httpx cannot process http/1.1 responses with headers and body delimited by \n\n or \n\n\n\n (but requests can)

[cdeler]

Checklist

• [x] The bug is reproducible against the latest release and/or master.
• [x] There are no similar issues or pull requests to fix it yet.

Describe the bug

httpcore treats an http/1.1 response with Headers and Body delimited by \n\n as invalid

To reproduce

server code

Just run this socket-based server and run the client

```python
import datetime

import locale

import socket

locale.setlocale(locale.LC_TIME, "en_US")

full_response = """HTTP/1.1 200 OK\r
Date: {right_now}\r
Accept-Ranges: bytes\r
Connection: close\r
Content-type: text/plain

Some body\r\n"""

if __name__ == "__main__":
sock = socket.socket(socket.AF_INET, socket.SOCK_STREAM)

try:
sock.bind(("127.0.0.1", 8080))
sock.listen(5)

  print(f"Started server on http://127.0.0.1:8080/")

  (conn, addr) = sock.accept()

  try:
      data = conn.recv(4096)
      print(f"income> {data}")

      right_now = datetime.datetime.utcnow().strftime(
          "%a, %d %b %Y %H:%M:%S GMT"
      )

      full_response = full_response.format(right_now=right_now)
      conn.send(full_response.encode())
  finally:
      conn.close()

finally:
sock.detach()

```

# client code

with httpx.Client() as client:
    client.get("http://localhost:8080/")

Expected behavior

The client above should work as the following

s = requests.Session()
s.get("http://localhost:8080/)

or the curl snippet:

$ curl -v http://localhost:8080/

Actual behavior

httpx client fails with an error

stacktrace

```
/Users/krotose1/.pyenv/versions/httpx/bin/python /Users/krotose1/workspace/skv/httpx/wotk_with_bugs.py
Traceback (most recent call last):
File "/Users/krotose1/workspace/skv/httpx/httpx/_exceptions.py", line 326, in map_exceptions
yield
File "/Users/krotose1/workspace/skv/httpx/httpx/_client.py", line 861, in _send_single_request
(status_code, headers, stream, ext) = transport.request(
File "/Users/krotose1/workspace/skv/httpcore/httpcore/_sync/connection_pool.py", line 218, in request
response = connection.request(
File "/Users/krotose1/workspace/skv/httpcore/httpcore/_sync/connection.py", line 105, in request
return self.connection.request(method, url, headers, stream, ext)
File "/Users/krotose1/workspace/skv/httpcore/httpcore/_sync/http11.py", line 72, in request
) = self._receive_response(timeout)
File "/Users/krotose1/workspace/skv/httpcore/httpcore/_sync/http11.py", line 131, in _receive_response
event = self._receive_event(timeout)
File "/Users/krotose1/workspace/skv/httpcore/httpcore/_sync/http11.py", line 167, in _receive_event
event = self.h11_state.next_event()
File "/Users/krotose1/.pyenv/versions/3.8.5/lib/python3.8/contextlib.py", line 131, in __exit__
self.gen.throw(type, value, traceback)
File "/Users/krotose1/workspace/skv/httpcore/httpcore/_exceptions.py", line 12, in map_exceptions
raise to_exc(exc) from None
httpcore.RemoteProtocolError: peer unexpectedly closed connection

The above exception was the direct cause of the following exception:

Traceback (most recent call last):
File "/Users/krotose1/workspace/skv/httpx/wotk_with_bugs.py", line 11, in
resp = client.get("http://127.0.0.1:8080")
File "/Users/krotose1/workspace/skv/httpx/httpx/_client.py", line 907, in get
return self.request(
File "/Users/krotose1/workspace/skv/httpx/httpx/_client.py", line 733, in request
return self.send(
File "/Users/krotose1/workspace/skv/httpx/httpx/_client.py", line 767, in send
response = self._send_handling_auth(
File "/Users/krotose1/workspace/skv/httpx/httpx/_client.py", line 805, in _send_handling_auth
response = self._send_handling_redirects(
File "/Users/krotose1/workspace/skv/httpx/httpx/_client.py", line 837, in _send_handling_redirects
response = self._send_single_request(request, timeout)
File "/Users/krotose1/workspace/skv/httpx/httpx/_client.py", line 861, in _send_single_request
(status_code, headers, stream, ext) = transport.request(
File "/Users/krotose1/.pyenv/versions/3.8.5/lib/python3.8/contextlib.py", line 131, in __exit__
self.gen.throw(type, value, traceback)
File "/Users/krotose1/workspace/skv/httpx/httpx/_exceptions.py", line 343, in map_exceptions
raise mapped_exc(message, **kwargs) from exc # type: ignore
httpx.RemoteProtocolError: peer unexpectedly closed connection

Process finished with exit code 1

```

Debugging material

The pcap file from this comment contains an original request-response, used to investigate this ticket

Hexdump of original requests-response

```
00000000 47 45 54 20 2f 61 78 69 73 2d 63 67 69 2f 70 77 GET /axi s-cgi/pw
00000010 64 67 72 70 2e 63 67 69 3f 61 63 74 69 6f 6e 3d dgrp.cgi ?action=
00000020 67 65 74 20 48 54 54 50 2f 31 2e 31 0d 0a 48 6f get HTTP /1.1..Ho
00000030 73 74 3a 20 31 30 2e 30 2e 30 2e 32 35 34 0d 0a st: 10.0 .0.254..
00000040 55 73 65 72 2d 41 67 65 6e 74 3a 20 70 79 74 68 User-Age nt: pyth
00000050 6f 6e 2d 72 65 71 75 65 73 74 73 2f 32 2e 32 34 on-reque sts/2.24
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00000090 0a 43 6f 6e 6e 65 63 74 69 6f 6e 3a 20 6b 65 65 .Connect ion: kee
000000A0 70 2d 61 6c 69 76 65 0d 0a 41 75 74 68 6f 72 69 p-alive. .Authori
000000B0 7a 61 74 69 6f 6e 3a 20 44 69 67 65 73 74 20 75 zation: Digest u
000000C0 73 65 72 6e 61 6d 65 3d 22 72 6f 6f 74 22 2c 20 sername= "root",
000000D0 72 65 61 6c 6d 3d 22 41 58 49 53 5f 30 30 34 30 realm="A XIS_0040
000000E0 38 43 41 43 43 35 41 34 22 2c 20 6e 6f 6e 63 65 8CACC5A4 ", nonce
000000F0 3d 22 30 30 30 30 31 32 38 66 59 37 39 37 38 39 ="000012 8fY79789
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000001A0 33 35 38 62 61 39 39 38 39 22 0d 0a 0d 0a 358ba998 9"....
00000000 48 54 54 50 2f 31 2e 31 20 32 30 30 20 4f 4b 0d HTTP/1.1 200 OK.
00000010 0a 58 2d 46 72 61 6d 65 2d 4f 70 74 69 6f 6e 73 .X-Frame -Options
00000020 3a 20 73 61 6d 65 6f 72 69 67 69 6e 0d 0a 44 61 : sameor igin..Da
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00000040 32 30 32 30 20 31 31 3a 33 37 3a 34 30 20 47 4d 2020 11: 37:40 GM
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000002F9 6e 74 22 0a 67 70 69 6f 3d 22 69 6f 64 2c 6c 65 nt".gpio ="iod,le
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00000669 73 3d 22 72 6f 6f 74 22 0d 0a s="root" ..

```

As you can see, here is \n\n delimiter between headers and body
00000100 74 2f 70 6c 61 69 6e 0a 0a t/plain. .

Environment

• OS: OS X
• Python version: Python 3.8.5
• HTTPX version: 0.16.1 (from 07229b8dff61d3e9d819244d4835f547cae67b4d)

Additional context

You can check https://github.com/Kane610/axis/issues/55 for more details and pcap files

[cdeler]

I found the rule how http/1.1 should determine the length of response: link

As the server response contains Connection: close header, we probably could use this rule:

When a message-body is included with a message, the transfer-length of that body is determined by one of the following (in order of precedence):
...
5.By the server closing the connection. (Closing the connection cannot be used to indicate the end of a request body, since that would leave no possibility for the server to send back a response.)

[cdeler]

New investigations

Trying to limit the "server code" snippet I found that the server response seems a bit malformed:

Server response hexdump

00000000 48 54 54 50 2f 31 2e 31 20 32 30 30 20 4f 4b 0d HTTP/1.1 200 OK. 00000010 0a 44 61 74 65 3a 20 54 75 65 2c 20 30 33 20 4e .Date: T ue, 03 N 00000020 6f 76 20 32 30 32 30 20 31 30 3a 31 30 3a 35 35 ov 2020 10:10:55 00000030 20 47 4d 54 0d 0a 41 63 63 65 70 74 2d 52 61 6e GMT..Ac cept-Ran 00000040 67 65 73 3a 20 62 79 74 65 73 0d 0a 43 6f 6e 6e ges: byt es..Conn 00000050 65 63 74 69 6f 6e 3a 20 63 6c 6f 73 65 0d 0a 41 ection: close..A 00000060 75 74 68 65 6e 74 69 63 61 74 69 6f 6e 2d 49 6e uthentic ation-In 00000070 66 6f 3a 20 71 6f 70 3d 61 75 74 68 2c 20 72 73 fo: qop= auth, rs 00000080 70 61 75 74 68 3d 22 34 31 38 65 30 33 66 65 39 pauth="4 18e03fe9 00000090 63 38 36 63 34 32 63 32 30 64 61 61 62 32 38 37 c86c42c2 0daab287 000000A0 61 32 35 31 62 38 33 22 2c 20 63 6e 6f 6e 63 65 a251b83" , cnonce 000000B0 3d 22 37 33 31 34 63 38 39 63 32 61 37 62 64 62 ="7314c8 9c2a7bdb 000000C0 37 36 22 2c 20 6e 63 3d 30 30 30 30 30 30 30 31 76", nc= 00000001 000000D0 0d 0a 43 6f 6e 74 65 6e 74 2d 74 79 70 65 3a 20 ..Conten t-type: 000000E0 74 65 78 74 2f 70 6c 61 69 6e 0a 0a text/pla in.. 000000EC 72 6f 6f 74 3d 22 72 6f 6f 74 22 0d 0a 62 69 6e root="ro ot"..bin 000000FC 3d 22 72 6f 6f 74 2c 62 69 6e 2c 64 61 65 6d 6f ="root,b in,daemo 0000010C 6e 22 0d 0a 64 61 65 6d 6f 6e 3d 22 72 6f 6f 74 n"..daem on="root

As you can see, headers and body are delimited using 0a 0a ~ \n\n instead of CRLF sequence

Having found that I tuned up the server snippet, and got that the following server caused the httpx exception:

bad_server.py

```python
import datetime

import locale

import socket

locale.setlocale(locale.LC_TIME, "en_US")

full_response = """HTTP/1.1 200 OK\r
Date: {right_now}\r
Accept-Ranges: bytes\r
Connection: close\r
Content-type: text/plain

Some body\r\n"""

if __name__ == "__main__":
sock = socket.socket(socket.AF_INET, socket.SOCK_STREAM)

try:
    sock.bind(("127.0.0.1", 8080))
    sock.listen(5)

    print(f"Started server on http://127.0.0.1:8080/")

    (conn, addr) = sock.accept()

    try:
        data = conn.recv(4096)
        print(f"income> {data}")

        right_now = datetime.datetime.utcnow().strftime(
            "%a, %d %b %Y %H:%M:%S GMT"
        )

        full_response = full_response.format(right_now=right_now)
        conn.send(full_response.encode())
    finally:
        conn.close()

finally:
    sock.detach()

```

but the following is accepted by httpx:

good_server.py

```python
import datetime

import locale

import socket

locale.setlocale(locale.LC_TIME, "en_US")

full_response = """HTTP/1.1 200 OK\r
Date: {right_now}\r
Accept-Ranges: bytes\r
Connection: close\r
Content-type: text/plain\r
\r
Some body\r\n"""

if __name__ == "__main__":
sock = socket.socket(socket.AF_INET, socket.SOCK_STREAM)

try:
    sock.bind(("127.0.0.1", 8080))
    sock.listen(5)

    print(f"Started server on http://127.0.0.1:8080/")

    (conn, addr) = sock.accept()

    try:
        data = conn.recv(4096)
        print(f"income> {data}")

        right_now = datetime.datetime.utcnow().strftime(
            "%a, %d %b %Y %H:%M:%S GMT"
        )

        full_response = full_response.format(right_now=right_now)
        conn.send(full_response.encode())
    finally:
        conn.close()

finally:
    sock.detach()

```

What the difference?

In bad_server.py headers and body are delimited by \n\n (\n\n\n\n raises exception too) whereas in good_server.py the \r\n\r\n is used to that.

rfc2616 says that

[request and response] ... consist of a start-line, zero or more header fields (also known as "headers"), an empty line (i.e., a line with nothing preceding the CRLF) indicating the end of the header fields, and possibly a message-body.

so looks like the server violates this rule. The only thing which is worrying me is curl and requests accepts \n\n as a delimiter

[cdeler]

I found this issue in h11: https://github.com/python-hyper/h11/issues/7

That's what we might expect from h11 to make https://github.com/encode/httpx/issues/1378 fixed. On other hand, looks like the server violates rfc.

[tomchristie]

I'm a little confused here, since the description...

httpcore treat http/1.1 response without neither Content-Length nor chunked encoding as invalid, whereas requests and curl successfully read the response

Doesn't seem to match the title?...

httpx cannot process http/1.1 responses with headers and body delimited by \n\n or \n\n\n\n

[tomchristie]

Also it would be helpful to be a little more careful with the wording, in your comment here...

I found this bug in h11: https://github.com/python-hyper/h11/issues/7

We shouldn't rightly describe that as a "bug" in any sense - h11 is doing the correct thing, it's the non-spec-compliant servers that have the bug. It would be more correct to describe it as an "open issue" to determine if h11 ought to deal with their broken behaviour or not. 🙂

[cdeler]

You are right. Having added new comments and updated the title, I forget to update the original issue description

Also it would be helpful to be a little more careful with the wording, in your comment here...

yes. I didn't want to offend anyone, I have got confused with the words. Having said "a bug" I meant "an issue in the tracker"