linux-kernel - Re: [PATCH 5/6] MODSIGN: Export module signature definitions.

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Message-ID: <21102.1492699057@warthog.procyon.org.uk>
Date:   Thu, 20 Apr 2017 15:37:37 +0100
From:   David Howells <dhowells@...hat.com>
To:     Mimi Zohar <zohar@...ux.vnet.ibm.com>
Cc:     dhowells@...hat.com,
        Thiago Jung Bauermann <bauerman@...ux.vnet.ibm.com>,
        linux-security-module@...r.kernel.org,
        linux-ima-devel@...ts.sourceforge.net, keyrings@...r.kernel.org,
        linux-crypto@...r.kernel.org, linux-kernel@...r.kernel.org,
        Dmitry Kasatkin <dmitry.kasatkin@...il.com>,
        Herbert Xu <herbert@...dor.apana.org.au>,
        "David S. Miller" <davem@...emloft.net>,
        Claudio Carvalho <cclaudio@...ux.vnet.ibm.com>
Subject: Re: [PATCH 5/6] MODSIGN: Export module signature definitions.

Mimi Zohar <zohar@...ux.vnet.ibm.com> wrote:

> On Tue, 2017-04-18 at 17:17 -0300, Thiago Jung Bauermann wrote:
> > IMA will use the module_signature format for append signatures, so export
> > the relevant definitions and factor out the code which verifies that the
> > appended signature trailer is valid.
> > 
> > Also, create a CONFIG_MODULE_SIG_FORMAT option so that IMA can select it
> > and be able to use validate_module_signature without having to depend on
> > CONFIG_MODULE_SIG.
> 
> Basically we want to generalize the concept of an appended signature.
>  Referring to it as a "module signature format" seems a bit confusing.
> 
> David, would you have a problem with changing the appended string from
> "~Module signature appended~\n" to something more generic?

Conceptually, no.  Is it possible that doing so could break someone's module
that they load on multiple versions of the kernel?  Say a module that only
exports things and doesn't use anything from the core or any other module.

Also, it needs to reasonably long and distinct enough to prevent a false
positive match.

David