netdev - RE: [PATCH] ima: Calculate digest in ima_inode

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Message-ID: <3d0bdb4599e340a78b06094797e42bc9@huawei.com>
Date:   Fri, 11 Feb 2022 12:57:52 +0000
From:   Roberto Sassu <roberto.sassu@...wei.com>
To:     Mimi Zohar <zohar@...ux.ibm.com>,
        "shuah@...nel.org" <shuah@...nel.org>,
        "ast@...nel.org" <ast@...nel.org>,
        "daniel@...earbox.net" <daniel@...earbox.net>,
        "andrii@...nel.org" <andrii@...nel.org>,
        "kpsingh@...nel.org" <kpsingh@...nel.org>
CC:     "linux-integrity@...r.kernel.org" <linux-integrity@...r.kernel.org>,
        "linux-security-module@...r.kernel.org" 
        <linux-security-module@...r.kernel.org>,
        "linux-kselftest@...r.kernel.org" <linux-kselftest@...r.kernel.org>,
        "netdev@...r.kernel.org" <netdev@...r.kernel.org>,
        "bpf@...r.kernel.org" <bpf@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        Florent Revest <revest@...gle.com>
Subject: RE: [PATCH] ima: Calculate digest in ima_inode_hash() if not
 available

> From: Mimi Zohar [mailto:zohar@...ux.ibm.com]
> Sent: Friday, February 11, 2022 1:41 PM
> Hi Roberto,
> 
> On Fri, 2022-02-11 at 11:48 +0100, Roberto Sassu wrote:
> > __ima_inode_hash() checks if a digest has been already calculated by
> > looking for the integrity_iint_cache structure associated to the passed
> > inode.
> >
> > Users of ima_file_hash() and ima_inode_hash() (e.g. eBPF) might be
> > interested in obtaining the information without having to setup an IMA
> > policy so that the digest is always available at the time they call one of
> > those functions.
> 
> Things obviously changed, but the original use case for this interface,
> as I recall, was a quick way to determine if a file had been accessed
> on the system.

Hi Mimi

thanks for the info. I was not sure if I should export a new
function or reuse the existing one. In my use case, just calculating
the digest would be sufficient.

For finding whether a file was accessed (assuming that it matches
the policy), probably bpf_ima_inode_hash() is not anyway too reliable.
If integrity_iint_cache is evicted from the memory, it would report
that the inode was not accessed even if it was.

Thanks

Roberto

HUAWEI TECHNOLOGIES Duesseldorf GmbH, HRB 56063
Managing Director: Li Peng, Zhong Ronghua

> --
> thanks,
> 
> Mimi