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From:   Roberto Sassu <roberto.sassu@huawei.com>
To:     Mimi Zohar <zohar@linux.ibm.com>,
        "shuah@kernel.org" <shuah@kernel.org>,
        "ast@kernel.org" <ast@kernel.org>,
        "daniel@iogearbox.net" <daniel@iogearbox.net>,
        "andrii@kernel.org" <andrii@kernel.org>,
        "kpsingh@kernel.org" <kpsingh@kernel.org>
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        "netdev@vger.kernel.org" <netdev@vger.kernel.org>,
        "bpf@vger.kernel.org" <bpf@vger.kernel.org>,
        "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
        Florent Revest <revest@google.com>
Subject: RE: [PATCH] ima: Calculate digest in ima_inode_hash() if not
 available
Thread-Topic: [PATCH] ima: Calculate digest in ima_inode_hash() if not
 available
Thread-Index: AQHYHzTu9kKzqhEAHUiW0cSG9MzvPayOOgmAgAAS5hA=
Date:   Fri, 11 Feb 2022 12:57:52 +0000
Message-ID: <3d0bdb4599e340a78b06094797e42bc9@huawei.com>
References: <20220211104828.4061334-1-roberto.sassu@huawei.com>
 <f9ccc9be6cc084e9cab6cd75e87735492d120002.camel@linux.ibm.com>
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> From: Mimi Zohar [mailto:zohar@linux.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