Re: calc_keyid_v2 producing different keyid for non-sha1 SKIDs

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

On 4/30/21 2:33 PM, Vitaly Chikunov wrote:
> Stefan,
> .
>> I have been using evmctl successfully with RSA and ECDSA keys now and
>> certificates created by **OpenSSL**. Problems may occur if the
>> certificate-generating tool uses something else than a sha1 to calculate the
>> subject key identifier (skid) and therefore the key id calculated by evmctl
>> (with a sha1) does not match. For the non-working case one could pass in a
>> keyidv2 that the user would have to determine from the certificate's subject
>> key identifier's last 4 bytes.
>>
>> It would be interesting to know which tools do not use a sha1 to calculate
>> the subject key identifier or what types of keys those are so that one could
>> give recommendations for tools to use. GnuTLS's certtool for example does
>> not seem to use the same algorithm to calculate the skid, so I would not
>> recommend using it for generating the certs to be used in conjunction with
>> evmctl and IMA signatures.
> You can also reproduce non-sha1 skid with openssl using subjectKeyIdentifier=
> config option, see x509v3_config(5).

"Subject Key Identifier.

This is really a string extension and can take two possible values. 
Either the word hash which will automatically follow the guidelines in 
RFC3280 or a hex string giving the extension value to include. The use 
of the hex string is strongly discouraged.

Example:

subjectKeyIdentifier=hash"

 From what I know it offers also the possibility of 'none'. It doesn't 
seem to be all that bad when using OpenSSL.

    Stefan