[issue28570] httplib mishandles unknown 1XX status codes

[Martin Panter]

Martin Panter added the comment:

Consuming and ignoring 1xx responses seems reasonable for general cases. 
Treating 101 (Switching Protocols) as a special case also seems reasonable.

I also agree it would be good to provide an API to return these responses (at 
least after the request is completely sent). Perhaps a new flag, 
c.getresponse(informational=True), or a new method, 
c.get_informational_response(timeout=...). The timeout is for servers that do 
not support “Expect: 100-continue” mode; see Issue 1346874.

There is also Issue 25919 discussing how to handle responses (including 1xx) 
while concurrently sending the request. That is a harder problem, but may be 
solvable with a few new APIs.

--
nosy: +martin.panter

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[issue28570] httplib mishandles unknown 1XX status codes

[Cory Benfield]

Cory Benfield added the comment:

101 should probably be special-cased, because in that case the underlying 
protocol is being totally changed.

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[issue28570] httplib mishandles unknown 1XX status codes

[SilentGhost]

SilentGhost added the comment:

The fix could be as small as the attached patched, though I'm not sure that is 
the correct way of handling 101 code.

--
keywords: +patch
nosy: +SilentGhost
Added file: http://bugs.python.org/file45296/28570.diff

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[issue28570] httplib mishandles unknown 1XX status codes

[Cory Benfield]

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'''

  

title


  
  
Hello, world!
  

'''

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: ; rel=preload; as=style\r\n'
b'Link: ; 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: ; rel=preload; as=style\r\n'
b'Link: ; 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', 
'; rel=preload; as=style'), ('Link', '; 
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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