Uncaught exception in http.server request handling (<=3.10) #103223
Description
Sending a null byte in an HTTP request path or URL triggers an uncaught ValueError in CPython 3.10 and below.
Reproduction Instructions
Open two terminals and do the following (requires python <=3.10; current 3.10 branch included):
Terminal 1:
$ ./python -m http.server --bind 127.0.0.1
Serving HTTP on 127.0.0.1 port 8000 (http://127.0.0.1:8000/) ...Terminal 2:
$ printf 'GET \x00 HTTP/1.1\r\n\r\n' | nc localhost 8000Terminal 1:
----------------------------------------
Exception occurred during processing of request from ('127.0.0.1', 56900)
Traceback (most recent call last):
File "/home/bkallus/clones/cpython/Lib/socketserver.py", line 683, in process_request_thread
self.finish_request(request, client_address)
File "/home/bkallus/clones/cpython/Lib/http/server.py", line 1304, in finish_request
self.RequestHandlerClass(request, client_address, self,
File "/home/bkallus/clones/cpython/Lib/http/server.py", line 668, in __init__
super().__init__(*args, **kwargs)
File "/home/bkallus/clones/cpython/Lib/socketserver.py", line 747, in __init__
self.handle()
File "/home/bkallus/clones/cpython/Lib/http/server.py", line 433, in handle
self.handle_one_request()
File "/home/bkallus/clones/cpython/Lib/http/server.py", line 421, in handle_one_request
method()
File "/home/bkallus/clones/cpython/Lib/http/server.py", line 672, in do_GET
f = self.send_head()
File "/home/bkallus/clones/cpython/Lib/http/server.py", line 727, in send_head
f = open(path, 'rb')
ValueError: embedded null byte
----------------------------------------
This bug is fixed in python 3.11+, but I haven't yet figured out why. As far as I can tell, the relevant portions of Lib/http/server.py and Lib/socketserver.py remain unchanged. I think the issue boils down to catching only OSErrors, but not ValueErrors, even though open can raise ValueErrors. I would guess that this happened because the docs do not clearly state that open(path, 'rb') can raise a ValueError.
Environment:
Arch Linux, x86_64
Python 3.10.10+
Activity
[-]Uncaught exception in `http.server` request handling (<=3.10 branch)[/-][+]Uncaught exception in `http.server` request handling (<=3.10)[/+]CCLDArjun commentedon Apr 4, 2023
did some debugging:
looks like
translate_path()insend_head()in 3.10 returns the path with a null character at the end, whereas in 3.11, it doesn't. Since intranslate_path():cpython/Lib/http/server.py
Line 848 in 9a8ce95
is called. the behavior of
posixpath.normpathvaries in 3.10 and 3.11:We error on this line in 3.10 because open() doesn't like null characters in the file path
cpython/Lib/http/server.py
Line 727 in 9a8ce95
So, should we catch the
ValueError, like @kenballus suggested? Unsure whether either of theposixpath.normpath()s are broken, but it's suspicious that they're returning different values.iritkatriel commentedon Apr 5, 2023
3.10 is in security-fix only mode now, so this is out of date.
kenballus commentedon Apr 5, 2023
Oops! Was going based on the chart on python.org and didn't notice that 3.10.11 came out.