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ミドルウェア

This document explains all middleware components that come with Django. For information on how to use them and how to write your own middleware, see the middleware usage guide.

使用できる middleware

Cache middleware

class UpdateCacheMiddleware
class FetchFromCacheMiddleware

サイト全体でキャッシュを有効にします。有効にすると、Django を利用している各ページは CACHE_MIDDLEWARE_SECONDS 設定で指定した時間だけキャッシュされます。詳しくは the cache documentation を読んでください。

Common middleware

class CommonMiddleware

完璧主義者のためにいくつかの便利な機能を提供します。

  • DISALLOWED_USER_AGENTS 設定に含まれるユーザーエージェントのアクセスを禁止します。この設定は、コンパイルした正規表現オブジェクトのリストである必要があります。

  • APPEND_SLASH および PREPEND_WWW 設定に基づいて、URL の書き換えを実行します。

    APPEND_SLASH が True で、与えられた URL がスラッシュで終わっていなくて、さらに URLconf に URL が見つからなければ、Django は / が最後に追加された新しい URL を作り、この新しい URL へリクエストをリダイレクトします。それ以外のときには、最初の URL を通常通りに処理します。

    たとえば、 foo.com/bar は、 foo.com/bar に対する有効な URL パタンがなく、foo.com/bar/ に対しては有効なパタンが 存在する 場合に、 foo.com/bar/ にリダイレクトされます。

    PREPEND_WWW を True にすると、先頭に "www." がない URL は "www." で始まる同じ URL にリダイレクトされます。

    2つのオプションが意味するのは、URL を正規化するということです。これは、1つの URL には1つの、かつただ1つだけの場所を指すべきだという考えです。技術的には URL foo.com/bar は foo.com/bar/ とは区別されます。実際、サーチエンジンのインデクスはこれらを区別して作成されます。よって、URL を正規化するというのがベストプラクティスなのです。

    If necessary, individual views may be excluded from the APPEND_SLASH behavior using the no_append_slash() decorator:

    Code
    from django.views.decorators.common import no_append_slash


@no_append_slash
def sensitive_fbv(request, *args, **kwargs):
    """View to be excluded from APPEND_SLASH."""
    return HttpResponse()

  • Sets the Content-Length header for non-streaming responses.

CommonMiddleware.response_redirect_class

Defaults to HttpResponsePermanentRedirect. Subclass CommonMiddleware and override the attribute to customize the redirects issued by the middleware.

class BrokenLinkEmailsMiddleware

GZip middleware

class GZipMiddleware
max_random_bytes

Defaults to 100. Subclass GZipMiddleware and override the attribute to change the maximum number of random bytes that is included with compressed responses.

The django.middleware.gzip.GZipMiddleware compresses content for browsers that understand GZip compression (all modern browsers).

This middleware should be placed before any other middleware that need to read or write the response body so that compression happens afterward.

It will NOT compress content if any of the following are true:

  • The content body is less than 200 bytes long.

  • The response has already set the Content-Encoding header.

  • The request (the browser) hasn't sent an Accept-Encoding header containing gzip.

If the response has an ETag header, the ETag is made weak to comply with RFC 9110 Section 8.8.1.

You can apply GZip compression to individual views using the gzip_page() decorator.

Conditional GET middleware

class ConditionalGetMiddleware

Handles conditional GET operations. If the response doesn't have an ETag header, the middleware adds one if needed. If the response has an ETag or Last-Modified header, and the request has If-None-Match or If-Modified-Since, the response is replaced by an HttpResponseNotModified.

Locale ミドルウェア

class LocaleMiddleware

リクエストからのデータに基づいた言語セクションを有効化します。この機能は、それぞれのユーザに対してコンテンツをカスタマイズします。 国際化のドキュメント を参照してください。

LocaleMiddleware.response_redirect_class

デフォルトは HttpResponseRedirect です。LocaleMiddleware をサブクラス化して属性をオーバーライドし、ミドルウェアによって発行されたリダイレクトをカスタマイズします。

Message ミドルウェア

class MessageMiddleware

クッキーおよびセッションをベースとしたメッセージサポートを有効化します。メッセージのドキュメント を参照してください。

Security middleware

class SecurityMiddleware

The django.middleware.security.SecurityMiddleware provides several security enhancements to the request/response cycle. Each one can be independently enabled or disabled with a setting.

HTTP Strict Transport Security

For sites that should only be accessed over HTTPS, you can instruct modern browsers to refuse to connect to your domain name via an insecure connection (for a given period of time) by setting the "Strict-Transport-Security" header. This reduces your exposure to some SSL-stripping man-in-the-middle (MITM) attacks.

SecurityMiddleware will set this header for you on all HTTPS responses if you set the SECURE_HSTS_SECONDS setting to a non-zero integer value.

When enabling HSTS, it's a good idea to first use a small value for testing, for example, SECURE_HSTS_SECONDS = 3600 for one hour. Each time a web browser sees the HSTS header from your site, it will refuse to communicate non-securely (using HTTP) with your domain for the given period of time. Once you confirm that all assets are served securely on your site (i.e. HSTS didn't break anything), it's a good idea to increase this value so that infrequent visitors will be protected (31536000 seconds, i.e. 1 year, is common).

Additionally, if you set the SECURE_HSTS_INCLUDE_SUBDOMAINS setting to True, SecurityMiddleware will add the includeSubDomains directive to the Strict-Transport-Security header. This is recommended (assuming all subdomains are served exclusively using HTTPS), otherwise your site may still be vulnerable via an insecure connection to a subdomain.

If you wish to submit your site to the browser preload list, set the SECURE_HSTS_PRELOAD setting to True. That appends the preload directive to the Strict-Transport-Security header.

Referrer Policy

Browsers use the Referer header as a way to send information to a site about how users got there. When a user clicks a link, the browser will send the full URL of the linking page as the referrer. While this can be useful for some purposes -- like figuring out who's linking to your site -- it also can cause privacy concerns by informing one site that a user was visiting another site.

Some browsers have the ability to accept hints about whether they should send the HTTP Referer header when a user clicks a link; this hint is provided via the Referrer-Policy header. This header can suggest any of three behaviors to browsers:

  • Full URL: send the entire URL in the Referer header. For example, if the user is visiting https://example.com/page.html, the Referer header would contain "https://example.com/page.html".

  • Origin only: send only the "origin" in the referrer. The origin consists of the scheme, host and (optionally) port number. For example, if the user is visiting https://example.com/page.html, the origin would be https://example.com/.

  • No referrer: do not send a Referer header at all.

There are two types of conditions this header can tell a browser to watch out for:

  • Same-origin versus cross-origin: a link from https://example.com/1.html to https://example.com/2.html is same-origin. A link from https://example.com/page.html to https://not.example.com/page.html is cross-origin.

  • Protocol downgrade: a downgrade occurs if the page containing the link is served via HTTPS, but the page being linked to is not served via HTTPS.

SecurityMiddleware can set the Referrer-Policy header for you, based on the SECURE_REFERRER_POLICY setting (note spelling: browsers send a Referer header when a user clicks a link, but the header instructing a browser whether to do so is spelled Referrer-Policy). The valid values for this setting are:

no-referrer

Instructs the browser to send no referrer for links clicked on this site.

no-referrer-when-downgrade

Instructs the browser to send a full URL as the referrer, but only when no protocol downgrade occurs.

origin

Instructs the browser to send only the origin, not the full URL, as the referrer.

origin-when-cross-origin

Instructs the browser to send the full URL as the referrer for same-origin links, and only the origin for cross-origin links.

same-origin

Instructs the browser to send a full URL, but only for same-origin links. No referrer will be sent for cross-origin links.

strict-origin

Instructs the browser to send only the origin, not the full URL, and to send no referrer when a protocol downgrade occurs.

strict-origin-when-cross-origin

Instructs the browser to send the full URL when the link is same-origin and no protocol downgrade occurs; send only the origin when the link is cross-origin and no protocol downgrade occurs; and no referrer when a protocol downgrade occurs.

unsafe-url

Instructs the browser to always send the full URL as the referrer.

Cross-Origin Opener Policy

Some browsers have the ability to isolate top-level windows from other documents by putting them in a separate browsing context group based on the value of the Cross-Origin Opener Policy (COOP) header. If a document that is isolated in this way opens a cross-origin popup window, the popup’s window.opener property will be null. Isolating windows using COOP is a defense-in-depth protection against cross-origin attacks, especially those like Spectre which allowed exfiltration of data loaded into a shared browsing context.

SecurityMiddleware can set the Cross-Origin-Opener-Policy header for you, based on the SECURE_CROSS_ORIGIN_OPENER_POLICY setting. The valid values for this setting are:

same-origin

Isolates the browsing context exclusively to same-origin documents. Cross-origin documents are not loaded in the same browsing context. This is the default and most secure option.

same-origin-allow-popups

Isolates the browsing context to same-origin documents or those which either don't set COOP or which opt out of isolation by setting a COOP of unsafe-none.

unsafe-none

Allows the document to be added to its opener's browsing context group unless the opener itself has a COOP of same-origin or same-origin-allow-popups.

X-Content-Type-Options: nosniff

Some browsers will try to guess the content types of the assets that they fetch, overriding the Content-Type header. While this can help display sites with improperly configured servers, it can also pose a security risk.

If your site serves user-uploaded files, a malicious user could upload a specially-crafted file that would be interpreted as HTML or JavaScript by the browser when you expected it to be something harmless.

To prevent the browser from guessing the content type and force it to always use the type provided in the Content-Type header, you can pass the X-Content-Type-Options: nosniff header. SecurityMiddleware will do this for all responses if the SECURE_CONTENT_TYPE_NOSNIFF setting is True.

Note that in most deployment situations where Django isn't involved in serving user-uploaded files, this setting won't help you. For example, if your MEDIA_URL is served directly by your front-end web server (nginx, Apache, etc.) then you'd want to set this header there. On the other hand, if you are using Django to do something like require authorization in order to download files and you cannot set the header using your web server, this setting will be useful.

SSL リダイレクト

サイトが HTTP と HTTPS 接続の両方をサポートしている場合、多くのユーザーはデフォルトでセキュアでない接続を行ってしまいます。最善のセキュリティのためには、すべての HTTP 接続を HTTPS 接続にリダイレクトするべきです。

SECURE_SSL_REDIRECT 設定を True に設定すれば、 SecurityMiddleware が すべての HTTP 接続を HTTPS に parmanent (HTTP 301) にリダイレクトしてくれます。

If the SECURE_SSL_HOST setting has a value, all redirects will be sent to that host instead of the originally-requested host.

If there are a few pages on your site that should be available over HTTP, and not redirected to HTTPS, you can list regular expressions to match those URLs in the SECURE_REDIRECT_EXEMPT setting.

Session middleware

class SessionMiddleware

セッションのサポートを有効にします。詳しくは セッションのドキュメント を読んでください。

Site middleware

class CurrentSiteMiddleware

受信側のすべての HttpRequest オブジェクトに、現在のサイトを表す site 属性を追加します。詳しくは sites documentation を読んでください。

Authentication middleware

class AuthenticationMiddleware

Adds the user attribute, representing the currently-logged-in user, to every incoming HttpRequest object. See Authentication in web requests.

class RemoteUserMiddleware

Middleware for utilizing web server provided authentication. See REMOTE_USER で認証する for usage details.

class PersistentRemoteUserMiddleware

Middleware for utilizing web server provided authentication when enabled only on the login page. See ログインページでのみ REMOTE_USER を使用する for usage details.

CSRF プロテクション middleware

class CsrfViewMiddleware

POST フォームに隠しフォームフィールドを追加し、リクエストの値が正しいかチェックすることで、Cross Site Request Forgery に対するプロテクションを追加します。詳しくは Cross Site Request Forgery プロテクションのドキュメント を読んでください。

X-Frame-Options middleware

class XFrameOptionsMiddleware

シンプルな クリックジャッキングに対する X-Frame-Options ヘッダ経由のプロテクション です。

Middleware の順序

Django の多様なミドルウェアクラスの順序に関する注意点を挙げておきます。

  1. SecurityMiddleware

    SSL リダイレクトを有効にしているなら、他のたくさんの必要のないミドルウェアが実行されないように、リストの先頭付近に置くべきです。

  2. UpdateCacheMiddleware

    Vary ヘッダに変更を加えるミドルウェア (SessionMiddleware, GZipMiddleware, LocaleMiddleware) の前に置きます。

  3. GZipMiddleware

    response body を変更・使用する可能性のあるミドルウェアの前に置きます。

    Vary ヘッダを修正するため、 UpdateCacheMiddleware の後に置きます。

  4. SessionMiddleware

    Before any middleware that may raise an exception to trigger an error view (such as PermissionDenied) if you're using CSRF_USE_SESSIONS.

    Vary ヘッダを修正するため、 UpdateCacheMiddleware の後に置きます。

  5. ConditionalGetMiddleware

    Before any middleware that may change the response (it sets the ETag header).

    gzip されたコンテンツに対して ETag ヘッダを計算しないように、 GZipMiddleware の後に置きます。

  6. LocaleMiddleware

    SessionMiddleware (session データを使う) と UpdateCacheMiddleware (Vary ヘッダを修正する) の後のできるだけ高い位置に置きます。

  7. CommonMiddleware

    Before any middleware that may change the response (it sets the Content-Length header). A middleware that appears before CommonMiddleware and changes the response must reset Content-Length.

    APPEND_SLASH か PREPEND_WWW が True に設定されているとリダイレクトされるので、先頭の近くに置きます。

    After SessionMiddleware if you're using CSRF_USE_SESSIONS.

  8. CsrfViewMiddleware

    CSRF 攻撃が可能なすべての view ミドルウェアの前に置きます。

    Before RemoteUserMiddleware, or any other authentication middleware that may perform a login, and hence rotate the CSRF token, before calling down the middleware chain.

    After SessionMiddleware if you're using CSRF_USE_SESSIONS.

  9. AuthenticationMiddleware

    session ストレージを使うので、 SessionMiddleware の後に置きます。

  10. MessageMiddleware

    After SessionMiddleware: can use session-based storage.

  11. FetchFromCacheMiddleware

    キャッシュのハッシュキーを生成するのに Vary ヘッダを使用するため、このヘッダを修正するすべてのミドルウェアのあとに置きます。

  12. FlatpageFallbackMiddleware

    最後に実行されるタイプのミドルウェアなので、できるだけ下に置く必要があります。

  13. RedirectFallbackMiddleware

    最後に実行されるタイプのミドルウェアなので、できるだけ下に置く必要があります。

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