Internet Engineering Task Force (IETF)                          A. Barth
Request for Comments: 6265                                 U.C. Berkeley
Obsoletes: 2965                                               April 2011
Category: Standards Track
ISSN: 2070-1721

HTTP State Management Mechanism




This document defines the HTTP Cookie and Set-Cookie header fields. These header fields can be used by HTTP servers to store state (called cookies) at HTTP user agents, letting the servers maintain a stateful session over the mostly stateless HTTP protocol. Although cookies have many historical infelicities that degrade their security and privacy, the Cookie and Set-Cookie header fields are widely used on the Internet. This document obsoletes RFC 2965.

このドキュメントでは、HTTP CookieおよびSet-Cookieヘッダーフィールドを定義します。これらのヘッダーフィールドは、HTTPサーバーが状態(Cookieと呼ばれる)をHTTPユーザーエージェントに格納するために使用でき、サーバーがほとんどステートレスなHTTPプロトコルを介してステートフルセッションを維持できるようにします。 Cookieには、セキュリティとプライバシーを低下させる多くの歴史的な欠点がありますが、CookieおよびSet-Cookieヘッダーフィールドはインターネットで広く使用されています。このドキュメントはRFC 2965を廃止します。

Status of This Memo


This is an Internet Standards Track document.

これはInternet Standards Trackドキュメントです。

This document is a product of the Internet Engineering Task Force (IETF). It represents the consensus of the IETF community. It has received public review and has been approved for publication by the Internet Engineering Steering Group (IESG). Further information on Internet Standards is available in Section 2 of RFC 5741.

このドキュメントは、IETF(Internet Engineering Task Force)の製品です。これは、IETFコミュニティのコンセンサスを表しています。公開レビューを受け、インターネットエンジニアリングステアリンググループ(IESG)による公開が承認されました。インターネット標準の詳細については、RFC 5741のセクション2をご覧ください。

Information about the current status of this document, any errata, and how to provide feedback on it may be obtained at


Copyright Notice


Copyright (c) 2011 IETF Trust and the persons identified as the document authors. All rights reserved.

Copyright(c)2011 IETF Trustおよびドキュメントの作成者として識別された人物。全著作権所有。

This document is subject to BCP 78 and the IETF Trust's Legal Provisions Relating to IETF Documents ( in effect on the date of publication of this document. Please review these documents carefully, as they describe your rights and restrictions with respect to this document. Code Components extracted from this document must include Simplified BSD License text as described in Section 4.e of the Trust Legal Provisions and are provided without warranty as described in the Simplified BSD License.

この文書は、BCP 78およびこの文書の発行日に有効なIETF文書に関するIETFトラストの法的規定(の対象となります。これらのドキュメントは、このドキュメントに関するあなたの権利と制限を説明しているため、注意深く確認してください。このドキュメントから抽出されたコードコンポーネントには、Trust Legal Provisionsのセクション4.eに記載されているSimplified BSD Licenseのテキストが含まれている必要があり、Simplified BSD Licenseに記載されているように保証なしで提供されます。

This document may contain material from IETF Documents or IETF Contributions published or made publicly available before November 10, 2008. The person(s) controlling the copyright in some of this material may not have granted the IETF Trust the right to allow modifications of such material outside the IETF Standards Process. Without obtaining an adequate license from the person(s) controlling the copyright in such materials, this document may not be modified outside the IETF Standards Process, and derivative works of it may not be created outside the IETF Standards Process, except to format it for publication as an RFC or to translate it into languages other than English.

このドキュメントには、2008年11月10日より前に公開または公開されたIETFドキュメントまたはIETFコントリビューションの素材が含まれている場合があります。この素材の一部で著作権を管理している人が、IETFトラストにそのような素材の変更を許可する権利を付与していない可能性がありますIETF標準プロセス外。このような資料の著作権を管理する人から適切なライセンスを取得せずに、このドキュメントをIETF標準プロセス外で変更したり、その派生物をIETF標準プロセス外で作成したりすることはできません。 RFCとして、またはそれを英語以外の言語に翻訳するための出版物。

Table of Contents


   1. Introduction ....................................................3
   2. Conventions .....................................................4
      2.1. Conformance Criteria .......................................4
      2.2. Syntax Notation ............................................5
      2.3. Terminology ................................................5
   3. Overview ........................................................6
      3.1. Examples ...................................................6
   4. Server Requirements .............................................8
      4.1. Set-Cookie .................................................8
           4.1.1. Syntax ..............................................8
           4.1.2. Semantics (Non-Normative) ..........................10
      4.2. Cookie ....................................................13
           4.2.1. Syntax .............................................13
           4.2.2. Semantics ..........................................13
   5. User Agent Requirements ........................................14
      5.1. Subcomponent Algorithms ...................................14
           5.1.1. Dates ..............................................14
           5.1.2. Canonicalized Host Names ...........................16
           5.1.3. Domain Matching ....................................16
           5.1.4. Paths and Path-Match ...............................16
      5.2. The Set-Cookie Header .....................................17
           5.2.1. The Expires Attribute ..............................19
           5.2.2. The Max-Age Attribute ..............................20
           5.2.3. The Domain Attribute ...............................20
           5.2.4. The Path Attribute .................................21
           5.2.5. The Secure Attribute ...............................21
           5.2.6. The HttpOnly Attribute .............................21
      5.3. Storage Model .............................................21
      5.4. The Cookie Header .........................................25
   6. Implementation Considerations ..................................27
      6.1. Limits ....................................................27
      6.2. Application Programming Interfaces ........................27
      6.3. IDNA Dependency and Migration .............................27
   7. Privacy Considerations .........................................28
      7.1. Third-Party Cookies .......................................28
      7.2. User Controls .............................................28
      7.3. Expiration Dates ..........................................29
   8. Security Considerations ........................................29
      8.1. Overview ..................................................29
      8.2. Ambient Authority .........................................30
      8.3. Clear Text ................................................30
      8.4. Session Identifiers .......................................31
      8.5. Weak Confidentiality ......................................32
      8.6. Weak Integrity ............................................32
      8.7. Reliance on DNS ...........................................33
   9. IANA Considerations ............................................33
      9.1. Cookie ....................................................34
      9.2. Set-Cookie ................................................34
      9.3. Cookie2 ...................................................34
      9.4. Set-Cookie2 ...............................................34
   10. References ....................................................35
      10.1. Normative References .....................................35
      10.2. Informative References ...................................35
   Appendix A. Acknowledgements ......................................37
1. Introduction
1. はじめに

This document defines the HTTP Cookie and Set-Cookie header fields. Using the Set-Cookie header field, an HTTP server can pass name/value pairs and associated metadata (called cookies) to a user agent. When the user agent makes subsequent requests to the server, the user agent uses the metadata and other information to determine whether to return the name/value pairs in the Cookie header.

このドキュメントでは、HTTP CookieおよびSet-Cookieヘッダーフィールドを定義します。 Set-Cookieヘッダーフィールドを使用して、HTTPサーバーは名前/値のペアと関連するメタデータ(Cookieと呼ばれる)をユーザーエージェントに渡すことができます。ユーザーエージェントがサーバーに後続のリクエストを行うと、ユーザーエージェントはメタデータとその他の情報を使用して、Cookieヘッダーで名前と値のペアを返すかどうかを決定します。

Although simple on their surface, cookies have a number of complexities. For example, the server indicates a scope for each cookie when sending it to the user agent. The scope indicates the maximum amount of time in which the user agent should return the cookie, the servers to which the user agent should return the cookie, and the URI schemes for which the cookie is applicable.


For historical reasons, cookies contain a number of security and privacy infelicities. For example, a server can indicate that a given cookie is intended for "secure" connections, but the Secure attribute does not provide integrity in the presence of an active network attacker. Similarly, cookies for a given host are shared across all the ports on that host, even though the usual "same-origin policy" used by web browsers isolates content retrieved via different ports.


There are two audiences for this specification: developers of cookie-generating servers and developers of cookie-consuming user agents.


To maximize interoperability with user agents, servers SHOULD limit themselves to the well-behaved profile defined in Section 4 when generating cookies.


User agents MUST implement the more liberal processing rules defined in Section 5, in order to maximize interoperability with existing servers that do not conform to the well-behaved profile defined in Section 4.


This document specifies the syntax and semantics of these headers as they are actually used on the Internet. In particular, this document does not create new syntax or semantics beyond those in use today. The recommendations for cookie generation provided in Section 4 represent a preferred subset of current server behavior, and even the more liberal cookie processing algorithm provided in Section 5 does not recommend all of the syntactic and semantic variations in use today. Where some existing software differs from the recommended protocol in significant ways, the document contains a note explaining the difference.


Prior to this document, there were at least three descriptions of cookies: the so-called "Netscape cookie specification" [Netscape], RFC 2109 [RFC2109], and RFC 2965 [RFC2965]. However, none of these documents describe how the Cookie and Set-Cookie headers are actually used on the Internet (see [Kri2001] for historical context). In relation to previous IETF specifications of HTTP state management mechanisms, this document requests the following actions:

このドキュメントの前には、Cookieについて少なくとも3つの説明がありました。いわゆる「Netscape Cookie仕様」[Netscape]、RFC 2109 [RFC2109]、およびRFC 2965 [RFC2965]です。ただし、これらのドキュメントには、CookieおよびSet-Cookieヘッダーがインターネットで実際にどのように使用されるかについては記載されていません(歴史的なコンテキストについては[Kri2001]を参照してください)。 HTTP状態管理メカニズムの以前のIETF仕様に関連して、このドキュメントは次のアクションを要求します。

1. Change the status of [RFC2109] to Historic (it has already been obsoleted by [RFC2965]).

1. [RFC2109]のステータスを[歴史的]に変更します([RFC2965]によってすでに廃止されています)。

2. Change the status of [RFC2965] to Historic.

2. [RFC2965]のステータスを履歴に変更します。

3. Indicate that [RFC2965] has been obsoleted by this document.

3. [RFC2965]がこのドキュメントで廃止されたことを示します。

In particular, in moving RFC 2965 to Historic and obsoleting it, this document deprecates the use of the Cookie2 and Set-Cookie2 header fields.

特に、RFC 2965をHistoricに移行して廃止するにあたり、このドキュメントではCookie2およびSet-Cookie2ヘッダーフィールドの使用を廃止しています。

2. Conventions
2. 規約
2.1. Conformance Criteria
2.1. 適合基準

The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this document are to be interpreted as described in [RFC2119].

このドキュメントのキーワード「MUST」、「MUST NOT」、「REQUIRED」、「SHALL」、「SHALL NOT」、「SHOULD」、「SHOULD NOT」、「RECOMMENDED」、「MAY」、および「OPTIONAL」は、 [RFC2119]で説明されているように解釈されます。

Requirements phrased in the imperative as part of algorithms (such as "strip any leading space characters" or "return false and abort these steps") are to be interpreted with the meaning of the key word ("MUST", "SHOULD", "MAY", etc.) used in introducing the algorithm.

アルゴリズムの一部として命令で語られた要件(「先頭の空白文字を取り除く」または「falseを返してこれらの手順を中止する」など)は、キーワードの意味(「MUST」、「SHOULD」、「 MAY "など)を使用してアルゴリズムを紹介します。

Conformance requirements phrased as algorithms or specific steps can be implemented in any manner, so long as the end result is equivalent. In particular, the algorithms defined in this specification are intended to be easy to understand and are not intended to be performant.


2.2. Syntax Notation
2.2. 構文表記

This specification uses the Augmented Backus-Naur Form (ABNF) notation of [RFC5234].


The following core rules are included by reference, as defined in [RFC5234], Appendix B.1: ALPHA (letters), CR (carriage return), CRLF (CR LF), CTLs (controls), DIGIT (decimal 0-9), DQUOTE (double quote), HEXDIG (hexadecimal 0-9/A-F/a-f), LF (line feed), NUL (null octet), OCTET (any 8-bit sequence of data except NUL), SP (space), HTAB (horizontal tab), CHAR (any [USASCII] character), VCHAR (any visible [USASCII] character), and WSP (whitespace).

[RFC5234]、付録B.1で定義されているように、次のコアルールが参照として含まれています:ALPHA(文字)、CR(キャリッジリターン)、CRLF(CR LF)、CTL(コントロール)、DIGIT(10進数の0-9) 、DQUOTE(二重引用符)、HEXDIG(16進数の0-9 / AF / af)、LF(改行)、NUL(ヌルオクテット)、OCTET(NULを除く任意の8ビットデータシーケンス)、SP(スペース)、HTAB (水平タブ)、CHAR(任意の[USASCII]文字)、VCHAR(任意の表示可能な[USASCII]文字)、およびWSP(空白)。

The OWS (optional whitespace) rule is used where zero or more linear whitespace characters MAY appear:


   OWS            = *( [ obs-fold ] WSP )
                    ; "optional" whitespace
   obs-fold       = CRLF

OWS SHOULD either not be produced or be produced as a single SP character.


2.3. Terminology
2.3. 用語

The terms user agent, client, server, proxy, and origin server have the same meaning as in the HTTP/1.1 specification ([RFC2616], Section 1.3).

ユーザーエージェント、クライアント、サーバー、プロキシ、オリジンサーバーという用語は、HTTP / 1.1仕様([RFC2616]、セクション1.3)と同じ意味です。

The request-host is the name of the host, as known by the user agent, to which the user agent is sending an HTTP request or from which it is receiving an HTTP response (i.e., the name of the host to which it sent the corresponding HTTP request).


The term request-uri is defined in Section 5.1.2 of [RFC2616].


Two sequences of octets are said to case-insensitively match each other if and only if they are equivalent under the i;ascii-casemap collation defined in [RFC4790].

オクテットの2つのシーケンスは、[RFC4790]で定義されているi; ascii-casemap照合で同等である場合にのみ、大文字と小文字を区別せずに互いに一致すると言われています。

The term string means a sequence of non-NUL octets.


3. Overview
3. 概観

This section outlines a way for an origin server to send state information to a user agent and for the user agent to return the state information to the origin server.


To store state, the origin server includes a Set-Cookie header in an HTTP response. In subsequent requests, the user agent returns a Cookie request header to the origin server. The Cookie header contains cookies the user agent received in previous Set-Cookie headers. The origin server is free to ignore the Cookie header or use its contents for an application-defined purpose.

状態を保存するために、オリジンサーバーはHTTP応答にSet-Cookieヘッダーを含めます。後続のリクエストでは、ユーザーエージェントはCookieリクエストヘッダーをオリジンサーバーに返します。 Cookieヘッダーには、ユーザーエージェントが以前のSet-Cookieヘッダーで受信したCookieが含まれています。オリジンサーバーはCookieヘッダーを無視するか、アプリケーション定義の目的でそのコンテンツを使用できます。

Origin servers MAY send a Set-Cookie response header with any response. User agents MAY ignore Set-Cookie headers contained in responses with 100-level status codes but MUST process Set-Cookie headers contained in other responses (including responses with 400- and 500-level status codes). An origin server can include multiple Set-Cookie header fields in a single response. The presence of a Cookie or a Set-Cookie header field does not preclude HTTP caches from storing and reusing a response.

オリジンサーバーは、任意の応答とともにSet-Cookie応答ヘッダーを送信する場合があります。ユーザーエージェントは、100レベルのステータスコードを含む応答に含まれるSet-Cookieヘッダーを無視できますが、他の応答(400および500レベルのステータスコードを含む応答を含む)に含まれるSet-Cookieヘッダーを処理する必要があります。オリジンサーバーは、単一の応答に複数のSet-Cookieヘッダーフィールドを含めることができます。 CookieまたはSet-Cookieヘッダーフィールドが存在しても、HTTPキャッシュが応答を保存および再利用することを妨げるものではありません。

Origin servers SHOULD NOT fold multiple Set-Cookie header fields into a single header field. The usual mechanism for folding HTTP headers fields (i.e., as defined in [RFC2616]) might change the semantics of the Set-Cookie header field because the %x2C (",") character is used by Set-Cookie in a way that conflicts with such folding.

オリジンサーバーは、複数のSet-Cookieヘッダーフィールドを単一のヘッダーフィールドに折りたたむべきではありません。 %x2C(",")文字が競合する方法でSet-Cookieによって使用されるため、HTTPヘッダーフィールドを折りたたむ通常のメカニズム(つまり、[RFC2616]で定義されている)は、Set-Cookieヘッダーフィールドのセマンティクスを変更する可能性があります。そのような折りたたみで。

3.1. Examples
3.1. 例

Using the Set-Cookie header, a server can send the user agent a short string in an HTTP response that the user agent will return in future HTTP requests that are within the scope of the cookie. For example, the server can send the user agent a "session identifier" named SID with the value 31d4d96e407aad42. The user agent then returns the session identifier in subsequent requests.


   == Server -> User Agent ==
   Set-Cookie: SID=31d4d96e407aad42
   == User Agent -> Server ==
    Cookie: SID=31d4d96e407aad42

The server can alter the default scope of the cookie using the Path and Domain attributes. For example, the server can instruct the user agent to return the cookie to every path and every subdomain of


   == Server -> User Agent ==
   Set-Cookie: SID=31d4d96e407aad42; Path=/;
   == User Agent -> Server ==
   Cookie: SID=31d4d96e407aad42

As shown in the next example, the server can store multiple cookies at the user agent. For example, the server can store a session identifier as well as the user's preferred language by returning two Set-Cookie header fields. Notice that the server uses the Secure and HttpOnly attributes to provide additional security protections for the more sensitive session identifier (see Section 4.1.2.)


   == Server -> User Agent ==
   Set-Cookie: SID=31d4d96e407aad42; Path=/; Secure; HttpOnly
   Set-Cookie: lang=en-US; Path=/;
   == User Agent -> Server ==
   Cookie: SID=31d4d96e407aad42; lang=en-US

Notice that the Cookie header above contains two cookies, one named SID and one named lang. If the server wishes the user agent to persist the cookie over multiple "sessions" (e.g., user agent restarts), the server can specify an expiration date in the Expires attribute. Note that the user agent might delete the cookie before the expiration date if the user agent's cookie store exceeds its quota or if the user manually deletes the server's cookie.


   == Server -> User Agent ==
   Set-Cookie: lang=en-US; Expires=Wed, 09 Jun 2021 10:18:14 GMT
   == User Agent -> Server ==
   Cookie: SID=31d4d96e407aad42; lang=en-US

Finally, to remove a cookie, the server returns a Set-Cookie header with an expiration date in the past. The server will be successful in removing the cookie only if the Path and the Domain attribute in the Set-Cookie header match the values used when the cookie was created.

最後に、Cookieを削除するために、サーバーは過去の有効期限のあるSet-Cookieヘッダーを返します。 Set-Cookieヘッダーのパスとドメイン属性がCookieの作成時に使用された値と一致する場合のみ、サーバーはCookieの削除に成功します。

   == Server -> User Agent ==
   Set-Cookie: lang=; Expires=Sun, 06 Nov 1994 08:49:37 GMT
   == User Agent -> Server ==

Cookie: SID=31d4d96e407aad42

4. Server Requirements
4. サーバー要件

This section describes the syntax and semantics of a well-behaved profile of the Cookie and Set-Cookie headers.


4.1. セットクッキー

The Set-Cookie HTTP response header is used to send cookies from the server to the user agent.

Set-Cookie HTTP応答ヘッダーは、サーバーからユーザーエージェントにCookieを送信するために使用されます。

4.1.1. Syntax
4.1.1. 構文

Informally, the Set-Cookie response header contains the header name "Set-Cookie" followed by a ":" and a cookie. Each cookie begins with a name-value-pair, followed by zero or more attribute-value pairs. Servers SHOULD NOT send Set-Cookie headers that fail to conform to the following grammar:

非公式には、Set-Cookie応答ヘッダーには、ヘッダー名「Set-Cookie」と、それに続く「:」とCookieが含まれます。各Cookieは名前と値のペアで始まり、その後に0個以上の属性と値のペアが続きます。サーバーは、次の文法に準拠しないSet-Cookieヘッダーを送信してはなりません(SHOULD NOT)。

 set-cookie-header = "Set-Cookie:" SP set-cookie-string
 set-cookie-string = cookie-pair *( ";" SP cookie-av )
 cookie-pair       = cookie-name "=" cookie-value
 cookie-name       = token
 cookie-value      = *cookie-octet / ( DQUOTE *cookie-octet DQUOTE )
 cookie-octet      = %x21 / %x23-2B / %x2D-3A / %x3C-5B / %x5D-7E
                       ; US-ASCII characters excluding CTLs,
                       ; whitespace DQUOTE, comma, semicolon,
                       ; and backslash
 token             = <token, defined in [RFC2616], Section 2.2>
 cookie-av         = expires-av / max-age-av / domain-av /
                     path-av / secure-av / httponly-av /
 expires-av        = "Expires=" sane-cookie-date
 sane-cookie-date  = <rfc1123-date, defined in [RFC2616], Section 3.3.1>
 max-age-av        = "Max-Age=" non-zero-digit *DIGIT
                       ; In practice, both expires-av and max-age-av
                       ; are limited to dates representable by the
                       ; user agent.
 non-zero-digit    = %x31-39
                       ; digits 1 through 9
 domain-av         = "Domain=" domain-value
 domain-value      = <subdomain>
                       ; defined in [RFC1034], Section 3.5, as
                       ; enhanced by [RFC1123], Section 2.1
 path-av           = "Path=" path-value
 path-value        = <any CHAR except CTLs or ";">
 secure-av         = "Secure"
 httponly-av       = "HttpOnly"
 extension-av      = <any CHAR except CTLs or ";">

Note that some of the grammatical terms above reference documents that use different grammatical notations than this document (which uses ABNF from [RFC5234]).


The semantics of the cookie-value are not defined by this document.


To maximize compatibility with user agents, servers that wish to store arbitrary data in a cookie-value SHOULD encode that data, for example, using Base64 [RFC4648].

ユーザーエージェントとの互換性を最大化するために、cookie-valueに任意のデータを格納するサーバーは、たとえばBase64 [RFC4648]を使用してそのデータをエンコードする必要があります(SHOULD)。

The portions of the set-cookie-string produced by the cookie-av term are known as attributes. To maximize compatibility with user agents, servers SHOULD NOT produce two attributes with the same name in the same set-cookie-string. (See Section 5.3 for how user agents handle this case.) Servers SHOULD NOT include more than one Set-Cookie header field in the same response with the same cookie-name. (See Section 5.2 for how user agents handle this case.)

cookie-av用語によって生成されるset-cookie-stringの部分は、属性と呼ばれます。ユーザーエージェントとの互換性を最大にするために、サーバーは、同じset-cookie-stringに同じ名前の2つの属性を生成するべきではありません(SHOULD NOT)。 (ユーザーエージェントがこのケースを処理する方法については、セクション5.3を参照してください。)サーバーは、同じcookie-nameを持つ同じ応答に複数のSet-Cookieヘッダーフィールドを含めないでください。 (ユーザーエージェントがこのケースを処理する方法については、セクション5.2を参照してください。)

If a server sends multiple responses containing Set-Cookie headers concurrently to the user agent (e.g., when communicating with the user agent over multiple sockets), these responses create a "race condition" that can lead to unpredictable behavior.


NOTE: Some existing user agents differ in their interpretation of two-digit years. To avoid compatibility issues, servers SHOULD use the rfc1123-date format, which requires a four-digit year.


NOTE: Some user agents store and process dates in cookies as 32-bit UNIX time_t values. Implementation bugs in the libraries supporting time_t processing on some systems might cause such user agents to process dates after the year 2038 incorrectly.

注:一部のユーザーエージェントは、日付を32ビットUNIX time_t値としてCookieに保存して処理します。一部のシステムでtime_t処理をサポートするライブラリの実装バグにより、そのようなユーザーエージェントは2038年以降の日付を誤って処理する可能性があります。

4.1.2. Semantics (Non-Normative)
4.1.2. セマンティクス(非規範的)

This section describes simplified semantics of the Set-Cookie header. These semantics are detailed enough to be useful for understanding the most common uses of cookies by servers. The full semantics are described in Section 5.


When the user agent receives a Set-Cookie header, the user agent stores the cookie together with its attributes. Subsequently, when the user agent makes an HTTP request, the user agent includes the applicable, non-expired cookies in the Cookie header.


If the user agent receives a new cookie with the same cookie-name, domain-value, and path-value as a cookie that it has already stored, the existing cookie is evicted and replaced with the new cookie. Notice that servers can delete cookies by sending the user agent a new cookie with an Expires attribute with a value in the past.


Unless the cookie's attributes indicate otherwise, the cookie is returned only to the origin server (and not, for example, to any subdomains), and it expires at the end of the current session (as defined by the user agent). User agents ignore unrecognized cookie attributes (but not the entire cookie).

Cookieの属性が別の方法を示していない限り、Cookieは元のサーバーにのみ返され(たとえば、サブドメインには返されません)、現在のセッションの終了時に期限切れになります(ユーザーエージェントによって定義されます)。ユーザーエージェントは、認識されないCookie属性を無視します(ただし、Cookie全体は無視しません)。 The Expires Attribute Expires属性

The Expires attribute indicates the maximum lifetime of the cookie, represented as the date and time at which the cookie expires. The user agent is not required to retain the cookie until the specified date has passed. In fact, user agents often evict cookies due to memory pressure or privacy concerns.

Expires属性は、Cookieの最大有効期間を示し、Cookieが期限切れになる日時として表されます。ユーザーエージェントは、指定された日付が経過するまでCookieを保持する必要はありません。実際、メモリプレッシャーやプライバシーの問題により、ユーザーエージェントはCookieを削除することがよくあります。 The Max-Age Attribute Max-Age属性

The Max-Age attribute indicates the maximum lifetime of the cookie, represented as the number of seconds until the cookie expires. The user agent is not required to retain the cookie for the specified duration. In fact, user agents often evict cookies due to memory pressure or privacy concerns.


NOTE: Some existing user agents do not support the Max-Age attribute. User agents that do not support the Max-Age attribute ignore the attribute.

注:一部の既存のユーザーエージェントは、Max-Age属性をサポートしていません。 Max-Age属性をサポートしないユーザーエージェントは、属性を無視します。

If a cookie has both the Max-Age and the Expires attribute, the Max-Age attribute has precedence and controls the expiration date of the cookie. If a cookie has neither the Max-Age nor the Expires attribute, the user agent will retain the cookie until "the current session is over" (as defined by the user agent).

CookieにMax-Age属性とExpires属性の両方がある場合、Max-Age属性が優先され、Cookieの有効期限を制御します。 CookieにMax-Age属性もExpires属性もない場合、ユーザーエージェントは「現在のセッションが終了する」まで(ユーザーエージェントによって定義されたとおり)Cookieを保持します。 The Domain Attribute ドメイン属性

The Domain attribute specifies those hosts to which the cookie will be sent. For example, if the value of the Domain attribute is "", the user agent will include the cookie in the Cookie header when making HTTP requests to,, and (Note that a leading %x2E ("."), if present, is ignored even though that character is not permitted, but a trailing %x2E ("."), if present, will cause the user agent to ignore the attribute.) If the server omits the Domain attribute, the user agent will return the cookie only to the origin server.

Domain属性は、Cookieの送信先となるホストを指定します。たとえば、ドメイン属性の値が「」の場合、ユーザーエージェントは、、、www.corp.exampleにHTTPリクエストを送信するときに、CookieヘッダーにCookieを含めます。 com。 (先頭の%x2E(".")が存在する場合、その文字は許可されていませんが無視されますが、末尾の%x2E(".")が存在する場合、ユーザーエージェントは属性を無視します。 )サーバーがドメイン属性を省略した場合、ユーザーエージェントはCookieを元のサーバーにのみ返します。

WARNING: Some existing user agents treat an absent Domain attribute as if the Domain attribute were present and contained the current host name. For example, if returns a Set-Cookie header without a Domain attribute, these user agents will erroneously send the cookie to as well.


The user agent will reject cookies unless the Domain attribute specifies a scope for the cookie that would include the origin server. For example, the user agent will accept a cookie with a Domain attribute of "" or of "" from, but the user agent will not accept a cookie with a Domain attribute of "" or of "".

ドメイン属性がオリジンサーバーを含むCookieのスコープを指定しない限り、ユーザーエージェントはCookieを拒否します。たとえば、ユーザーエージェントは、ドメイン属性が「」または「」のcookieをfoo.example.comから受け入れますが、ユーザーエージェントは、ドメイン属性のCookieを受け入れません。 ""または ""。

NOTE: For security reasons, many user agents are configured to reject Domain attributes that correspond to "public suffixes". For example, some user agents will reject Domain attributes of "com" or "". (See Section 5.3 for more information.)

注:セキュリティ上の理由から、多くのユーザーエージェントは、「パブリックサフィックス」に対応するドメイン属性を拒否するように構成されています。たとえば、一部のユーザーエージェントは、「com」または「」のドメイン属性を拒否します。 (詳細については、セクション5.3を参照してください。) The Path Attribute パス属性

The scope of each cookie is limited to a set of paths, controlled by the Path attribute. If the server omits the Path attribute, the user agent will use the "directory" of the request-uri's path component as the default value. (See Section 5.1.4 for more details.)

各Cookieのスコープは、Path属性で制御される一連のパスに制限されています。サーバーがPath属性を省略した場合、ユーザーエージェントはrequest-uriのパスコンポーネントの「ディレクトリ」をデフォルト値として使用します。 (詳細については、セクション5.1.4を参照してください。)

The user agent will include the cookie in an HTTP request only if the path portion of the request-uri matches (or is a subdirectory of) the cookie's Path attribute, where the %x2F ("/") character is interpreted as a directory separator.


Although seemingly useful for isolating cookies between different paths within a given host, the Path attribute cannot be relied upon for security (see Section 8).

特定のホスト内の異なるパス間でcookieを分離するのに役立つように見えますが、Path属性はセキュリティに依存できません(セクション8を参照)。 The Secure Attribute 安全な属性

The Secure attribute limits the scope of the cookie to "secure" channels (where "secure" is defined by the user agent). When a cookie has the Secure attribute, the user agent will include the cookie in an HTTP request only if the request is transmitted over a secure channel (typically HTTP over Transport Layer Security (TLS) [RFC2818]).

Secure属性は、Cookieの範囲を「セキュア」チャネルに制限します(「セキュア」はユーザーエージェントによって定義されます)。 CookieにSecure属性が設定されている場合、ユーザーエージェントは、要求がセキュリティで保護されたチャネル(通常はHTTP over Transport Layer Security(TLS)[RFC2818])経由で送信される場合にのみ、HTTP要求にCookieを含めます。

Although seemingly useful for protecting cookies from active network attackers, the Secure attribute protects only the cookie's confidentiality. An active network attacker can overwrite Secure cookies from an insecure channel, disrupting their integrity (see Section 8.6 for more details).

Secure属性は、アクティブなネットワーク攻撃者からCookieを保護するのに役立つように見えますが、Cookieの機密性のみを保護します。アクティブなネットワーク攻撃者は、安全でないチャネルからセキュアCookieを上書きして、整合性を破壊する可能性があります(詳細については、セクション8.6を参照してください)。 The HttpOnly Attribute HttpOnly属性

The HttpOnly attribute limits the scope of the cookie to HTTP requests. In particular, the attribute instructs the user agent to omit the cookie when providing access to cookies via "non-HTTP" APIs (such as a web browser API that exposes cookies to scripts).


Note that the HttpOnly attribute is independent of the Secure attribute: a cookie can have both the HttpOnly and the Secure attribute.


4.2. クッキー
4.2.1. Syntax
4.2.1. 構文

The user agent sends stored cookies to the origin server in the Cookie header. If the server conforms to the requirements in Section 4.1 (and the user agent conforms to the requirements in Section 5), the user agent will send a Cookie header that conforms to the following grammar:


   cookie-header = "Cookie:" OWS cookie-string OWS
   cookie-string = cookie-pair *( ";" SP cookie-pair )
4.2.2. Semantics
4.2.2. 意味論

Each cookie-pair represents a cookie stored by the user agent. The cookie-pair contains the cookie-name and cookie-value the user agent received in the Set-Cookie header.

各cookieペアは、ユーザーエージェントによって保存されたcookieを表します。 cookie-pairには、ユーザーエージェントがSet-Cookieヘッダーで受信したcookie-nameとcookie-valueが含まれます。

Notice that the cookie attributes are not returned. In particular, the server cannot determine from the Cookie header alone when a cookie will expire, for which hosts the cookie is valid, for which paths the cookie is valid, or whether the cookie was set with the Secure or HttpOnly attributes.


The semantics of individual cookies in the Cookie header are not defined by this document. Servers are expected to imbue these cookies with application-specific semantics.


Although cookies are serialized linearly in the Cookie header, servers SHOULD NOT rely upon the serialization order. In particular, if the Cookie header contains two cookies with the same name (e.g., that were set with different Path or Domain attributes), servers SHOULD NOT rely upon the order in which these cookies appear in the header.


5. User Agent Requirements
5. ユーザーエージェントの要件

This section specifies the Cookie and Set-Cookie headers in sufficient detail that a user agent implementing these requirements precisely can interoperate with existing servers (even those that do not conform to the well-behaved profile described in Section 4).


A user agent could enforce more restrictions than those specified herein (e.g., for the sake of improved security); however, experiments have shown that such strictness reduces the likelihood that a user agent will be able to interoperate with existing servers.


5.1. Subcomponent Algorithms
5.1. サブコンポーネントアルゴリズム

This section defines some algorithms used by user agents to process specific subcomponents of the Cookie and Set-Cookie headers.


5.1.1. Dates
5.1.1. 日付

The user agent MUST use an algorithm equivalent to the following algorithm to parse a cookie-date. Note that the various boolean flags defined as a part of the algorithm (i.e., found-time, found-day-of-month, found-month, found-year) are initially "not set".


1. Using the grammar below, divide the cookie-date into date-tokens.

1. 以下の文法を使用して、cookie-dateを日付トークンに分割します。

   cookie-date     = *delimiter date-token-list *delimiter
   date-token-list = date-token *( 1*delimiter date-token )
   date-token      = 1*non-delimiter
   delimiter       = %x09 / %x20-2F / %x3B-40 / %x5B-60 / %x7B-7E
   non-delimiter   = %x00-08 / %x0A-1F / DIGIT / ":" / ALPHA / %x7F-FF
   non-digit       = %x00-2F / %x3A-FF
   day-of-month    = 1*2DIGIT ( non-digit *OCTET )
   month           = ( "jan" / "feb" / "mar" / "apr" /
                       "may" / "jun" / "jul" / "aug" /
                       "sep" / "oct" / "nov" / "dec" ) *OCTET
   year            = 2*4DIGIT ( non-digit *OCTET )
   time            = hms-time ( non-digit *OCTET )
   hms-time        = time-field ":" time-field ":" time-field
   time-field      = 1*2DIGIT

2. Process each date-token sequentially in the order the date-tokens appear in the cookie-date: 1. If the found-time flag is not set and the token matches the time production, set the found-time flag and set the hour-value, minute-value, and second-value to the numbers denoted by the digits in the date-token, respectively. Skip the remaining sub-steps and continue to the next date-token.

2.日付トークンがcookie-dateに表示される順序で各日付トークンを順番に処理します。1. found-timeフラグが設定されておらず、トークンが時刻の生産と一致する場合、found-timeフラグを設定し、時間値、分値、秒値をそれぞれ、日付トークンの数字で示される数値に変換します。残りのサブステップをスキップして、次の日付トークンに進みます。

2. If the found-day-of-month flag is not set and the date-token matches the day-of-month production, set the found-day-of-month flag and set the day-of-month-value to the number denoted by the date-token. Skip the remaining sub-steps and continue to the next date-token.

2. found-day-of-monthフラグが設定されておらず、date-tokenがday-of-monthの生産と一致する場合は、found-day-of-monthフラグを設定し、day-of-month-valueを数値に設定します。日付トークンで示されます。残りのサブステップをスキップして、次の日付トークンに進みます。

3. If the found-month flag is not set and the date-token matches the month production, set the found-month flag and set the month-value to the month denoted by the date-token. Skip the remaining sub-steps and continue to the next date-token.

3. found-monthフラグが設定されておらず、date-tokenが月の生産と一致している場合は、found-monthフラグを設定し、month-valueをdate-tokenで示される月に設定します。残りのサブステップをスキップして、次の日付トークンに進みます。

4. If the found-year flag is not set and the date-token matches the year production, set the found-year flag and set the year-value to the number denoted by the date-token. Skip the remaining sub-steps and continue to the next date-token.

4. found-yearフラグが設定されておらず、date-tokenがyear productionと一致している場合は、found-yearフラグを設定して、year-valueをdate-tokenで示される数値に設定します。残りのサブステップをスキップして、次の日付トークンに進みます。

3. If the year-value is greater than or equal to 70 and less than or equal to 99, increment the year-value by 1900.

3. 年の値が70以上99以下の場合、年の値を1900だけ増やします。

4. If the year-value is greater than or equal to 0 and less than or equal to 69, increment the year-value by 2000.

4. 年の値が0以上69以下の場合、年の値を2000だけ増やします。

1. NOTE: Some existing user agents interpret two-digit years differently.

1. 注:一部の既存のユーザーエージェントでは、2桁の年の解釈が異なります。

5. Abort these steps and fail to parse the cookie-date if:

5. 次の場合、これらの手順を中止し、cookie-dateの解析に失敗します。

* at least one of the found-day-of-month, found-month, found-year, or found-time flags is not set,

* 発見日、発見月、発見年、発見時刻のフラグの少なくとも1つが設定されていない。

* the day-of-month-value is less than 1 or greater than 31,

* 日の値が1未満または31より大きい

* the year-value is less than 1601,

* 年の値が1601未満

* the hour-value is greater than 23,

* 時間の値が23より大きい

* the minute-value is greater than 59, or

* 分の値が59より大きい

* the second-value is greater than 59.

* 2番目の値が59より大きい

(Note that leap seconds cannot be represented in this syntax.)


6. Let the parsed-cookie-date be the date whose day-of-month, month, year, hour, minute, and second (in UTC) are the day-of-month-value, the month-value, the year-value, the hour-value, the minute-value, and the second-value, respectively. If no such date exists, abort these steps and fail to parse the cookie-date.

6. parsed-cookie-dateを、日、月、年、時、分、秒(UTC)が、月の値、月の値、年の値である日付とする、時間値、分値、秒値。そのような日付が存在しない場合、これらの手順を中止し、cookie-dateの解析に失敗します。

7. Return the parsed-cookie-date as the result of this algorithm.

7. このアルゴリズムの結果としてparsed-cookie-dateを返します。

5.1.2. Canonicalized Host Names
5.1.2. 正規化されたホスト名

A canonicalized host name is the string generated by the following algorithm:


1. Convert the host name to a sequence of individual domain name labels.

1. ホスト名を個々のドメイン名ラベルのシーケンスに変換します。

2. Convert each label that is not a Non-Reserved LDH (NR-LDH) label, to an A-label (see Section of [RFC5890] for the former and latter), or to a "punycode label" (a label resulting from the "ToASCII" conversion in Section 4 of [RFC3490]), as appropriate (see Section 6.3 of this specification).

2. Non-Reserved LDH(NR-LDH)ラベルではない各ラベルをAラベル(前者と後者については[RFC5890]のセクション2.3.2.1を参照)、または「punycodeラベル」(ラベル[RFC3490]のセクション4の「ToASCII」変換の結果として)(必要に応じて)(この仕様のセクション6.3を参照)。

3. Concatenate the resulting labels, separated by a %x2E (".") character.

3. %x2E(".")文字で区切られた結果のラベルを連結します。

5.1.3. Domain Matching
5.1.3. ドメインマッチング

A string domain-matches a given domain string if at least one of the following conditions hold:


o The domain string and the string are identical. (Note that both the domain string and the string will have been canonicalized to lower case at this point.)

o ドメイン文字列と文字列は同じです。 (この時点では、ドメイン文字列と文字列の両方が小文字に正規化されていることに注意してください。)

o All of the following conditions hold:

o 次の条件がすべて満たされます。

* The domain string is a suffix of the string.

* ドメイン文字列は、文字列のサフィックスです。

* The last character of the string that is not included in the domain string is a %x2E (".") character.

* ドメイン文字列に含まれていない文字列の最後の文字は、%x2E(".")文字です。

* The string is a host name (i.e., not an IP address).

* 文字列はホスト名です(つまり、IPアドレスではありません)。

5.1.4. Paths and Path-Match
5.1.4. パスとパスマッチ

The user agent MUST use an algorithm equivalent to the following algorithm to compute the default-path of a cookie: 1. Let uri-path be the path portion of the request-uri if such a portion exists (and empty otherwise). For example, if the request-uri contains just a path (and optional query string), then the uri-path is that path (without the %x3F ("?") character or query string), and if the request-uri contains a full absoluteURI, the uri-path is the path component of that URI.


2. If the uri-path is empty or if the first character of the uri-path is not a %x2F ("/") character, output %x2F ("/") and skip the remaining steps.

2. uri-pathが空の場合、またはuri-pathの最初の文字が%x2F("/")文字でない場合は、%x2F("/")を出力し、残りの手順をスキップします。

3. If the uri-path contains no more than one %x2F ("/") character, output %x2F ("/") and skip the remaining step.

3. uri-pathに含まれる%x2F("/")文字が1つ以下の場合は、%x2F("/")を出力し、残りの手順をスキップします。

4. Output the characters of the uri-path from the first character up to, but not including, the right-most %x2F ("/").

4. 最初の文字から右端の%x2F("/")までのuri-pathの文字を出力します。

A request-path path-matches a given cookie-path if at least one of the following conditions holds:


o The cookie-path and the request-path are identical.

o cookie-pathとrequest-pathは同じです。

o The cookie-path is a prefix of the request-path, and the last character of the cookie-path is %x2F ("/").

o cookie-pathはrequest-pathのプレフィックスであり、cookie-pathの最後の文字は%x2F("/")です。

o The cookie-path is a prefix of the request-path, and the first character of the request-path that is not included in the cookie-path is a %x2F ("/") character.

o cookie-pathはrequest-pathのプレフィックスであり、cookie-pathに含まれていないrequest-pathの最初の文字は%x2F("/")文字です。

5.2. Set-Cookieヘッダー

When a user agent receives a Set-Cookie header field in an HTTP response, the user agent MAY ignore the Set-Cookie header field in its entirety. For example, the user agent might wish to block responses to "third-party" requests from setting cookies (see Section 7.1).


If the user agent does not ignore the Set-Cookie header field in its entirety, the user agent MUST parse the field-value of the Set-Cookie header field as a set-cookie-string (defined below).


NOTE: The algorithm below is more permissive than the grammar in Section 4.1. For example, the algorithm strips leading and trailing whitespace from the cookie name and value (but maintains internal whitespace), whereas the grammar in Section 4.1 forbids whitespace in these positions. User agents use this algorithm so as to interoperate with servers that do not follow the recommendations in Section 4.


A user agent MUST use an algorithm equivalent to the following algorithm to parse a "set-cookie-string":


1. If the set-cookie-string contains a %x3B (";") character:

1. set-cookie-stringに%x3B(";")文字が含まれている場合:

The name-value-pair string consists of the characters up to, but not including, the first %x3B (";"), and the unparsed-attributes consist of the remainder of the set-cookie-string (including the %x3B (";") in question).




The name-value-pair string consists of all the characters contained in the set-cookie-string, and the unparsed-attributes is the empty string.


2. If the name-value-pair string lacks a %x3D ("=") character, ignore the set-cookie-string entirely.

2. 名前と値のペアの文字列に%x3D("=")文字がない場合は、set-cookie-stringを完全に無視してください。

3. The (possibly empty) name string consists of the characters up to, but not including, the first %x3D ("=") character, and the (possibly empty) value string consists of the characters after the first %x3D ("=") character.

3. (場合によっては空の)名前文字列は、最初の%x3D("=")文字までの文字で構成され、(おそらく空の)値文字列は、最初の%x3D("="の後の文字で構成されます) キャラクター。

4. Remove any leading or trailing WSP characters from the name string and the value string.

4. 名前文字列と値文字列から先頭または末尾のWSP文字を削除します。

5. If the name string is empty, ignore the set-cookie-string entirely.

5. 名前文字列が空の場合は、set-cookie-stringを完全に無視してください。

6. The cookie-name is the name string, and the cookie-value is the value string.

6. cookie-nameは名前の文字列で、cookie-valueは値の文字列です。

The user agent MUST use an algorithm equivalent to the following algorithm to parse the unparsed-attributes:


1. If the unparsed-attributes string is empty, skip the rest of these steps.

1. unparsed-attributes文字列が空の場合、残りの手順をスキップします。

2. Discard the first character of the unparsed-attributes (which will be a %x3B (";") character).

2. 解析されていない属性の最初の文字(%x3B(";")文字になります)を破棄します。

3. If the remaining unparsed-attributes contains a %x3B (";") character:

3. 残りの解析されていない属性に%x3B(";")文字が含まれている場合:

Consume the characters of the unparsed-attributes up to, but not including, the first %x3B (";") character.




Consume the remainder of the unparsed-attributes.


Let the cookie-av string be the characters consumed in this step.


4. If the cookie-av string contains a %x3D ("=") character:

4. cookie-av文字列に%x3D("=")文字が含まれている場合:

The (possibly empty) attribute-name string consists of the characters up to, but not including, the first %x3D ("=") character, and the (possibly empty) attribute-value string consists of the characters after the first %x3D ("=") character.




The attribute-name string consists of the entire cookie-av string, and the attribute-value string is empty.


5. Remove any leading or trailing WSP characters from the attribute-name string and the attribute-value string.

5. 属性名の文字列と属性値の文字列から、先頭または末尾のWSP文字を削除します。

6. Process the attribute-name and attribute-value according to the requirements in the following subsections. (Notice that attributes with unrecognized attribute-names are ignored.)

6. 以下のサブセクションの要件に従って、属性名と属性値を処理します。 (認識されない属性名を持つ属性は無視されることに注意してください。)

7. Return to Step 1 of this algorithm.

7. このアルゴリズムのステップ1に戻ります。

When the user agent finishes parsing the set-cookie-string, the user agent is said to "receive a cookie" from the request-uri with name cookie-name, value cookie-value, and attributes cookie-attribute-list. (See Section 5.3 for additional requirements triggered by receiving a cookie.)

ユーザーエージェントがset-cookie-stringの解析を完了すると、ユーザーエージェントは、名前cookie-name、値cookie-value、および属性cookie-attribute-listを使用して、request-uriから「Cookieを受信する」と言います。 (Cookieの受信によってトリガーされる追加の要件については、セクション5.3を参照してください。)

5.2.1. The Expires Attribute
5.2.1. Expires属性

If the attribute-name case-insensitively matches the string "Expires", the user agent MUST process the cookie-av as follows.


Let the expiry-time be the result of parsing the attribute-value as cookie-date (see Section 5.1.1).


If the attribute-value failed to parse as a cookie date, ignore the cookie-av.


If the expiry-time is later than the last date the user agent can represent, the user agent MAY replace the expiry-time with the last representable date.


If the expiry-time is earlier than the earliest date the user agent can represent, the user agent MAY replace the expiry-time with the earliest representable date.


Append an attribute to the cookie-attribute-list with an attribute-name of Expires and an attribute-value of expiry-time.


5.2.2. The Max-Age Attribute
5.2.2. Max-Age属性

If the attribute-name case-insensitively matches the string "Max-Age", the user agent MUST process the cookie-av as follows.


If the first character of the attribute-value is not a DIGIT or a "-" character, ignore the cookie-av.

attribute-valueの最初の文字がDIGITまたは "-"文字でない場合は、cookie-avを無視してください。

If the remainder of attribute-value contains a non-DIGIT character, ignore the cookie-av.


Let delta-seconds be the attribute-value converted to an integer.


If delta-seconds is less than or equal to zero (0), let expiry-time be the earliest representable date and time. Otherwise, let the expiry-time be the current date and time plus delta-seconds seconds.


Append an attribute to the cookie-attribute-list with an attribute-name of Max-Age and an attribute-value of expiry-time.


5.2.3. The Domain Attribute
5.2.3. ドメイン属性

If the attribute-name case-insensitively matches the string "Domain", the user agent MUST process the cookie-av as follows.


If the attribute-value is empty, the behavior is undefined. However, the user agent SHOULD ignore the cookie-av entirely.


If the first character of the attribute-value string is %x2E ("."):


Let cookie-domain be the attribute-value without the leading %x2E (".") character.




Let cookie-domain be the entire attribute-value.


Convert the cookie-domain to lower case.


Append an attribute to the cookie-attribute-list with an attribute-name of Domain and an attribute-value of cookie-domain.


5.2.4. The Path Attribute
5.2.4. パス属性

If the attribute-name case-insensitively matches the string "Path", the user agent MUST process the cookie-av as follows.


If the attribute-value is empty or if the first character of the attribute-value is not %x2F ("/"):


Let cookie-path be the default-path.




Let cookie-path be the attribute-value.


Append an attribute to the cookie-attribute-list with an attribute-name of Path and an attribute-value of cookie-path.


5.2.5. The Secure Attribute
5.2.5. 安全な属性

If the attribute-name case-insensitively matches the string "Secure", the user agent MUST append an attribute to the cookie-attribute-list with an attribute-name of Secure and an empty attribute-value.


5.2.6. The HttpOnly Attribute
5.2.6. HttpOnly属性

If the attribute-name case-insensitively matches the string "HttpOnly", the user agent MUST append an attribute to the cookie-attribute-list with an attribute-name of HttpOnly and an empty attribute-value.


5.3. Storage Model
5.3. ストレージモデル

The user agent stores the following fields about each cookie: name, value, expiry-time, domain, path, creation-time, last-access-time, persistent-flag, host-only-flag, secure-only-flag, and http-only-flag.


When the user agent "receives a cookie" from a request-uri with name cookie-name, value cookie-value, and attributes cookie-attribute-list, the user agent MUST process the cookie as follows:


1. A user agent MAY ignore a received cookie in its entirety. For example, the user agent might wish to block receiving cookies from "third-party" responses or the user agent might not wish to store cookies that exceed some size.

1. ユーザーエージェントは、受け取ったクッキーを完全に無視してもよい(MAY)。たとえば、ユーザーエージェントが「サードパーティ」の応答からのCookieの受信をブロックしたい場合や、ユーザーエージェントが一定のサイズを超えるCookieを保存したくない場合があります。

2. Create a new cookie with name cookie-name, value cookie-value. Set the creation-time and the last-access-time to the current date and time.

2. 名前cookie-name、値cookie-valueで新しいcookieを作成します。作成時刻と最終アクセス時刻を現在の日付と時刻に設定します。

3. If the cookie-attribute-list contains an attribute with an attribute-name of "Max-Age":

3. cookie-attribute-listに属性名が「Max-Age」の属性が含まれている場合:

Set the cookie's persistent-flag to true.


Set the cookie's expiry-time to attribute-value of the last attribute in the cookie-attribute-list with an attribute-name of "Max-Age".


Otherwise, if the cookie-attribute-list contains an attribute with an attribute-name of "Expires" (and does not contain an attribute with an attribute-name of "Max-Age"):


Set the cookie's persistent-flag to true.


Set the cookie's expiry-time to attribute-value of the last attribute in the cookie-attribute-list with an attribute-name of "Expires".




Set the cookie's persistent-flag to false.


Set the cookie's expiry-time to the latest representable date.


4. If the cookie-attribute-list contains an attribute with an attribute-name of "Domain":

4. cookie-attribute-listに「ドメイン」の属性名を持つ属性が含まれている場合:

Let the domain-attribute be the attribute-value of the last attribute in the cookie-attribute-list with an attribute-name of "Domain".




Let the domain-attribute be the empty string.


5. If the user agent is configured to reject "public suffixes" and the domain-attribute is a public suffix:

5. ユーザーエージェントが「パブリックサフィックス」を拒否するように構成されていて、ドメイン属性がパブリックサフィックスである場合:

If the domain-attribute is identical to the canonicalized request-host:


Let the domain-attribute be the empty string.




Ignore the cookie entirely and abort these steps.


NOTE: A "public suffix" is a domain that is controlled by a public registry, such as "com", "", and "". This step is essential for preventing from disrupting the integrity of by setting a cookie with a Domain attribute of "com". Unfortunately, the set of public suffixes (also known as "registry controlled domains") changes over time. If feasible, user agents SHOULD use an up-to-date public suffix list, such as the one maintained by the Mozilla project at <>.


6. If the domain-attribute is non-empty:

6. ドメイン属性が空でない場合:

If the canonicalized request-host does not domain-match the domain-attribute:


Ignore the cookie entirely and abort these steps.




Set the cookie's host-only-flag to false.


Set the cookie's domain to the domain-attribute.




Set the cookie's host-only-flag to true.


Set the cookie's domain to the canonicalized request-host.


7. If the cookie-attribute-list contains an attribute with an attribute-name of "Path", set the cookie's path to attribute-value of the last attribute in the cookie-attribute-list with an attribute-name of "Path". Otherwise, set the cookie's path to the default-path of the request-uri.

7. cookie-attribute-listにattribute-nameが「Path」の属性が含まれている場合、cookieのパスを、cookie-attribute-listの最後の属性のattribute-valueに「path」の属性名を付けて設定します。それ以外の場合は、cookieのパスをrequest-uriのdefault-pathに設定します。

8. If the cookie-attribute-list contains an attribute with an attribute-name of "Secure", set the cookie's secure-only-flag to true. Otherwise, set the cookie's secure-only-flag to false.

8. cookie-attribute-listにattribute-nameが「Secure」の属性が含まれている場合は、cookieのsecure-only-flagをtrueに設定します。それ以外の場合は、Cookieのsecure-only-flagをfalseに設定します。

9. If the cookie-attribute-list contains an attribute with an attribute-name of "HttpOnly", set the cookie's http-only-flag to true. Otherwise, set the cookie's http-only-flag to false.

9. cookie-attribute-listにattribute-nameが「HttpOnly」の属性が含まれている場合は、Cookieのhttp-only-flagをtrueに設定します。それ以外の場合は、Cookieのhttp-only-flagをfalseに設定します。

10. If the cookie was received from a "non-HTTP" API and the cookie's http-only-flag is set, abort these steps and ignore the cookie entirely.

10. Cookieが「非HTTP」APIから受信され、Cookieのhttp-only-flagが設定されている場合、これらの手順を中止し、Cookieを完全に無視します。

11. If the cookie store contains a cookie with the same name, domain, and path as the newly created cookie:

11. Cookieストアに、新しく作成されたCookieと同じ名前、ドメイン、パスのCookieが含まれている場合:

1. Let old-cookie be the existing cookie with the same name, domain, and path as the newly created cookie. (Notice that this algorithm maintains the invariant that there is at most one such cookie.)

1. old-cookieを、新しく作成されたcookieと同じ名前、ドメイン、パスを持つ既存のcookieとします。 (このアルゴリズムでは、このようなcookieが1つしか存在しないという不変条件が維持されることに注意してください。)

2. If the newly created cookie was received from a "non-HTTP" API and the old-cookie's http-only-flag is set, abort these steps and ignore the newly created cookie entirely.

2. 新しく作成されたcookieが「非HTTP」APIから受信され、古いcookieのhttp-only-flagが設定されている場合、これらの手順を中止し、新しく作成されたcookieを完全に無視します。

3. Update the creation-time of the newly created cookie to match the creation-time of the old-cookie.

3. 新しく作成されたCookieの作成時刻を更新して、古いCookieの作成時刻と一致させます。

4. Remove the old-cookie from the cookie store.

4. 古いcookieをcookieストアから削除します。

12. Insert the newly created cookie into the cookie store.

12. 新しく作成したCookieをCookieストアに挿入します。

A cookie is "expired" if the cookie has an expiry date in the past.


The user agent MUST evict all expired cookies from the cookie store if, at any time, an expired cookie exists in the cookie store.


At any time, the user agent MAY "remove excess cookies" from the cookie store if the number of cookies sharing a domain field exceeds some implementation-defined upper bound (such as 50 cookies).

ドメインフィールドを共有するCookieの数が実装で定義された上限(50 Cookieなど)を超える場合、ユーザーエージェントはいつでもCookieストアから「余分なCookieを削除」することができます(MAY)。

At any time, the user agent MAY "remove excess cookies" from the cookie store if the cookie store exceeds some predetermined upper bound (such as 3000 cookies).

Cookieストアが事前に決められた上限(3000 Cookieなど)を超えた場合、ユーザーエージェントはいつでもCookieストアから「余分なCookieを削除」できます(MAY)。

When the user agent removes excess cookies from the cookie store, the user agent MUST evict cookies in the following priority order:


1. Expired cookies.

1. 期限切れのCookie。

2. Cookies that share a domain field with more than a predetermined number of other cookies.

2. 所定の数を超える他のCookieとドメインフィールドを共有するCookie。

3. All cookies.

3. すべてのCookie。

If two cookies have the same removal priority, the user agent MUST evict the cookie with the earliest last-access date first.


When "the current session is over" (as defined by the user agent), the user agent MUST remove from the cookie store all cookies with the persistent-flag set to false.


5.4. Cookieヘッダー

The user agent includes stored cookies in the Cookie HTTP request header.

ユーザーエージェントは、Cookie HTTPリクエストヘッダーに保存されたCookieを含めます。

When the user agent generates an HTTP request, the user agent MUST NOT attach more than one Cookie header field.

ユーザーエージェントがHTTPリクエストを生成するとき、ユーザーエージェントは複数のCookieヘッダーフィールドを添付してはなりません(MUST NOT)。

A user agent MAY omit the Cookie header in its entirety. For example, the user agent might wish to block sending cookies during "third-party" requests from setting cookies (see Section 7.1).


If the user agent does attach a Cookie header field to an HTTP request, the user agent MUST send the cookie-string (defined below) as the value of the header field.


The user agent MUST use an algorithm equivalent to the following algorithm to compute the "cookie-string" from a cookie store and a request-uri:


1. Let cookie-list be the set of cookies from the cookie store that meets all of the following requirements:

1. cookie-listを、以下のすべての要件を満たすCookieストアからのCookieのセットとします。

* Either:

* どちらか:

The cookie's host-only-flag is true and the canonicalized request-host is identical to the cookie's domain.




The cookie's host-only-flag is false and the canonicalized request-host domain-matches the cookie's domain.


* The request-uri's path path-matches the cookie's path.

* リクエストURIのパスは、Cookieのパスと一致します。

* If the cookie's secure-only-flag is true, then the request-uri's scheme must denote a "secure" protocol (as defined by the user agent).

* Cookieのsecure-only-flagがtrueの場合、request-uriのスキームは(ユーザーエージェントによって定義された)「安全な」プロトコルを示す必要があります。

NOTE: The notion of a "secure" protocol is not defined by this document. Typically, user agents consider a protocol secure if the protocol makes use of transport-layer security, such as SSL or TLS. For example, most user agents consider "https" to be a scheme that denotes a secure protocol.


* If the cookie's http-only-flag is true, then exclude the cookie if the cookie-string is being generated for a "non-HTTP" API (as defined by the user agent).

* Cookieのhttp-only-flagがtrueの場合、「非HTTP」API(ユーザーエージェントによって定義されている)に対してcookie-stringが生成される場合は、cookieを除外します。

2. The user agent SHOULD sort the cookie-list in the following order:

2. ユーザーエージェントは、次の順序でcookie-listをソートする必要があります。

* Cookies with longer paths are listed before cookies with shorter paths.

* 長いパスのCookieは、短いパスのCookieより前にリストされます。

* Among cookies that have equal-length path fields, cookies with earlier creation-times are listed before cookies with later creation-times.

* 等しい長さのパスフィールドを持つCookieのうち、作成時間が早いCookieは、作成時間が遅いCookieより前にリストされます。

NOTE: Not all user agents sort the cookie-list in this order, but this order reflects common practice when this document was written, and, historically, there have been servers that (erroneously) depended on this order.


3. Update the last-access-time of each cookie in the cookie-list to the current date and time.

3. cookie-list内の各cookieの最終アクセス時刻を現在の日付と時刻に更新します。

4. Serialize the cookie-list into a cookie-string by processing each cookie in the cookie-list in order:

4. cookie-listの各cookieを順番に処理して、cookie-listをcookie-stringにシリアル化します。

1. Output the cookie's name, the %x3D ("=") character, and the cookie's value.

1. Cookieの名前、%x3D("=")文字、およびCookieの値を出力します。

2. If there is an unprocessed cookie in the cookie-list, output the characters %x3B and %x20 ("; ").

2. cookie-listに未処理のcookieがある場合は、文字%x3Bおよび%x20("; ")を出力します。

NOTE: Despite its name, the cookie-string is actually a sequence of octets, not a sequence of characters. To convert the cookie-string (or components thereof) into a sequence of characters (e.g., for presentation to the user), the user agent might wish to try using the UTF-8 character encoding [RFC3629] to decode the octet sequence. This decoding might fail, however, because not every sequence of octets is valid UTF-8.

注:その名前にもかかわらず、cookie-stringは実際には文字のシーケンスではなく、オクテットのシーケンスです。 cookie-string(またはそのコンポーネント)を一連の文字に変換するには(たとえば、ユーザーに提示するため)、ユーザーエージェントはUTF-8文字エンコード[RFC3629]を使用してオクテットシーケンスをデコードしようとする場合があります。ただし、オクテットのすべてのシーケンスが有効なUTF-8であるとは限らないため、このデコードは失敗する可能性があります。

6. Implementation Considerations
6. 実装に関する考慮事項
6.1. Limits
6.1. 限界

Practical user agent implementations have limits on the number and size of cookies that they can store. General-use user agents SHOULD provide each of the following minimum capabilities:


o At least 4096 bytes per cookie (as measured by the sum of the length of the cookie's name, value, and attributes).

o Cookieごとに少なくとも4096バイト(Cookieの名前、値、および属性の長さの合計で測定)。

o At least 50 cookies per domain.

o ドメインごとに少なくとも50のCookie。

o At least 3000 cookies total.

o 合計で少なくとも3,000のクッキー。

Servers SHOULD use as few and as small cookies as possible to avoid reaching these implementation limits and to minimize network bandwidth due to the Cookie header being included in every request.


Servers SHOULD gracefully degrade if the user agent fails to return one or more cookies in the Cookie header because the user agent might evict any cookie at any time on orders from the user.


6.2. Application Programming Interfaces
6.2. アプリケーションプログラミングインターフェイス

One reason the Cookie and Set-Cookie headers use such esoteric syntax is that many platforms (both in servers and user agents) provide a string-based application programming interface (API) to cookies, requiring application-layer programmers to generate and parse the syntax used by the Cookie and Set-Cookie headers, which many programmers have done incorrectly, resulting in interoperability problems.


Instead of providing string-based APIs to cookies, platforms would be well-served by providing more semantic APIs. It is beyond the scope of this document to recommend specific API designs, but there are clear benefits to accepting an abstract "Date" object instead of a serialized date string.


6.3. IDNA Dependency and Migration
6.3. IDNAの依存関係と移行

IDNA2008 [RFC5890] supersedes IDNA2003 [RFC3490]. However, there are differences between the two specifications, and thus there can be differences in processing (e.g., converting) domain name labels that have been registered under one from those registered under the other. There will be a transition period of some time during which IDNA2003- based domain name labels will exist in the wild. User agents SHOULD implement IDNA2008 [RFC5890] and MAY implement [UTS46] or [RFC5895]

IDNA2008 [RFC5890]はIDNA2003 [RFC3490]に優先します。ただし、2つの仕様には違いがあるため、一方に登録されているドメイン名ラベルと他方に登録されているドメイン名ラベルの処理(変換など)が異なる場合があります。 IDNA2003ベースのドメイン名ラベルが実際に存在する期間は、しばらくの間移行します。ユーザーエージェントはIDNA2008 [RFC5890]を実装し、[UTS46]または[RFC5895]を実装する必要があります(SHOULD)。

in order to facilitate their IDNA transition. If a user agent does not implement IDNA2008, the user agent MUST implement IDNA2003 [RFC3490].

IDNA移行を容易にするため。ユーザーエージェントがIDNA2008を実装しない場合、ユーザーエージェントはIDNA2003 [RFC3490]を実装する必要があります。

7. Privacy Considerations
7. プライバシーに関する考慮事項

Cookies are often criticized for letting servers track users. For example, a number of "web analytics" companies use cookies to recognize when a user returns to a web site or visits another web site. Although cookies are not the only mechanism servers can use to track users across HTTP requests, cookies facilitate tracking because they are persistent across user agent sessions and can be shared between hosts.

Cookieは、サーバーにユーザーを追跡させるためにしばしば批判されます。たとえば、多くの「Webアナリティクス」企業は、Cookieを使用して、ユーザーがWebサイトに戻ったときや別のWebサイトにアクセスしたときを認識しています。 Cookieは、サーバーがHTTPリクエスト全体でユーザーを追跡するために使用できる唯一のメカニズムではありませんが、ユーザーエージェントセッション全体で永続的であり、ホスト間で共有できるため、追跡を容易にします。

7.1. Third-Party Cookies
7.1. サードパーティのCookie

Particularly worrisome are so-called "third-party" cookies. In rendering an HTML document, a user agent often requests resources from other servers (such as advertising networks). These third-party servers can use cookies to track the user even if the user never visits the server directly. For example, if a user visits a site that contains content from a third party and then later visits another site that contains content from the same third party, the third party can track the user between the two sites.

特に気になるのは、いわゆる「サードパーティ」Cookieです。 HTMLドキュメントのレンダリングでは、ユーザーエージェントは他のサーバー(広告ネットワークなど)にリソースを要求することがよくあります。これらのサードパーティのサーバーは、ユーザーがサーバーに直接アクセスしたことがない場合でも、Cookieを使用してユーザーを追跡できます。たとえば、ユーザーがサードパーティのコンテンツを含むサイトにアクセスし、その後同じサードパーティのコンテンツを含む別のサイトにアクセスした場合、サードパーティは2つのサイト間でユーザーを追跡できます。

Some user agents restrict how third-party cookies behave. For example, some of these user agents refuse to send the Cookie header in third-party requests. Others refuse to process the Set-Cookie header in responses to third-party requests. User agents vary widely in their third-party cookie policies. This document grants user agents wide latitude to experiment with third-party cookie policies that balance the privacy and compatibility needs of their users. However, this document does not endorse any particular third-party cookie policy.


Third-party cookie blocking policies are often ineffective at achieving their privacy goals if servers attempt to work around their restrictions to track users. In particular, two collaborating servers can often track users without using cookies at all by injecting identifying information into dynamic URLs.


7.2. User Controls
7.2. ユーザーコントロール

User agents SHOULD provide users with a mechanism for managing the cookies stored in the cookie store. For example, a user agent might let users delete all cookies received during a specified time period or all the cookies related to a particular domain. In addition, many user agents include a user interface element that lets users examine the cookies stored in their cookie store.


User agents SHOULD provide users with a mechanism for disabling cookies. When cookies are disabled, the user agent MUST NOT include a Cookie header in outbound HTTP requests and the user agent MUST NOT process Set-Cookie headers in inbound HTTP responses.

ユーザーエージェントは、Cookieを無効にするメカニズムをユーザーに提供する必要があります(SHOULD)。 Cookieが無効になっている場合、ユーザーエージェントは送信HTTP要求にCookieヘッダーを含めてはならず(MUST NOT)、ユーザーエージェントは受信HTTP応答のSet-Cookieヘッダーを処理してはなりません(MUST NOT)。

Some user agents provide users the option of preventing persistent storage of cookies across sessions. When configured thusly, user agents MUST treat all received cookies as if the persistent-flag were set to false. Some popular user agents expose this functionality via "private browsing" mode [Aggarwal2010].


Some user agents provide users with the ability to approve individual writes to the cookie store. In many common usage scenarios, these controls generate a large number of prompts. However, some privacy-conscious users find these controls useful nonetheless.


7.3. Expiration Dates
7.3. 有効期限

Although servers can set the expiration date for cookies to the distant future, most user agents do not actually retain cookies for multiple decades. Rather than choosing gratuitously long expiration periods, servers SHOULD promote user privacy by selecting reasonable cookie expiration periods based on the purpose of the cookie. For example, a typical session identifier might reasonably be set to expire in two weeks.


8. Security Considerations
8. セキュリティに関する考慮事項
8.1. Overview
8.1. 概観

Cookies have a number of security pitfalls. This section overviews a few of the more salient issues.


In particular, cookies encourage developers to rely on ambient authority for authentication, often becoming vulnerable to attacks such as cross-site request forgery [CSRF]. Also, when storing session identifiers in cookies, developers often create session fixation vulnerabilities.


Transport-layer encryption, such as that employed in HTTPS, is insufficient to prevent a network attacker from obtaining or altering a victim's cookies because the cookie protocol itself has various vulnerabilities (see "Weak Confidentiality" and "Weak Integrity", below). In addition, by default, cookies do not provide confidentiality or integrity from network attackers, even when used in conjunction with HTTPS.


8.2. Ambient Authority
8.2. Ambient Authority

A server that uses cookies to authenticate users can suffer security vulnerabilities because some user agents let remote parties issue HTTP requests from the user agent (e.g., via HTTP redirects or HTML forms). When issuing those requests, user agents attach cookies even if the remote party does not know the contents of the cookies, potentially letting the remote party exercise authority at an unwary server.


Although this security concern goes by a number of names (e.g., cross-site request forgery, confused deputy), the issue stems from cookies being a form of ambient authority. Cookies encourage server operators to separate designation (in the form of URLs) from authorization (in the form of cookies). Consequently, the user agent might supply the authorization for a resource designated by the attacker, possibly causing the server or its clients to undertake actions designated by the attacker as though they were authorized by the user.

このセキュリティ上の懸念は、多くの名前(たとえば、クロスサイトリクエストフォージェリやConfused Deputy問題)によるものですが、問題はCookieがAmbient Authorityの一種であることから生じています。 Cookieにより、サーバーオペレーターは指定(URLの形式)と承認(Cookieの形式)を区別することができます。その結果、ユーザーエージェントは攻撃者が指定したリソースの承認を提供し、サーバーまたはそのクライアントに、ユーザーが承認したかのように攻撃者が指定したアクションを実行させる可能性があります。

Instead of using cookies for authorization, server operators might wish to consider entangling designation and authorization by treating URLs as capabilities. Instead of storing secrets in cookies, this approach stores secrets in URLs, requiring the remote entity to supply the secret itself. Although this approach is not a panacea, judicious application of these principles can lead to more robust security.


8.3. Clear Text
8.3. クリアテキスト

Unless sent over a secure channel (such as TLS), the information in the Cookie and Set-Cookie headers is transmitted in the clear.


1. All sensitive information conveyed in these headers is exposed to an eavesdropper.

1. これらのヘッダーで伝えられるすべての機密情報は、盗聴者に公開されます。

2. A malicious intermediary could alter the headers as they travel in either direction, with unpredictable results.

2. 悪意のある仲介者がヘッダーをいずれかの方向に移動すると、ヘッダーが変更され、予期しない結果が生じる可能性があります。

3. A malicious client could alter the Cookie header before transmission, with unpredictable results.

3. 悪意のあるクライアントが送信前にCookieヘッダーを変更し、予期しない結果をもたらす可能性があります。

Servers SHOULD encrypt and sign the contents of cookies (using whatever format the server desires) when transmitting them to the user agent (even when sending the cookies over a secure channel). However, encrypting and signing cookie contents does not prevent an attacker from transplanting a cookie from one user agent to another or from replaying the cookie at a later time.


In addition to encrypting and signing the contents of every cookie, servers that require a higher level of security SHOULD use the Cookie and Set-Cookie headers only over a secure channel. When using cookies over a secure channel, servers SHOULD set the Secure attribute (see Section for every cookie. If a server does not set the Secure attribute, the protection provided by the secure channel will be largely moot.


For example, consider a webmail server that stores a session identifier in a cookie and is typically accessed over HTTPS. If the server does not set the Secure attribute on its cookies, an active network attacker can intercept any outbound HTTP request from the user agent and redirect that request to the webmail server over HTTP. Even if the webmail server is not listening for HTTP connections, the user agent will still include cookies in the request. The active network attacker can intercept these cookies, replay them against the server, and learn the contents of the user's email. If, instead, the server had set the Secure attribute on its cookies, the user agent would not have included the cookies in the clear-text request.


8.4. Session Identifiers
8.4. セッション識別子

Instead of storing session information directly in a cookie (where it might be exposed to or replayed by an attacker), servers commonly store a nonce (or "session identifier") in a cookie. When the server receives an HTTP request with a nonce, the server can look up state information associated with the cookie using the nonce as a key.


Using session identifier cookies limits the damage an attacker can cause if the attacker learns the contents of a cookie because the nonce is useful only for interacting with the server (unlike non-nonce cookie content, which might itself be sensitive). Furthermore, using a single nonce prevents an attacker from "splicing" together cookie content from two interactions with the server, which could cause the server to behave unexpectedly.

nonceはサーバーとのやり取りにのみ役立つため、攻撃者がCookieの内容を学習した場合に攻撃者が引き起こす可能性のあるダメージを制限します(non-nonce cookieの内容とは異なり、ナンスはそれ自体が機密である可能性があります)。さらに、単一のナンスを使用することで、攻撃者がサーバーとの2つの対話からのCookieコンテンツを「スプライス」して、サーバーが予期しない動作をするのを防ぐことができます。

Using session identifiers is not without risk. For example, the server SHOULD take care to avoid "session fixation" vulnerabilities. A session fixation attack proceeds in three steps. First, the attacker transplants a session identifier from his or her user agent to the victim's user agent. Second, the victim uses that session identifier to interact with the server, possibly imbuing the session identifier with the user's credentials or confidential information. Third, the attacker uses the session identifier to interact with server directly, possibly obtaining the user's authority or confidential information.

セッション識別子の使用にはリスクがないわけではありません。たとえば、サーバーは「セッション固定」脆弱性を回避するように注意する必要があります。セッション固定攻撃は3つのステップで進行します。まず、攻撃者はセッション識別子を自分のユーザーエージェントから被害者のユーザーエージェントに移植します。次に、被害者はそのセッション識別子を使用してサーバーとやり取りし、ユーザーの資格情報や機密情報をセッション識別子に埋め込む可能性があります。 3番目に、攻撃者はセッション識別子を使用してサーバーと直接やり取りし、ユーザーの権限や機密情報を入手する可能性があります。

8.5. Weak Confidentiality
8.5. 機密性が弱い

Cookies do not provide isolation by port. If a cookie is readable by a service running on one port, the cookie is also readable by a service running on another port of the same server. If a cookie is writable by a service on one port, the cookie is also writable by a service running on another port of the same server. For this reason, servers SHOULD NOT both run mutually distrusting services on different ports of the same host and use cookies to store security-sensitive information.

Cookieはポートによる分離を提供しません。あるポートで実行されているサービスがCookieを読み取ることができる場合、同じサーバーの別のポートで実行されているサービスもCookieを読み取ることができます。 Cookieが1つのポートのサービスによって書き込み可能である場合、Cookieは同じサーバーの別のポートで実行されているサービスによっても書き込み可能です。このため、サーバーは同じホストの異なるポートで相互に信頼できないサービスを実行してはならず、Cookieを使用してセキュリティ上の機密情報を保存するべきではありません。

Cookies do not provide isolation by scheme. Although most commonly used with the http and https schemes, the cookies for a given host might also be available to other schemes, such as ftp and gopher. Although this lack of isolation by scheme is most apparent in non-HTTP APIs that permit access to cookies (e.g., HTML's document.cookie API), the lack of isolation by scheme is actually present in requirements for processing cookies themselves (e.g., consider retrieving a URI with the gopher scheme via HTTP).

Cookieはスキームによる分離を提供しません。 httpおよびhttpsスキームで最も一般的に使用されますが、特定のホストのCookieは、ftpやgopherなどの他のスキームでも使用できる場合があります。スキームによる分離の欠如は、Cookieへのアクセスを許可する非HTTP API(HTMLのdocument.cookie APIなど)で最も明白ですが、スキームによる分離の欠如は、Cookie自体を処理するための要件に実際に存在します(たとえば、取得を検討することHTTP経由のgopherスキームを使用したURI)。

Cookies do not always provide isolation by path. Although the network-level protocol does not send cookies stored for one path to another, some user agents expose cookies via non-HTTP APIs, such as HTML's document.cookie API. Because some of these user agents (e.g., web browsers) do not isolate resources received from different paths, a resource retrieved from one path might be able to access cookies stored for another path.

Cookieは常にパスによる分離を提供するとは限りません。ネットワークレベルのプロトコルは、あるパスに保存されたCookieを別のパスに送信しませんが、一部のユーザーエージェントは、HTMLのdocument.cookie APIなどの非HTTP APIを介してCookieを公開します。これらのユーザーエージェントの一部(ウェブブラウザなど)は、異なるパスから受信したリソースを分離しないため、あるパスから取得したリソースは、別のパスに保存されているCookieにアクセスできる場合があります。

8.6. Weak Integrity
8.6. 整合性が弱い

Cookies do not provide integrity guarantees for sibling domains (and their subdomains). For example, consider and The server can set a cookie with a Domain attribute of "" (possibly overwriting an existing "" cookie set by, and the user agent will include that cookie in HTTP requests to In the worst case, will be unable to distinguish this cookie from a cookie it set itself. The server might be able to leverage this ability to mount an attack against

Cookieは兄弟ドメイン(およびそのサブドメイン)の整合性を保証しません。たとえば、foo.example.comとbar.example.comを考えてみます。 foo.example.comサーバーは、「」のドメイン属性でcookieを設定でき(bar.example.comによって設定された既存の「」cookieを上書きする可能性があります)、ユーザーエージェントはそのcookieをbar.example.comへのHTTPリクエスト。最悪の場合、bar.example.comは、このCookieをそれ自体が設定したCookieと区別できなくなります。 foo.example.comサーバーは、この機能を利用してbar.example.comに対する攻撃を仕掛けることができる場合があります。

Even though the Set-Cookie header supports the Path attribute, the Path attribute does not provide any integrity protection because the user agent will accept an arbitrary Path attribute in a Set-Cookie header. For example, an HTTP response to a request for can set a cookie with a Path attribute of "/qux". Consequently, servers SHOULD NOT both run mutually distrusting services on different paths of the same host and use cookies to store security-sensitive information.


An active network attacker can also inject cookies into the Cookie header sent to by impersonating a response from and injecting a Set-Cookie header. The HTTPS server at will be unable to distinguish these cookies from cookies that it set itself in an HTTPS response. An active network attacker might be able to leverage this ability to mount an attack against even if uses HTTPS exclusively.

アクティブなネットワーク攻撃者は、からの応答を偽装してSet-Cookieヘッダーを挿入することにより、に送信されたCookieヘッダーにCookieを挿入することもできます。 example.comのHTTPSサーバーは、これらのCookieをHTTPS応答で設定したCookieと区別できません。アクティブなネットワーク攻撃者は、example.comがHTTPSのみを使用している場合でも、この機能を利用してexample.comに対する攻撃を仕掛けることができる可能性があります。

Servers can partially mitigate these attacks by encrypting and signing the contents of their cookies. However, using cryptography does not mitigate the issue completely because an attacker can replay a cookie he or she received from the authentic server in the user's session, with unpredictable results.


Finally, an attacker might be able to force the user agent to delete cookies by storing a large number of cookies. Once the user agent reaches its storage limit, the user agent will be forced to evict some cookies. Servers SHOULD NOT rely upon user agents retaining cookies.


8.7. Reliance on DNS
8.7. DNSへの依存

Cookies rely upon the Domain Name System (DNS) for security. If the DNS is partially or fully compromised, the cookie protocol might fail to provide the security properties required by applications.

Cookieは、セキュリティのためにドメインネームシステム(DNS)に依存しています。 DNSが部分的または完全に侵害されている場合、Cookieプロトコルはアプリケーションに必要なセキュリティプロパティを提供できない可能性があります。

9. IANA Considerations
9. IANAに関する考慮事項

The permanent message header field registry (see [RFC3864]) has been updated with the following registrations.


9.1. クッキー

Header field name: Cookie


Applicable protocol: http


Status: standard


Author/Change controller: IETF


Specification document: this specification (Section 5.4)


9.2. セットクッキー

Header field name: Set-Cookie


Applicable protocol: http


Status: standard


Author/Change controller: IETF


Specification document: this specification (Section 5.2)


9.3. Cookie2
9.3. cookie2

Header field name: Cookie2


Applicable protocol: http


Status: obsoleted


Author/Change controller: IETF


Specification document: [RFC2965]


9.4. Set-Cookie2
9.4. Set-Cookie2

Header field name: Set-Cookie2


Applicable protocol: http


Status: obsoleted


Author/Change controller: IETF


Specification document: [RFC2965]


10. References
10. 参考文献
10.1. Normative References
10.1. 引用文献

[RFC1034] Mockapetris, P., "Domain names - concepts and facilities", STD 13, RFC 1034, November 1987.

[RFC1123] Braden, R., "Requirements for Internet Hosts - Application and Support", STD 3, RFC 1123, October 1989.

[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate Requirement Levels", BCP 14, RFC 2119, March 1997.

[RFC2616] Fielding, R., Gettys, J., Mogul, J., Frystyk, H., Masinter, L., Leach, P., and T. Berners-Lee, "Hypertext Transfer Protocol -- HTTP/1.1", RFC 2616, June 1999.

[RFC3490] Faltstrom, P., Hoffman, P., and A. Costello, "Internationalizing Domain Names in Applications (IDNA)", RFC 3490, March 2003.

See Section 6.3 for an explanation why the normative reference to an obsoleted specification is needed.


[RFC4790] Newman, C., Duerst, M., and A. Gulbrandsen, "Internet Application Protocol Collation Registry", RFC 4790, March 2007.

[RFC5234] Crocker, D., Ed. and P. Overell, "Augmented BNF for Syntax Specifications: ABNF", STD 68, RFC 5234, January 2008.

[RFC5890] Klensin, J., "Internationalized Domain Names for Applications (IDNA): Definitions and Document Framework", RFC 5890, August 2010.

[USASCII] American National Standards Institute, "Coded Character Set -- 7-bit American Standard Code for Information Interchange", ANSI X3.4, 1986.

10.2. Informative References
10.2. 参考引用

[RFC2109] Kristol, D. and L. Montulli, "HTTP State Management Mechanism", RFC 2109, February 1997.

[RFC2965] Kristol, D. and L. Montulli, "HTTP State Management Mechanism", RFC 2965, October 2000.

[RFC2818] Rescorla, E., "HTTP Over TLS", RFC 2818, May 2000.

[Netscape] Netscape Communications Corp., "Persistent Client State -- HTTP Cookies", 1999, < 20020803110822/ cookie_spec.html>.

[Kri2001] Kristol, D., "HTTP Cookies: Standards, Privacy, and Politics", ACM Transactions on Internet Technology Vol. 1, #2, November 2001, <>.

[RFC3629] Yergeau, F., "UTF-8, a transformation format of ISO 10646", STD 63, RFC 3629, November 2003.

[RFC4648] Josefsson, S., "The Base16, Base32, and Base64 Data Encodings", RFC 4648, October 2006.

[RFC3864] Klyne, G., Nottingham, M., and J. Mogul, "Registration Procedures for Message Header Fields", BCP 90, RFC 3864, September 2004.

[RFC5895] Resnick, P. and P. Hoffman, "Mapping Characters for Internationalized Domain Names in Applications (IDNA) 2008", RFC 5895, September 2010.

[UTS46] Davis, M. and M. Suignard, "Unicode IDNA Compatibility Processing", Unicode Technical Standards # 46, 2010, <>.

[CSRF] Barth, A., Jackson, C., and J. Mitchell, "Robust Defenses for Cross-Site Request Forgery", 2008, <>.

[Aggarwal2010] Aggarwal, G., Burzstein, E., Jackson, C., and D. Boneh, "An Analysis of Private Browsing Modes in Modern Browsers", 2010, < full_papers/Aggarwal.pdf>.

Appendix A. Acknowledgements
付録A. 謝辞

This document borrows heavily from RFC 2109 [RFC2109]. We are indebted to David M. Kristol and Lou Montulli for their efforts to specify cookies. David M. Kristol, in particular, provided invaluable advice on navigating the IETF process. We would also like to thank Thomas Broyer, Tyler Close, Alissa Cooper, Bil Corry, corvid, Lisa Dusseault, Roy T. Fielding, Blake Frantz, Anne van Kesteren, Eran Hammer-Lahav, Jeff Hodges, Bjoern Hoehrmann, Achim Hoffmann, Georg Koppen, Dean McNamee, Alexey Melnikov, Mark Miller, Mark Pauley, Yngve N. Pettersen, Julian Reschke, Peter Saint-Andre, Mark Seaborn, Maciej Stachowiak, Daniel Stenberg, Tatsuhiro Tsujikawa, David Wagner, Dan Winship, and Dan Witte for their valuable feedback on this document.

このドキュメントは、RFC 2109 [RFC2109]から大いに借りています。クッキーを特定する努力をしてくれたDavid M. KristolとLou Montulliに感謝します。特に、David M. Kristolは、IETFプロセスのナビゲートに関して非常に貴重なアドバイスを提供しました。また、Thomas Broyer、Tyler Close、Alissa Cooper、Bil Corry、corvid、Lisa Dusseault、Roy T. Fielding、Blake Frantz、Anne van Kesteren、Eran Hammer-Lahav、Jeff Hodges、Bjoern Hoehrmann、Achim Hoffmann、Georgにも感謝します。 Koppen、Dean McNamee、Alexey Melnikov、Mark Miller、Mark Pauley、Yngve N. Pettersen、Julian Reschke、Peter Saint-Andre、Mark Seaborn、Maciej Stachowiak、Daniel Stenberg、Tatsuhiro Tsujikawa、David Wagner、Dan Winship、Dan Witteこのドキュメントに関する貴重なフィードバック。

Author's Address


Adam Barth University of California, Berkeley

カリフォルニア大学バークレー校 Adam Barth