RFC 5035, "Enhanced Security Services (ESS) Update: Adding CertID Algorithm Agility", August 2007

Errata ID: 6566
Status: Reported
Type: Technical
Publication Format(s) : TEXT
Reported By: David von Oheimb
Date Reported: 2021-04-29

Section 3 says:

   certs
      contains the list of certificates that are to be used in
      validating the message.  The first certificate identified in the
      sequence of certificate identifiers MUST be the certificate used
      to verify the signature.  The encoding of the ESSCertIDv2 for this
      certificate SHOULD include the issuerSerial field.  If other
      constraints ensure that issuerAndSerialNumber will be present in
      the SignerInfo, the issuerSerial field MAY be omitted.  The
      certificate identified is used during the signature verification
      process.  If the hash of the certificate does not match the
      certificate used to verify the signature, the signature MUST be
      considered invalid.

      If more than one certificate is present, subsequent certificates
      limit the set of certificates that are used during validation.

It should say:

   certs
      contains the list of certificates that are to be used in
      validating the message. It MUST contain at least one element.
      The first certificate identified in the
      sequence of certificate identifiers MUST be the certificate used
      to verify the signature.  The encoding of the ESSCertIDv2 for this
      certificate SHOULD include the issuerSerial field.  If other
      constraints ensure that issuerAndSerialNumber will be present in
      the SignerInfo, the issuerSerial field MAY be omitted.  The
      certificate identified is used during the signature verification
      process.  If the hash of the certificate does not match the
      certificate used to verify the signature, the signature MUST be
      considered invalid.

      If more than one certificate identifier is present in the sequence of ESSCertIDv2s,
      all certificates referenced there MUST be part of the signature validation chain.

Notes:

Some aspects of the 'certs' field of a SigningCertificateV2 attribute:

SigningCertificateV2 ::= SEQUENCE {
certs SEQUENCE OF ESSCertIDv2,
policies SEQUENCE OF PolicyInformation OPTIONAL
}

described in the sentences quoted above are rather vague.
This lead to major confusion and wrong implementations.
As meanwhile has been clarified, they should be re-phrased;
see suggested new version above.

(One may further mandate/clarify that the certificate identifiers must be given in the same order
as they are expected in the validation chain, but I think this is not important because
the order should not play a critical role and will be determined by the validation chain anyway.)

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