CSRF ミドルウェアとテンプレートタグは、簡単に扱える Cross Site Request Forgeries 対策を提供しています。このタイプの攻撃は、訪問者のログイン情報を悪用してあなたのサイトに何らかの操作を行うことを目的とした、リンクやフォームボタン、 JavaScript を設置した悪意のあるウェブサイトによって行われます。また、関連する攻撃として、ユーザーを騙して別のユーザー権限でログインさせる 'ログイン CSRF' と呼ばれる攻撃もありますが、これも対策に含まれます。
\nCSRF 攻撃に対する第一の防御は、 GET リクエスト (および RFC 7231 Section 4.2.1 で定義された ‘安全な’ メソッド) から副作用を取り除くというものです。そして、 POST、PUT、DELETE のような、’安全でない’ メソッ ドによるリクエストについては、下記の手順に従うことで対策することができます。
\nCSRF 対策をあなたのビューで有効にするには、以下の手順に従ってください:
\nCSRF ミドルウェアは、デフォルトで MIDDLEWARE 設定で有効になっています。もし設定をオーバーライドするときは、'django.middleware.csrf.CsrfViewMiddleware' が、 CSRF 攻撃への対策がされていることを前提とした他の全てのビュー・ミドルウェアの前に来るようにしてください。
(推奨されませんが) もし対策を無効にする場合は、csrf_protect() を使って特定のビューを保護することができます. (下記をご覧ください)
POST フォームを使う全てのテンプレートで、POST が内部 URL に使われる場合は、<form> 要素の内部で csrf_token タグを使用してください。
<form method="post">{% csrf_token %}\nこの方法は、外部の URL を対象にする POST フォームで使ってはなりません。CSRF トークンが外部に漏れ、脆弱性の原因となります。
\n一致するビュー機能の中で、{% csrf_token %} が適切に動作するように、RequestContext がレスポンスをレンダリングするようにしてください。render() 、汎用ビューもしくは contrib アプリケーションを使う場合は、これら全て RequestContext を使用するためすでに CSRF 対策はなされています。
While the above method can be used for AJAX POST requests, it has some\ninconveniences: you have to remember to pass the CSRF token in as POST data with\nevery POST request. For this reason, there is an alternative method: on each\nXMLHttpRequest, set a custom X-CSRFToken header (as specified by the\nCSRF_HEADER_NAME setting) to the value of the CSRF token. This is\noften easier because many JavaScript frameworks provide hooks that allow\nheaders to be set on every request.
First, you must get the CSRF token. How to do that depends on whether or not\nthe CSRF_USE_SESSIONS and CSRF_COOKIE_HTTPONLY settings\nare enabled.
Finally, you'll have to actually set the header on your AJAX request, while\nprotecting the CSRF token from being sent to other domains using\nsettings.crossDomain in jQuery 1.5.1\nand newer:
\nfunction csrfSafeMethod(method) {\n // these HTTP methods do not require CSRF protection\n return (/^(GET|HEAD|OPTIONS|TRACE)$/.test(method));\n}\n$.ajaxSetup({\n beforeSend: function(xhr, settings) {\n if (!csrfSafeMethod(settings.type) && !this.crossDomain) {\n xhr.setRequestHeader("X-CSRFToken", csrftoken);\n }\n }\n});\nAngularJS 1.1.3 以降を使っている場合は、以下のクッキーとヘッダ名で $http プロバイダを設定すれば十分です。
$httpProvider.defaults.xsrfCookieName = 'csrftoken';\n$httpProvider.defaults.xsrfHeaderName = 'X-CSRFToken';\nDjango の Jinja2 テンプレートバックエンドは、すべてのテンプレートのコンテキストに {{ csrf_input }} を追加します。これは、Django テンプレート言語内の {% csrf_token %} と同じ意味です。例えば:
<form method="post">{{ csrf_input }}\n全体を保護するために CsrfViewMiddleware を追加する代わりに、保護を必要とする特定のビューにおいて、(まったく同じ機能を持つ) csrf_protect デコレータを使えます。アウトプット内に CSRF トークンを挿入するビューと、POST フォームデータを受け入れるビューの両方で使用する必要があります (多くの場合同じビュー関数ですが、そうでない場合もあります)。
デコレータ自体で使うことは 非推奨 です。もし使い忘れた場合、セキュリティホールを抱えることになるからです。二重対策として両方を使うのは構いませんが、わずかにオーバーヘッドが増加します。
\nビューに対する CsrfViewMiddleware の保護を提供するデコレータです。
使い方は以下の通りです:
\nfrom django.shortcuts import render\nfrom django.views.decorators.csrf import csrf_protect\n\n@csrf_protect\ndef my_view(request):\n c = {}\n # ...\n return render(request, "a_template.html", c)\nクラスベースのビューを使っている場合は、 Decorating class-based views を参照してください。
\n受け取ったリクエストが CsrfViewMiddleware による認証に失敗した場合、デフォルトでは、ユーザーには '403 Forbidden' レスポンスが送信されます。これは通常、本当にクロスサイトリクエストフォージェリが行われたか、プログラミングのミスによって POST フォームに CSRF トークンが含まれていない場合に発生します。
けれども、エラーページがあまり親切ではないので、このような場面を処理 するために、自作のビューを設定することができます。 そうするには、単に settings の CSRF_FAILURE_VIEW を設定してください。
CSRF failures are logged as warnings to the django.security.csrf logger.
\nThe CSRF protection is based on the following things:
\nA CSRF cookie that is based on a random secret value, which other sites\nwill not have access to.
\nThis cookie is set by CsrfViewMiddleware. It is sent with every\nresponse that has called django.middleware.csrf.get_token() (the\nfunction used internally to retrieve the CSRF token), if it wasn't already\nset on the request.
In order to protect against BREACH attacks, the token is not simply the\nsecret; a random salt is prepended to the secret and used to scramble it.
\nFor security reasons, the value of the secret is changed each time a\nuser logs in.
\nA hidden form field with the name 'csrfmiddlewaretoken' present in all\noutgoing POST forms. The value of this field is, again, the value of the\nsecret, with a salt which is both added to it and used to scramble it. The\nsalt is regenerated on every call to get_token() so that the form field\nvalue is changed in every such response.
This part is done by the template tag.
\nFor all incoming requests that are not using HTTP GET, HEAD, OPTIONS or\nTRACE, a CSRF cookie must be present, and the 'csrfmiddlewaretoken' field\nmust be present and correct. If it isn't, the user will get a 403 error.
\nWhen validating the 'csrfmiddlewaretoken' field value, only the secret,\nnot the full token, is compared with the secret in the cookie value.\nThis allows the use of ever-changing tokens. While each request may use its\nown token, the secret remains common to all.
\nThis check is done by CsrfViewMiddleware.
In addition, for HTTPS requests, strict referer checking is done by\nCsrfViewMiddleware. This means that even if a subdomain can set or\nmodify cookies on your domain, it can't force a user to post to your\napplication since that request won't come from your own exact domain.
This also addresses a man-in-the-middle attack that's possible under HTTPS\nwhen using a session independent secret, due to the fact that HTTP\nSet-Cookie headers are (unfortunately) accepted by clients even when\nthey are talking to a site under HTTPS. (Referer checking is not done for\nHTTP requests because the presence of the Referer header isn't reliable\nenough under HTTP.)
If the CSRF_COOKIE_DOMAIN setting is set, the referer is compared\nagainst it. This setting supports subdomains. For example,\nCSRF_COOKIE_DOMAIN = '.example.com' will allow POST requests from\nwww.example.com and api.example.com. If the setting is not set, then\nthe referer must match the HTTP Host header.
Expanding the accepted referers beyond the current host or cookie domain can\nbe done with the CSRF_TRUSTED_ORIGINS setting.
This ensures that only forms that have originated from trusted domains can be\nused to POST data back.
\nIt deliberately ignores GET requests (and other requests that are defined as\n'safe' by RFC 7231). These requests ought never to have any potentially\ndangerous side effects , and so a CSRF attack with a GET request ought to be\nharmless. RFC 7231 defines POST, PUT, and DELETE as 'unsafe', and all other\nmethods are also assumed to be unsafe, for maximum protection.
\nThe CSRF protection cannot protect against man-in-the-middle attacks, so use\nHTTPS with\nHTTP Strict Transport Security. It also assumes validation of\nthe HOST header and that there aren't any\ncross-site scripting vulnerabilities on your site\n(because XSS vulnerabilities already let an attacker do anything a CSRF\nvulnerability allows and much worse).
\n\nIf the csrf_token template tag is used by a template (or the\nget_token function is called some other way), CsrfViewMiddleware will\nadd a cookie and a Vary: Cookie header to the response. This means that the\nmiddleware will play well with the cache middleware if it is used as instructed\n(UpdateCacheMiddleware goes before all other middleware).
However, if you use cache decorators on individual views, the CSRF middleware\nwill not yet have been able to set the Vary header or the CSRF cookie, and the\nresponse will be cached without either one. In this case, on any views that\nwill require a CSRF token to be inserted you should use the\ndjango.views.decorators.csrf.csrf_protect() decorator first:
from django.views.decorators.cache import cache_page\nfrom django.views.decorators.csrf import csrf_protect\n\n@cache_page(60 * 15)\n@csrf_protect\ndef my_view(request):\n ...\nクラスベースのビューを使っている場合は、 Decorating class-based views を参照してください。
\nThe CsrfViewMiddleware will usually be a big hindrance to testing view\nfunctions, due to the need for the CSRF token which must be sent with every POST\nrequest. For this reason, Django's HTTP client for tests has been modified to\nset a flag on requests which relaxes the middleware and the csrf_protect\ndecorator so that they no longer rejects requests. In every other respect\n(e.g. sending cookies etc.), they behave the same.
If, for some reason, you want the test client to perform CSRF\nchecks, you can create an instance of the test client that enforces\nCSRF checks:
\n>>> from django.test import Client\n>>> csrf_client = Client(enforce_csrf_checks=True)\nSubdomains within a site will be able to set cookies on the client for the whole\ndomain. By setting the cookie and using a corresponding token, subdomains will\nbe able to circumvent the CSRF protection. The only way to avoid this is to\nensure that subdomains are controlled by trusted users (or, are at least unable\nto set cookies). Note that even without CSRF, there are other vulnerabilities,\nsuch as session fixation, that make giving subdomains to untrusted parties a bad\nidea, and these vulnerabilities cannot easily be fixed with current browsers.
\nCertain views can have unusual requirements that mean they don't fit the normal\npattern envisaged here. A number of utilities can be useful in these\nsituations. The scenarios they might be needed in are described in the following\nsection.
\nThe examples below assume you are using function-based views. If you\nare working with class-based views, you can refer to Decorating\nclass-based views.
\nThis decorator marks a view as being exempt from the protection ensured by\nthe middleware. Example:
\nfrom django.http import HttpResponse\nfrom django.views.decorators.csrf import csrf_exempt\n\n@csrf_exempt\ndef my_view(request):\n return HttpResponse('Hello world')\nNormally the csrf_token template tag will not work if\nCsrfViewMiddleware.process_view or an equivalent like csrf_protect\nhas not run. The view decorator requires_csrf_token can be used to\nensure the template tag does work. This decorator works similarly to\ncsrf_protect, but never rejects an incoming request.
実装例:
\nfrom django.shortcuts import render\nfrom django.views.decorators.csrf import requires_csrf_token\n\n@requires_csrf_token\ndef my_view(request):\n c = {}\n # ...\n return render(request, "a_template.html", c)\nThis decorator forces a view to send the CSRF cookie.
\nMost views requires CSRF protection, but a few do not.
\nSolution: rather than disabling the middleware and applying csrf_protect to\nall the views that need it, enable the middleware and use\ncsrf_exempt().
There are cases when CsrfViewMiddleware.process_view may not have run\nbefore your view is run - 404 and 500 handlers, for example - but you still\nneed the CSRF token in a form.
Solution: use requires_csrf_token()
There may be some views that are unprotected and have been exempted by\ncsrf_exempt, but still need to include the CSRF token.
Solution: use csrf_exempt() followed by\nrequires_csrf_token(). (i.e. requires_csrf_token\nshould be the innermost decorator).
A view needs CSRF protection under one set of conditions only, and mustn't have\nit for the rest of the time.
\nSolution: use csrf_exempt() for the whole\nview function, and csrf_protect() for the\npath within it that needs protection. Example:
from django.views.decorators.csrf import csrf_exempt, csrf_protect\n\n@csrf_exempt\ndef my_view(request):\n\n @csrf_protect\n def protected_path(request):\n do_something()\n\n if some_condition():\n return protected_path(request)\n else:\n do_something_else()\nA page makes a POST request via AJAX, and the page does not have an HTML form\nwith a csrf_token that would cause the required CSRF cookie to be sent.
Solution: use ensure_csrf_cookie() on the\nview that sends the page.
Because it is possible for the developer to turn off the CsrfViewMiddleware,\nall relevant views in contrib apps use the csrf_protect decorator to ensure\nthe security of these applications against CSRF. It is recommended that the\ndevelopers of other reusable apps that want the same guarantees also use the\ncsrf_protect decorator on their views.
A number of settings can be used to control Django's CSRF behavior:
\n\nNo, this is by design. Not linking CSRF protection to a session allows using\nthe protection on sites such as a pastebin that allow submissions from\nanonymous users which don't have a session.
\nIf you wish to store the CSRF token in the user's session, use the\nCSRF_USE_SESSIONS setting.
For security reasons, CSRF tokens are rotated each time a user logs in. Any\npage with a form generated before a login will have an old, invalid CSRF token\nand need to be reloaded. This might happen if a user uses the back button after\na login or if they log in a different browser tab.
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