Network Working Group S. Santesson
Internet-Draft IDsec Solutions
Intended status: Standards Track R. Housley
Expires: 24 April 2021 Vigil Security
21 October 2020
Signature Validation Token
draft-santesson-svt-xml-00
Abstract
This document defines a XML profile for the Signature Validation
Token defined in [SVT].
Status of This Memo
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2
2. Definitions . . . . . . . . . . . . . . . . . . . . . . . . . 3
2.1. Notation . . . . . . . . . . . . . . . . . . . . . . . . 3
2.1.1. References to XML Elements from XML Schemas . . . . . 3
3. SVT in XML Documents . . . . . . . . . . . . . . . . . . . . 3
3.1. SignatureValidationToken Signature Property . . . . . . . 3
3.2. Multiple SVT in a signature . . . . . . . . . . . . . . . 5
4. SVT Claims . . . . . . . . . . . . . . . . . . . . . . . . . 5
4.1. Signature Reference Data . . . . . . . . . . . . . . . . 5
4.2. Signed Data Reference Data . . . . . . . . . . . . . . . 6
4.3. Signer Certificate References . . . . . . . . . . . . . . 6
5. JOSE Header . . . . . . . . . . . . . . . . . . . . . . . . . 6
5.1. SVT Signing Key Reference . . . . . . . . . . . . . . . . 6
6. Normative References . . . . . . . . . . . . . . . . . . . . 7
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 7
1. Introduction
The "Signature Validation Token" specification [SVT] defines the
basic token to support signature validation in a way that can
significantly extend the lifetime of a signature.
This specification defines a profile for implementing SVT with a
signed XML document, and defines the following aspects of SVT usage:
* How to include reference data related to XML signatures and XML
documents in an SVT.
* How to add an SVT token to a XML signature.
XML documents can have any number of signature elements, signing an
arbitrary number of fragments of XML documents. The actual signature
element may be included in the signed XML document (enveloped),
include the signed data (enveloping) or may be separate from the
signed content (detached).
To provide a generic solution for any type of XML signature an SVT is
added to each XML signature element within the XML signature
<ds:Object> element.
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2. Definitions
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and
"OPTIONAL" in this document are to be interpreted as described in
BCP 14 [RFC2119] [RFC8174] when, and only when, they appear in all
capitals, as shown here.
The definitions in [SVT] apply also to this document.
2.1. Notation
2.1.1. References to XML Elements from XML Schemas
When referring to elements from the W3C XML Signature namespace
(http://www.w3.org/2000/09/xmldsig#) the following syntax is used:
* <ds:Signature>
When referring to elements from the ETSI XAdES XML Signature
namespace (http://uri.etsi.org/01903/v1.3.2#) the following syntax is
used:
* <xades:CertDigest>
When referring to elements defined in this specification
(http://id.swedenconnect.se/svt/1.0/sig-prop/ns) the following syntax
is used:
* <svt:Element>
3. SVT in XML Documents
When SVT is provided for XML signatures then one SVT SHALL be
provided for each XML signature.
An SVT embedded within the XML signature element SHALL be placed in a
<svt:SignatureValidationToken> element as defined in Section 3.1.
3.1. SignatureValidationToken Signature Property
The <svt:SignatureValidationToken> element SHALL be placed in a
<ds:SignatureProperty> element in accordance with [XMLDSIG11]. The
<ds:SignatureProperty> element SHALL be placed inside a
<ds:SignatureProperties> element inside a <ds:Object> element inside
a <ds:Signature> element.
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Note: [XMLDSIG11] requires the Target attribute to be present in
<ds:SignatureProperty>, referencing the signature targeted by this
signature property. If an SVT is added to a signature that do not
have an Id attribute, implementations SHOULD add an Id attribute to
the <ds:Signature> element and reference that Id in the Target
attribute. This Id attribute and Target attribute value matching is
required by the [XMLDSIG11] standard, but it is redundant in the
context of SVT validation as the SVT already contains information
that uniquely identifies the target signature. Validation
applications SHOULD not reject an SVT token because of Id and Target
attribute mismatch, and MUST rely on matching against signature using
signed information in the SVT itself.
The <svt:SignatureValidationToken> element is defined by the
following XML Schema:
<?xml version="1.0" encoding="UTF-8"?>
<xs:schema xmlns:xs="http://www.w3.org/2001/XMLSchema"
elementFormDefault="qualified"
targetNamespace="http://id.swedenconnect.se/svt/1.0/sig-prop/ns"
xmlns:svt="http://id.swedenconnect.se/svt/1.0/sig-prop/ns">
<xs:element name="SignatureValidationToken"
type="svt:SignatureValidationTokenType" />
<xs:complexType name="SignatureValidationTokenType">
<xs:simpleContent>
<xs:extension base="xs:string">
</xs:extension>
</xs:simpleContent>
</xs:complexType>
</xs:schema>
The SVT token SHALL be included as a string representation of the SVT
JWT. Note that this is the string representation of the JWT without
further encoding. The SVT MUST NOT be represented by the Base64
encoded bytes of the JWT string.
Example:
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<ds:Signature Id="MySignatureId">
...
<ds:Object>
<ds:SignatureProperties>
<ds:SignatureProperty Target="#MySignatureId">
<svt:SignatureValidationToken>
eyJ0eXAiOiJKV1QiLCJhb...2aNZ
</svt:SignatureValidationToken>
</ds:SignatureProperty>
</ds:SignatureProperties>
</ds:Object>
</ds:Signature>
3.2. Multiple SVT in a signature
If a new SVT is stored in a signature which already contains a
previously issued SVT, implementations can choose to either replace
the existing SVT or to store the new SVT in addition to the existing
SVT.
If the new SVT is stored in addition to the old SVT, it SHOULD be
stored in a new <ds:SignatureProperty> element inside the existing
<ds:SignatureProperties> element where the old SVT is located.
For interoperability robustness, signature validation applications
MUST be able to handle signatures where the new SVT is located in a
new <ds:Object> element.
4. SVT Claims
4.1. Signature Reference Data
The SVT SHALL contain a SigReference claims object that SHALL contain
the following data:
* id - The Id-attribute of the XML signature, if present.
* sig_hash - The hash over the signature value bytes.
* sb_hash - The hash over the canonicalized <ds:SignedInfo> element
(the bytes the XML signature algorithm has signed to generated the
signature value).
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4.2. Signed Data Reference Data
An SVT according to this profile SHALL contain one instance of the
SignedData claims object for each <ds:Reference> element in the
<ds:SignedInfo> element. The SignedData claims object shall contain
the following data:
* ref - The value of the URI attribute of the corresponding
<ds:Reference> element.
* hash - The hash of all bytes identified corresponding
<ds:Reference> element after applying all identified
canonicalization and transformation algorithms. These are the
same bytes that is hashed by the hash value in the
<ds:DigestValue> element inside the <ds:Reference> element.
4.3. Signer Certificate References
The SVT SHALL contain a CertReference claims object. The type claim
of the CertReference claims object SHALL be either chain or
chain_hash`.
* The chain type SHALL be used when signature validation was
performed using one or more certificates where some or all of the
certificates in the chain are not present in the target signature.
* The chain_hash type SHALL be used when signature validation was
performed using one or more certificates where all of the
certificates are present in the target signature.
5. JOSE Header
5.1. SVT Signing Key Reference
The SVT JOSE header must contain one of the following header
parameters in accordance with [RFC7515], for storing a reference to
the public key used to verify the signature on the SVT:
* x5c - Holds an X.509 certificate [RFC5280] or a chain of
certificates. The certificate holding the public key that
verifies the signature on the SVT MUST be the first certificate in
the chain.
* kid - A key identifier holding the Base64 encoded hash value of
the certificate that can verify the signature on the SVT. The
hash algorithm MUST be the same hash algorithm used when signing
the SVT as specified by the "alg" header parameter.
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6. Normative References
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119,
DOI 10.17487/RFC2119, March 1997,
<https://www.rfc-editor.org/info/rfc2119>.
[RFC5280] Cooper, D., Santesson, S., Farrell, S., Boeyen, S.,
Housley, R., and W. Polk, "Internet X.509 Public Key
Infrastructure Certificate and Certificate Revocation List
(CRL) Profile", RFC 5280, DOI 10.17487/RFC5280, May 2008,
<https://www.rfc-editor.org/info/rfc5280>.
[RFC7515] Jones, M., Bradley, J., and N. Sakimura, "JSON Web
Signature (JWS)", RFC 7515, DOI 10.17487/RFC7515, May
2015, <https://www.rfc-editor.org/info/rfc7515>.
[RFC8174] Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC
2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174,
May 2017, <https://www.rfc-editor.org/info/rfc8174>.
[SVT] Santesson, S. and R. Housley, "Signature Validation
Token", IETF draft-santesson-svt-00, October 2020.
[XMLDSIG11]
Eastlake, D., Reagle, J., Solo, D., Hirsch, F., Nystrom,
M., Roessler, T., and K. Yiu, "XML Signature Syntax and
Processing Version 1.1", W3C Proposed Recommendation, 11
April 2013.
Authors' Addresses
Stefan Santesson
IDsec Solutions AB
Forskningsbyn Ideon
SE-223 70 Lund
Sweden
Email: sts@aaa-sec.com
Russ Housley
Vigil Security, LLC
516 Dranesville Road
Herndon, VA, 20170
United States of America
Email: housley@vigilsec.com
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