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Date:   Fri, 31 Aug 2018 22:05:23 +0200
From:   Jan Lübbe <>
To:     Eric Biggers <>,,,
        Mimi Zohar <>,
        Dmitry Kasatkin <>,
        Michael Halcrow <>,
        Victor Hsieh <>
Subject: Re: [RFC PATCH 00/10] fs-verity: filesystem-level integrity

On Fri, 2018-08-24 at 09:16 -0700, Eric Biggers wrote:
> Since fs-verity provides the Merkle tree root hash in constant time and
> verifies data blocks on-demand, it is useful for efficiently verifying
> the authenticity of, or "appraising", large files of which only a small
> portion may be accessed -- such as Android application (APK) files.  It
> can also be useful in "audit" use cases where file hashes are logged.
> fs-verity also provides better protection against malicious disk
> firmware than an ahead-of-time hash, since fs-verity re-verifies data
> each time it's paged in.
> Feedback on the design and implementation is greatly appreciated.


I've looked at the series and the slides linked form the recent
article, but I'm not sure how fs-verity intends to protect against
malicious firmware (or offline modification). Similar to IMA/EVM, fs-
verity doesn't seem to include the name/location of the file into it's
verification. So the firmware/an attacker could replace one fs-verity-
protected file with another (maybe a trusted system APK with another
one for which a vulnerability was discovered, or /sbin/init with

Is the expected root hash of the file provided from somewhere else, so
this is not a problem on Android? Or is this problem out-of-scope for

For IMA/EVM, there were patches by Dmitry to address this class of
attacks (they were not merged, though):


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