Signature value for EC signatures is not DER encoded

[JanSlabon]

While it is possible to use an RSA signature directly as a signature value in a CMS SignedData structure the value of an EC signature is a raw 64 byte-string which needs to be processed and embedded into a valid structure.

From RFC5753, item 2.1.1:

• signature MUST contain the DER encoding (as an octet string) of a
  value of the ASN.1 type ECDSA-Sig-Value (see Section 7.2).

  ECDSA-Sig-Value ::= SEQUENCE {
    r INTEGER,
    s INTEGER }

This should be documented or fixed. It is also required to rebuild such structure to be able validate this kind of signature with common tools.

[aasaru]

Internal issue id: DDS-2851

[ykshatroff]

The EC signature format used here is called X.962 or CVC, but I totally agree that since most libraries do not contain code to convert X.962 to DER, one has to reimplement it, and as it is not explicitly documented, this is a problem.