XML Profile for Signature Validation Tokens

Version 1.0 - 2020-02-04 - Draft version

Registration number: 2020-62


Table of Contents

  1. Introduction

    1.1. Requirements Notation

    1.2. Definitions

    1.2. Notation

    1.2.1 References to XML Elements from XML Schemas

  2. SVT in XML Documents

    2.1.1. SignatureValidationToken Signature Property

  3. SVT Claims

    3.1. Signature Reference Data

    3.2. Signed Data Reference Data

    3.3. Signer Certificate References

  4. JOSE Header

    4.1. SVT Signing Key Reference

  5. Normative References


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:

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.

1.1. Requirements Notation

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 BCP 14 [RFC2119] [RFC8174] when, and only when, they appear in all capitals, as shown here.

These keywords are capitalized when used to unambiguously specify requirements over protocol features and behavior that affect the interoperability and security of implementations. When these words are not capitalized, they are meant in their natural-language sense.

1.2. Definitions

The definitions in [SVT] apply also to this document.

1.2. Notation

1.2.1 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:

When referring to elements from the ETSI XAdES XML Signature namespace (http://uri.etsi.org/01903/v1.3.2#) the following syntax is used:

When referring to elements defined in this specification (http://id.swedenconnect.se/svt/1.0/sig-prop/ns) the following syntax is used:

2. 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> as defined in section 2.1.1.

2.1.1. SignatureValidationToken Signature Property

The <svt:SignatureValidationToken> element SHALL be placed in a <ds:SignatureProperty> element in accordance with [XMLDsig]. The <ds:SignatureProperty> element SHALL be placed inside a <ds:SignatureProperties> element inside a <ds:Object> element inside a <ds:Signature> element.

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:

<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. SVT Claims

3.1. Signature Reference Data

The SVT SHALL contain a SigReference claims object that SHALL contain the following data:

Claim Value
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).

3.2. 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:

Claim Value
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.

3.3. Signer Certificate References

The SVT SHALL contain a CertReference claims object. The type claim of the CertReference claims object SHALL be either cert, chain, cert_hash or cert_and_chain_hash.

Note: The cert type MUST NOT be used with a XAdES signatures where the signing certificate in the target signature is bound to the signature through a <xades:CertDigest> element.

4. JOSE Header

4.1. 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:

Header Parameter Value
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.

5. Normative References

[RFC2119]

Bradner, S., Key words for use in RFCs to Indicate Requirement Levels, March 1997.

[RFC5280]

D. Cooper, S. Santesson, S. Farrell, S. Boeyen, R. Housley, W. Polk, Internet X.509 Public Key Infrastructure Certificate and Certificate Revocation List (CRL) Profile, May 2008.

[RFC8174]

Leiba, B., Ambiguity of Uppercase vs Lowercase in RFC 2119 Key Words, May 2017.

[XMLDsig]

XML Signature Syntax and Processing Version 1.1 - W3C Recommendation 11 April 2013.

[EidRegistry]

Swedish eID Framework - Registry for identifiers.

[SVT]

Signature Validation Token.