去掉django rest framework强制的csrf检查

近期的项目，前端的js是在localhost上跑的，然后向我们后端的开发服务器进行请求。但是突然前端说所有的post请求都报csrf校验错误了，甚是奇怪，之前为了开发方便已经把django的csrf middleware注释掉了啊，为什么还会错误，由于返回值格式还是django rest的通用格式，肯定问题是出在这里面，于是翻了一下它的源代码看了看。

from django.middleware.csrf import CsrfViewMiddleware

class CSRFCheck(CsrfViewMiddleware):

def _reject(self, request, reason):

# Return the failure reason instead of an HttpResponse

return reason

class SessionAuthentication(BaseAuthentication):

“””

Use Django’s session framework for authentication.

“”“

def authenticate(self, request):
"""
Returns a `User` if the request session currently has a logged in user.
Otherwise returns `None`.
"""

# Get the underlying HttpRequest object
request = request._request
user = getattr(request, 'user', None)

# Unauthenticated, CSRF validation not required
if not user or not user.is_active:
return None

self.enforce_csrf(request)

# CSRF passed with authenticated user
return (user, None)

def enforce_csrf(self, request):
"""
Enforce CSRF validation for session based authentication.
"""
reason = CSRFCheck().process_view(request, None, (), {})
if reason:
# CSRF failed, bail with explicit error message
raise exceptions.PermissionDenied('CSRF Failed: %s' % reason)

原来是这样，最近给系统增加了用户登陆功能，使用的就是SessionAuthorization和TokenAuthorization，然后在SessionAuthorization中调用了self.enforce_csrf(request)而这个调用的又是上面的CSRFCheck，这个类是重载了django里面的csrf middleware，而且没发现有地方可以关掉这个功能，即使在django里面去掉这个middleware，但是这个还是会调用的。

那怎么去掉这个功能呢，我们现在就是要进行跨域请求。

最简单了，直接注释掉上面的self.enforce_csrf(request)这一行代码就行了或者在设置中添加一项，比如改成

GLOBAL_CSRF_CHECK = True

if GLOBAL_CSRF_CHECK：

self.enforce_csrf(request)

我们继续看源代码，到middleware的代码里面去。

class CsrfViewMiddleware(object):

“””

Middleware that requires a present and correct csrfmiddlewaretoken

for POST requests that have a CSRF cookie, and sets an outgoing

CSRF cookie.

This middleware should be used in conjunction with the csrf_token template
tag.
"""
# The _accept and _reject methods currently only exist for the sake of the
# requires_csrf_token decorator.
def _accept(self, request):
# Avoid checking the request twice by adding a custom attribute to
# request.  This will be relevant when both decorator and middleware
# are used.
request.csrf_processing_done = True
return None

def _reject(self, request, reason):
logger.warning('Forbidden (%s): %s',
reason, request.path,
extra={
'status_code': 403,
'request': request,
}
)
return _get_failure_view()(request, reason=reason)

def process_view(self, request, callback, callback_args, callback_kwargs):

if getattr(request, 'csrf_processing_done', False):
return None

try:
csrf_token = _sanitize_token(
request.COOKIES[settings.CSRF_COOKIE_NAME])
# Use same token next time
request.META['CSRF_COOKIE'] = csrf_token
except KeyError:
csrf_token = None
# Generate token and store it in the request, so it's
# available to the view.
request.META["CSRF_COOKIE"] = _get_new_csrf_key()

# Wait until request.META["CSRF_COOKIE"] has been manipulated before
# bailing out, so that get_token still works
if getattr(callback, 'csrf_exempt', False):
return None

# Assume that anything not defined as 'safe' by RFC2616 needs protection
if request.method not in ('GET', 'HEAD', 'OPTIONS', 'TRACE'):
if getattr(request, '_dont_enforce_csrf_checks', False):
# Mechanism to turn off CSRF checks for test suite.
# It comes after the creation of CSRF cookies, so that
# everything else continues to work exactly the same
# (e.g. cookies are sent, etc.), but before any
# branches that call reject().
return self._accept(request)

if request.is_secure():
# Suppose user visits http://example.com/ # An active network attacker (man-in-the-middle, MITM) sends a
# POST form that targets https://example.com/detonate-bomb/ and
# submits it via JavaScript.
#
# The attacker will need to provide a CSRF cookie and token, but
# that's no problem for a MITM and the session-independent
# nonce we're using. So the MITM can circumvent the CSRF
# protection. This is true for any HTTP connection, but anyone
# using HTTPS expects better! For this reason, for
# https://example.com/ we need additional protection that treats
# http://example.com/ as completely untrusted. Under HTTPS,
# Barth et al. found that the Referer header is missing for
# same-domain requests in only about 0.2% of cases or less, so
# we can use strict Referer checking.
referer = request.META.get('HTTP_REFERER')
if referer is None:
return self._reject(request, REASON_NO_REFERER)

# Note that request.get_host() includes the port.
good_referer = 'https://%s/' % request.get_host()
if not same_origin(referer, good_referer):
reason = REASON_BAD_REFERER % (referer, good_referer)
return self._reject(request, reason)

if csrf_token is None:
# No CSRF cookie. For POST requests, we insist on a CSRF cookie,
# and in this way we can avoid all CSRF attacks, including login
# CSRF.
return self._reject(request, REASON_NO_CSRF_COOKIE)

# Check non-cookie token for match.
request_csrf_token = ""
if request.method == "POST":
request_csrf_token = request.POST.get('csrfmiddlewaretoken', '')

if request_csrf_token == "":
# Fall back to X-CSRFToken, to make things easier for AJAX,
# and possible for PUT/DELETE.
request_csrf_token = request.META.get('HTTP_X_CSRFTOKEN', '')

if not constant_time_compare(request_csrf_token, csrf_token):
return self._reject(request, REASON_BAD_TOKEN)

return self._accept(request)

def process_response(self, request, response):
if getattr(response, 'csrf_processing_done', False):
return response

# If CSRF_COOKIE is unset, then CsrfViewMiddleware.process_view was
# never called, probaby because a request middleware returned a response
# (for example, contrib.auth redirecting to a login page).
if request.META.get("CSRF_COOKIE") is None:
return response

if not request.META.get("CSRF_COOKIE_USED", False):
return response

# Set the CSRF cookie even if it's already set, so we renew
# the expiry timer.
response.set_cookie(settings.CSRF_COOKIE_NAME,
request.META["CSRF_COOKIE"],
max_age = 60 * 60 * 24 * 7 * 52,
domain=settings.CSRF_COOKIE_DOMAIN,
path=settings.CSRF_COOKIE_PATH,
secure=settings.CSRF_COOKIE_SECURE,
httponly=settings.CSRF_COOKIE_HTTPONLY
)
# Content varies with the CSRF cookie, so set the Vary header.
patch_vary_headers(response, ('Cookie',))
response.csrf_processing_done = True
return response

里面主要有两个函数，一个是process view，另一个是process response。这里就不得不说django middleware的工作原理了。

https://docs.djangoproject.com/en/1.6/topics/http/middleware/

process_request() is called on each request, before Django decides which view to execute.

process_view() is called just before Django calls the view.

process_response() is called on all responses before they’re returned to the browser.

所以这个middleware的process view会在请求到达view函数之前被调用，可以理解为一个过滤器吧。

if request.method not in (‘GET’, ‘HEAD’, ‘OPTIONS’, ‘TRACE’):

if getattr(request, ‘_dont_enforce_csrf_checks’, False):

return self._accept(request)

这里request里面有_dont_enforce_csrf_checks就直接进入view了，没有下面的检查了。所以我们只要自己给request添加一个这样的属性就好了。最直接的方法还是去写一个middleware啊，哈哈。

代码很简单

class DisableCSRFCheck(object):

def process_request(self, request):

setattr(request, ‘_dont_enforce_csrf_checks’, True)