On Thu, Feb 14, 2013 at 10:35:59AM -0500, Mimi Zohar wrote:
> On Thu, 2013-02-14 at 10:23 -0500, Vivek Goyal wrote:
> > On Thu, Feb 14, 2013 at 07:57:16AM -0500, Mimi Zohar wrote:
> >
> > [..]
> > > > Ok, I will cleanup the code to do above. Just wanted to clear up one
> > > > point.
> > > >
> > > > Above option will not have any effect on evm behavior? This only impacts
> > > > IMA appraisal behavior. For example, if security.ima is not present it
> > > > is fine and file access is allowed. But if EVM is enabled and
> > > > initialized
> > > > and EVM does not find security.evm label (INTEGRITY_NOLABEL) or returns
> > > > INTEGRITY_NOXATTRS, file access should still be denied?
> > >
> > > Can't happen. evm_verifyxattr() is called from
> > > ima_appraise_measurement(), only if 'security.ima' exists.
> >
> > Actually what I meant is following.
> >
> > Currently in process_measurement(), I will allow access if
> > ima_appraise_measurement() returns INTEGRITY_NOLABEL.
>
> I think you're making this more complicated than it needs to be. Allow
> the execution unless the file failed signature verification. The
> additional capability is given only if the signature verification
> succeeds.
I am just trying to bring it inline with module signature verification.
There also module loading fails if signatures are present but kernel
can't verify it.
Following behavior is strange.
rc = integrity_digsig_verify(INTEGRITY_KEYRING_IMA,
xattr_value->digest, rc - 1,
iint->ima_xattr.digest,
IMA_DIGEST_SIZE);
if (rc == -EOPNOTSUPP) {
status = INTEGRITY_UNKNOWN;
} else if (rc) {
cause = "invalid-signature";
status = INTEGRITY_FAIL;
} else {
status = INTEGRITY_PASS;
}
signature verification can fail for so many reasons.
- EINVAL
- keyring is not present
- key is not present -ENOKEY
- ENOTSUPP
- ENOMEM
..
..
And in all these cases we return INTEGRITY_FAIL. But only in case of
-EOPNOTSUPP we return INTEGRITY_UNKNOWN. So why this discrepancy.
So to me it makes sense to return INTEGRITY_FAIL if rc == -EOPNOTSUPP.
This will bring it inline with other error codes. And then in
process_measurement() I can allow access in every case except
INTEGRITY_FAIL.
Thanks
Vivek
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