Network Working Group B. Ramsdell, Editor
Request for Comments: 3850 Sendmail, Inc.
Obsoletes: 2632 July 2004
Category: Standards Track
Network Working Group B. Ramsdell, Editor
Request for Comments: 3850 Sendmail, Inc.
Obsoletes: 2632 July 2004
Category: Standards Track
Secure/Multipurpose Internet Mail Extensions (S/MIME) Version 3.1 Certificate Handling
安全/多用途Internet邮件扩展（S/MIME）版本3.1证书处理
Status of this Memo
本备忘录的状况
This document specifies an Internet standards track protocol for the Internet community, and requests discussion and suggestions for improvements. Please refer to the current edition of the "Internet Official Protocol Standards" (STD 1) for the standardization state and status of this protocol. Distribution of this memo is unlimited.
本文件规定了互联网社区的互联网标准跟踪协议，并要求进行讨论和提出改进建议。有关本协议的标准化状态和状态，请参考当前版本的“互联网官方协议标准”（STD 1）。本备忘录的分发不受限制。
Copyright Notice
版权公告
Copyright (C) The Internet Society (2004).
版权所有（C）互联网协会（2004年）。
Abstract
摘要
This document specifies conventions for X.509 certificate usage by Secure/Multipurpose Internet Mail Extensions (S/MIME) agents. S/MIME provides a method to send and receive secure MIME messages, and certificates are an integral part of S/MIME agent processing. S/MIME agents validate certificates as described in RFC 3280, the Internet X.509 Public Key Infrastructure Certificate and CRL Profile. S/MIME agents must meet the certificate processing requirements in this document as well as those in RFC 3280.
本文档指定安全/多用途Internet邮件扩展（S/MIME）代理使用X.509证书的约定。S/MIME提供了一种发送和接收安全MIME消息的方法，证书是S/MIME代理处理的组成部分。S/MIME代理验证RFC 3280、Internet X.509公钥基础结构证书和CRL配置文件中所述的证书。S/MIME代理必须满足本文档以及RFC 3280中的证书处理要求。
Table of Contents
目录
1. Overview . . . . . . . . . . . . . . . . . . . . . . . . . . . 2
1.1. Definitions. . . . . . . . . . . . . . . . . . . . . . . 2
1.2. Compatibility with Prior Practice of S/MIME. . . . . . . 3
1.3. Terminology. . . . . . . . . . . . . . . . . . . . . . . 3
1.4. Changes Since S/MIME v3 (RFC 2632) . . . . . . . . . . . 3
2. CMS Options. . . . . . . . . . . . . . . . . . . . . . . . . . 4
2.1 . CertificateRevocationLists . . . . . . . . . . . . . . . 4
2.2. CertificateChoices . . . . . . . . . . . . . . . . . . . 4
2.3. CertificateSet . . . . . . . . . . . . . . . . . . . . . 5
3. Using Distinguished Names for Internet Mail . . . . . . . . . . 6
4. Certificate Processing . . . . . . . . . . . . . . . . . . . . 7
4.1. Certificate Revocation Lists . . . . . . . . . . . . . . 8
4.2. Certification Path Validation. . . . . . . . . . . . . . 8
4.3. Certificate and CRL Signing Algorithms . . . . . . . . . 9
1. Overview . . . . . . . . . . . . . . . . . . . . . . . . . . . 2
1.1. Definitions. . . . . . . . . . . . . . . . . . . . . . . 2
1.2. Compatibility with Prior Practice of S/MIME. . . . . . . 3
1.3. Terminology. . . . . . . . . . . . . . . . . . . . . . . 3
1.4. Changes Since S/MIME v3 (RFC 2632) . . . . . . . . . . . 3
2. CMS Options. . . . . . . . . . . . . . . . . . . . . . . . . . 4
2.1 . CertificateRevocationLists . . . . . . . . . . . . . . . 4
2.2. CertificateChoices . . . . . . . . . . . . . . . . . . . 4
2.3. CertificateSet . . . . . . . . . . . . . . . . . . . . . 5
3. Using Distinguished Names for Internet Mail . . . . . . . . . . 6
4. Certificate Processing . . . . . . . . . . . . . . . . . . . . 7
4.1. Certificate Revocation Lists . . . . . . . . . . . . . . 8
4.2. Certification Path Validation. . . . . . . . . . . . . . 8
4.3. Certificate and CRL Signing Algorithms . . . . . . . . . 9
4.4. PKIX Certificate Extensions. . . . . . . . . . . . . . . 9
5. Security Considerations. . . . . . . . . . . . . . . . . . . . 11
A. References . . . . . . . . . . . . . . . . . . . . . . . . . . 13
A.1. Normative References . . . . . . . . . . . . . . . . . . 13
A.2. Informative References . . . . . . . . . . . . . . . . . 14
B. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 15
C. Editor's Address . . . . . . . . . . . . . . . . . . . . . . . 15
Full Copyright Statement . . . . . . . . . . . . . . . . . . . . . 16
4.4. PKIX Certificate Extensions. . . . . . . . . . . . . . . 9
5. Security Considerations. . . . . . . . . . . . . . . . . . . . 11
A. References . . . . . . . . . . . . . . . . . . . . . . . . . . 13
A.1. Normative References . . . . . . . . . . . . . . . . . . 13
A.2. Informative References . . . . . . . . . . . . . . . . . 14
B. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 15
C. Editor's Address . . . . . . . . . . . . . . . . . . . . . . . 15
Full Copyright Statement . . . . . . . . . . . . . . . . . . . . . 16
S/MIME (Secure/Multipurpose Internet Mail Extensions), described in [SMIME-MSG], provides a method to send and receive secure MIME messages. Before using a public key to provide security services, the S/MIME agent MUST verify that the public key is valid. S/MIME agents MUST use PKIX certificates to validate public keys as described in the Internet X.509 Public Key Infrastructure (PKIX) Certificate and CRL Profile [KEYM]. S/MIME agents MUST meet the certificate processing requirements documented in this document in addition to those stated in [KEYM].
[SMIME-MSG]中描述的S/MIME（安全/多用途Internet邮件扩展）提供了发送和接收安全MIME消息的方法。在使用公钥提供安全服务之前，S/MIME代理必须验证公钥是否有效。S/MIME代理必须使用PKIX证书来验证公钥，如Internet X.509公钥基础设施（PKIX）证书和CRL配置文件[KEYM]中所述。除了[KEYM]中规定的要求外，S/MIME代理还必须满足本文件中记录的证书处理要求。
This specification is compatible with the Cryptographic Message Syntax [CMS] in that it uses the data types defined by CMS. It also inherits all the varieties of architectures for certificate-based key management supported by CMS.
此规范与加密消息语法[CMS]兼容，因为它使用CMS定义的数据类型。它还继承了CMS支持的所有基于证书的密钥管理体系结构。
For the purposes of this document, the following definitions apply.
在本文件中，以下定义适用。
ASN.1: Abstract Syntax Notation One, as defined in ITU-T X.208 [X.208-88].
ASN.1:ITU-T X.208[X.208-88]中定义的抽象语法符号1。
Attribute Certificate (AC): An X.509 AC is a separate structure from a subject's public key X.509 Certificate. A subject may have multiple X.509 ACs associated with each of its public key X.509 Certificates. Each X.509 AC binds one or more Attributes with one of the subject's public key X.509 Certificates. The X.509 AC syntax is defined in [ACAUTH].
属性证书（AC）：X.509 AC是主体公钥X.509证书的独立结构。一个主体可能有多个与其公钥X.509证书相关联的X.509 ACs。每个X.509 AC将一个或多个属性与主体的公钥X.509证书之一绑定。X.509 AC语法在[ACAUTH]中定义。
Certificate: A type that binds an entity's name to a public key with a digital signature. This type is defined in the Internet X.509 Public Key Infrastructure (PKIX) Certificate and CRL Profile [KEYM]. This type also contains the distinguished name of the certificate issuer (the signer), an issuer-specific serial number, the issuer's signature algorithm identifier, a validity period, and extensions also defined in that document.
证书：用数字签名将实体名称绑定到公钥的类型。此类型在Internet X.509公钥基础设施（PKIX）证书和CRL配置文件[KEYM]中定义。此类型还包含证书颁发者（签名者）的可分辨名称、特定于颁发者的序列号、颁发者的签名算法标识符、有效期以及该文档中定义的扩展名。
Certificate Revocation List (CRL): A type that contains information about certificates whose validity an issuer has prematurely revoked. The information consists of an issuer name, the time of issue, the next scheduled time of issue, a list of certificate serial numbers and their associated revocation times, and extensions as defined in [KEYM]. The CRL is signed by the issuer. The type intended by this specification is the one defined in [KEYM].
证书吊销列表（CRL）：一种类型，其中包含有关颁发者已提前吊销其有效性的证书的信息。该信息包括发行人名称、发行时间、下一个计划发行时间、证书序列号列表及其相关撤销时间，以及[KEYM]中定义的扩展名。CRL由发行人签署。本规范规定的类型为[KEYM]中定义的类型。
Receiving agent: software that interprets and processes S/MIME CMS objects, MIME body parts that contain CMS objects, or both.
接收代理：解释和处理S/MIME CMS对象、包含CMS对象的MIME主体部分或两者的软件。
Sending agent: software that creates S/MIME CMS objects, MIME body parts that contain CMS objects, or both.
发送代理：创建S/MIME CMS对象、包含CMS对象的MIME身体部位或两者的软件。
S/MIME agent: user software that is a receiving agent, a sending agent, or both.
S/MIME代理：作为接收代理、发送代理或两者兼有的用户软件。
S/MIME version 3.1 agents should attempt to have the greatest interoperability possible with agents for prior versions of S/MIME. S/MIME version 2 is described in RFC 2311 through RFC 2315, inclusive and S/MIME version 3 is described in RFC 2630 through RFC 2634 inclusive. RFC 2311 also has historical information about the development of S/MIME.
S/MIME版本3.1代理应尽可能与S/MIME早期版本的代理具有最大的互操作性。S/MIME版本2在RFC 2311至RFC 2315（含）中描述，S/MIME版本3在RFC 2630至RFC 2634（含）中描述。RFC2311也有关于S/MIME发展的历史信息。
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 [MUSTSHOULD].
本文件中的关键词“必须”、“不得”、“必需”、“应”、“不应”、“应”、“不应”、“建议”、“可”和“可选”应按照[必须”中的说明进行解释。
Version 1 and Version 2 CRLs MUST be supported.
必须支持版本1和版本2 CRL。
Multiple CA certificates with the same subject and public key, but with overlapping validity periods, MUST be supported.
必须支持具有相同主题和公钥但有效期重叠的多个CA证书。
Version 2 attribute certificates SHOULD be supported, and version 1 attributes certificates MUST NOT be used.
应支持版本2属性证书，不得使用版本1属性证书。
The use of the MD2 digest algorithm for certificate signatures is discouraged and security language added.
不鼓励对证书签名使用MD2摘要算法，并添加了安全语言。
Clarified use of email address use in certificates. Certificates that do not contain an email address have no requirements for verifying the email address associated with the certificate.
澄清了证书中电子邮件地址的使用。不包含电子邮件地址的证书不需要验证与证书关联的电子邮件地址。
Receiving agents SHOULD display certificate information when displaying the results of signature verification.
接收代理在显示签名验证结果时应显示证书信息。
Receiving agents MUST NOT accept a signature made with a certificate that does not have the digitalSignature or nonRepudiation bit set.
接收代理不得接受使用未设置数字签名或不可否认位的证书进行的签名。
Clarifications for the interpretation of the key usage and extended key usage extensions.
解释密钥用法和扩展密钥用法扩展的说明。
The CMS message format allows for a wide variety of options in content and algorithm support. This section puts forth a number of support requirements and recommendations in order to achieve a base level of interoperability among all S/MIME implementations. Most of the CMS format for S/MIME messages is defined in [SMIME-MSG].
CMS消息格式允许在内容和算法支持方面有多种选择。本节提出了一些支持需求和建议，以实现所有S/MIME实现之间的基本互操作性。S/MIME消息的大多数CMS格式在[SMIME-MSG]中定义。
Receiving agents MUST support the Certificate Revocation List (CRL) format defined in [KEYM]. If sending agents include CRLs in outgoing messages, the CRL format defined in [KEYM] MUST be used. In all cases, both v1 and v2 CRLs MUST be supported.
接收代理必须支持[KEYM]中定义的证书吊销列表（CRL）格式。如果发送代理在传出消息中包含CRL，则必须使用[KEYM]中定义的CRL格式。在所有情况下，必须同时支持v1和v2 CRL。
All agents MUST be capable of performing revocation checks using CRLs as specified in [KEYM]. All agents MUST perform revocation status checking in accordance with [KEYM]. Receiving agents MUST recognize CRLs in received S/MIME messages.
所有代理必须能够使用[KEYM]中指定的CRL执行撤销检查。所有代理必须根据[KEYM]执行撤销状态检查。接收代理必须识别接收到的S/MIME消息中的CRL。
Agents SHOULD store CRLs received in messages for use in processing later messages.
代理应该存储在消息中接收的CRL，以便在以后处理消息时使用。
Receiving agents MUST support v1 X.509 and v3 X.509 identity certificates as profiled in [KEYM]. End entity certificates MAY include an Internet mail address, as described in section 3.
接收代理必须支持[KEYM]中描述的v1 X.509和v3 X.509身份证书。终端实体证书可能包括互联网邮件地址，如第3节所述。
Receiving agents SHOULD support X.509 version 2 attribute certificates. See [ACAUTH] for details about the profile for attribute certificates.
接收代理应支持X.509版本2属性证书。有关属性证书的配置文件的详细信息，请参见[ACAUTH]。
The CMS message format supports a choice of certificate formats for public key content types: PKIX, PKCS #6 Extended Certificates [PKCS6] and PKIX Attribute Certificates.
CMS消息格式支持公钥内容类型的证书格式选择：PKIX、PKCS#6扩展证书[PKCS6]和PKIX属性证书。
The PKCS #6 format is not in widespread use. In addition, PKIX certificate extensions address much of the same functionality and flexibility as was intended in the PKCS #6. Thus, sending and receiving agents MUST NOT use PKCS #6 extended certificates.
PKCS#6格式没有得到广泛使用。此外，PKIX证书扩展解决了与PKCS#6中预期相同的功能和灵活性。因此，发送和接收代理不得使用PKCS#6扩展证书。
X.509 version 1 attribute certificates are also not widely implemented, and have been superseded with version 2 attribute certificates. Sending agents MUST NOT send version 1 attribute certificates.
X.509版本1属性证书也没有得到广泛实施，已被版本2属性证书取代。发送代理不能发送版本1属性证书。
Receiving agents MUST be able to handle an arbitrary number of certificates of arbitrary relationship to the message sender and to each other in arbitrary order. In many cases, the certificates included in a signed message may represent a chain of certification from the sender to a particular root. There may be, however, situations where the certificates in a signed message may be unrelated and included for convenience.
接收代理必须能够处理任意数量的证书，这些证书与消息发送方以及彼此之间的关系是任意的。在许多情况下，签名消息中包含的证书可能表示从发送方到特定根的证书链。然而，可能存在这样的情况，即签名消息中的证书可能是无关的，并且为了方便而包括在内。
Sending agents SHOULD include any certificates for the user's public key(s) and associated issuer certificates. This increases the likelihood that the intended recipient can establish trust in the originator's public key(s). This is especially important when sending a message to recipients that may not have access to the sender's public key through any other means or when sending a signed message to a new recipient. The inclusion of certificates in outgoing messages can be omitted if S/MIME objects are sent within a group of correspondents that has established access to each other's certificates by some other means such as a shared directory or manual certificate distribution. Receiving S/MIME agents SHOULD be able to handle messages without certificates using a database or directory lookup scheme.
发送代理应包括用户公钥和相关颁发者证书的任何证书。这增加了预期接收者对发端人公钥建立信任的可能性。当向可能无法通过任何其他方式访问发件人公钥的收件人发送邮件或向新收件人发送签名邮件时，这一点尤为重要。如果S/MIME对象是在通过共享目录或手动证书分发等其他方式建立了对彼此证书的访问权限的通信者组中发送的，则可以省略在传出消息中包含证书。接收S/MIME代理应该能够使用数据库或目录查找方案处理没有证书的消息。
A sending agent SHOULD include at least one chain of certificates up to, but not including, a Certificate Authority (CA) that it believes that the recipient may trust as authoritative. A receiving agent MUST be able to handle an arbitrarily large number of certificates and chains.
发送代理应包括至少一个证书链，该证书链最多包括但不包括它认为接收方可以信任为权威的证书颁发机构（CA）。接收代理必须能够处理任意数量的证书和链。
Agents MAY send CA certificates, that is, certificates which can be considered the "root" of other chains, and which MAY be self-signed. Note that receiving agents SHOULD NOT simply trust any self-signed certificates as valid CAs, but SHOULD use some other mechanism to determine if this is a CA that should be trusted. Also note that when certificates contain DSA public keys the parameters may be located in the root certificate. This would require that the recipient possess both the end-entity certificate as well as the root
代理可以发送CA证书，即可以被视为其他链的“根”并且可以是自签名的证书。请注意，接收代理不应该简单地将任何自签名证书作为有效CA来信任，而应该使用其他机制来确定这是否是一个应该信任的CA。还要注意，当证书包含DSA公钥时，参数可能位于根证书中。这将要求接收方同时拥有最终实体证书和根证书
certificate to perform a signature verification, and is a valid example of a case where transmitting the root certificate may be required.
用于执行签名验证的证书，并且是可能需要传输根证书的情况的有效示例。
Receiving agents MUST support chaining based on the distinguished name fields. Other methods of building certificate chains MAY be supported.
接收代理必须支持基于可分辨名称字段的链接。可以支持构建证书链的其他方法。
Receiving agents SHOULD support the decoding of X.509 attribute certificates included in CMS objects. All other issues regarding the generation and use of X.509 attribute certificates are outside of the scope of this specification. One specification that addresses attribute certificate use is defined in [SECLABEL].
接收代理应支持对CMS对象中包含的X.509属性证书进行解码。有关生成和使用X.509属性证书的所有其他问题不在本规范的范围内。[SECLABEL]中定义了一个解决属性证书使用的规范。
End-entity certificates MAY contain an Internet mail address as described in [RFC-2822]. The address must be an "addr-spec" as defined in Section 3.4.1 of that specification. The email address SHOULD be in the subjectAltName extension, and SHOULD NOT be in the subject distinguished name.
终端实体证书可能包含[RFC-2822]中所述的Internet邮件地址。地址必须是该规范第3.4.1节中定义的“地址规范”。电子邮件地址应位于subjectAltName扩展名中，而不应位于subject可分辨名称中。
Receiving agents MUST recognize and accept certificates that contain no email address. Agents are allowed to provide an alternative mechanism for associating an email address with a certificate that does not contain an email address, such as through the use of the agent's address book, if available. Receiving agents MUST recognize email addresses in the subjectAltName field. Receiving agents MUST recognize email addresses in the Distinguished Name field in the PKCS #9 [PKCS9] emailAddress attribute:
接收代理必须识别并接受不包含电子邮件地址的证书。允许代理提供将电子邮件地址与不包含电子邮件地址的证书相关联的替代机制，例如通过使用代理的通讯簿（如果可用）。接收代理必须识别subjectAltName字段中的电子邮件地址。接收代理必须识别PKCS#9[PKCS9]emailAddress属性中可分辨名称字段中的电子邮件地址：
pkcs-9-at-emailAddress OBJECT IDENTIFIER ::=
{iso(1) member-body(2) us(840) rsadsi(113549) pkcs(1) pkcs-9(9) 1 }
pkcs-9-at-emailAddress OBJECT IDENTIFIER ::=
{iso(1) member-body(2) us(840) rsadsi(113549) pkcs(1) pkcs-9(9) 1 }
Note that this attribute MUST be encoded as IA5String.
请注意，此属性必须编码为IA5String。
Sending agents SHOULD make the address in the From or Sender header in a mail message match an Internet mail address in the signer's certificate. Receiving agents MUST check that the address in the From or Sender header of a mail message matches an Internet mail address, if present, in the signer's certificate, if mail addresses are present in the certificate. A receiving agent SHOULD provide some explicit alternate processing of the message if this comparison fails, which may be to display a message that shows the recipient the addresses in the certificate or other certificate details.
发送代理应使邮件消息中“发件人”或“发件人”标题中的地址与签名者证书中的Internet邮件地址匹配。接收代理必须检查邮件消息的发件人或发件人标头中的地址是否与签名者证书中的Internet邮件地址（如果存在）匹配（如果证书中存在邮件地址）。如果此比较失败，则接收代理应提供一些明确的消息替代处理，这可能是显示一条消息，向收件人显示证书中的地址或其他证书详细信息。
A receiving agent SHOULD display a subject name or other certificate details when displaying an indication of successful or unsuccessful signature verification.
当显示签名验证成功或失败的指示时，接收代理应显示主题名称或其他证书详细信息。
All subject and issuer names MUST be populated (i.e., not an empty SEQUENCE) in S/MIME-compliant X.509 identity certificates, except that the subject DN in a user's (i.e., end-entity) certificate MAY be an empty SEQUENCE in which case the subjectAltName extension will include the subject's identifier and MUST be marked as critical.
必须在S/MIME兼容的X.509身份证书中填充所有使用者和颁发者名称（即，非空序列），但用户（即终端实体）证书中的使用者DN可能是空序列，在这种情况下，使用者名称扩展将包括使用者的标识符，并且必须标记为关键。
A receiving agent needs to provide some certificate retrieval mechanism in order to gain access to certificates for recipients of digital envelopes. There are many ways to implement certificate retrieval mechanisms. X.500 directory service is an excellent example of a certificate retrieval-only mechanism that is compatible with classic X.500 Distinguished Names. Another method under consideration by the IETF is to provide certificate retrieval services as part of the existing Domain Name System (DNS). Until such mechanisms are widely used, their utility may be limited by the small number of correspondent's certificates that can be retrieved. At a minimum, for initial S/MIME deployment, a user agent could automatically generate a message to an intended recipient requesting that recipient's certificate in a signed return message.
接收代理需要提供一些证书检索机制，以便为数字信封的收件人访问证书。有许多方法可以实现证书检索机制。X.500目录服务是与经典的X.500可分辨名称兼容的仅证书检索机制的一个极好示例。IETF正在考虑的另一种方法是作为现有域名系统（DNS）的一部分提供证书检索服务。在这些机制被广泛使用之前，它们的实用性可能会受到可检索的少量通信者证书的限制。对于初始S/MIME部署，用户代理至少可以自动生成一条消息，发送给指定的收件人，在签名的返回消息中请求该收件人的证书。
Receiving and sending agents SHOULD also provide a mechanism to allow a user to "store and protect" certificates for correspondents in such a way so as to guarantee their later retrieval. In many environments, it may be desirable to link the certificate retrieval/storage mechanisms together in some sort of certificate database. In its simplest form, a certificate database would be local to a particular user and would function in a similar way as an "address book" that stores a user's frequent correspondents. In this way, the certificate retrieval mechanism would be limited to the certificates that a user has stored (presumably from incoming messages). A comprehensive certificate retrieval/storage solution may combine two or more mechanisms to allow the greatest flexibility and utility to the user. For instance, a secure Internet mail agent may resort to checking a centralized certificate retrieval mechanism for a certificate if it can not be found in a user's local certificate storage/retrieval database.
接收和发送代理还应提供一种机制，允许用户以这种方式“存储和保护”通信员的证书，以保证其以后的检索。在许多环境中，可能需要在某种证书数据库中将证书检索/存储机制链接在一起。最简单的形式是，证书数据库是特定用户的本地数据库，其功能类似于存储用户频繁通信者的“地址簿”。这样，证书检索机制将限于用户存储的证书（可能来自传入消息）。一个全面的证书检索/存储解决方案可以结合两种或两种以上的机制，以便为用户提供最大的灵活性和实用性。例如，如果在用户的本地证书存储/检索数据库中找不到证书，安全Internet邮件代理可能会求助于检查集中式证书检索机制以获取证书。
Receiving and sending agents SHOULD provide a mechanism for the import and export of certificates, using a CMS certs-only message. This allows for import and export of full certificate chains as opposed to just a single certificate. This is described in [SMIME-MSG].
接收和发送代理应使用CMS certs only消息提供证书导入和导出机制。这允许导入和导出完整的证书链，而不仅仅是单个证书。这在[SMIME-MSG]中有描述。
Agents MUST handle multiple valid Certification Authority (CA) certificates containing the same subject name and the same public keys but with overlapping validity intervals.
代理必须处理多个有效的证书颁发机构（CA）证书，这些证书包含相同的使用者名称和相同的公钥，但有效期间隔重叠。
In general, it is always better to get the latest CRL information from a CA than to get information stored away from incoming messages. A receiving agent SHOULD have access to some certificate revocation list (CRL) retrieval mechanism in order to gain access to certificate revocation information when validating certification paths. A receiving or sending agent SHOULD also provide a mechanism to allow a user to store incoming certificate revocation information for correspondents in such a way so as to guarantee its later retrieval.
通常，从CA获取最新的CRL信息总比从传入消息中获取存储的信息要好。接收代理应该可以访问某些证书吊销列表（CRL）检索机制，以便在验证证书路径时访问证书吊销信息。接收或发送代理还应提供一种机制，允许用户以这种方式为通信方存储传入的证书撤销信息，以保证其以后的检索。
Receiving and sending agents SHOULD retrieve and utilize CRL information every time a certificate is verified as part of a certification path validation even if the certificate was already verified in the past. However, in many instances (such as off-line verification) access to the latest CRL information may be difficult or impossible. The use of CRL information, therefore, may be dictated by the value of the information that is protected. The value of the CRL information in a particular context is beyond the scope of this specification but may be governed by the policies associated with particular certification paths.
接收和发送代理应在每次证书作为证书路径验证的一部分进行验证时检索和利用CRL信息，即使该证书在过去已经过验证。然而，在许多情况下（如离线验证），访问最新的CRL信息可能很困难或不可能。因此，CRL信息的使用可能由受保护信息的价值决定。特定上下文中CRL信息的值超出了本规范的范围，但可能受与特定认证路径相关联的策略控制。
All agents MUST be capable of performing revocation checks using CRLs as specified in [KEYM]. All agents MUST perform revocation status checking in accordance with [KEYM]. Receiving agents MUST recognize CRLs in received S/MIME messages.
所有代理必须能够使用[KEYM]中指定的CRL执行撤销检查。所有代理必须根据[KEYM]执行撤销状态检查。接收代理必须识别接收到的S/MIME消息中的CRL。
In creating a user agent for secure messaging, certificate, CRL, and certification path validation SHOULD be highly automated while still acting in the best interests of the user. Certificate, CRL, and path validation MUST be performed as per [KEYM] when validating a correspondent's public key. This is necessary before using a public key to provide security services such as: verifying a signature; encrypting a content-encryption key (ex: RSA); or forming a pairwise symmetric key (ex: Diffie-Hellman) to be used to encrypt or decrypt a content-encryption key.
在创建用于安全消息传递的用户代理时，证书、CRL和证书路径验证应该高度自动化，同时仍然符合用户的最佳利益。验证通信方的公钥时，必须按照[KEYM]执行证书、CRL和路径验证。这在使用公钥提供安全服务之前是必要的，例如：验证签名；加密内容加密密钥（例如：RSA）；或者形成成对对称密钥（例如：Diffie Hellman），用于加密或解密内容加密密钥。
Certificates and CRLs are made available to the path validation procedure in two ways: a) incoming messages, and b) certificate and CRL retrieval mechanisms. Certificates and CRLs in incoming messages are not required to be in any particular order nor are they required to be in any way related to the sender or recipient of the message
证书和CRL以两种方式提供给路径验证过程：a）传入消息，b）证书和CRL检索机制。传入邮件中的证书和CRL不需要按任何特定顺序排列，也不需要以任何方式与邮件的发件人或收件人相关
(although in most cases they will be related to the sender). Incoming certificates and CRLs SHOULD be cached for use in path validation and optionally stored for later use. This temporary certificate and CRL cache SHOULD be used to augment any other certificate and CRL retrieval mechanisms for path validation on incoming signed messages.
（尽管在大多数情况下，它们与发送者相关）。传入的证书和CRL应缓存以用于路径验证，并可选择存储以供以后使用。此临时证书和CRL缓存应用于增强任何其他证书和CRL检索机制，以便对传入的签名消息进行路径验证。
Certificates and Certificate Revocation Lists (CRLs) are signed by the certificate issuer. A receiving agent MUST be capable of verifying the signatures on certificates and CRLs made with id-dsa-with-sha1 [CMSALG].
证书和证书吊销列表（CRL）由证书颁发者签名。接收代理必须能够验证id-dsa-with-sha1[CMSALG]的证书和CRL上的签名。
A receiving agent MUST be capable of verifying the signatures on certificates and CRLs made with md5WithRSAEncryption and sha1WithRSAEncryption signature algorithms with key sizes from 512 bits to 2048 bits described in [CMSALG].
接收代理必须能够验证证书和CRL上的签名，这些证书和CRL使用[CMSALG]中所述的MD5WithRSANCRYPTION和SHA1 WithRSANCRYPTION签名算法，密钥大小从512位到2048位。
Because of the security issues surrounding MD2 [RC95], and in light of current use, md2WithRSAEncryption MAY be supported.
由于围绕MD2[RC95]的安全问题，并且根据当前的使用情况，可能支持MD2 WithRSA加密。
PKIX describes an extensible framework in which the basic certificate information can be extended and how such extensions can be used to control the process of issuing and validating certificates. The PKIX Working Group has ongoing efforts to identify and create extensions which have value in particular certification environments. Further, there are active efforts underway to issue PKIX certificates for business purposes. This document identifies the minimum required set of certificate extensions which have the greatest value in the S/MIME environment. The syntax and semantics of all the identified extensions are defined in [KEYM].
PKIX描述了一个可扩展的框架，其中可以扩展基本证书信息，以及如何使用这些扩展来控制证书的颁发和验证过程。PKIX工作组正在努力确定和创建在特定认证环境中具有价值的扩展。此外，正在积极努力为商业目的颁发PKIX证书。本文档确定了在S/MIME环境中具有最大价值的最小所需证书扩展集。[KEYM]中定义了所有已识别扩展的语法和语义。
Sending and receiving agents MUST correctly handle the basic constraints, key usage, authority key identifier, subject key identifier, and subject alternative names certificate extensions when they appear in end-entity and CA certificates. Some mechanism SHOULD exist to gracefully handle other certificate extensions when they appear in end-entity or CA certificates.
当基本约束、密钥使用、权限密钥标识符、使用者密钥标识符和使用者替代名称证书扩展出现在最终实体和CA证书中时，发送和接收代理必须正确处理这些约束、密钥使用、权限密钥标识符、使用者密钥标识符和使用者替代名称证书扩展。当其他证书扩展出现在最终实体或CA证书中时，应该存在一些机制来优雅地处理它们。
Certificates issued for the S/MIME environment SHOULD NOT contain any critical extensions (extensions that have the critical field set to TRUE) other than those listed here. These extensions SHOULD be marked as non-critical unless the proper handling of the extension is
为S/MIME环境颁发的证书不应包含此处列出的以外的任何关键扩展（关键字段设置为TRUE的扩展）。除非正确处理扩展，否则这些扩展应标记为非关键
deemed critical to the correct interpretation of the associated certificate. Other extensions may be included, but those extensions SHOULD NOT be marked as critical.
被视为对相关证书的正确解释至关重要。可以包括其他扩展，但不应将这些扩展标记为关键扩展。
Interpretation and syntax for all extensions MUST follow [KEYM], unless otherwise specified here.
除非此处另有规定，否则所有扩展的解释和语法必须遵循[KEYM]。
The basic constraints extension serves to delimit the role and position that an issuing authority or end-entity certificate plays in a certification path.
基本约束扩展用于定义颁发机构或最终实体证书在证书路径中所扮演的角色和位置。
For example, certificates issued to CAs and subordinate CAs contain a basic constraint extension that identifies them as issuing authority certificates. End-entity certificates contain an extension that constrains the certificate from being an issuing authority certificate.
例如，颁发给CA和下级CA的证书包含一个基本约束扩展，该扩展将它们标识为颁发机构证书。终端实体证书包含一个扩展，该扩展限制证书为颁发机构证书。
Certificates SHOULD contain a basicConstraints extension in CA certificates, and SHOULD NOT contain that extension in end entity certificates.
证书应在CA证书中包含basicConstraints扩展，而不应在最终实体证书中包含该扩展。
The key usage extension serves to limit the technical purposes for which a public key listed in a valid certificate may be used. Issuing authority certificates may contain a key usage extension that restricts the key to signing certificates, certificate revocation lists and other data.
密钥使用扩展用于限制有效证书中列出的公钥可用于的技术目的。颁发机构证书可能包含密钥使用扩展，该扩展将密钥限制为签名证书、证书吊销列表和其他数据。
For example, a certification authority may create subordinate issuer certificates which contain a key usage extension which specifies that the corresponding public key can be used to sign end user certificates and sign CRLs.
例如，证书颁发机构可以创建包含密钥使用扩展的从属颁发者证书，该扩展指定可以使用相应的公钥来签署最终用户证书和签署CRL。
If a key usage extension is included in a PKIX certificate, then it MUST be marked as critical.
如果PKIX证书中包含密钥使用扩展，则必须将其标记为关键。
S/MIME receiving agents MUST NOT accept the signature of a message if it was verified using a certificate which contains the key usage extension without either the digitalSignature or nonRepudiation bit set. Sometimes S/MIME is used as a secure message transport for applications beyond interpersonal messaging. In such cases, the S/MIME-enabled application can specify additional requirements concerning the digitalSignature or nonRepudiation bits within this extension.
如果使用包含密钥使用扩展且未设置数字签名或不可否认位的证书对消息进行验证，则S/MIME接收代理不得接受消息的签名。有时，S/MIME被用作人际消息传递以外的应用程序的安全消息传输。在这种情况下，支持S/MIME的应用程序可以指定与此扩展中的数字签名或不可否认性位有关的附加要求。
If the key usage extension is not specified, receiving clients MUST presume that the digitalSignature and nonRepudiation bits are set.
如果未指定密钥使用扩展，则接收客户端必须假定设置了数字签名和非否认位。
The subject alternative name extension is used in S/MIME as the preferred means to convey the RFC-2822 email address(es) that correspond(s) to the entity for this certificate. Any RFC-2822 email addresses present MUST be encoded using the rfc822Name CHOICE of the GeneralName type. Since the SubjectAltName type is a SEQUENCE OF GeneralName, multiple RFC-2822 email addresses MAY be present.
subject alternative name extension在S/MIME中用作传递与此证书的实体相对应的RFC-2822电子邮件地址的首选方式。必须使用GeneralName类型的rfc822Name选项对存在的任何RFC-2822电子邮件地址进行编码。由于SubjectAltName类型是GeneralName的序列，因此可能存在多个RFC-2822电子邮件地址。
The extended key usage extension also serves to limit the technical purposes for which a public key listed in a valid certificate may be used. The set of technical purposes for the certificate therefore are the intersection of the uses indicated in the key usage and extended key usage extensions.
扩展密钥使用扩展还用于限制有效证书中列出的公钥可用于的技术目的。因此，证书的技术用途集是密钥使用和扩展密钥使用扩展中指示的用途的交叉点。
For example, if the certificate contains a key usage extension indicating digital signature and an extended key usage extension which includes the email protection OID, then the certificate may be used for signing but not encrypting S/MIME messages. If the certificate contains a key usage extension indicating digital signature, but no extended key usage extension then the certificate may also be used to sign but not encrypt S/MIME messages.
例如，如果证书包含指示数字签名的密钥使用扩展和包括电子邮件保护OID的扩展密钥使用扩展，则该证书可用于签名但不加密S/MIME消息。如果证书包含指示数字签名的密钥使用扩展，但没有扩展的密钥使用扩展，则该证书也可用于签名但不加密S/MIME消息。
If the extended key usage extension is present in the certificate then interpersonal message S/MIME receiving agents MUST check that it contains either the emailProtection or the anyExtendedKeyUsage OID as defined in [KEYM]. S/MIME uses other than interpersonal messaging MAY require the explicit presence of the extended key usage extension or other OIDs to be present in the extension or both.
如果证书中存在扩展密钥使用扩展，则人际消息S/MIME接收代理必须检查它是否包含[KEYM]中定义的emailProtection或anyExtendedKeyUsage OID。除人际消息传递之外的S/MIME使用可能要求扩展密钥使用扩展显式存在或扩展中存在其他OID，或两者都存在。
All of the security issues faced by any cryptographic application must be faced by a S/MIME agent. Among these issues are protecting the user's private key, preventing various attacks, and helping the user avoid mistakes such as inadvertently encrypting a message for the wrong recipient. The entire list of security considerations is beyond the scope of this document, but some significant concerns are listed here.
任何加密应用程序所面临的所有安全问题都必须由S/MIME代理来解决。这些问题包括保护用户的私钥、防止各种攻击以及帮助用户避免错误，例如无意中为错误的收件人加密消息。整个安全注意事项列表超出了本文档的范围，但此处列出了一些重要的注意事项。
When processing certificates, there are many situations where the processing might fail. Because the processing may be done by a user agent, a security gateway, or other program, there is no single way
在处理证书时，有许多情况下处理可能会失败。因为处理可以由用户代理、安全网关或其他程序完成，所以没有单一的方法
to handle such failures. Just because the methods to handle the failures has not been listed, however, the reader should not assume that they are not important. The opposite is true: if a certificate is not provably valid and associated with the message, the processing software should take immediate and noticeable steps to inform the end user about it.
处理这样的失败。然而，仅仅因为没有列出处理故障的方法，读者就不应该认为它们不重要。反之亦然：如果证书不可证明有效且与消息关联，则处理软件应立即采取明显的步骤通知最终用户。
Some of the many places where signature and certificate checking might fail include:
签名和证书检查可能失败的许多地方包括：
- no Internet mail addresses in a certificate matches the sender of a message, if the certificate contains at least one mail address - no certificate chain leads to a trusted CA - no ability to check the CRL for a certificate - an invalid CRL was received - the CRL being checked is expired - the certificate is expired - the certificate has been revoked
- 证书中没有与邮件发件人匹配的Internet邮件地址，如果证书至少包含一个邮件地址-没有证书链导致受信任的CA-无法检查证书的CRL-收到无效的CRL-正在检查的CRL已过期-证书已过期-证书已吊销
There are certainly other instances where a certificate may be invalid, and it is the responsibility of the processing software to check them all thoroughly, and to decide what to do if the check fails.
当然，在其他情况下，证书可能是无效的，处理软件有责任彻底检查所有证书，并决定如果检查失败怎么办。
At the Selected Areas in Cryptography '95 conference in May 1995, Rogier and Chauvaud presented an attack on MD2 that can nearly find collisions [RC95]. Collisions occur when one can find two different messages that generate the same message digest. A checksum operation in MD2 is the only remaining obstacle to the success of the attack. For this reason, the use of MD2 for new applications is discouraged. It is still reasonable to use MD2 to verify existing signatures, as the ability to find collisions in MD2 does not enable an attacker to find new messages having a previously computed hash value.
在1995年5月的95年密码学会议上，Rogier和Chauvaud提出了一种对MD2的攻击，这种攻击几乎可以找到碰撞[RC95]。当可以找到生成相同消息摘要的两条不同消息时，就会发生冲突。MD2中的校验和操作是攻击成功的唯一障碍。因此，不鼓励在新应用程序中使用MD2。使用MD2来验证现有签名仍然是合理的，因为在MD2中查找冲突的能力无法使攻击者找到具有先前计算的哈希值的新消息。
It is possible for there to be multiple unexpired CRLs for a CA. If an agent is consulting CRLs for certificate validation, it SHOULD make sure that the most recently issued CRL for that CA is consulted, since an S/MIME message sender could deliberately include an older unexpired CRL in an S/MIME message. This older CRL might not include recent revoked certificates, which might lead an agent to accept a certificate that has been revoked in a subsequent CRL.
CA可能存在多个未过期的CRL。如果代理正在咨询CRL以进行证书验证，则应确保咨询该CA最近发布的CRL，因为S/MIME消息发送方可能有意在S/MIME消息中包含较旧的未过期CRL。此旧CRL可能不包括最近吊销的证书，这可能会导致代理接受在后续CRL中已吊销的证书。
When determining the time for a certificate validity check, agents have to be careful to use a reliable time. Unless it is from a trusted agent, this time MUST NOT be the SigningTime attribute found in an S/MIME message. For most sending agents, the SigningTime attribute could be deliberately set to direct the receiving agent to
在确定证书有效性检查的时间时，代理必须小心使用可靠的时间。除非它来自受信任的代理，否则此时间不能是S/MIME消息中的SigningTime属性。对于大多数发送代理，可以故意设置SigningTime属性以指示接收代理
check a CRL that could have out-of-date revocation status for a certificate, or cause an improper result when checking the Validity field of a certificate.
检查证书的CRL，该CRL可能具有过期的吊销状态，或者在检查证书的有效性字段时导致不正确的结果。
A. References
A.参考资料
[ACAUTH] Farrell, S. and R. Housley, "An Internet Attribute Certificate Profile for Authorization", RFC 3281, April 2002.
[ACAUTH]Farrell，S.和R.Housley，“用于授权的Internet属性证书配置文件”，RFC 3281，2002年4月。
[CMS] Housely, R., "Cryptographic Message Syntax (CMS)", RFC 3852, July 2004.
[CMS]Housely，R.，“加密消息语法（CMS）”，RFC 38522004年7月。
[CMSALG] Housley, R., "Cryptographic Message Syntax (CMS) Algorithms", RFC 3370, August 2002.
[CMSALG]Housley，R.，“加密消息语法（CMS）算法”，RFC3370，2002年8月。
[KEYM] Housley, R., Polk, W., Ford, W., and D. Solo, "Internet X.509 Public Key Infrastructure Certificate and Certificate Revocation List (CRL) Profile", RFC 3280, April 2002.
[KEYM]Housley，R.，Polk，W.，Ford，W.，和D.Solo，“互联网X.509公钥基础设施证书和证书撤销列表（CRL）概要”，RFC 32802002年4月。
[KEYMALG] Bassham, L., Polk, W., and R. Housley, "Algorithms and Identifiers for the Internet X.509 Public Key Infrastructure Certificate and Certificate Revocation List (CRL) Profile", RFC 3279, April 2002.
[KEYMALG]Bassham，L.，Polk，W.，和R.Housley，“互联网X.509公钥基础设施证书和证书撤销列表（CRL）配置文件的算法和标识符”，RFC 3279，2002年4月。
[MUSTSHOULD] Bradner, S., "Key words for use in RFCs to Indicate Requirement Levels", BCP 14, RFC 2119, March 1997.
[MUSTSHOULD]Bradner，S.，“RFC中用于表示需求水平的关键词”，BCP 14，RFC 2119，1997年3月。
[PKCS9] Nystrom, M. and B. Kaliski, "PKCS #9: Selected Object Classes and Attribute Types Version 2.0", RFC 2985, November 2000.
[PKCS9]Nystrom，M.和B.Kaliski，“PKCS#9：选定对象类和属性类型版本2.0”，RFC 29852000年11月。
[RFC-2822], Resnick, P., "Internet Message Format", RFC 2822, April 2001.
[RFC-2822]，Resnick，P.，“互联网信息格式”，RFC 2822，2001年4月。
[SMIME-MSG] Ramsdell, B., Ed., "S/MIME Version 3.1 Message Specification", RFC 3851, July 2004.
[SMIME-MSG]Ramsdell，B.，编辑，“S/MIME版本3.1消息规范”，RFC 38512004年7月。
[x.208-88] ITU-T. Recommendation X.208: Specification of Abstract Syntax Notation One (ASN.1). 1988.
[x.208-88]ITU-T.建议x.208：抽象语法符号一规范（ASN.1）。1988
[CERTV2] Dusse, S., Hoffman, P., Ramsdell, B., and J. Weinstein, "S/MIME Version 2 Certificate Handling", RFC 2312, March 1998.
[CERTV2]Dusse，S.，Hoffman，P.，Ramsdell，B.，和J.Weinstein，“S/MIME版本2证书处理”，RFC 2312，1998年3月。
[PKCS6] RSA Laboratories, "PKCS #6: Extended-Certificate Syntax Standard", November 1993.
[PKCS6]RSA实验室，“PKCS#6：扩展证书语法标准”，1993年11月。
[RC95] Rogier, N. and Chauvaud, P., "The compression function of MD2 is not collision free," Presented at Selected Areas in Cryptography '95, May 1995.
[RC95]Rogier，N.和Chauvaud，P.，“MD2的压缩功能不是无冲突的”，发表于1995年5月《密码学》95的选定领域。
[SECLABEL] Nicolls, W., "Implementing Company Classification Policy with the S/MIME Security Label", RFC 3114, May 2002.
[SECLABEL]Nicols，W.“使用S/MIME安全标签实施公司分类政策”，RFC3114，2002年5月。
[X.500] ITU-T Recommendation X.500 (1997) | ISO/IEC 9594-1:1997, Information technology - Open Systems Interconnection - The Directory: Overview of concepts, models and services.
[X.500]ITU-T建议X.500（1997）| ISO/IEC 9594-1:1997，信息技术-开放系统互连-目录：概念、模型和服务概述。
[X.501] ITU-T Recommendation X.501 (1997) | ISO/IEC 9594-2:1997, Information technology - Open Systems Interconnection - The Directory: Models.
[X.501]ITU-T建议X.501（1997）| ISO/IEC 9594-2:1997，信息技术-开放系统互连-目录：模型。
[X.509] ITU-T Recommendation X.509 (1997) | ISO/IEC 9594-8:1997, Information technology - Open Systems Interconnection - The Directory: Authentication framework.
[X.509]ITU-T建议X.509（1997）| ISO/IEC 9594-8:1997，信息技术-开放系统互连-目录：认证框架。
[X.520] ITU-T Recommendation X.520 (1997) | ISO/IEC 9594-6:1997, Information technology - Open Systems Interconnection - The Directory: Selected attribute types.
[X.520]ITU-T建议X.520（1997）| ISO/IEC 9594-6:1997，信息技术-开放系统互连-目录：选定属性类型。
B. Acknowledgements
B.致谢
Many thanks go out to the other authors of the S/MIME v2 RFC: Steve Dusse, Paul Hoffman and Jeff Weinstein. Without v2, there wouldn't be a v3.
非常感谢S/MIME v2 RFC的其他作者：史蒂夫·杜塞、保罗·霍夫曼和杰夫·温斯坦。没有v2，就不会有v3。
A number of the members of the S/MIME Working Group have also worked very hard and contributed to this document. Any list of people is doomed to omission and for that I apologize. In alphabetical order, the following people stand out in my mind due to the fact that they made direct contributions to this document.
S/MIME工作组的一些成员也非常努力地工作，为本文件作出了贡献。任何人的名单都注定会被遗漏，对此我深表歉意。按字母顺序排列，以下人员在我心目中脱颖而出，因为他们对本文件作出了直接贡献。
Bill Flanigan Trevor Freeman Elliott Ginsburg Paul Hoffman Russ Housley David P. Kemp Michael Myers John Pawling Denis Pinkas Jim Schaad
比尔·弗拉尼根·特雷弗·弗里曼·艾略特·金斯堡·保罗·霍夫曼·罗斯斯·霍斯利·大卫·P·肯普·迈克尔·迈尔斯·约翰·波林·丹尼斯·平卡斯·吉姆·沙德
C. Editor's Address
C.编辑地址
Blake Ramsdell Sendmail, Inc. 704 228th Ave NE #775 Sammamish, WA 98074
Blake Ramsdell Sendmail，Inc.地址：华盛顿州Sammamish东北775号第228大道704号，邮编：98074
EMail: blake@sendmail.com
EMail: blake@sendmail.com
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Acknowledgement
确认
Funding for the RFC Editor function is currently provided by the Internet Society.
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