CSRF Middleware regular expression doesn't take in account spaces.

[Ryszard Szopa <ryszard.szopa@…>]

The CSRF protection middleware regular expression that looks for forms with method POST assumes that there are no spaces between the attribute name and the '=' sign or between the '=' sign and the attribute value.
This means that forms like this:

<form method = "post">
    ...
</form>

(which browsers generally accept and interpret correctly) won't be caught by the regexp, the inputs with the magic tokens be inserted, and the user will get a 403 Forbidden error. Moreover, additional whitespace is rather dificult to spot (and isn't obviously relevant to the issue of CSRF), making the whole thing rather frustrating to debug.

A very easy fix is to change the regular expression:

_POST_FORM_RE = \
    re.compile(r'(<form\W[^>]*\bmethod\s*=\s*(\'|"|)POST(\'|"|)\b[^>]*>)', re.IGNORECASE)

[Ryszard Szopa <ryszard.szopa@…>]

patch with new csrf form regexp

[Luke Plant]

(In [10617]) Fixed #10884 - more lenient regexp for matching forms in CSRF post-processing

Thanks to Ryszard Szopa for the report and fix

[Jacob]

Milestone 1.1 deleted