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 CsrfViewMiddlewareclass CSRFCheck(CsrfViewMiddleware):  def _reject(self, request, reason):    # Return the failure reason instead of an HttpResponse    return reasonclass 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 = Trueif 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)