[New-bugs-announce] [issue28570] httplib mishandles unknown 1XX status codes

Mon Oct 31 15:51:23 EDT 2016

New submission from Cory Benfield:

Long story short
~~~~~~~~~~~~~~~~

http.client does not tolerate non-100 or 101 status codes from the 1XX block in a sensible manner: it treats them as final responses, rather than as provisional ones.

Expected behaviour
~~~~~~~~~~~~~~~~~~

When http.client receives a 1XX status code that it does not recognise, it should either surface these to a user that expects them by means of a callback, or it should ignore them and only show the user the eventual final status code. This is required by RFC 7231 Section 6.2 (Informational 1xx), which reads:

> A client MUST be able to parse one or more 1xx responses received prior to a final response, even if the client does not expect one. A user agent MAY ignore unexpected 1xx responses.

Actual behaviour
~~~~~~~~~~~~~~~~

http.client treats the 1XX status code as final. It parses the header block as though it were a response in the 2XX or higher range. http.client will assume that there is no content in the 1XX response, and so will leave the following final response unconsumed in the socket buffer. This means that if the HTTPConnection is re-used, the user will see the final response following the 1XX as the response to the next request, even though it is not.

Steps to reproduce
~~~~~~~~~~~~~~~~~~

The following "server" can demonstrate the issue:

import socket
import time

document = b'''<!DOCTYPE html>
<html lang="en">
  <head>
    <meta charset="utf-8">
    <title>title</title>
    <link rel="stylesheet" href="/other/styles.css">
    <script src="/other/action.js"></script>
  </head>
  <body>
    <h1>Hello, world!</h1>
  </body>
</html>
'''

s = socket.socket()
s.setsockopt(socket.SOL_SOCKET, socket.SO_REUSEADDR, 1)
s.bind(('localhost', 8080))
s.listen(5)

while True:
    new_socket, _ = s.accept()
    data = b''

    while not data.endswith(b'\r\n\r\n'):
        data += new_socket.recv(8192)

    new_socket.sendall(
        b'HTTP/1.1 103 Early Hints\r\n'
        b'Server: socketserver/1.0.0\r\n'
        b'Link: </other/styles.css>; rel=preload; as=style\r\n'
        b'Link: </other/action.js>; rel=preload; as=script\r\n'
        b'\r\n'
    )
    time.sleep(1)
    new_socket.sendall(
        b'HTTP/1.1 200 OK\r\n'
        b'Server: socketserver/1.0.0\r\n'
        b'Content-Type: text/html\r\n'
        b'Content-Length: %s\r\n'
        b'Link: </other/styles.css>; rel=preload; as=style\r\n'
        b'Link: </other/action.js>; rel=preload; as=script\r\n'
        b'Connection: close\r\n'
        b'\r\n' % len(document)
    )
    new_socket.sendall(document)
    new_socket.close()

If this server is run directly, the following client can be used to test it:

from http.client import HTTPConnection

c = HTTPConnection('localhost', 8080)
c.request('GET', '/')
r = c.getresponse()

print("Status: {} {}".format(r.status, r.reason))
print("Headers: {}".format(r.getheaders()))
print("Body: {}".format(r.read()))

This client will print

Status: 103 Early Hints
Headers: [('Content-Length', '0'), ('Server', 'socketserver/1.0.0'), ('Link', '</other/styles.css>; rel=preload; as=style'), ('Link', '</other/action.js>; rel=preload; as=script')]
Body: b''

This response is wrong: the 200 header block is hidden from the client. Unfortunately, http.client doesn't allow us to ask for the next response: another call to "getresponse()" raises a "ResponseNotReady: Idle" exception.

----------
components: Library (Lib)
messages: 279823
nosy: Lukasa
priority: normal
severity: normal
status: open
title: httplib mishandles unknown 1XX status codes
type: behavior
versions: Python 3.7

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Python tracker <report at bugs.python.org>
<http://bugs.python.org/issue28570>
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