1.csrf原理 csrf要求发送post,put或delete请求的时候，是先以get方式发送请求，服务端响应时会分配一个随机字符串给客户端，客户端第二次发送post,put或delete请求时携带上次分配的随机字符串到服务端进行校验 2.Django中的CSRF中间件
在一个项目中，如果想对全局所有视图函数或视图类起作用时，就可以在中间件中实现，比如想实现用户登录判断，基于用户的权限管理（RBAC）等都可以在Django中间件中来进行操作
Django内置了很多中间件,其中之一就是CSRF中间件
MIDDLEWARE_CLASSES = [ 'django.middleware.security.SecurityMiddleware', 'django.contrib.sessions.middleware.SessionMiddleware', 'django.middleware.common.CommonMiddleware', 'django.middleware.csrf.CsrfViewMiddleware', 'django.contrib.auth.middleware.AuthenticationMiddleware', 'django.contrib.auth.middleware.SessionAuthenticationMiddleware', 'django.contrib.messages.middleware.MessageMiddleware', 'django.middleware.clickjacking.XFrameOptionsMiddleware', ]上面第四个就是Django内置的CSRF中间件
3.Django中间件的执行流程Django中间件中最多可以定义5个方法
process_request process_response process_view process_exception process_template_responseDjango中间件的执行顺序
1.请求进入到Django后，会按中间件的注册顺序执行每个中间件中的process_request方法 如果所有的中间件的process_request方法都没有定义return语句，则进入路由映射，进行url匹配 否则直接执行return语句，返回响应给客户端 2.依次按顺序执行中间件中的process_view方法 如果某个中间件的process_view方法没有return语句，则根据第1步中匹配到的URL执行对应的视图函数或视图类 如果某个中间件的process_view方法中定义了return语句，则后面的视图函数或视图类不会执行,程序会直接返回 3.视图函数或视图类执行完成之后，会按照中间件的注册顺序逆序执行中间件中的process_response方法 如果中间件中定义了return语句，程序会正常执行，把视图函数或视图类的执行结果返回给客户端 否则程序会抛出异常 4.程序在视图函数或视图类的正常执行过程中 如果出现异常，则会执行按顺序执行中间件中的process_exception方法 否则process_exception方法不会执行 如果某个中间件的process_exception方法中定义了return语句，则后面的中间件中的process_exception方法不会继续执行了 5.如果视图函数或视图类中使用render方法来向客户端返回数据，则会触发中间件中的process_template_response方法 4.Django CSRF中间件的源码解析Django CSRF中间件的源码
class CsrfViewMiddleware(MiddlewareMixin): def _accept(self, request): 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 _get_token(self, request): if settings.CSRF_USE_SESSIONS: try: return request.session.get(CSRF_SESSION_KEY) except AttributeError: raise ImproperlyConfigured( 'CSRF_USE_SESSIONS is enabled, but request.session is not ' 'set. SessionMiddleware must appear before CsrfViewMiddleware ' 'in MIDDLEWARE%s.' % ('_CLASSES' if settings.MIDDLEWARE is None else '') ) else: try: cookie_token = request.COOKIES[settings.CSRF_COOKIE_NAME] except KeyError: return None csrf_token = _sanitize_token(cookie_token) if csrf_token != cookie_token: # Cookie token needed to be replaced; # the cookie needs to be reset. request.csrf_cookie_needs_reset = True return csrf_token def _set_token(self, request, response): if settings.CSRF_USE_SESSIONS: request.session[CSRF_SESSION_KEY] = request.META['CSRF_COOKIE'] else: response.set_cookie( settings.CSRF_COOKIE_NAME, request.META['CSRF_COOKIE'], max_age=settings.CSRF_COOKIE_AGE, domain=settings.CSRF_COOKIE_DOMAIN, path=settings.CSRF_COOKIE_PATH, secure=settings.CSRF_COOKIE_SECURE, httponly=settings.CSRF_COOKIE_HTTPONLY, ) patch_vary_headers(response, ('Cookie',)) def process_request(self, request): csrf_token = self._get_token(request) if csrf_token is not None: # Use same token next time. request.META['CSRF_COOKIE'] = csrf_token def process_view(self, request, callback, callback_args, callback_kwargs): if getattr(request, 'csrf_processing_done', False): return None if getattr(callback, 'csrf_exempt', False): return None if request.method not in ('GET', 'HEAD', 'OPTIONS', 'TRACE'): if getattr(request, '_dont_enforce_csrf_checks', False): return self._accept(request) if request.is_secure(): referer = force_text( request.META.get('HTTP_REFERER'), strings_only=True, errors='replace' ) if referer is None: return self._reject(request, REASON_NO_REFERER) referer = urlparse(referer) if '' in (referer.scheme, referer.netloc): return self._reject(request, REASON_MALFORMED_REFERER) if referer.scheme != 'https': return self._reject(request, REASON_INSECURE_REFERER) good_referer = ( settings.SESSION_COOKIE_DOMAIN if settings.CSRF_USE_SESSIONS else settings.CSRF_COOKIE_DOMAIN ) if good_referer is not None: server_port = request.get_port() if server_port not in ('443', '80'): good_referer = '%s:%s' % (good_referer, server_port) else: good_referer = request.get_host() good_hosts = list(settings.CSRF_TRUSTED_ORIGINS) good_hosts.append(good_referer) if not any(is_same_domain(referer.netloc, host) for host in good_hosts): reason = REASON_BAD_REFERER % referer.geturl() return self._reject(request, reason) csrf_token = request.META.get('CSRF_COOKIE') if csrf_token is None: return self._reject(request, REASON_NO_CSRF_COOKIE) request_csrf_token = "" if request.method == "POST": try: request_csrf_token = request.POST.get('csrfmiddlewaretoken', '') except IOError: pass if request_csrf_token == "": request_csrf_token = request.META.get(settings.CSRF_HEADER_NAME, '') request_csrf_token = _sanitize_token(request_csrf_token) if not _compare_salted_tokens(request_csrf_token, csrf_token): return self._reject(request, REASON_BAD_TOKEN) return self._accept(request) def process_response(self, request, response): if not getattr(request, 'csrf_cookie_needs_reset', False): if getattr(response, 'csrf_cookie_set', False): return response if not request.META.get("CSRF_COOKIE_USED", False): return response self._set_token(request, response) response.csrf_cookie_set = True return response从上面的源码中可以看到，CsrfViewMiddleware中间件中定义了process_request，process_view和process_response三个方法