Class: HTTP2::Framer

Inherits:
Object
  • Object
show all
Includes:
Error
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**14
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
}.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: {}
}.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

Constructor Details

#initialize ⇒ Framer

Initializes new framer object.



107
108
109
 
# File 'lib/http/2/framer.rb', line 107

def initialize
  @max_frame_size = DEFAULT_MAX_FRAME_SIZE
end

Instance Attribute Details

#max_frame_size ⇒ Object

Current maximum frame size



13
14
15
 
# File 'lib/http/2/framer.rb', line 13

def max_frame_size
  @max_frame_size
end

Instance Method Details

#common_header(frame) ⇒ String

Generates common 9-byte frame header.

Parameters:

  • frame (Hash)

Returns:

  • (String)

Raises:



116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
 
# File 'lib/http/2/framer.rb', line 116

def common_header(frame)
  header = []

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

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

  raise CompressionError, "Frame size is invalid: #{frame[:length]}" if (frame[:length]).negative?

  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

  header << (frame[:length] >> FRAME_LENGTH_HISHIFT)
  header << (frame[:length] & FRAME_LENGTH_LOMASK)
  header << FRAME_TYPES[frame[:type]]
  header << 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

  header << frame[:stream]
  header.pack(HEADERPACK) # 8+16,8,8,32
end

#generate(frame) ⇒ Object

Generates encoded HTTP/2 frame.

Parameters:

  • frame (Hash) 


168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
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
 
# File 'lib/http/2/framer.rb', line 168

def generate(frame)
  bytes  = Buffer.new
  length = 0

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

  case frame[:type]
  when :data
    bytes << frame[:payload]
    length += frame[:payload].bytesize

  when :headers
    if frame[:weight] || frame[:stream_dependency] || !frame[:exclusive].nil?
      unless frame[:weight] && frame[:stream_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
      bytes << [(frame[:exclusive] ? EBIT : 0) | (frame[:stream_dependency] & RBIT)].pack(UINT32)
      bytes << [frame[:weight] - 1].pack(UINT8)
      length += 5
    end

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

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

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

  when :rst_stream
    bytes << pack_error(frame[:error])
    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
        DEFINED_SETTINGS.value?(k) || next
      else
        k = DEFINED_SETTINGS[k]

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

      bytes << [k].pack(UINT16)
      bytes << [v].pack(UINT32)
      length += 6
    end

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

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

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

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

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

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

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

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

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

      bytes << [frame[:host].bytesize].pack(UINT8)
      bytes << frame[:host].force_encoding(Encoding::BINARY)
      length += 1 + frame[:host].bytesize
    else
      bytes << [0].pack(UINT8)
      length += 1
    end
    if frame[:origin]
      bytes << frame[:origin]
      length += frame[: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 > @max_frame_size
      raise CompressionError, "Invalid padding #{padlen}"
    end

    length += padlen
    bytes.prepend([padlen -= 1].pack(UINT8))
    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
  bytes.prepend(common_header(frame))
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:

Raises:



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
368
369
370
371
372
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
 
# File 'lib/http/2/framer.rb', line 320

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

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

  raise ProtocolError, 'payload too large' if frame[:length] > DEFAULT_MAX_FRAME_SIZE

  buf.read(9)
  payload = buf.read(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 nil if frame[:type].nil?

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

      payload.slice!(-padlen, padlen) if padlen.positive?
      frame[:length] -= frame[:padding]
      frame[:flags].delete(:padded)
    end
  end

  case frame[:type]
  when :data
    frame[:payload] = payload.read(frame[:length])
  when :headers
    if frame[:flags].include? :priority
      e_sd = payload.read_uint32
      frame[:stream_dependency] = e_sd & RBIT
      frame[:exclusive] = (e_sd & EBIT) != 0
      frame[:weight] = payload.getbyte + 1
    end
    frame[:payload] = payload.read(frame[:length])
  when :priority
    e_sd = payload.read_uint32
    frame[:stream_dependency] = e_sd & RBIT
    frame[:exclusive] = (e_sd & EBIT) != 0
    frame[:weight] = payload.getbyte + 1
  when :rst_stream
    frame[:error] = unpack_error payload.read_uint32

  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  = payload.read(2).unpack1(UINT16)
      val = payload.read_uint32

      # 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] = payload.read_uint32 & RBIT
    frame[:payload] = payload.read(frame[:length])
  when :ping
    frame[:payload] = payload.read(frame[:length])
  when :goaway
    frame[:last_stream] = payload.read_uint32 & RBIT
    frame[:error] = unpack_error payload.read_uint32

    size = frame[:length] - 8 # for last_stream and error
    frame[:payload] = payload.read(size) if size.positive?
  when :window_update
    frame[:increment] = payload.read_uint32 & RBIT
  when :continuation
    frame[:payload] = payload.read(frame[:length])
  when :altsvc
    frame[:max_age], frame[:port] = payload.read(6).unpack(UINT32 + UINT16)

    len = payload.getbyte
    frame[:proto] = payload.read(len) if len.positive?

    len = payload.getbyte
    frame[:host] = payload.read(len) if len.positive?

    frame[:origin] = payload.read(payload.size) unless payload.empty?
    # else # Unknown frame type is explicitly allowed
  end

  frame
end

#read_common_header(buf) ⇒ Object

Decodes common 9-byte header.

Parameters:



148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
 
# File 'lib/http/2/framer.rb', line 148

def read_common_header(buf)
  frame = {}
  len_hi, len_lo, type, flags, stream = buf.slice(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 & (1 << pos)).positive?
    end
  end

  frame[:stream] = stream & RBIT
  frame
end