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Bad BaseHTTPRequestHandler response when using HTTP/0.9 #70765
Description
| BPO | 26578 |
|---|---|
| Nosy | @warsaw, @gpshead, @vadmium, @zhangyangyu |
| Dependencies | |
| Files |
Note: these values reflect the state of the issue at the time it was migrated and might not reflect the current state.
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GitHub fields:
assignee = None
closed_at = None
created_at = <Date 2016-03-17.07:42:36.782>
labels = ['type-bug', 'library']
title = 'Bad BaseHTTPRequestHandler response when using HTTP/0.9'
updated_at = <Date 2016-10-29.11:19:59.882>
user = 'https://github.com/zhangyangyu'bugs.python.org fields:
activity = <Date 2016-10-29.11:19:59.882>
actor = 'xiang.zhang'
assignee = 'none'
closed = False
closed_date = None
closer = None
components = ['Library (Lib)']
creation = <Date 2016-03-17.07:42:36.782>
creator = 'xiang.zhang'
dependencies = ['10721']
files = ['45257']
hgrepos = []
issue_num = 26578
keywords = ['patch']
message_count = 6.0
messages = ['261898', '261899', '261949', '261952', '279642', '279671']
nosy_count = 4.0
nosy_names = ['barry', 'gregory.p.smith', 'martin.panter', 'xiang.zhang']
pr_nums = []
priority = 'normal'
resolution = None
stage = None
status = 'open'
superseder = None
type = 'behavior'
url = 'https://bugs.python.org/issue26578'
versions = ['Python 3.6']Linked PRs
- gh-70765: avoid waiting for HTTP headers when parsing HTTP/0.9 requests #139514
- [3.14] gh-70765: avoid waiting for HTTP headers when parsing HTTP/0.9 requests (GH-139514) #139600
- [3.13] gh-70765: avoid waiting for HTTP headers when parsing HTTP/0.9 requests (GH-139514) #139602
- gh-70765: fix an HTTP/0.9 flaky test post GH-139514 #139610
- gh-70765: Remove unnecessary extra backtick from Changelog entry #140071
- [3.13] gh-70765: Remove unnecessary extra backtick from Changelog entry (GH-140071) #140101
- [3.14] gh-70765: Remove unnecessary extra backtick from Changelog entry (GH-140071) #140102
Activity
zhangyangyu commentedon Mar 17, 2016
BaseHTTPRequestHandler in http.server supports HTTP/0.9. But the response for HTTP/0.9 request is implemented wrong.
Response of HTTP/0.9 request returns message body directly without status line and headers. But if you inherit BaseHTTPRequestHandler and set the default_request_version to "HTTP/1.x", then self.request_version can never be "HTTP/0.9" since in the https://hg.python.org/cpython/file/tip/Lib/http/server.py#l315 branch it does not set version to "HTTP/0.9" and then always sends the status line and headers back.
A trivial patch can fix this problem that set version to "HTTP/0.9" in the branch. But this will cause some failure in tests. The tests in test_httpservers use http.client.HTTPConnection to send and receive HTTP message. But since 3.4, HTTPConnection doesn't support HTTP/0.9-style simple responses. We can use it to test HTTP/0.9 connection if the server is implemented in the right way.
And since http.client.HTTPConnection has dropped the support for HTTP/0.9, is it reasonable to drop the support in http.server too?
zhangyangyu commentedon Mar 17, 2016
can should be can not.
And not only HTTPConnection, support for HTTP/0.9 seems to have been totally abandoned since Python3.4 in http.client.
vadmium commentedon Mar 18, 2016
As I understand it, you are saying if you override the undocumented (but publicly-named) default_request_version attribute, HTTP 0.9 requests no longer work.
I suspect it is even broken by default. My understanding is with HTTP 0.9 you should be able to send b"GET <path>\r\n" and get a response, but Python’s server will deadlock waiting for a second blank line or EOF. It looks like this deadlock has been there since ~forever (1995).
See bpo-10721 which already proposes to remove 0.9 server support. I would be weakly in favour of this (or more strongly if someone can prove my theory that the current support is broken).
zhangyangyu commentedon Mar 18, 2016
I think you are right. Simply run http.server.test() and then telnet to send "GET /", the client hangs. Or add a timeout to BaseHTTPRequestHandler, you can see the timeout error on server output.
vadmium commentedon Oct 29, 2016
Since my last comment, I have become more confident that Python’s request parsing never supported proper HTTP 0.9. So I would prefer to remove it in the next version of Python, and not bother fixing Xiang’s bug in existing versions (unless someone offers a practical reason to fix it).
For the record, this patch is what a fix might look like.
zhangyangyu commentedon Oct 29, 2016
+1. In rfc7230, "The expectation to support HTTP/0.9 requests has been removed".
BaseHTTPRequestHandlerincorrectly expects headers from HTTP/0.9 requests #139492 as a duplicate of this issuepicnixz commentedon Oct 2, 2025
There was a simple fix which consisted in not parsing the rest of the request as there shouldn't be headers. But deprecating the support would also be fine (there is a lot of code that is still assuming HTTP/0.9 but it's actually never tested because we never get past
parse_requestwhere it hangs because it expects some headers).Note that HTTPConnection has no support for HTTP/0.9 so a client would need to use raw sockets.
gh-70765: avoid waiting for HTTP headers when parsing HTTP/0.9 reques…
pythongh-70765: avoid waiting for HTTP headers when parsing HTTP/0.9 …
[3.13] pythongh-70765: avoid waiting for HTTP headers when parsing HT…
test_httpserversis flaky on macOS #139611 as a duplicate of this issue1 remaining item
pythongh-70765: avoid waiting for HTTP headers when parsing HTTP/0.9 …
[3.13] pythongh-70765: avoid waiting for HTTP headers when parsing HT…
[3.14] pythongh-70765: avoid waiting for HTTP headers when parsing HT…
[3.14] pythongh-70765: avoid waiting for HTTP headers when parsing HT…
[3.13] pythongh-70765: avoid waiting for HTTP headers when parsing HT…
pythongh-70765: avoid waiting for HTTP headers when parsing HTTP/0.9 …
pythongh-70765: fix an HTTP/0.9 flaky test post pythonGH-139514 (pyth…
[3.13] gh-70765: avoid waiting for HTTP headers when parsing HTTP/0.9…
[3.14] gh-70765: avoid waiting for HTTP headers when parsing HTTP/0.9…
gh-70765: Remove unnecessary extra backtick from Changelog entry (#14…
pythongh-70765: Remove unnecessary extra backtick from Changelog entry (
pythongh-70765: Remove unnecessary extra backtick from Changelog entry (
[3.14] gh-70765: Remove unnecessary extra backtick from Changelog ent…
[3.13] gh-70765: Remove unnecessary extra backtick from Changelog ent…