADERS frame contains a Headers Block
Serializer.HEADERS = function writeHeadersPriority(frame, buffers) {
if (frame.flags.PRIORITY) {
var buffer = Buffer.alloc(5);
assert((0 <= frame.priorityDependency) && (frame.priorityDependency <= 0x7fffffff), frame.priorityDependency);
buffer.writeUInt32BE(frame.priorityDependency, 0);
if (frame.exclusiveDependency) {
buffer[0] |= 0x80;
}
assert((0 <= frame.priorityWeight) && (frame.priorityWeight <= 0xff), frame.priorityWeight);
buffer.writeUInt8(frame.priorityWeight, 4);
buffers.push(buffer);
}
buffers.push(frame.data);
};
Deserializer.HEADERS = function readHeadersPriority(buffer, frame) {
var minFrameLength = 0;
if (frame.flags.PADDED) {
minFrameLength += 1;
}
if (frame.flags.PRIORITY) {
minFrameLength += 5;
}
if (buffer.length < minFrameLength) {
// Peer didn't send enough data - bad peer!
return 'FRAME_SIZE_ERROR';
}
var dataOffset = 0;
var paddingLength = 0;
if (frame.flags.PADDED) {
paddingLength = (buffer.readUInt8(dataOffset) & 0xff);
dataOffset = 1;
}
if (frame.flags.PRIORITY) {
var dependencyData = Buffer.alloc(4);
buffer.copy(dependencyData, 0, dataOffset, dataOffset + 4);
dataOffset += 4;
frame.exclusiveDependency = !!(dependencyData[0] & 0x80);
dependencyData[0] &= 0x7f;
frame.priorityDependency = dependencyData.readUInt32BE(0);
frame.priorityWeight = buffer.readUInt8(dataOffset);
dataOffset += 1;
}
if (paddingLength) {
if ((buffer.length - dataOffset) < paddingLength) {
// Not enough data left to satisfy the advertised padding - bad peer!
return 'FRAME_SIZE_ERROR';
}
frame.data = buffer.slice(dataOffset, -1 * paddingLength);
} else {
frame.data = buffer.slice(dataOffset);
}
};
// -------------------------------------------------------
//
// The PRIORITY frame (type=0x2) specifies the sender-advised priority of a stream.
//
// The PRIORITY frame does not define any flags.
frameTypes[0x2] = 'PRIORITY';
frameFlags.PRIORITY = [];
typeSpecificAttributes.PRIORITY = ['priorityDependency', 'priorityWeight', 'exclusiveDependency'];
// 0 1 2 3
// 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
// +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
// |E| Stream Dependency? (31) |
// +-+-------------+-----------------------------------------------+
// | Weight? (8) |
// +-+-------------+
//
// The payload of a PRIORITY frame contains an exclusive bit, a 31-bit dependency, and an 8-bit weight
Serializer.PRIORITY = function writePriority(frame, buffers) {
var buffer = Buffer.alloc(5);
assert((0 <= frame.priorityDependency) && (frame.priorityDependency <= 0x7fffffff), frame.priorityDependency);
buffer.writeUInt32BE(frame.priorityDependency, 0);
if (frame.exclusiveDependency) {
buffer[0] |= 0x80;
}
assert((0 <= frame.priorityWeight) && (frame.priorityWeight <= 0xff), frame.priorityWeight);
buffer.writeUInt8(frame.priorityWeight, 4);
buffers.push(buffer);
};
Deserializer.PRIORITY = function readPriority(buffer, frame) {
if (buffer.length < 5) {
// PRIORITY frames are 5 bytes long. Bad peer!
return 'FRAME_SIZE_ERROR';
}
var dependencyData = Buffer.alloc(4);
buffer.copy(dependencyData, 0, 0, 4);
frame.exclusiveDependency = !!(dependencyData[0] & 0x80);
dependencyData[0] &= 0x7f;
frame.priorityDependency = dependencyData.readUInt32BE(0);
frame.priorityWeight = buffer.readUInt8(4);
};
// -----------------------------------------------------------
//
// The RST_STREAM frame (type=0x3) allows for abnormal termination of a stream.
//
// No type-flags are defined.
frameTypes[0x3] = 'RST_STREAM';
frameFlags.RST_STREAM = [];
typeSpecificAttributes.RST_STREAM = ['error'];
// 0 1 2 3
// 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
// +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
// | Error Code (32) |
// +---------------------------------------------------------------+
//
// The RST_STREAM frame contains a single unsigned, 32-bit integer identifying the error
// code (see Error Codes). The error code indicates why the stream is being terminated.
Serializer.RST_STREAM = function writeRstStream(frame, buffers) {
var buffer = Buffer.alloc(4);
var code = errorCodes.indexOf(frame.error);
assert((0 <= code) && (code <= 0xffffffff), code);
buffer.writeUInt32BE(code, 0);
buffers.push(buffer);
};
Deserializer.RST_STREAM = function readRstStream(buffer, frame) {
if (buffer.length < 4) {
// RST_STREAM is 4 bytes long. Bad peer!
return 'FRAME_SIZE_ERROR';
}
frame.error = errorCodes[buffer.readUInt32BE(0)];
if (!frame.error) {
// Unknown error codes are considered equivalent to INTERNAL_ERROR
frame.error = 'INTERNAL_ERROR';
}
};
// -------------------------------------------------------
//
// The SETTINGS frame (type=0x4) conveys configuration parameters that affect how endpoints
// communicate.
//
// The SETTINGS frame defines the following flag:
// * ACK (0x1):
// Bit 1 being set indicates that this frame acknowledges receipt and application of the peer's
// SETTINGS frame.
frameTypes[0x4] = 'SETTINGS';
frameFlags.SETTINGS = ['ACK'];
typeSpecificAttributes.SETTINGS = ['settings'];
// The payload of a SETTINGS frame consists of zero or more settings. Each setting consists of a
// 16-bit identifier, and an unsigned 32-bit value.
//
// 0 1 2 3
// 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
// +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
// | Identifier(16) | Value (32) |
// +-----------------+---------------------------------------------+
// ...Value |
// +---------------------------------+
//
// Each setting in a SETTINGS frame replaces the existing value for that setting. Settings are
// processed in the order in which they appear, and a receiver of a SETTINGS frame does not need to
// maintain any state other than the current value of settings. Therefore, the value of a setting
// is the last value that is seen by a receiver. This permits the inclusion of the same settings
// multiple times in the same SETTINGS frame, though doing so does nothing other than waste
// connection capacity.
Serializer.SETTINGS = function writeSettings(frame, buffers) {
var settings = [], settingsLeft = Object.keys(frame.settings);
definedSettings.forEach(function(setting, id) {
if (setting.name in frame.settings) {
settingsLeft.splice(settingsLeft.indexOf(setting.name), 1);
var value = frame.settings[setting.name];
settings.push({ id: id, value: setting.flag ? Boolean(value) : value });
}
});
assert(settingsLeft.length === 0, 'Unknown settings: ' + settingsLeft.join(', '));
var buffer = Buffer.alloc(settings.length * 6);
for (var i = 0; i < settings.length; i++) {
buffer.writeUInt16BE(settings[i].id & 0xffff, i*6);
buffer.writeUInt32BE(settings[i].value, i*6 + 2);
}
buffers.push(buffer);
};
Deserializer.SETTINGS = function readSettings(buffer, frame, role) {
frame.settings = {};
// Receipt of a SETTINGS frame with the ACK flag set and a length
// field value other than 0 MUST be treated as a connection error
// (Section 5.4.1) of type FRAME_SIZE_ERROR.
if(frame.flags.ACK && buffer.length != 0) {
return 'FRAME_SIZE_ERROR';
}
if (buffer.length % 6 !== 0) {
return 'PROTOCOL_ERROR';
}
for (var i = 0; i < buffer.length / 6; i++) {
var id = buffer.readUInt16BE(i*6) & 0xffff;
var setting = definedSettings[id];
if (setting) {
if (role == 'CLIENT' && setting.name == 'SETTINGS_ENABLE_PUSH') {
return 'SETTINGS frame on client got SETTINGS_ENABLE_PUSH';
}
var value = buffer.readUInt32BE(i*6 + 2);
frame.settings[setting.name] = setting.flag ? Boolean(value & 0x1) : value;
}
}
};
// The following settings are defined:
var definedSettings = [];
// * SETTINGS_HEADER_TABLE_SIZE (1):
// Allows the sender to inform the remote endpoint of the size of the header compression table
// used to decode header blocks.
definedSettings[1] = { name: 'SETTINGS_HEADER_TABLE_SIZE', flag: false };
// * SETTINGS_ENABLE_PUSH (2):
// This setting can be use to disable server push. An endpoint MUST NOT send a PUSH_PROMISE frame
// if it receives this setting set to a value of 0. The default value is 1, which indicates that
// push is permitted.
definedSettings[2] = { name: 'SETTINGS_ENABLE_PUSH', flag: true };
// * SETTINGS_MAX_CONCURRENT_STREAMS (3):
// indicates the maximum number of concurrent streams that the sender will allow.
definedSettings[3] = { name: 'SETTINGS_MAX_CONCURRENT_STREAMS', flag: false };
// * SETTINGS_INITIAL_WINDOW_SIZE (4):
// indicates the sender's initial stream window size (in bytes) for new streams.
definedSettings[4] = { name: 'SETTINGS_INITIAL_WINDOW_SIZE', flag: false };
// * SETTINGS_MAX_FRAME_SIZE (5):
// indicates the maximum size of a frame the receiver will allow.
definedSettings[5] = { name: 'SETTINGS_MAX_FRAME_SIZE', flag: false };
// ---------------------------------------------------------------
//
// The PUSH_PROMISE frame (type=0x5) is used to notify the peer endpoint in advance of streams the
// sender intends to initiate.
//
// The PUSH_PROMISE frame defines the following flags:
//
// * END_PUSH_PROMISE (0x4):
// The END_PUSH_PROMISE bit indicates that this frame contains the entire payload necessary to
// provide a complete set of headers.
frameTypes[0x5] = 'PUSH_PROMISE';
frameFlags.PUSH_PROMISE = ['RESERVED1', 'RESERVED2', 'END_PUSH_PROMISE', 'PADDED'];
typeSpecificAttributes.PUSH_PROMISE = ['promised_stream', 'headers', 'data'];
// 0 1 2 3
// 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
// +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
// |Pad Length? (8)|
// +-+-------------+-----------------------------------------------+
// |X| Promised-Stream-ID (31) |
// +-+-------------------------------------------------------------+
// | Header Block Fragment (*) ...
// +---------------------------------------------------------------+
// | Padding (*) ...
// +---------------------------------------------------------------+
//
// The PUSH_PROMISE frame includes the unsigned 31-bit identifier of
// the stream the endpoint plans to create along with a minimal set of headers that provide
// additional context for the stream.
Serializer.PUSH_PROMISE = function writePushPromise(frame, buffers) {
var buffer = Buffer.alloc(4);
var promised_stream = frame.promised_stream;
assert((0 <= promised_stream) && (promised_stream <= 0x7fffffff), promised_stream);
buffer.writeUInt32BE(promised_stream, 0);
buffers.push(buffer);
buffers.push(frame.data);
};
Deserializer.PUSH_PROMISE = function readPushPromise(buffer, frame) {
if (buffer.length < 4) {
return 'FRAME_SIZE_ERROR';
}
var dataOffset = 0;
var paddingLength = 0;
if (frame.flags.PADDED) {
if (buffer.length < 5) {
return 'FRAME_SIZE_ERROR';
}
paddingLength = (buffer.readUInt8(dataOffset) & 0xff);
dataOffset = 1;
}
frame.promised_stream = buffer.readUInt32BE(dataOffset) & 0x7fffffff;
dataOffset += 4;
if (paddingLength) {
if ((buffer.length - dataOffset) < paddingLength) {
return 'FRAME_SIZE_ERROR';
}
frame.data = buffer.slice(dataOffset, -1 * paddingLength);
} else {
frame.data = buffer.slice(dataOffset);
}
};
// -----------------------------------------------
//
// The PING frame (type=0x6) is a mechanism for measuring a minimal round-trip time from the
// sender, as well as determining whether an idle connection is still functional.
//
// The PING frame defines one type-specific flag:
//
// * ACK (0x1):
// Bit 1 being set indicates that this PING frame is a PING response.
frameTypes[0x6] = 'PING';
frameFlags.PING = ['ACK'];
typeSpecificAttributes.PING = ['data'];
// In addition to the frame header, PING frames MUST contain 8 additional octets of opaque data.
Serializer.PING = function writePing(frame, buffers) {
buffers.push(frame.data);
};
Deserializer.PING = function readPing(buffer, frame) {
if (buffer.length !== 8) {
return 'FRAME_SIZE_ERROR';
}
frame.data = buffer;
};
// ---------------------------------------------------
//
// The GOAWAY frame (type=0x7) informs the remote peer to stop creating streams on this connection.
//
// The GOAWAY frame does not define any flags.
frameTypes[0x7] = 'GOAWAY';
frameFlags.GOAWAY = [];
typeSpecificAttributes.GOAWAY = ['last_stream', 'error'];
// 0 1 2 3
// 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
// +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
// |X| Last-Stream-ID (31) |
// +-+-------------------------------------------------------------+
// | Error Code (32) |
// +---------------------------------------------------------------+
//
// The last stream identifier in the GOAWAY frame contains the highest numbered stream identifier
// for which the sender of the GOAWAY frame has received frames on and might have taken some action
// on.
//
// The GOAWAY frame also contains a 32-bit error code (see Error Codes) that contains the reason for
// closing the connection.
Serializer.GOAWAY = function writeGoaway(frame, buffers) {
var buffer = Buffer.alloc(8);
var last_stream = frame.last_stream;
assert((0 <= last_stream) && (last_stream <= 0x7fffffff), last_stream);
buffer.writeUInt32BE(last_stream, 0);
var code = errorCodes.indexOf(frame.error);
assert((0 <= code) && (code <= 0xffffffff), code);
buffer.writeUInt32BE(code, 4);
buffers.push(buffer);
};
Deserializer.GOAWAY = function readGoaway(buffer, frame) {
if (buffer.length !== 8) {
// GOAWAY must have 8 bytes
return 'FRAME_SIZE_ERROR';
}
frame.last_stream = buffer.readUInt32BE(0) & 0x7fffffff;
frame.error = errorCodes[buffer.readUInt32BE(4)];
if (!frame.error) {
// Unknown error types are to be considered equivalent to INTERNAL ERROR
frame.error = 'INTERNAL_ERROR';
}
};
// -----------------------------------------------------------------
//
// The WINDOW_UPDATE frame (type=0x8) is used to implement flow control.
//
// The WINDOW_UPDATE frame does not define any flags.
frameTypes[0x8] = 'WINDOW_UPDATE';
frameFlags.WINDOW_UPDATE = [];
typeSpecificAttributes.WINDOW_UPDATE = ['window_size'];
// The payload of a WINDOW_UPDATE frame is a 32-bit value indicating the additional number of bytes
// that the sender can transmit in addition to the existing flow control window. The legal range
// for this field is 1 to 2^31 - 1 (0x7fffffff) bytes; the most significant bit of this value is
// reserved.
Serializer.WINDOW_UPDATE = function writeWindowUpdate(frame, buffers) {
var buffer = Buffer.alloc(4);
var window_size = frame.window_size;
assert((0 < window_size) && (window_size <= 0x7fffffff), window_size);
buffer.writeUInt32BE(window_size, 0);
buffers.push(buffer);
};
Deserializer.WINDOW_UPDATE = function readWindowUpdate(buffer, frame) {
if (buffer.length !== WINDOW_UPDATE_PAYLOAD_SIZE) {
return 'FRAME_SIZE_ERROR';
}
frame.window_size = buffer.readUInt32BE(0) & 0x7fffffff;
if (frame.window_size === 0) {
return 'PROTOCOL_ERROR';
}
};
// ------------------------------------------------------------
//
// The CONTINUATION frame (type=0x9) is used to continue a sequence of header block fragments.
//
// The CONTINUATION frame defines the following flag:
//
// * END_HEADERS (0x4):
// The END_HEADERS bit indicates that this frame ends the sequence of header block fragments
// necessary to provide a complete set of headers.
frameTypes[0x9] = 'CONTINUATION';
frameFlags.CONTINUATION = ['RESERVED1', 'RESERVED2', 'END_HEADERS'];
typeSpecificAttributes.CONTINUATION = ['headers', 'data'];
Serializer.CONTINUATION = function writeContinuation(frame, buffers) {
buffers.push(frame.data);
};
Deserializer.CONTINUATION = function readContinuation(buffer, frame) {
frame.data = buffer;
};
// ------------------------------------------------------------
//
// The ALTSVC frame (type=0xA) advertises the availability of an alternative service to the client.
//
// The ALTSVC frame does not define any flags.
frameTypes[0xA] = 'ALTSVC';
frameFlags.ALTSVC = [];
// 0 1 2 3
// 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
// +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
// | Origin-Len (16) | Origin? (*) ...
// +-------------------------------+----------------+--------------+
// | Alt-Svc-Field-Value (*) ...
// +---------------------------------------------------------------+
//
// The ALTSVC frame contains the following fields:
//
// Origin-Len: An unsigned, 16-bit integer indicating the length, in
// octets, of the Origin field.
//
// Origin: An OPTIONAL sequence of characters containing ASCII
// Section 6.2) that the alternate service is applicable to.
//
// Alt-Svc-Field-Value: A sequence of octets (length determined by
// subtracting the length of all preceding fields from the frame
// length) containing a value identical to the Alt-Svc field value
// (ABNF production "Alt-Svc").
typeSpecificAttributes.ALTSVC = ['maxAge', 'port', 'protocolID', 'host',
'origin'];
function istchar(c) {
return ('!#$&\'*+-.^_`|~1234567890ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz'.indexOf(c) > -1);
}
function hexencode(s) {
var t = '';
for (var i = 0; i < s.length; i++) {
if (!istchar(s[i])) {
t += '%';
t += Buffer.from(s[i]).toString('hex');
} else {
t += s[i];
}
}
return t;
}
Serializer.ALTSVC = function writeAltSvc(frame, buffers) {
var buffer = Buffer.alloc(2);
buffer.writeUInt16BE(frame.origin.length, 0);
buffers.push(buffer);
buffers.push(Buffer.from(frame.origin, 'ascii'));
var fieldValue = hexencode(frame.protocolID) + '="' + frame.host + ':' + frame.port + '"';
if (frame.maxAge !== 86400) { // 86400 is the default
fieldValue += "; ma=" + frame.maxAge;
}
buffers.push(Buffer.from(fieldValue, 'ascii'));
};
function stripquotes(s) {
var start = 0;
var end = s.length;
while ((start < end) && (s[start] === '"')) {
start++;
}
while ((end > start) && (s[end - 1] === '"')) {
end--;
}
if (start >= end) {
return "";
}
return s.substring(start, end);
}
function splitNameValue(nvpair) {
var eq = -1;
var inQuotes = false;
for (var i = 0; i < nvpair.length; i++) {
if (nvpair[i] === '"') {
inQuotes = !inQuotes;
continue;
}
if (inQuotes) {
continue;
}
if (nvpair[i] === '=') {
eq = i;
break;
}
}
if (eq === -1) {
return {'name': nvpair, 'value': null};
}
var name = stripquotes(nvpair.substring(0, eq).trim());
var value = stripquotes(nvpair.substring(eq + 1).trim());
return {'name': name, 'value': value};
}
function splitHeaderParameters(hv) {
return parseHeaderValue(hv, ';', splitNameValue);
}
function parseHeaderValue(hv, separator, callback) {
var start = 0;
var inQuotes = false;
var values = [];
for (var i = 0; i < hv.length; i++) {
if (hv[i] === '"') {
inQuotes = !inQuotes;
continue;
}
if (inQuotes) {
// Just skip this
continue;
}
if (hv[i] === separator) {
var newValue = hv.substring(start, i).trim();
if (newValue.length > 0) {
newValue = callback(newValue);
values.push(newValue);
}
start = i + 1;
}
}
var newValue = hv.substring(start).trim();
if (newValue.length > 0) {
newValue = callback(newValue);
values.push(newValue);
}
return values;
}
function rsplit(s, delim, count) {
var nsplits = 0;
var end = s.length;
var rval = [];
for (var i = s.length - 1; i >= 0; i--) {
if (s[i] === delim) {
var t = s.substring(i + 1, end);
end = i;
rval.unshift(t);
nsplits++;
if (nsplits === count) {
break;
}
}
}
if (end !== 0) {
rval.unshift(s.substring(0, end));
}
return rval;
}
function ishex(c) {
return ('0123456789ABCDEFabcdef'.indexOf(c) > -1);
}
function unescape(s) {
var i = 0;
var t = '';
while (i < s.length) {
if (s[i] != '%' || !ishex(s[i + 1]) || !ishex(s[i + 2])) {
t += s[i];
} else {
++i;
var hexvalue = '';
if (i < s.length) {
hexvalue += s[i];
++i;
}
if (i < s.length) {
hexvalue += s[i];
}
if (hexvalue.length > 0) {
t += Buffer.from(hexvalue, 'hex').toString();
} else {
t += '%';
}
}
++i;
}
return t;
}
Deserializer.ALTSVC = function readAltSvc(buffer, frame) {
if (buffer.length < 2) {
return 'FRAME_SIZE_ERROR';
}
var originLength = buffer.readUInt16BE(0);
if ((buffer.length - 2) < originLength) {
return 'FRAME_SIZE_ERROR';
}
frame.origin = buffer.toString('ascii', 2, 2 + originLength);
var fieldValue = buffer.toString('ascii', 2 + originLength);
var values = parseHeaderValue(fieldValue, ',', splitHeaderParameters);
if (values.length > 1) {
// TODO - warn that we only use one here
}
if (values.length === 0) {
// Well that's a malformed frame. Just ignore it.
return;
}
var chosenAltSvc = values[0];
frame.maxAge = 86400; // Default
for (var i = 0; i < chosenAltSvc.length; i++) {
if (i === 0) {
// This corresponds to the protocolID="<host>:<port>" item
frame.protocolID = unescape(chosenAltSvc[i].name);
var hostport = rsplit(chosenAltSvc[i].value, ':', 1);
frame.host = hostport[0];
frame.port = parseInt(hostport[1], 10);
} else if (chosenAltSvc[i].name == 'ma') {
frame.maxAge = parseInt(chosenAltSvc[i].value, 10);
}
// Otherwise, we just ignore this
}
};
// frame 0xB was BLOCKED and some versions of chrome will
// throw PROTOCOL_ERROR upon seeing it with non 0 payload
frameTypes[0xC] = 'ORIGIN';
frameFlags.ORIGIN = [];
typeSpecificAttributes.ORIGIN = ['originList'];
Serializer.ORIGIN = function writeOrigin(frame, buffers) {
for (var i = 0; i < frame.originList.length; i++) {
var buffer = Buffer.alloc(2);
buffer.writeUInt16BE(frame.originList[i].length, 0);
buffers.push(buffer);
buffers.push(Buffer.from(frame.originList[i], 'ascii'));
}
};
Deserializer.ORIGIN = function readOrigin(buffer, frame) {
// ignored
};
// ------------------------------------------------------------
var errorCodes = [
'NO_ERROR',
'PROTOCOL_ERROR',
'INTERNAL_ERROR',
'FLOW_CONTROL_ERROR',
'SETTINGS_TIMEOUT',
'STREAM_CLOSED',
'FRAME_SIZE_ERROR',
'REFUSED_STREAM',
'CANCEL',
'COMPRESSION_ERROR',
'CONNECT_ERROR',
'ENHANCE_YOUR_CALM',
'INADEQUATE_SECURITY',
'HTTP_1_1_REQUIRED'
];
// Logging
// -------
// [Bunyan serializers](https://github.com/trentm/node-bunyan#serializers) to improve logging output
// for debug messages emitted in this component.
exports.serializers = {};
// * `frame` serializer: it transforms data attributes from Buffers to hex strings and filters out
// flags that are not present.
var frameCounter = 0;
exports.serializers.frame = function(frame) {
if (!frame) {
return null;
}
if ('id' in frame) {
return frame.id;
}
frame.id = frameCounter;
frameCounter += 1;
var logEntry = { id: frame.id };
genericAttributes.concat(typeSpecificAttributes[frame.type]).forEach(function(name) {
logEntry[name] = frame[name];
});
if (frame.data instanceof Buffer) {
if (logEntry.data.length > 50) {
logEntry.data = frame.data.slice(0, 47).toString('hex') + '...';
} else {
logEntry.data = frame.data.toString('hex');
}
if (!('length' in logEntry)) {
logEntry.length = frame.data.length;
}
}
if (frame.promised_stream instanceof Object) {
logEntry.promised_stream = 'stream-' + frame.promised_stream.id;
}
logEntry.flags = Object.keys(frame.flags || {}).filter(function(name) {
return frame.flags[name] === true;
});
return logEntry;
};
// * `data` serializer: it simply transforms a buffer to a hex string.
exports.serializers.data = function(data) {
return data.toString('hex');
};