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module websocket
import encoding.utf8
const (
header_len_offset = 2 // offset for lengthpart of websocket header
buffer_size = 256 // default buffer size
extended_payload16_end_byte = 4 // header length with 16-bit extended payload
extended_payload64_end_byte = 10 // header length with 64-bit extended payload
)
// Fragment represents a websocket data fragment
struct Fragment {
data []byte // included data payload data in a fragment
opcode OPCode // interpretation of the payload data
}
// Frame represents a data frame header
struct Frame {
mut:
// length of the websocket header part
header_len int = 2
// size of total frame
frame_size int = 2
fin bool // true if final fragment of message
rsv1 bool // reserved for future use in websocket RFC
rsv2 bool // reserved for future use in websocket RFC
rsv3 bool // reserved for future use in websocket RFC
opcode OPCode // interpretation of the payload data
has_mask bool // true if the payload data is masked
payload_len int // payload length
masking_key [4]byte // all frames from client to server is masked with this key
}
const (
invalid_close_codes = [999, 1004, 1005, 1006, 1014, 1015, 1016, 1100, 2000, 2999, 5000, 65536]
)
// validate_client validates client frame rules from RFC6455
pub fn (mut ws Client) validate_frame(frame &Frame) ? {
if frame.rsv1 || frame.rsv2 || frame.rsv3 {
ws.close(1002, 'rsv cannot be other than 0, not negotiated') ?
return error('rsv cannot be other than 0, not negotiated')
}
if (int(frame.opcode) >= 3 && int(frame.opcode) <= 7)
|| (int(frame.opcode) >= 11 && int(frame.opcode) <= 15) {
ws.close(1002, 'use of reserved opcode') ?
return error('use of reserved opcode')
}
if frame.has_mask && !ws.is_server {
// server should never send masked frames
// to client, close connection
ws.close(1002, 'client got masked frame') ?
return error('client sent masked frame')
}
if is_control_frame(frame.opcode) {
if !frame.fin {
ws.close(1002, 'control message must not be fragmented') ?
return error('unexpected control frame with no fin')
}
if frame.payload_len > 125 {
ws.close(1002, 'control frames must not exceed 125 bytes') ?
return error('unexpected control frame payload length')
}
}
if frame.fin == false && ws.fragments.len == 0 && frame.opcode == .continuation {
err_msg := 'unexecpected continuation, there are no frames to continue, $frame'
ws.close(1002, err_msg) ?
return error(err_msg)
}
}
// is_control_frame returns true if the frame is a control frame
fn is_control_frame(opcode OPCode) bool {
return opcode !in [.text_frame, .binary_frame, .continuation]
}
// is_data_frame returns true if the frame is a control frame
fn is_data_frame(opcode OPCode) bool {
return opcode in [.text_frame, .binary_frame]
}
// read_payload reads the message payload from the socket
fn (mut ws Client) read_payload(frame &Frame) ?[]byte {
if frame.payload_len == 0 {
return []byte{}
}
mut buffer := []byte{cap: frame.payload_len}
mut read_buf := [1]byte{}
mut bytes_read := 0
for bytes_read < frame.payload_len {
len := ws.socket_read_ptr(&read_buf[0], 1) ?
if len != 1 {
return error('expected read all message, got zero')
}
bytes_read += len
buffer << read_buf[0]
}
if bytes_read != frame.payload_len {
return error('failed to read payload')
}
if frame.has_mask {
for i in 0 .. frame.payload_len {
buffer[i] ^= frame.masking_key[i % 4] & 0xff
}
}
return buffer
}
// validate_utf_8 validates payload for valid utf8 encoding
// - Future implementation needs to support fail fast utf errors for strict autobahn conformance
fn (mut ws Client) validate_utf_8(opcode OPCode, payload []byte) ? {
if opcode in [.text_frame, .close] && !utf8.validate(payload.data, payload.len) {
ws.logger.error('malformed utf8 payload, payload len: ($payload.len)')
ws.send_error_event('Recieved malformed utf8.')
ws.close(1007, 'malformed utf8 payload') ?
return error('malformed utf8 payload')
}
}
// read_next_message reads 1 to n frames to compose a message
pub fn (mut ws Client) read_next_message() ?Message {
for {
frame := ws.parse_frame_header() ?
ws.validate_frame(&frame) ?
frame_payload := ws.read_payload(&frame) ?
if is_control_frame(frame.opcode) {
// Control frames can interject other frames
// and need to be returned immediately
msg := Message{
opcode: OPCode(frame.opcode)
payload: frame_payload.clone()
}
unsafe { frame_payload.free() }
return msg
}
// if the message is fragmented we just put it on fragments
// a fragment is allowed to have zero size payload
if !frame.fin {
ws.fragments << &Fragment{
data: frame_payload.clone()
opcode: frame.opcode
}
unsafe { frame_payload.free() }
continue
}
if ws.fragments.len == 0 {
ws.validate_utf_8(frame.opcode, frame_payload) or {
ws.logger.error('UTF8 validation error: $err, len of payload($frame_payload.len)')
ws.send_error_event('UTF8 validation error: $err, len of payload($frame_payload.len)')
return err
}
msg := Message{
opcode: OPCode(frame.opcode)
payload: frame_payload.clone()
}
unsafe { frame_payload.free() }
return msg
}
defer {
ws.fragments = []
}
if is_data_frame(frame.opcode) {
ws.close(0, '') ?
return error('Unexpected frame opcode')
}
payload := ws.payload_from_fragments(frame_payload) ?
opcode := ws.opcode_from_fragments()
ws.validate_utf_8(opcode, payload) ?
msg := Message{
opcode: opcode
payload: payload.clone()
}
unsafe {
frame_payload.free()
payload.free()
}
return msg
}
return none
}
// payload_from_fragments returs the whole paylaod from fragmented message
fn (ws Client) payload_from_fragments(fin_payload []byte) ?[]byte {
mut total_size := 0
for f in ws.fragments {
if f.data.len > 0 {
total_size += f.data.len
}
}
total_size += fin_payload.len
if total_size == 0 {
return []byte{}
}
mut total_buffer := []byte{cap: total_size}
for f in ws.fragments {
if f.data.len > 0 {
total_buffer << f.data
}
}
total_buffer << fin_payload
return total_buffer
}
// opcode_from_fragments returns the opcode for message from the first fragment sent
fn (ws Client) opcode_from_fragments() OPCode {
return OPCode(ws.fragments[0].opcode)
}
// parse_frame_header parses next message by decoding the incoming frames
pub fn (mut ws Client) parse_frame_header() ?Frame {
mut buffer := [256]byte{}
mut bytes_read := 0
mut frame := Frame{}
mut rbuff := [1]byte{}
mut mask_end_byte := 0
for ws.state == .open {
read_bytes := ws.socket_read_ptr(&rbuff[0], 1) ?
if read_bytes == 0 {
// this is probably a timeout or close
continue
}
buffer[bytes_read] = rbuff[0]
bytes_read++
// parses the first two header bytes to get basic frame information
if bytes_read == u64(websocket.header_len_offset) {
frame.fin = (buffer[0] & 0x80) == 0x80
frame.rsv1 = (buffer[0] & 0x40) == 0x40
frame.rsv2 = (buffer[0] & 0x20) == 0x20
frame.rsv3 = (buffer[0] & 0x10) == 0x10
frame.opcode = OPCode(int(buffer[0] & 0x7F))
frame.has_mask = (buffer[1] & 0x80) == 0x80
frame.payload_len = buffer[1] & 0x7F
// if has mask set the byte postition where mask ends
if frame.has_mask {
mask_end_byte = if frame.payload_len < 126 {
websocket.header_len_offset + 4
} else if frame.payload_len == 126 {
websocket.header_len_offset + 6
} else if frame.payload_len == 127 {
websocket.header_len_offset + 12
} else {
0
} // impossible
}
frame.payload_len = frame.payload_len
frame.frame_size = frame.header_len + frame.payload_len
if !frame.has_mask && frame.payload_len < 126 {
break
}
}
if frame.payload_len == 126 && bytes_read == u64(websocket.extended_payload16_end_byte) {
frame.header_len += 2
frame.payload_len = 0
frame.payload_len |= buffer[2] << 8
frame.payload_len |= buffer[3]
frame.frame_size = frame.header_len + frame.payload_len
if !frame.has_mask {
break
}
}
if frame.payload_len == 127 && bytes_read == u64(websocket.extended_payload64_end_byte) {
frame.header_len += 8
// these shift operators needs 64 bit on clang with -prod flag
mut payload_len := u64(0)
payload_len |= u64(buffer[2]) << 56
payload_len |= u64(buffer[3]) << 48
payload_len |= u64(buffer[4]) << 40
payload_len |= u64(buffer[5]) << 32
payload_len |= u64(buffer[6]) << 24
payload_len |= u64(buffer[7]) << 16
payload_len |= u64(buffer[8]) << 8
payload_len |= u64(buffer[9])
frame.payload_len = int(payload_len)
if !frame.has_mask {
break
}
}
if frame.has_mask && bytes_read == mask_end_byte {
frame.masking_key[0] = buffer[mask_end_byte - 4]
frame.masking_key[1] = buffer[mask_end_byte - 3]
frame.masking_key[2] = buffer[mask_end_byte - 2]
frame.masking_key[3] = buffer[mask_end_byte - 1]
break
}
}
return frame
}
// unmask_sequence unmask any given sequence
fn (f Frame) unmask_sequence(mut buffer []byte) {
for i in 0 .. buffer.len {
buffer[i] ^= f.masking_key[i % 4] & 0xff
}
}
|
