Re: calc_keyid_v2 producing different keyid for non-sha1 SKIDs

[Stefan Berger <stefanb@linux.ibm.com>]

On 4/26/21 3:37 PM, Vitaly Chikunov wrote:
> Hi,
>
> I am reported that IMA signatures where SKID is not just sha1 of the
> public key (but something different, for example different hash algo,
> such as Streebog) have "wrong" keyid in the signature. This is because
> a) kernel extracting keyid from the cert's subjectKeyIdentifier (SKID)
> x509 extension, (or if this fails it takes just serial, perhaps, we can
> disregard this corner case), it never does sha1 over the public key).


Is it wrong for ecrdsa keys? What is the spec?

Here's the spec that describes using sha1 for the skid which seems to 
work like this for RSA and ECDSA keys from what I can tell:

https://tools.ietf.org/html/rfc3280#section-4.2.1.2


> But, b) evmctl, when signing, uses just private key (not even knowing
> certificate where SKID should be) and calculating sha1 of public key.
> Thus, keyids could mismatch each other, and it's even not easy to fix
> evmctl, because there is no cert at the time of signing.
>
> Perhaps, we should fix this somehow. For example, when signing,
> introduce new option --cert, where SKID should be extracted. Does it
> looks reasonable?
>
> Vitaly,
>
>
>