Class: HTTP2::Framer

Inherits:
Object
  • Object
show all
Includes:
BufferUtils, Error, PackingExtensions
Defined in:
lib/http/2/framer.rb

Overview

Performs encoding, decoding, and validation of binary HTTP/2 frames.

Constant Summary collapse

DEFAULT_MAX_FRAME_SIZE =

Default value of max frame size (16384 bytes)

2 << 13
MAX_STREAM_ID =

Maximum stream ID (2^31)

0x7fffffff
MAX_WINDOWINC =

Maximum window increment value (2^31)

0x7fffffff
FRAME_TYPES =

HTTP/2 frame type mapping as defined by the spec

{
  data: 0x0,
  headers: 0x1,
  priority: 0x2,
  rst_stream: 0x3,
  settings: 0x4,
  push_promise: 0x5,
  ping: 0x6,
  goaway: 0x7,
  window_update: 0x8,
  continuation: 0x9,
  altsvc: 0xa,
  origin: 0xc
}.freeze
FRAME_TYPES_WITH_PADDING = 
%i[data headers push_promise].freeze
FRAME_FLAGS =

Per frame flags as defined by the spec

{
  data: {
    end_stream: 0,
    padded: 3,
    compressed: 5
  },
  headers: {
    end_stream: 0,
    end_headers: 2,
    padded: 3,
    priority: 5
  },
  priority: {},
  rst_stream: {},
  settings: { ack: 0 },
  push_promise: {
    end_headers: 2,
    padded: 3
  },
  ping: { ack: 0 },
  goaway: {},
  window_update: {},
  continuation: { end_headers: 2 },
  altsvc: {},
  origin: {
    reserved: 1,
    reserved2: 2,
    reserved3: 4,
    reserved4: 8
  }
}.each_value(&:freeze).freeze
DEFINED_SETTINGS =

Default settings as defined by the spec

{
  settings_header_table_size: 1,
  settings_enable_push: 2,
  settings_max_concurrent_streams: 3,
  settings_initial_window_size: 4,
  settings_max_frame_size: 5,
  settings_max_header_list_size: 6
}.freeze
DEFINED_ERRORS =

Default error types as defined by the spec

{
  no_error: 0,
  protocol_error: 1,
  internal_error: 2,
  flow_control_error: 3,
  settings_timeout: 4,
  stream_closed: 5,
  frame_size_error: 6,
  refused_stream: 7,
  cancel: 8,
  compression_error: 9,
  connect_error: 10,
  enhance_your_calm: 11,
  inadequate_security: 12,
  http_1_1_required: 13
}.freeze
FRAME_LENGTH_HISHIFT = 
16
FRAME_LENGTH_LOMASK = 
0xFFFF

Instance Attribute Summary collapse

Instance Method Summary collapse

Methods included from BufferUtils

#read_str, #read_uint32, #shift_byte

Methods included from PackingExtensions

#pack

Constructor Details

#initialize(local_max_frame_size = DEFAULT_MAX_FRAME_SIZE, remote_max_frame_size = DEFAULT_MAX_FRAME_SIZE) ⇒ Framer

Initializes new framer object.



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# File 'lib/http/2/framer.rb', line 116

def initialize(local_max_frame_size = DEFAULT_MAX_FRAME_SIZE,
               remote_max_frame_size = DEFAULT_MAX_FRAME_SIZE)
  @local_max_frame_size = local_max_frame_size
  @remote_max_frame_size = remote_max_frame_size
end

Instance Attribute Details

#local_max_frame_size ⇒ Object

maximum frame size



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# File 'lib/http/2/framer.rb', line 15

def local_max_frame_size
  @local_max_frame_size
end

#remote_max_frame_size ⇒ Object

maximum frame size



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# File 'lib/http/2/framer.rb', line 15

def remote_max_frame_size
  @remote_max_frame_size
end

Instance Method Details

#common_header(frame, buffer:) ⇒ String

Generates common 9-byte frame header.

Parameters:

  • frame (Hash)
  • buffer (String) —

    buffer to pack bytes into

Returns:

  • (String)

Raises:



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# File 'lib/http/2/framer.rb', line 128

def common_header(frame, buffer:)
  raise CompressionError, "Invalid frame type (#{frame[:type]})" unless FRAME_TYPES[frame[:type]]

  raise CompressionError, "Frame size is too large: #{frame[:length]}" if frame[:length] > @remote_max_frame_size

  raise CompressionError, "Frame size is invalid: #{frame[:length]}" if frame[:length] < 0

  raise CompressionError, "Stream ID (#{frame[:stream]}) is too large" if frame[:stream] > MAX_STREAM_ID

  if frame[:type] == :window_update && frame[:increment] > MAX_WINDOWINC
    raise CompressionError, "Window increment (#{frame[:increment]}) is too large"
  end

  pack([
         (frame[:length] >> FRAME_LENGTH_HISHIFT),
         (frame[:length] & FRAME_LENGTH_LOMASK),
         FRAME_TYPES[frame[:type]],
         frame[:flags].reduce(0) do |acc, f|
           position = FRAME_FLAGS[frame[:type]][f]
           raise CompressionError, "Invalid frame flag (#{f}) for #{frame[:type]}" unless position

           acc | (1 << position)
         end,
         frame[:stream]
       ], HEADERPACK, buffer: buffer, offset: 0) # 8+16,8,8,32
end

#generate(frame) ⇒ Object

Generates encoded HTTP/2 frame.

Parameters:

  • frame (Hash) 


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# File 'lib/http/2/framer.rb', line 179

def generate(frame)
  bytes  = "".b
  length = 0

  frame[:flags] ||= []
  frame[:stream] ||= 0

  case frame[:type]
  when :data
    bytes << frame[:payload]
    bytes.force_encoding(Encoding::BINARY)
    length += frame[:payload].bytesize

  when :headers
    if frame[:weight] || frame[:dependency] || !frame[:exclusive].nil?
      unless frame[:weight] && frame[:dependency] && !frame[:exclusive].nil?
        raise CompressionError, "Must specify all of priority parameters for #{frame[:type]}"
      end

      frame[:flags] += [:priority] unless frame[:flags].include? :priority
    end

    if frame[:flags].include? :priority
      pack([(frame[:exclusive] ? EBIT : 0) | (frame[:dependency] & RBIT)], UINT32, buffer: bytes)
      pack([frame[:weight] - 1], UINT8, buffer: bytes)
      length += 5
    end

    bytes << frame[:payload]
    length += frame[:payload].bytesize

  when :priority
    unless frame[:weight] && frame[:dependency] && !frame[:exclusive].nil?
      raise CompressionError, "Must specify all of priority parameters for #{frame[:type]}"
    end

    pack([(frame[:exclusive] ? EBIT : 0) | (frame[:dependency] & RBIT)], UINT32, buffer: bytes)
    pack([frame[:weight] - 1], UINT8, buffer: bytes)
    length += 5

  when :rst_stream
    pack_error(frame[:error], buffer: bytes)
    length += 4

  when :settings
    raise CompressionError, "Invalid stream ID (#{frame[:stream]})" if (frame[:stream]).nonzero?

    frame[:payload].each do |(k, v)|
      if k.is_a? Integer # rubocop:disable Style/GuardClause
        DEFINED_SETTINGS.value?(k) || next
      else
        k = DEFINED_SETTINGS[k]

        raise CompressionError, "Unknown settings ID for #{k}" if k.nil?
      end

      pack([k], UINT16, buffer: bytes)
      pack([v], UINT32, buffer: bytes)
      length += 6
    end

  when :push_promise
    pack([frame[:promise_stream] & RBIT], UINT32, buffer: bytes)
    bytes << frame[:payload]
    length += 4 + frame[:payload].bytesize

  when :ping
    raise CompressionError, "Invalid payload size (#{frame[:payload].size} != 8 bytes)" if frame[:payload].bytesize != 8

    bytes << frame[:payload]
    length += 8

  when :goaway
    pack([frame[:last_stream] & RBIT], UINT32, buffer: bytes)
    pack_error(frame[:error], buffer: bytes)
    length += 8

    if frame[:payload]
      bytes << frame[:payload]
      length += frame[:payload].bytesize
    end

  when :window_update
    pack([frame[:increment] & RBIT], UINT32, buffer: bytes)
    length += 4

  when :continuation
    bytes << frame[:payload]
    length += frame[:payload].bytesize

  when :altsvc
    pack([frame[:max_age], frame[:port]], UINT32 + UINT16, buffer: bytes)
    length += 6
    if frame[:proto]
      raise CompressionError, "Proto too long" if frame[:proto].bytesize > 255

      pack([frame[:proto].bytesize], UINT8, buffer: bytes)
      bytes << frame[:proto]
      length += 1 + frame[:proto].bytesize
    else
      pack([0], UINT8, buffer: bytes)
      length += 1
    end
    if frame[:host]
      raise CompressionError, "Host too long" if frame[:host].bytesize > 255

      pack([frame[:host].bytesize], UINT8, buffer: bytes)
      bytes << frame[:host]
      length += 1 + frame[:host].bytesize
    else
      pack([0], UINT8, buffer: bytes)
      length += 1
    end
    if frame[:origin]
      bytes << frame[:origin]
      length += frame[:origin].bytesize
    end

  when :origin
    frame[:payload].each do |origin|
      pack([origin.bytesize], UINT16, buffer: bytes)
      bytes << origin
      length += 2 + origin.bytesize
    end

  end

  # Process padding.
  #  frame[:padding] gives number of extra octets to be added.
  # - http://tools.ietf.org/html/draft-ietf-httpbis-http2-16#section-6.1
  if frame[:padding]
    unless FRAME_TYPES_WITH_PADDING.include?(frame[:type])
      raise CompressionError, "Invalid padding flag for #{frame[:type]}"
    end

    padlen = frame[:padding]

    if padlen <= 0 || padlen > 256 || padlen + length > @remote_max_frame_size
      raise CompressionError, "Invalid padding #{padlen}"
    end

    length += padlen
    pack([padlen -= 1], UINT8, buffer: bytes, offset: 0)
    frame[:flags] << :padded

    # Padding:  Padding octets that contain no application semantic value.
    # Padding octets MUST be set to zero when sending and ignored when
    # receiving.
    bytes << ("\0" * padlen)
  end

  frame[:length] = length
  common_header(frame, buffer: bytes)
end

#parse(buf) ⇒ Object

Decodes complete HTTP/2 frame from provided buffer. If the buffer does not contain enough data, no further work is performed.

Parameters:

  • buf (Buffer)

Raises:



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# File 'lib/http/2/framer.rb', line 338

def parse(buf)
  return if buf.size < 9

  frame = read_common_header(buf)
  return if buf.size < 9 + frame[:length]

  raise ProtocolError, "payload too large" if frame[:length] > @local_max_frame_size

  read_str(buf, 9)
  payload = read_str(buf, frame[:length])

  # Implementations MUST discard frames
  # that have unknown or unsupported types.
  # - http://tools.ietf.org/html/draft-ietf-httpbis-http2-16#section-5.5
  return frame if frame[:type].nil?

  # Process padding
  padlen = 0
  if FRAME_TYPES_WITH_PADDING.include?(frame[:type])
    padded = frame[:flags].include?(:padded)
    if padded
      padlen = read_str(payload, 1).unpack1(UINT8)
      frame[:padding] = padlen + 1
      raise ProtocolError, "padding too long" if padlen > payload.bytesize

      payload = payload.byteslice(0, payload.bytesize - padlen) if padlen > 0
      frame[:length] -= frame[:padding]
      frame[:flags].delete(:padded)
    end
  end

  case frame[:type]
  when :data, :ping, :continuation
    frame[:payload] = read_str(payload, frame[:length])
  when :headers
    if frame[:flags].include? :priority
      e_sd = read_uint32(payload)
      frame[:dependency] = e_sd & RBIT
      frame[:exclusive] = e_sd.anybits?(EBIT)
      weight = payload.byteslice(0, 1).ord + 1
      frame[:weight] = weight
      payload = payload.byteslice(1..-1)
    end
    frame[:payload] = read_str(payload, frame[:length])
  when :priority
    raise FrameSizeError, "Invalid length for PRIORITY_STREAM (#{frame[:length]} != 5)" if frame[:length] != 5

    e_sd = read_uint32(payload)
    frame[:dependency] = e_sd & RBIT
    frame[:exclusive] = e_sd.anybits?(EBIT)
    weight = payload.byteslice(0, 1).ord + 1
    frame[:weight] = weight
    payload = payload.byteslice(1..-1)
  when :rst_stream
    raise FrameSizeError, "Invalid length for RST_STREAM (#{frame[:length]} != 4)" if frame[:length] != 4

    frame[:error] = unpack_error read_uint32(payload)

  when :settings
    # NOTE: frame[:length] might not match the number of frame[:payload]
    # because unknown extensions are ignored.
    frame[:payload] = []
    raise ProtocolError, "Invalid settings payload length" unless (frame[:length] % 6).zero?

    raise ProtocolError, "Invalid stream ID (#{frame[:stream]})" if (frame[:stream]).nonzero?

    (frame[:length] / 6).times do
      id  = read_str(payload, 2).unpack1(UINT16)
      val = read_uint32(payload)

      # Unsupported or unrecognized settings MUST be ignored.
      # Here we send it along.
      name, = DEFINED_SETTINGS.find { |_name, v| v == id }
      frame[:payload] << [name, val] if name
    end
  when :push_promise
    frame[:promise_stream] = read_uint32(payload) & RBIT
    frame[:payload] = read_str(payload, frame[:length])
  when :goaway
    frame[:last_stream] = read_uint32(payload) & RBIT
    frame[:error] = unpack_error read_uint32(payload)

    size = frame[:length] - 8 # for last_stream and error
    frame[:payload] = read_str(payload, size) if size > 0
  when :window_update
    if frame[:length] % 4 != 0
      raise FrameSizeError, "Invalid length for WINDOW_UPDATE (#{frame[:length]} not multiple of 4)"
    end

    frame[:increment] = read_uint32(payload) & RBIT
  when :altsvc
    frame[:max_age], frame[:port] = read_str(payload, 6).unpack(UINT32 + UINT16)

    len = payload.byteslice(0, 1).ord
    payload = payload.byteslice(1..-1)
    frame[:proto] = read_str(payload, len) if len > 0

    len = payload.byteslice(0, 1).ord
    payload = payload.byteslice(1..-1)
    frame[:host] = read_str(payload, len) if len > 0

    frame[:origin] = read_str(payload, payload.size) unless payload.empty?

  when :origin
    origins = []

    until payload.empty?
      len = read_str(payload, 2).unpack1(UINT16)
      origins << read_str(payload, len)
    end

    frame[:payload] = origins
    # else # Unknown frame type is explicitly allowed
  end

  frame
end

#read_common_header(buf) ⇒ Hash

Decodes common 9-byte header.

Parameters:

  • buf (Buffer)

Returns:

  • (Hash) —

    the corresponding frame



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# File 'lib/http/2/framer.rb', line 159

def read_common_header(buf)
  frame = {}
  len_hi, len_lo, type, flags, stream = buf.byteslice(0, 9).unpack(HEADERPACK)

  frame[:length] = (len_hi << FRAME_LENGTH_HISHIFT) | len_lo
  frame[:type], = FRAME_TYPES.find { |_t, pos| type == pos }
  if frame[:type]
    frame[:flags] = FRAME_FLAGS[frame[:type]].each_with_object([]) do |(name, pos), acc|
      acc << name if flags.anybits?((1 << pos))
    end
  end

  frame[:stream] = stream & RBIT
  frame
end