h2 3.1.0

HTTP/2 State-Machine based protocol implementation

This repository contains a pure-Python implementation of a HTTP/2 protocol stack. It’s written from the ground up to be embeddable in whatever program you choose to use, ensuring that you can speak HTTP/2 regardless of your programming paradigm.

You use it like this:

import h2.connection

conn = h2.connection.H2Connection()
conn.send_headers(stream_id=stream_id, headers=headers)
conn.send_data(stream_id, data)
socket.sendall(conn.data_to_send())
events = conn.receive_data(socket_data)

This repository does not provide a parsing layer, a network layer, or any rules about concurrency. Instead, it’s a purely in-memory solution, defined in terms of data actions and HTTP/2 frames. This is one building block of a full Python HTTP implementation.

To install it, just run:

$ pip install h2

Documentation

Documentation is available at http://python-hyper.org/h2/.

Contributing

hyper-h2 welcomes contributions from anyone! Unlike many other projects we are happy to accept cosmetic contributions and small contributions, in addition to large feature requests and changes.

Before you contribute (either by opening an issue or filing a pull request), please read the contribution guidelines.

License

hyper-h2 is made available under the MIT License. For more details, see the LICENSE file in the repository.

Authors

hyper-h2 is maintained by Cory Benfield, with contributions from others. For more details about the contributors, please see CONTRIBUTORS.rst.

Release History

3.1.0 (2019-01-22)

API Changes (Backward-Incompatible)

• h2.connection.H2Connection.data_to_send first and only argument amt was renamed to amount.
• Support for Python 3.3 has been removed.

API Changes (Backward-Compatible)

• h2.connection.H2Connection.send_data now supports data parameter being a memoryview object.
• Refactor ping-related events: a h2.events.PingReceived event is fired when a PING frame is received and a h2.events.PingAckReceived event is fired when a PING frame with an ACK flag is received. h2.events.PingAcknowledged is deprecated in favour of the identical h2.events.PingAckReceived.
• Added ENABLE_CONNECT_PROTOCOL to h2.settings.SettingCodes.
• Support CONNECT requests with a :protocol pseudo header thereby supporting RFC 8441.
• A limit to the number of closed streams kept in memory by the connection is applied. It can be configured by h2.connection.H2Connection.MAX_CLOSED_STREAMS.

Bugfixes

• Debug logging when stream_id is None is now fixed and no longer errors.

3.0.1 (2017-04-03)

Bugfixes

• CONTINUATION frames sent on closed streams previously caused stream errors of type STREAM_CLOSED. RFC 7540 § 6.10 requires that these be connection errors of type PROTOCOL_ERROR, and so this release changes to match that behaviour.
• Remote peers incrementing their inbound connection window beyond the maximum allowed value now cause stream-level errors, rather than connection-level errors, allowing connections to stay up longer.
• h2 now rejects receiving and sending request header blocks that are missing any of the mandatory pseudo-header fields (:path, :scheme, and :method).
• h2 now rejects receiving and sending request header blocks that have an empty :path pseudo-header value.
• h2 now rejects receiving and sending request header blocks that contain response-only pseudo-headers, and vice versa.
• h2 now correct respects user-initiated changes to the HEADER_TABLE_SIZE local setting, and ensures that if users shrink or increase the header table size it is policed appropriately.

2.6.2 (2017-04-03)

Bugfixes

• CONTINUATION frames sent on closed streams previously caused stream errors of type STREAM_CLOSED. RFC 7540 § 6.10 requires that these be connection errors of type PROTOCOL_ERROR, and so this release changes to match that behaviour.
• Remote peers incrementing their inbound connection window beyond the maximum allowed value now cause stream-level errors, rather than connection-level errors, allowing connections to stay up longer.
• h2 now rejects receiving and sending request header blocks that are missing any of the mandatory pseudo-header fields (:path, :scheme, and :method).
• h2 now rejects receiving and sending request header blocks that have an empty :path pseudo-header value.
• h2 now rejects receiving and sending request header blocks that contain response-only pseudo-headers, and vice versa.
• h2 now correct respects user-initiated changes to the HEADER_TABLE_SIZE local setting, and ensures that if users shrink or increase the header table size it is policed appropriately.

2.5.4 (2017-04-03)

Bugfixes

• CONTINUATION frames sent on closed streams previously caused stream errors of type STREAM_CLOSED. RFC 7540 § 6.10 requires that these be connection errors of type PROTOCOL_ERROR, and so this release changes to match that behaviour.
• Remote peers incrementing their inbound connection window beyond the maximum allowed value now cause stream-level errors, rather than connection-level errors, allowing connections to stay up longer.
• h2 now correct respects user-initiated changes to the HEADER_TABLE_SIZE local setting, and ensures that if users shrink or increase the header table size it is policed appropriately.

3.0.0 (2017-03-24)

API Changes (Backward-Incompatible)

• By default, hyper-h2 now joins together received cookie header fields, per RFC 7540 Section 8.1.2.5.
• Added a normalize_inbound_headers flag to the H2Configuration object that defaults to True. Setting this to False changes the behaviour from the previous point back to the v2 behaviour.
• Removed deprecated fields from h2.errors module.
• Removed deprecated fields from h2.settings module.
• Removed deprecated client_side and header_encoding arguments from H2Connection.
• Removed deprecated client_side and header_encoding properties from H2Connection.
• dict objects are no longer allowed for user-supplied headers.
• The default header encoding is now None, not utf-8: this means that all events that carry headers now return those headers as byte strings by default. The header encoding can be set back to utf-8 to restore the old behaviour.

API Changes (Backward-Compatible)

• Added new UnknownFrameReceived event that fires when unknown extension frames have been received. This only fires when using hyperframe 5.0 or later: earlier versions of hyperframe cause us to silently ignore extension frames.

Bugfixes

None

2.6.1 (2017-03-16)

Bugfixes

• Allowed hyperframe v5 support while continuing to ignore unexpected frames.

2.5.3 (2017-03-16)

Bugfixes

• Allowed hyperframe v5 support while continuing to ignore unexpected frames.

2.4.4 (2017-03-16)

Bugfixes

• Allowed hyperframe v5 support while continuing to ignore unexpected frames.

2.6.0 (2017-02-28)

API Changes (Backward-Compatible)

• Added a new h2.events.Event class that acts as a base class for all events.
• Rather than reject outbound Connection-specific headers, h2 will now normalize the header block by removing them.
• Implement equality for the h2.settings.Settings class.
• Added h2.settings.SettingCodes, an enum that is used to store all the HTTP/2 setting codes. This allows us to use a better printed representation of the setting code in most places that it is used.
• The setting field in ChangedSetting for the RemoteSettingsChanged and SettingsAcknowledged events has been updated to be instances of SettingCodes whenever they correspond to a known setting code. When they are an unknown setting code, they are instead int. As SettingCodes is a subclass of int, this is non-breaking.
• Deprecated the other fields in h2.settings. These will be removed in 3.0.0.
• Added an optional pad_length parameter to H2Connection.send_data to allow the user to include padding on a data frame.
• Added a new parameter to the h2.config.H2Configuration initializer which takes a logger. This allows us to log by providing a logger that conforms to the requirements of this module so that it can be used in different environments.

Bugfixes

• Correctly reject pushed request header blocks whenever they have malformed request header blocks.
• Correctly normalize pushed request header blocks whenever they have normalizable header fields.
• Remote peers are now allowed to send zero or any positive number as a value for SETTINGS_MAX_HEADER_LIST_SIZE, where previously sending zero would raise a InvalidSettingsValueError.
• Resolved issue where the HTTP2-Settings header value for plaintext upgrade that was emitted by initiate_upgrade_connection included the entire SETTINGS frame, instead of just the payload.
• Resolved issue where the HTTP2-Settings header value sent by a client for plaintext upgrade would be ignored by initiate_upgrade_connection, rather than have those settings applied appropriately.
• Resolved an issue whereby certain frames received from a peer in the CLOSED state would trigger connection errors when RFC 7540 says they should have triggered stream errors instead. Added more detailed stream closure tracking to ensure we don’t throw away connections unnecessarily.

2.5.2 (2017-01-27)

• Resolved issue where the HTTP2-Settings header value for plaintext upgrade that was emitted by initiate_upgrade_connection included the entire SETTINGS frame, instead of just the payload.
• Resolved issue where the HTTP2-Settings header value sent by a client for plaintext upgrade would be ignored by initiate_upgrade_connection, rather than have those settings applied appropriately.

2.4.3 (2017-01-27)

• Resolved issue where the HTTP2-Settings header value for plaintext upgrade that was emitted by initiate_upgrade_connection included the entire SETTINGS frame, instead of just the payload.
• Resolved issue where the HTTP2-Settings header value sent by a client for plaintext upgrade would be ignored by initiate_upgrade_connection, rather than have those settings applied appropriately.

2.3.4 (2017-01-27)

• Resolved issue where the HTTP2-Settings header value for plaintext upgrade that was emitted by initiate_upgrade_connection included the entire SETTINGS frame, instead of just the payload.
• Resolved issue where the HTTP2-Settings header value sent by a client for plaintext upgrade would be ignored by initiate_upgrade_connection, rather than have those settings applied appropriately.

2.5.1 (2016-12-17)

Bugfixes

• Remote peers are now allowed to send zero or any positive number as a value for SETTINGS_MAX_HEADER_LIST_SIZE, where previously sending zero would raise a InvalidSettingsValueError.

2.5.0 (2016-10-25)

API Changes (Backward-Compatible)

• Added a new H2Configuration object that allows rich configuration of a H2Connection. This object supersedes the prior keyword arguments to the H2Connection object, which are now deprecated and will be removed in 3.0.
• Added support for automated window management via the acknowledge_received_data method. See the documentation for more details.
• Added a DenialOfServiceError that is raised whenever a behaviour that looks like a DoS attempt is encountered: for example, an overly large decompressed header list. This is a subclass of ProtocolError.
• Added support for setting and managing SETTINGS_MAX_HEADER_LIST_SIZE. This setting is now defaulted to 64kB.
• Added h2.errors.ErrorCodes, an enum that is used to store all the HTTP/2 error codes. This allows us to use a better printed representation of the error code in most places that it is used.
• The error_code fields on ConnectionTerminated and StreamReset events have been updated to be instances of ErrorCodes whenever they correspond to a known error code. When they are an unknown error code, they are instead int. As ErrorCodes is a subclass of int, this is non-breaking.
• Deprecated the other fields in h2.errors. These will be removed in 3.0.0.

Bugfixes

• Correctly reject request header blocks with neither :authority nor Host headers, or header blocks which contain mismatched :authority and Host headers, per RFC 7540 Section 8.1.2.3.

• Correctly expect that responses to HEAD requests will have no body regardless of the value of the Content-Length header, and reject those that do.

• Correctly refuse to send header blocks that contain neither :authority nor Host headers, or header blocks which contain mismatched :authority and Host headers, per RFC 7540 Section 8.1.2.3.

• Hyper-h2 will now reject header field names and values that contain leading or trailing whitespace.

• Correctly strip leading/trailing whitespace from header field names and values.

• Correctly refuse to send header blocks with a TE header whose value is not trailers, per RFC 7540 Section 8.1.2.2.

• Correctly refuse to send header blocks with connection-specific headers, per RFC 7540 Section 8.1.2.2.

• Correctly refuse to send header blocks that contain duplicate pseudo-header fields, or with pseudo-header fields that appear after ordinary header fields, per RFC 7540 Section 8.1.2.1.

  This may cause passing a dictionary as the header block to send_headers to throw a ProtocolError, because dictionaries are unordered and so they may trip this check. Passing dictionaries here is deprecated, and callers should change to using a sequence of 2-tuples as their header blocks.

• Correctly reject trailers that contain HTTP/2 pseudo-header fields, per RFC 7540 Section 8.1.2.1.

• Correctly refuse to send trailers that contain HTTP/2 pseudo-header fields, per RFC 7540 Section 8.1.2.1.

• Correctly reject responses that do not contain the :status header field, per RFC 7540 Section 8.1.2.4.

• Correctly refuse to send responses that do not contain the :status header field, per RFC 7540 Section 8.1.2.4.

• Correctly update the maximum frame size when the user updates the value of that setting. Prior to this release, if the user updated the maximum frame size hyper-h2 would ignore the update, preventing the remote peer from using the higher frame sizes.

2.4.2 (2016-10-25)

Bugfixes

• Correctly update the maximum frame size when the user updates the value of that setting. Prior to this release, if the user updated the maximum frame size hyper-h2 would ignore the update, preventing the remote peer from using the higher frame sizes.

2.3.3 (2016-10-25)

Bugfixes

• Correctly update the maximum frame size when the user updates the value of that setting. Prior to this release, if the user updated the maximum frame size hyper-h2 would ignore the update, preventing the remote peer from using the higher frame sizes.

2.2.7 (2016-10-25)

Final 2.2.X release

Bugfixes

• Correctly update the maximum frame size when the user updates the value of that setting. Prior to this release, if the user updated the maximum frame size hyper-h2 would ignore the update, preventing the remote peer from using the higher frame sizes.

2.4.1 (2016-08-23)

Bugfixes

• Correctly expect that responses to HEAD requests will have no body regardless of the value of the Content-Length header, and reject those that do.

2.3.2 (2016-08-23)

Bugfixes

• Correctly expect that responses to HEAD requests will have no body regardless of the value of the Content-Length header, and reject those that do.

2.4.0 (2016-07-01)

API Changes (Backward-Compatible)

• Adds additional_data to H2Connection.close_connection, allowing the user to send additional debug data on the GOAWAY frame.
• Adds last_stream_id to H2Connection.close_connection, allowing the user to manually control what the reported last stream ID is.
• Add new method: prioritize.
• Add support for emitting stream priority information when sending headers frames using three new keyword arguments: priority_weight, priority_depends_on, and priority_exclusive.
• Add support for “related events”: events that fire simultaneously on a single frame.

2.3.1 (2016-05-12)

Bugfixes

• Resolved AttributeError encountered when receiving more than one sequence of CONTINUATION frames on a given connection.

2.2.5 (2016-05-12)

Bugfixes

• Resolved AttributeError encountered when receiving more than one sequence of CONTINUATION frames on a given connection.

2.3.0 (2016-04-26)

API Changes (Backward-Compatible)

• Added a new flag to the H2Connection constructor: header_encoding, that controls what encoding is used (if any) to decode the headers from bytes to unicode. This defaults to UTF-8 for backward compatibility. To disable the decode and use bytes exclusively, set the field to False, None, or the empty string. This affects all headers, including those pushed by servers.
• Bumped the minimum version of HPACK allowed from 2.0 to 2.2.
• Added support for advertising RFC 7838 Alternative services.
• Allowed users to provide hpack.HeaderTuple and hpack.NeverIndexedHeaderTuple objects to all methods that send headers.
• Changed all events that carry headers to emit hpack.HeaderTuple and hpack.NeverIndexedHeaderTuple instead of plain tuples. This allows users to maintain header indexing state.
• Added support for plaintext upgrade with the initiate_upgrade_connection method.

Bugfixes

• Automatically ensure that all Authorization and Proxy-Authorization headers, as well as short Cookie headers, are prevented from being added to encoding contexts.

2.2.4 (2016-04-25)

Bugfixes

• Correctly forbid pseudo-headers that were not defined in RFC 7540.
• Ignore AltSvc frames, rather than exploding when receiving them.

2.1.5 (2016-04-25)

Final 2.1.X release

Bugfixes

• Correctly forbid pseudo-headers that were not defined in RFC 7540.
• Ignore AltSvc frames, rather than exploding when receiving them.

2.2.3 (2016-04-13)

Bugfixes

• Allowed the 4.X series of hyperframe releases as dependencies.

2.1.4 (2016-04-13)

Bugfixes

• Allowed the 4.X series of hyperframe releases as dependencies.

2.2.2 (2016-04-05)

Bugfixes

• Fixed issue where informational responses were erroneously not allowed to be sent in the HALF_CLOSED_REMOTE state.
• Fixed issue where informational responses were erroneously not allowed to be received in the HALF_CLOSED_LOCAL state.
• Fixed issue where we allowed information responses to be sent or received after final responses.

2.2.1 (2016-03-23)

Bugfixes

• Fixed issue where users using locales that did not default to UTF-8 were unable to install source distributions of the package.

2.2.0 (2016-03-23)

API Changes (Backward-Compatible)

• Added support for sending informational responses (responses with 1XX status) codes as part of the standard flow. HTTP/2 allows zero or more informational responses with no upper limit: hyper-h2 does too.
• Added support for receiving informational responses (responses with 1XX status) codes as part of the standard flow. HTTP/2 allows zero or more informational responses with no upper limit: hyper-h2 does too.
• Added a new event: ReceivedInformationalResponse. This response is fired when informational responses (those with 1XX status codes).
• Added an additional_data field to the ConnectionTerminated event that carries any additional data sent on the GOAWAY frame. May be None if no such data was sent.
• Added the initial_values optional argument to the Settings object.

Bugfixes

• Correctly reject all of the connection-specific headers mentioned in RFC 7540 § 8.1.2.2, not just the Connection: header.
• Defaulted the value of SETTINGS_MAX_CONCURRENT_STREAMS to 100, unless explicitly overridden. This is a safe defensive initial value for this setting.

2.1.3 (2016-03-16)

Deprecations

• Passing dictionaries to send_headers as the header block is deprecated, and will be removed in 3.0.

2.1.2 (2016-02-17)

Bugfixes

• Reject attempts to push streams on streams that were themselves pushed: streams can only be pushed on streams that were initiated by the client.

• Correctly allow CONTINUATION frames to extend the header block started by a PUSH_PROMISE frame.

• Changed our handling of frames received on streams that were reset by the user.

  Previously these would, at best, cause ProtocolErrors to be raised and the connection to be torn down (rather defeating the point of resetting streams at all) and, at worst, would cause subtle inconsistencies in state between hyper-h2 and the remote peer that could lead to header block decoding errors or flow control blockages.

  Now when the user resets a stream all further frames received on that stream are ignored except where they affect some form of connection-level state, where they have their effect and are then ignored.

• Fixed a bug whereby receiving a PUSH_PROMISE frame on a stream that was closed would cause a RST_STREAM frame to be emitted on the closed-stream, but not the newly-pushed one. Now this causes a ProtocolError.

2.1.1 (2016-02-05)

Bugfixes

• Added debug representations for all events.
• Fixed problems with setup.py that caused trouble on older setuptools/pip installs.

2.1.0 (2016-02-02)

API Changes (Backward-Compatible)

• Added new field to DataReceived: flow_controlled_length. This is the length of the frame including padded data, allowing users to correctly track changes to the flow control window.
• Defined new UnsupportedFrameError, thrown when frames that are known to hyperframe but not supported by hyper-h2 are received. For backward-compatibility reasons, this is a ProtocolError and a KeyError.

Bugfixes

• Hyper-h2 now correctly accounts for padding when maintaining flow control windows.
• Resolved a bug where hyper-h2 would mistakenly apply SETTINGS_INITIAL_WINDOW_SIZE to the connection flow control window in addition to the stream-level flow control windows.
• Invalid Content-Length headers now throw ProtocolError exceptions and correctly tear the connection down, instead of leaving the connection in an indeterminate state.
• Invalid header blocks now throw ProtocolError, rather than a grab bag of possible other exceptions.

2.0.0 (2016-01-25)

API Changes (Breaking)

• Attempts to open streams with invalid stream IDs, either by the remote peer or by the user, are now rejected as a ProtocolError. Previously these were allowed, and would cause remote peers to error.

• Receiving frames that have invalid padding now causes the connection to be terminated with a ProtocolError being raised. Previously these passed undetected.

• Settings values set by both the user and the remote peer are now validated when they’re set. If they’re invalid, a new InvalidSettingsValueError is raised and, if set by the remote peer, a connection error is signaled. Previously, it was possible to set invalid values. These would either be caught when building frames, or would be allowed to stand.

• Settings changes no longer require user action to be acknowledged: hyper-h2 acknowledges them automatically. This moves the location where some exceptions may be thrown, and also causes the acknowledge_settings method to be removed from the public API.

• Removed a number of methods on the H2Connection object from the public, semantically versioned API, by renaming them to have leading underscores. Specifically, removed:

  • get_stream_by_id
  • get_or_create_stream
  • begin_new_stream
  • receive_frame
  • acknowledge_settings

• Added full support for receiving CONTINUATION frames, including policing logic about when and how they are received. Previously, receiving CONTINUATION frames was not supported and would throw exceptions.

• All public API functions on H2Connection except for receive_data no longer return lists of events, because these lists were always empty. Events are now only raised by receive_data.

• Calls to increment_flow_control_window with out of range values now raise ValueError exceptions. Previously they would be allowed, or would cause errors when serializing frames.

API Changes (Backward-Compatible)

• Added PriorityUpdated event for signaling priority changes.
• Added get_next_available_stream_id function.
• Receiving DATA frames on streams not in the OPEN or HALF_CLOSED_LOCAL states now causes a stream reset, rather than a connection reset. The error is now also classified as a StreamClosedError, rather than a more generic ProtocolError.
• Receiving HEADERS or PUSH_PROMISE frames in the HALF_CLOSED_REMOTE state now causes a stream reset, rather than a connection reset.
• Receiving frames that violate the max frame size now causes connection errors with error code FRAME_SIZE_ERROR, not a generic PROTOCOL_ERROR. This condition now also raises a FrameTooLargeError, a new subclass of ProtocolError.
• Made NoSuchStreamError a subclass of ProtocolError.
• The StreamReset event is now also fired whenever a protocol error from the remote peer forces a stream to close early. This is only fired once.
• The StreamReset event now carries a flag, remote_reset, that is set to True in all cases where StreamReset would previously have fired (e.g. when the remote peer sent a RST_STREAM), and is set to False when it fires because the remote peer made a protocol error.
• Hyper-h2 now rejects attempts by peers to increment a flow control window by zero bytes.
• Hyper-h2 now rejects peers sending header blocks that are ill-formed for a number of reasons as set out in RFC 7540 Section 8.1.2.
• Attempting to send non-PRIORITY frames on closed streams now raises StreamClosedError.
• Remote peers attempting to increase the flow control window beyond 2**31 - 1, either by window increment or by settings frame, are now rejected as ProtocolError.
• Local attempts to increase the flow control window beyond 2**31 - 1 by window increment are now rejected as ProtocolError.
• The bytes that represent individual settings are now available in h2.settings, instead of needing users to import them from hyperframe.

Bugfixes

• RFC 7540 requires that a separate minimum stream ID be used for inbound and outbound streams. Hyper-h2 now obeys this requirement.
• Hyper-h2 now does a better job of reporting the last stream ID it has partially handled when terminating connections.
• Fixed an error in the arguments of StreamIDTooLowError.
• Prevent ValueError leaking from Hyperframe.
• Prevent struct.error and InvalidFrameError leaking from Hyperframe.

1.1.1 (2015-11-17)

Bugfixes

• Forcibly lowercase all header names to improve compatibility with implementations that demand lower-case header names.

1.1.0 (2015-10-28)

API Changes (Backward-Compatible)

• Added a new ConnectionTerminated event, which fires when GOAWAY frames are received.
• Added a subclass of NoSuchStreamError, called StreamClosedError, that fires when actions are taken on a stream that is closed and has had its state flushed from the system.
• Added StreamIDTooLowError, raised when the user or the remote peer attempts to create a stream with an ID lower than one previously used in the dialog. Inherits from ValueError for backward-compatibility reasons.

Bugfixes

• Do not throw ProtocolError when attempting to send multiple GOAWAY frames on one connection.
• We no longer forcefully change the decoder table size when settings changes are ACKed, instead waiting for remote acknowledgement of the change.
• Improve the performance of checking whether a stream is open.
• We now attempt to lazily garbage collect closed streams, to avoid having the state hang around indefinitely, leaking memory.
• Avoid further per-stream allocations, leading to substantial performance improvements when many short-lived streams are used.

1.0.0 (2015-10-15)

• First production release!