#32800: CsrfViewMiddleware unnecessarily masks CSRF cookie
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Reporter: Chris Jerdonek | Owner: nobody
Type: Cleanup/optimization | Status: new
Component: CSRF | Version: dev
Severity: Normal | Keywords:
Triage Stage: Unreviewed | Has patch: 0
Needs documentation: 0 | Needs tests: 0
Patch needs improvement: 0 | Easy pickings: 0
UI/UX: 0 |
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I noticed that `CsrfViewMiddleware` unnecessarily masks the CSRF cookie.
See, for example:
https://github.com/django/django/blob/d270dd584e0af12fe6229fb712d0704c232dc7e5/django/middleware/csrf.py#L91
My understanding of the [http://breachattack.com/ BREACH attack] is that
the vulnerability comes from not masking the CSRF token in the response
body (e.g. what is included in the HTML). Masking the cookie itself
doesn't help with this. (Django also
[https://github.com/django/django/blob/d270dd584e0af12fe6229fb712d0704c232dc7e5/django/middleware/csrf.py#L308-L309
doesn't change the mask] of the cookie with each request, so the mask
wouldn't help in this regard anyways.)
Some advantages of not masking the cookie are: It would simplify the code
in `CsrfViewMiddleware` because it would remove some complexity and
operations that aren't needed for security. Currently, masking the CSRF
cookie is a red herring for someone wanting to understand the various
security features. Also, not masking the cookie would make requests and
responses smaller when `CSRF_USE_SESSIONS` is false or when true and
cookie-based sessions are used. This is because masking doubles the length
of the string.
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Ticket URL: <https://code.djangoproject.com/ticket/32800>
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