Re: [RFC PATCH] ima-evm-utils: Allow manual setting keyid for signing

[Vitaly Chikunov <vt@altlinux.org>]

Stefan,

On Mon, May 03, 2021 at 04:25:08PM -0400, Stefan Berger wrote:
> 
> On 4/30/21 4:13 PM, Vitaly Chikunov wrote:
> > Allow user to set signature's keyid using `--keyid' option. Keyid should
> > correspond to SKID in certificate, when keyid is calculated using SHA-1
> > in libimaevm it may mismatch keyid extracted by the kernel from SKID of
> > certificate (the way public key is presented to the kernel), thus making
> > signatures not verifiable. This may happen when certificate is using non
> > SHA-1 SKID (see rfc7093) or just 'unique number' (see rfc5280 4.2.1.2).
> > As a last resort user may specify arbitrary keyid using the new option.
> > 
> > This commit creates backward compatible ABI change for libimaevm,
> > because of adding additional parameter to imaevm_params - older
> > libimaevm can work with newer client.
> > 
> > Signed-off-by: Vitaly Chikunov <vt@altlinux.org>
> > ---
> > 
> > +		case 143:
> > +			errno = 0;
> > +			keyid = strtoul(optarg, &eptr, 16);
> > +			if (errno || eptr - optarg != strlen(optarg) ||
> > +			    keyid > UINT_MAX || keyid == 0) {
> > +				log_err("Invalid keyid value.\n");
> > +				exit(1);
> > +			}
> > +			imaevm_params.keyid = htonl(keyid);
> 
> 
> I would leave it in native format here ...
> 
> 
> >   		log_err("sign_hash_v2: hash is null\n");
> > @@ -932,8 +931,10 @@ static int sign_hash_v2(const char *algo, const unsigned char *hash,
> >   		return -1;
> >   	}
> > -	calc_keyid_v2(&keyid, name, pkey);
> > -	hdr->keyid = keyid;
> > +	if (imaevm_params.keyid)
> > +		hdr->keyid = imaevm_params.keyid;
> 
> 
> ... and convert it to big endian here when you write it out and where it
> needs to be in big endian format.

I agree.

Also, I have additional idea - when user specify private signing key
with `--key' they can have combined key+cert pem file, in that case we
could try to extract appropriate keyid from the same file. I will send
another patch set.

Thanks,