RFC7193
Internet Engineering Task Force (IETF) S. Turner Request for Comments: 7193 IECA Category: Informational R. Housley ISSN: 2070-1721 Vigil Security
J. Schaad
Soaring Hawk Consulting
April 2014
The application/cms Media Type
Abstract
This document registers the application/cms media type for use with the corresponding CMS (Cryptographic Message Syntax) content types.
Status of This Memo
This document is not an Internet Standards Track specification; it is published for informational purposes.
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). Not all documents approved by the IESG are a candidate for any level of Internet Standard; see Section 2 of RFC 5741.
Information about the current status of this document, any errata, and how to provide feedback on it may be obtained at http://www.rfc-editor.org/info/rfc7193.
Copyright Notice
Copyright (c) 2014 IETF Trust and the persons identified as the document authors. All rights reserved.
This document is subject to BCP 78 and the IETF Trust's Legal Provisions Relating to IETF Documents (http://trustee.ietf.org/license-info) 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.
Contents
Introduction
RFC5751 registered the application/pkc7-mime media type. That document defined five optional smime-type parameters. The smime-type parameter originally conveyed details about the security applied to the data content type, indicating whether it was signed or enveloped, as well as the name of the data content; it was later expanded to indicate whether the data content is compressed and whether the data content contained a certs-only message. This document does not affect those registrations as this document places no requirements on S/MIME (Secure Multipurpose Internet Mail Extensions) agents.
The registration done by the S/MIME documents was done assuming that there would be a MIME (Multipurpose Internet Mail Extensions) wrapping layer around each of the different enveloping contents; thus, there was no need to include more than one item in each smime- type. This is no longer the case with some of the more advanced enveloping types. Some protocols such as the CMC (Certificate Management over Cryptographic Message Syntax) RFC5273 have defined additional S/MIME types. New protocols that intend to wrap MIME content should continue to define a smime-type string; however, new protocols that intend to wrap non-MIME types should use this mechanism instead.
CMS (Cryptographic Message Syntax) RFC5652 associates a content type identifier (OID) with specific content; CMS content types have been widely used to define contents that can be enveloped using other CMS content types and to define enveloping content types some of which provide security services. CMS protecting content types, those that provide security services, include: Signed-Data RFC5652, Enveloped-Data RFC5652, Digested-Data RFC5652, Encrypted-Data RFC5652, Authenticated-Data RFC5652, Authenticated-Enveloped-Data RFC5083, and Encrypted Key Package RFC6032. CMS non-protecting content types, those that provide no security services but encapsulate other CMS content types, include: Content Information RFC5652, Compressed Data RFC3274, Content Collection RFC4073, and Content With Attributes RFC4073. Then, there are the innermost content types that include: Data RFC5652, Asymmetric Key Package RFC5958, Symmetric Key Package RFC6031, Firmware Package RFC4108, Firmware Package Load Receipt RFC4108, Firmware Package Load Error RFC4108, Trust Anchor List RFC5914, TAMP Status Query, TAMP Status Response, TAMP Update, TAMP Update Confirm, TAMP Apex Update, TAMP Apex Update Confirmation, TAMP Community Update, TAMP Community Update Confirm, TAMP Sequence Adjust, TAMP Sequence Adjust Confirmation, TAMP Error RFC5934, Key Package Error, and Key Package Receipt RFC7191.
To support conveying CMS content types, this document defines a media type and parameters that indicate the enveloping and embedded CMS content types.
New CMS content types should be affirmative in defining the string that identifies the new content type and should additionally define if the new content type is expected to appear in the encapsulatedContent or innerContent parameter.
Requirements Terminology
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.
CMS Media Type Registration Applications
This section provides the media type registration application for the application/cms media type (see RFC6838, Section 5.6).
Type name: application
Subtype name: cms
Required parameters: None.
Optional parameters:
encapsulatingContent=y; where y is one or more CMS ECT (Encapsulating Content Type) identifiers; multiple values are encapsulated in quotes and separated by a folding-whitespace, a comma, and folding-whitespace. ECT values are based on content types found in RFC3274, RFC4073, RFC5083, RFC5652, and RFC6032. This list can later be extended; see Section 4.
authData
compressedData
contentCollection
contentInfo
contentWithAttrs
authEnvelopedData
encryptedKeyPkg
digestData
encryptedData
envelopedData
signedData
innerContent=x; where x is one or more CMS ICT (Inner Content Type) identifiers; multiple values encapsulated in quotes and are separated by a folding-whitespace, a comma, and folding-whitespace. ICT values are based on content types found in RFC4108, RFC5914, RFC5934, RFC5958, RFC6031, and RFC7191. This list can later be extended; see Section 4.
firmwarePackage
firmwareLoadReceipt
firmwareLoadError
aKeyPackage
sKeyPackage
trustAnchorList
TAMP-statusQuery
TAMP-statusResponse
TAMP-update
TAMP-updateConfirm
TAMP-apexUpdate
TAMP-apexUpdateConfirm
TAMP-communityUpdate
TAMP-communityUpdateConfirm
TAMP-seqNumAdjust
TAMP-seqNumAdjustConfirm
TAMP-error
keyPackageReceipt
keyPackageError
The optional parameters are case sensitive.
Encoding considerations:
Binary.
RFC5652 requires that the outermost encapsulation be ContentInfo.
Security considerations:
The following security considerations apply:
RFC | CMS Protecting Content Type and Algorithms ----------+------------------------------------------- RFC3370 | signedData, envelopedData, RFC5652 | digestedData, encryptedData, and RFC5753 | authData RFC5754 | ----------+------------------------------------------- RFC5958 | aKeyPackage RFC5959 | RFC6162 | ----------+------------------------------------------- RFC6031 | sKeyPackage RFC6160 | ----------+------------------------------------------- RFC6032 | encryptedKeyPkg RFC6033 | RFC6161 | ----------+------------------------------------------- RFC5914 | trustAnchorList ----------+------------------------------------------- RFC3274 | compressedData ----------+------------------------------------------- RFC5083 | authEnvelopedData RFC5084 | ----------+------------------------------------------- RFC4073 | contentCollection and | contentWithAttrs ----------+------------------------------------------- RFC4108 | firmwarePackage, | firmwareLoadReceipt, and | firmwareLoadError ----------+------------------------------------------- RFC5934 | TAMP-statusQuery, TAMP-statusResponse, | TAMP-update, TAMP-updateConfirm, | TAMP-apexUpdate, | TAMP-apexUpdateConfirm, | TAMP-communityUpdate, | TAMP-communityUpdateConfirm, | TAMP-seqNumAdjust, | TAMP-seqNumAdjustConfirm, and | TAMP-error ----------+------------------------------------------- RFC7191 |keyPackageReceipt and keyPackageError ----------+-------------------------------------------
In some circumstances, significant information can be leaked by disclosing what the innermost ASN.1 structure is. In these cases, it is acceptable to disclose the wrappers without disclosing the inner content type.
ASN.1 encoding rules (e.g., DER and BER) have a type-length-value structure, and it is easy to construct malicious content with invalid length fields that can cause buffer overrun conditions. ASN.1 encoding rules allows for arbitrary levels of nesting, which may make it possible to construct malicious content that will cause a stack overflow. Interpreters of ASN.1 structures should be aware of these issues and should take appropriate measures to guard against buffer overflows and stack overruns in particular and malicious content in general.
Interoperability considerations:
See RFC3274, RFC4073, RFC4108, RFC5083, RFC5652, RFC5914, RFC5934, RFC5958, RFC6031, RFC6032, and RFC7191.
In all cases, CMS content types are encapsulated within ContentInfo structures RFC5652; that is the outermost enveloping structure is ContentInfo.
CMS RFC5652 defines slightly different processing rules for SignedData than does PKCS #7 RFC2315. This media type employs the CMS processing rules.
The Content-Type header field of all application/cms objects SHOULD include the optional "encapsulatingContent" and "innerContent" parameters.
The Content-Disposition header field RFC4021 can also be included along with Content-Type's optional name parameter.
Published specification: This specification.
Applications that use this media type:
Applications that support CMS (Cryptographic Message Syntax) content types.
Fragment identifier considerations: N/A
Additional information:
Magic number(s): None File extension(s): .cmsc Macintosh File Type Code(s):
Person & email address to contact for further information:
Sean Turner <[email protected]>
Intended usage: COMMON
Restrictions on usage: none
Author: Sean Turner <[email protected]>
Change controller: The IESG <[email protected]>
Example
The following is an example encrypted status response message:
MIME-Version: 1.0
Content-Type: application/cms; encapsulatingContent=encryptedData;
innerContent=TAMP-statusResponse; name=status.cmsc
Content-Transfer-Encoding: base64
MIIFLQYJKoZIhvcNAQcDoIIFHjCCBRoCAQAxggFhMIIBXQIBADBFMEAxC zAJBgNVBAYTAlVTMR8wHQYDVQQKExZUZXN0IENlcnRpZmljYXRlcyAyMD ExMRAwDgYDVQQDEwdHb29kIENBAgEBMA0GCSqGSIb3DQEBAQUABIIBAEa uaXQeVsOyZ7gz0pJikRQ6Jqr64k2dbHBE4SDZL/uErP9FJUIja9LaJrc5 S83EZ7wf3mODUBaDhGfQVKoPrNTsLmw98fE/O+wcdpI2XKaILOR62xDJR emQQST+EPfMwZmCwgsImmY3AxefAgzp8hVgK7SDiXGXfa9ux9PMdCSjHP IgcAUFHmTiqxYd72Gl08kLCMIXmn3g5RsYUggxooeFNHiFNR28TV5HctG i6Ay5++iKUGrUQyXD+GlwakFToGFmFj3FMyZi7+kYV/X00BiBP3kpIgVJ 4jCj+nYtKWh6JXPoEqEsa39GmDEFGq4/58GEu70amWvW1DA++7kDP4gwg gOuBgkqhkiG9w0BBwEwHQYJYIZIAWUDBAECBBCH5yTQqZ4KYiTTeYdjoY 4sgIIDgArSpOcengKnZS4SCjfuQkMxB5wfSaud1thlZ+gUFCgzbFtkfYM Qx/T7gnkneniyj2rwOmZxCQXpPlCDXH6mS83ngfrNN8ay3HrMPpVkEOmW UMc5jI6oNObwqi8a3ezzhYRxF06jzdD2R/6SAPALz3Q4NU8eX+PnuekgR oxo/INzhT4iGvokn9xVah6piSbjhPA+QZp1HgQrlWyyM3lG9jn4thchKl FQqZEy/EBaCWq+sJG7LLxqS5k29CiAVx0JSItqAPvX1ZvLMY2aq//MQMw 0VFEx7Kt5aWNvKHTor9RUuuzwiZ5kwXt2vJt6bFiV7yS+EXofpFEmqyJP VJzyAFIXJRTv4k007n0M1UpXQpGjywECI6DbIhfBL8CsNskTCjrsfU+Tw RRkRKAbtJYughs9bDYkDu9UsKd/AE4zXk4prwo8/f1chpmzpHKOXiWzt+ xaCj648I4rOjdI9s4JP8J0qwVKoLEMGeiZlf2UlaiyMzZYzTOxI03PHp1 Whk6TXhnmMVPWGYjjelvE38gq/XynobbQRGEJdnnHzH7SrS27FmgRcnBO 3QQUPJChVn7iBHmdui++GAxpHoGdS6nSo4kQ6d5u5rL/Ctcnwu0k+s0Xi ZMzOqp7L31xl1jvYUWIswLQYsIFoiejU3UTKzq/Cpd5MK+I8cwCM3aQ2c D08URTPgu+U92pnYqm3auptywyjGAU/hkZ13XN7YRhLk/kuX8QXo3tZdj dKA4f/uNf1DURpJK9004uCkxuAtu5HemMv7YPTTx9Ua2pZFW5O+k2Mf2Z F/geOvtNw7UV8wOT1nokXu9lnIZ9Xcs1cGGmRYE7jW15F07uGnMi1s2Gt LAST7t/PlTNZU6h0rVExErVa7T+VNidrgwGIke0YqYIwvTINRs+9VeJE3 AJeatDlQs+01jrqqFWWmGmmsEBTTRuoDQHK7YBFFy4xIwQqZGW0EVre39 OU5CL5LHIYiAVoV16YwiGd5WvFF8P1ZJK4ki8GFgYiMcPKmjQgP7DumqG n7eQtMD5tezTQeC07ntV3bi5pdznZHVcF2Kqg+qHjJQlhUdK7Pew3kq7k mfCdQV0BmQSYyjEAaTijaw4fAMxAbiw4OU0eNeU//zcpp04AuTFfJorIg oZ+iCTYei8HMUA9/ysLFXA64wdsuCj0zXmNiYwosisuNg3TXfoBOzohKq fkeXt
IANA Considerations
IANA has registered the media type application/cms in the Standards tree using the applications provided in Section 2 of this document.
IANA has established two subtype registries called "CMS Encapsulating Content Types" and "CMS Inner Content Types". Entries in these registries are allocated by Expert Review RFC5226. The Expert will determine whether the content is an ECT or an ICT, where the rule is that an ICT does not encapsulate another content type while an ECT does encapsulate another content type.
Initial values are as follows:
CMS Encapsulating Content Types
Name | Document | Object Identifier
+----------+---------------------------
authData |RFC5652 | 1.2.840.113549.1.9.16.1.2 compressedData |RFC3274 | 1.2.840.113549.1.9.16.1.9 contentCollection |RFC4073 | 1.2.840.113549.1.9.16.1.19 contentInfo |RFC5652 | 1.2.840.113549.1.9.16.1.6 contentWithAttrs |RFC4073 | 1.2.840.113549.1.9.16.1.20 authEnvelopedData |RFC5083 | 1.2.840.113549.1.9.16.1.23 encryptedKeyPkg |RFC6032 | 2.16.840.1.101.2.1.2.78.2 digestData |RFC5652 | 1.2.840.113549.1.9.16.1.5 encryptedData |RFC5652 | 1.2.840.113549.1.9.16.1.6 envelopedData |RFC5652 | 1.2.840.113549.1.9.16.1.3 signedData |RFC5652 | 1.2.840.113549.1.9.16.1.2
CMS Inner Content Types
Name | Document | Object Identifier
+----------+---------------------------
firmwarePackage |RFC4108 | 1.2.840.113549.1.9.16.1.16 firmwareLoadReceipt |RFC4108 | 1.2.840.113549.1.9.16.1.17 firmwareLoadError |RFC4108 | 1.2.840.113549.1.9.16.1.18 aKeyPackage |RFC5958 | 2.16.840.1.101.2.1.2.78.5 sKeyPackage |RFC6031 | 1.2.840.113549.1.9.16.1.25 trustAnchorList |RFC5914 | 1.2.840.113549.1.9.16.1.34 TAMP-statusQuery |RFC5934 | 2.16.840.1.101.2.1.2.77.1 TAMP-statusResponse |RFC5934 | 2.16.840.1.101.2.1.2.77.2 TAMP-update |RFC5934 | 2.16.840.1.101.2.1.2.77.3 TAMP-updateConfirm |RFC5934 | 2.16.840.1.101.2.1.2.77.4 TAMP-apexUpdate |RFC5934 | 2.16.840.1.101.2.1.2.77.5 TAMP-apexUpdateConfirm |RFC5934 | 2.16.840.1.101.2.1.2.77.6 TAMP-communityUpdate |RFC5934 | 2.16.840.1.101.2.1.2.77.7 TAMP-communityUpdateConfirm |RFC5934 | 2.16.840.1.101.2.1.2.77.8 TAMP-seqNumAdjust |RFC5934 | 2.16.840.1.101.2.1.2.77.10 TAMP-seqNumAdjustConfirm |RFC5934 | 2.16.840.1.101.2.1.2.77.11 TAMP-error |RFC5934 | 2.16.840.1.101.2.1.2.77.9 keyPackageReceipt |RFC7191 | 2.16.840.1.101.2.1.2.78.3 keyPackageError |RFC7191 | 2.16.840.1.101.2.1.2.78.6
Security Considerations
See the answer to the Security Considerations template questions in Section 2.
Acknowledgments
Special thanks to Carl Wallace for generating the example in Section 3.
References
Normative References
RFC2119 Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, March 1997.
RFC3274 Gutmann, P., "Compressed Data Content Type for
Cryptographic Message Syntax (CMS)", RFC 3274, June 2002.
RFC3370 Housley, R., "Cryptographic Message Syntax (CMS)
Algorithms", RFC 3370, August 2002.
RFC4021 Klyne, G. and J. Palme, "Registration of Mail and MIME
Header Fields", RFC 4021, March 2005.
RFC4073 Housley, R., "Protecting Multiple Contents with the
Cryptographic Message Syntax (CMS)", RFC 4073, May 2005.
RFC4108 Housley, R., "Using Cryptographic Message Syntax (CMS) to
Protect Firmware Packages", RFC 4108, August 2005.
RFC5083 Housley, R., "Cryptographic Message Syntax (CMS)
Authenticated-Enveloped-Data Content Type", RFC 5083, November 2007.
RFC5084 Housley, R., "Using AES-CCM and AES-GCM Authenticated
Encryption in the Cryptographic Message Syntax (CMS)", RFC
5084, November 2007.
RFC5226 Narten, T. and H. Alvestrand, "Guidelines for Writing an
IANA Considerations Section in RFCs", BCP 26, RFC 5226, May 2008.
RFC5273 Schaad, J. and M. Myers, "Certificate Management over CMS
(CMC): Transport Protocols", RFC 5273, June 2008.
RFC5652 Housley, R., "Cryptographic Message Syntax (CMS)", STD 70,
RFC 5652, September 2009.
RFC5753 Turner, S. and D. Brown, "Use of Elliptic Curve
Cryptography (ECC) Algorithms in Cryptographic Message
Syntax (CMS)", RFC 5753, January 2010.
RFC5754 Turner, S., "Using SHA2 Algorithms with Cryptographic
Message Syntax", RFC 5754, January 2010.
RFC5914 Housley, R., Ashmore, S., and C. Wallace, "Trust Anchor
Format", RFC 5914, June 2010.
RFC5934 Housley, R., Ashmore, S., and C. Wallace, "Trust Anchor
Management Protocol (TAMP)", RFC 5934, August 2010.
RFC5958 Turner, S., "Asymmetric Key Packages", RFC 5958, August
2010.
RFC5959 Turner, S., "Algorithms for Asymmetric Key Package Content
Type", RFC 5959, August 2010.
RFC6031 Turner, S. and R. Housley, "Cryptographic Message Syntax
(CMS) Symmetric Key Package Content Type", RFC 6031, December 2010.
RFC6032 Turner, S. and R. Housley, "Cryptographic Message Syntax
(CMS) Encrypted Key Package Content Type", RFC 6032, December 2010.
RFC6033 Turner, S., "Algorithms for Cryptographic Message Syntax
(CMS) Encrypted Key Package Content Type", RFC 6033, December 2010.
RFC6160 Turner, S., "Algorithms for Cryptographic Message Syntax
(CMS) Protection of Symmetric Key Package Content Types",
RFC 6160, April 2011.
RFC6161 Turner, S., "Elliptic Curve Algorithms for Cryptographic
Message Syntax (CMS) Encrypted Key Package Content Type",
RFC 6161, April 2011.
RFC6162 Turner, S., "Elliptic Curve Algorithms for Cryptographic
Message Syntax (CMS) Asymmetric Key Package Content Type",
RFC 6162, April 2011.
RFC6838 Freed, N., Klensin, J., and T. Hansen, "Media Type
Specifications and Registration Procedures", BCP 13, RFC 6838, January 2013.
RFC7191 Housley, R., "Cryptographic Message Syntax (CMS) Key
Package Receipt and Error Content Types", RFC 7191, April 2014.
Informative References
RFC2315 Kaliski, B., "PKCS #7: Cryptographic Message Syntax
Version 1.5", RFC 2315, March 1998.
RFC5751 Ramsdell, B. and S. Turner, "Secure/Multipurpose Internet
Mail Extensions (S/MIME) Version 3.2 Message
Specification", RFC 5751, January 2010.
Authors' Addresses
Sean Turner IECA, Inc. 3057 Nutley Street, Suite 106 Fairfax, VA 22031 USA
EMail: [email protected] Phone: +1.703.628.3180
Russell Housley Vigil Security, LLC 918 Spring Knoll Drive Herndon, VA 20170 USA
EMail: [email protected]
Jim Schaad Soaring Hawk Consulting
EMail: [email protected]
