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_BY_NAME = 
FRAME_TYPES.invert.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

#append_str, #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.



118
119
120
121
122
 
# File 'lib/http/2/framer.rb', line 118

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



15
16
17
 
# 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



15
16
17
 
# 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:



130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
 
# File 'lib/http/2/framer.rb', line 130

def common_header(frame, buffer:)
  type = frame[:type]

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

  length = frame[:length]

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

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

  stream_id = frame.fetch(:stream, 0)

  raise CompressionError, "Stream ID (#{stream_id}) is too large" if stream_id > MAX_STREAM_ID

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

  header = buffer

  # make sure the buffer is binary and unfrozen
  if buffer.frozen?
    header = String.new("", encoding: Encoding::BINARY, capacity: buffer.bytesize + 9) # header length
    append_str(header, buffer)
  else
    header.force_encoding(Encoding::BINARY)
  end

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

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

#generate(frame) ⇒ Object

Generates encoded HTTP/2 frame.

Parameters:

  • frame (Hash) 


199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
 
# File 'lib/http/2/framer.rb', line 199

def generate(frame)
  length = 0
  frame[:flags] ||= EMPTY

  case frame[:type]
  when :data, :continuation
    bytes = frame[:payload]
    length = bytes.bytesize

  when :headers
    headers = frame[:payload]

    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)
      length = 5 + headers.bytesize
      bytes = String.new("", encoding: Encoding::BINARY, capacity: length)
      pack([(frame[:exclusive] ? EBIT : 0) | (frame[:dependency] & RBIT)], UINT32, buffer: bytes)
      pack([frame[:weight] - 1], UINT8, buffer: bytes)
      append_str(bytes, headers)
    else
      length = headers.bytesize
      bytes = headers
    end

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

    length = 5
    bytes = String.new("", encoding: Encoding::BINARY, capacity: length)
    pack([(frame[:exclusive] ? EBIT : 0) | (frame[:dependency] & RBIT)], UINT32, buffer: bytes)
    pack([frame[:weight] - 1], UINT8, buffer: bytes)

  when :rst_stream
    length = 4
    bytes = String.new("", encoding: Encoding::BINARY, capacity: length)
    pack_error(frame[:error], buffer: bytes)

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

    settings = frame[:payload]
    bytes = String.new("", encoding: Encoding::BINARY, capacity: length)

    settings.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
    length = 4 + frame[:payload].bytesize
    bytes = String.new("", encoding: Encoding::BINARY, capacity: length)
    pack([frame[:promise_stream] & RBIT], UINT32, buffer: bytes)
    append_str(bytes, frame[:payload])

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

    length = 8

  when :goaway
    data = frame[:payload]
    length = 8
    length += data.bytesize if data
    bytes = String.new("", encoding: Encoding::BINARY, capacity: length)

    pack([frame[:last_stream] & RBIT], UINT32, buffer: bytes)
    pack_error(frame[:error], buffer: bytes)

    append_str(bytes, data) if data

  when :window_update
    length = 4
    bytes = String.new("", encoding: Encoding::BINARY, capacity: length)
    pack([frame[:increment] & RBIT], UINT32, buffer: bytes)

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

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

  when :origin
    origins = frame[:payload]
    length = origins.sum(&:bytesize) + (2 * origins.size)
    bytes = String.new("", encoding: Encoding::BINARY, capacity: length)
    origins.each do |origin|
      pack([origin.bytesize], UINT16, buffer: bytes)
      append_str(bytes, origin)
    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

    # make sure the buffer is binary and unfrozen
    if bytes.frozen?
      bytes = bytes.b
    else
      bytes.force_encoding(Encoding::BINARY)
    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.
    append_str(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:



373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
403
404
405
406
407
408
409
410
411
412
413
414
415
416
417
418
419
420
421
422
423
424
425
426
427
428
429
430
431
432
433
434
435
436
437
438
439
440
441
442
443
444
445
446
447
448
449
450
451
452
453
454
455
456
457
458
459
460
461
462
463
464
465
466
467
468
469
470
471
472
473
474
475
476
477
478
479
480
481
482
483
484
485
486
487
488
489
490
491
492
 
# File 'lib/http/2/framer.rb', line 373

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

  frame = read_common_header(buf)

  type = frame[:type]
  length = frame[:length]
  flags = frame[:flags]

  return if buf.size < 9 + length

  raise ProtocolError, "payload too large" if length > @local_max_frame_size

  read_str(buf, 9)
  payload = read_str(buf, 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 unless type

  # Process padding
  padlen = 0
  if FRAME_TYPES_WITH_PADDING.include?(type)
    padded = 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]
      flags.delete(:padded)
    end
  end

  case type
  when :data, :ping, :continuation
    frame[:payload] = read_str(payload, length)
  when :headers
    if 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, length)
  when :priority
    raise FrameSizeError, "Invalid length for PRIORITY_STREAM (#{length} != 5)" if 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 (#{length} != 4)" if 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 (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, length)
  when :goaway
    frame[:last_stream] = read_uint32(payload) & RBIT
    frame[:error] = unpack_error read_uint32(payload)

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

    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



177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
 
# File 'lib/http/2/framer.rb', line 177

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

  type = FRAME_TYPES_BY_NAME[type]
  length = (len_hi << FRAME_LENGTH_HISHIFT) | len_lo

  return { length: length } unless type

  {
    type: type,
    flags: FRAME_FLAGS[type].filter_map do |name, pos|
      name if flags.anybits?((1 << pos))
    end,
    length: length,
    stream: stream & RBIT
  }
end