Opened 8 weeks ago

Closed 8 weeks ago

Last modified 8 weeks ago

#30530 closed Bug (wontfix)

url `path` accepts newlines in various places.

Reported by: Sjoerd Job Postmus Owned by: nobody
Component: Core (URLs) Version: master
Severity: Normal Keywords:
Cc: Triage Stage: Unreviewed
Has patch: no Needs documentation: no
Needs tests: no Patch needs improvement: no
Easy pickings: no UI/UX: no

Description

Consider the following simplified urls.py.

from django.http import HttpResponse
from django.urls import path


def path_view(request):
    return HttpResponse('<pre>===&gt;' + request.path + '&lt;===</pre>')


def render_something(request, something):
    return HttpResponse('<pre>===&gt;' + something + '&lt;===</pre>')


urlpatterns = [
    path('hello/', path_view),
    path('foo/<something>/bar/', render_something),
]

By accessing http://localhost:8000/hello/%0a, it's clear that the newline is accepted in the URL. This is because the underlying logic uses a $ in the regular expression, instead of \Z..

By accessing http://localhost:8000/foo/hello%0aworld/bar/, it's clear that the default str converter accepts anywhere in the segment. This is because it uses a negative match [^/]+, which happily accepts a newline character (both %0a and %0d).

I propose changing the $ to \Z, and the negative match to [^/\r\n]+.

I would also suggest changing the documentation on the re_path to suggest \Z instead of $, though that may be more controversial.

Change History (4)

comment:1 Changed 8 weeks ago by felixxm

Thanks for this report, however is there any reason to add this restriction? I don't see any issue in accepting encoded newline characters in URL parameters. Moreover this behavior is documented and can be used by users.

comment:2 Changed 8 weeks ago by Carlton Gibson

Resolution: wontfix
Status: newclosed

Escaped newlines are legitimate in URLs (and required in cases, e.g. #24962).

comment:3 Changed 8 weeks ago by Sjoerd Job Postmus

In that case, isn't the path converter incorrect in not accepting newlines?

comment:4 Changed 8 weeks ago by Carlton Gibson

The converters are as they are as a result of design decisions made when introducing the feature. Anyone needing different can implement custom converters.

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