On 5/5/22 08:31, Mimi Zohar wrote:
> IMA may verify a file's integrity against a "good" value stored in the
> 'security.ima' xattr or as an appended signature, based on policy. When
> the "good value" is stored in the xattr, the xattr may contain a file
> hash or signature. In either case, the "good" value is preceded by a
> header. The first byte of the xattr header indicates the type of data
> - hash, signature - stored in the xattr. To support storing fs-verity
> signatures in the 'security.ima' xattr requires further differentiating
> the fs-verity signature from the existing IMA signature.
>
> In addition the signatures stored in 'security.ima' xattr, need to be
> disambiguated. Instead of directly signing the fs-verity digest, a new
> signature format version 3 is defined as the hash of the ima_file_id
> structure, which identifies the type of signature and the digest.
>
> The IMA policy defines "which" files are to be measured, verified, and/or
> audited. For those files being verified, the policy rules indicate "how"
> the file should be verified. For example to require a file be signed,
> the appraise policy rule must include the 'appraise_type' option.
>
> appraise_type:= [imasig] | [imasig|modsig] | [sigv3]
> where 'imasig' is the original or signature format v2 (default),
> where 'modsig' is an appended signature,
> where 'sigv3' is the signature format v3.
>
> The policy rule must also indicate the type of digest, if not the IMA
> default, by first specifying the digest type:
>
> digest_type:= [verity]
>
> The following policy rule requires fsverity signatures. The rule may be
> constrained, for example based on a fsuuid or LSM label.
>
> appraise func=BPRM_CHECK digest_type=verity appraise_type=sigv3
>
> Signed-off-by: Mimi Zohar <[email protected]>
Acked-by: Stefan Berger <[email protected]>
On Thu, 2022-05-05 at 13:12 -0400, Stefan Berger wrote:
>
> On 5/5/22 08:31, Mimi Zohar wrote:
> > IMA may verify a file's integrity against a "good" value stored in the
> > 'security.ima' xattr or as an appended signature, based on policy. When
> > the "good value" is stored in the xattr, the xattr may contain a file
> > hash or signature. In either case, the "good" value is preceded by a
> > header. The first byte of the xattr header indicates the type of data
> > - hash, signature - stored in the xattr. To support storing fs-verity
> > signatures in the 'security.ima' xattr requires further differentiating
> > the fs-verity signature from the existing IMA signature.
> >
> > In addition the signatures stored in 'security.ima' xattr, need to be
> > disambiguated. Instead of directly signing the fs-verity digest, a new
> > signature format version 3 is defined as the hash of the ima_file_id
> > structure, which identifies the type of signature and the digest.
> >
> > The IMA policy defines "which" files are to be measured, verified, and/or
> > audited. For those files being verified, the policy rules indicate "how"
> > the file should be verified. For example to require a file be signed,
> > the appraise policy rule must include the 'appraise_type' option.
> >
> > appraise_type:= [imasig] | [imasig|modsig] | [sigv3]
> > where 'imasig' is the original or signature format v2 (default),
> > where 'modsig' is an appended signature,
> > where 'sigv3' is the signature format v3.
> >
> > The policy rule must also indicate the type of digest, if not the IMA
> > default, by first specifying the digest type:
> >
> > digest_type:= [verity]
> >
> > The following policy rule requires fsverity signatures. The rule may be
> > constrained, for example based on a fsuuid or LSM label.
> >
> > appraise func=BPRM_CHECK digest_type=verity appraise_type=sigv3
> >
> > Signed-off-by: Mimi Zohar <[email protected]>
>
> Acked-by: Stefan Berger <[email protected]>
Thanks, Stefan!
This patch set is now queued in the next-integrity-testing branch,
waiting additional review/tags.
thanks,
Mimi