Messages in this thread | | | Subject | Re: [PATCH 2/6] ima: Return INTEGRITY_FAIL if digital signature can't be verified | From | Mimi Zohar <> | Date | Mon, 04 Mar 2013 08:48:36 -0500 |
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On Thu, 2013-02-14 at 14:55 -0500, Vivek Goyal wrote: > Digital signature verification happens using integrity_digsig_verify(). > Curently we set integrity to FAIL for all error codes except -EOPNOTSUPP. > This sounds out of line. > > - If appropriate kernel code is not compiled in to verify signature of > a file, then prractically it is a failed signature. > > - For so many other possible errors we are setting the status to fail. > For example, -EINVAL, -ENOKEY, -ENOMEM, -EINVAL, -ENOTSUPP etc, it > beats me that why -EOPNOTSUPP is special. > > This patch should make the semantics more consistent. That is, if digital > signature is present in security.ima, then any error happened during > signature processing leads to status INTEGRITY_FAIL. > > AFAICS, it should not have any user visible effect on existing > application. In some cases we will start returning INTEGRITY_FAIL > instead of INTEGRITY_UNKNOWN. And process_measurement() will deny access > to file both in case of INTEGRITY_UNKNOWN and INTEGRITY_FAIL. > > Signed-off-by: Vivek Goyal <vgoyal@redhat.com>
A number of patches in this patchset more finely differentiate return codes, which is good. I agree with you totally that there is no good reason for -EOPNOTSUPP to be handled differently. Unfortunately, the initramfs is CPIO, which doesn't support xattrs. With the proposed change and 'ima_appraise_tcb' flag enabled, we wouldn't be able to boot. I really dislike hard coding policy in the kernel.
thanks,
Mimi
> --- > security/integrity/ima/ima_appraise.c | 4 +--- > 1 files changed, 1 insertions(+), 3 deletions(-) > > diff --git a/security/integrity/ima/ima_appraise.c b/security/integrity/ima/ima_appraise.c > index 3710f44..6f1eeb8 100644 > --- a/security/integrity/ima/ima_appraise.c > +++ b/security/integrity/ima/ima_appraise.c > @@ -178,9 +178,7 @@ int ima_appraise_measurement(int func, struct integrity_iint_cache *iint, > xattr_value->digest, rc - 1, > iint->ima_xattr.digest, > IMA_DIGEST_SIZE); > - if (rc == -EOPNOTSUPP) { > - status = INTEGRITY_UNKNOWN; > - } else if (rc) { > + if (rc) { > cause = "invalid-signature"; > status = INTEGRITY_FAIL; > } else {
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