linux-kernel - Re: [RFC PATCH] X.509: Don't check the signature on apparently self-signed keys [ver #2]

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Message-ID: <32191.1452009340@warthog.procyon.org.uk>
Date:	Tue, 05 Jan 2016 15:55:40 +0000
From:	David Howells <dhowells@...hat.com>
To:	unlisted-recipients:; (no To-header on input)
Cc:	dhowells@...hat.com, dwmw2@...radead.org,
	David Woodhouse <David.Woodhouse@...el.com>,
	linux-kernel@...r.kernel.org,
	linux-security-module@...r.kernel.org, keyrings@...r.kernel.org,
	Mimi Zohar <zohar@...ux.vnet.ibm.com>
Subject: Re: [RFC PATCH] X.509: Don't check the signature on apparently self-signed keys [ver #2]

David Howells <dhowells@...hat.com> wrote:

> If a certificate is self-signed, don't bother checking the validity of the
> signature.  The cert cannot be checked by validation against the next one
> in the chain as this is the root of the chain.  Trust for this certificate
> can only be determined by whether we obtained it from a trusted location
> (ie. it was built into the kernel at compile time).
> 
> This also fixes a bug whereby certificates were being assumed to be
> self-signed if they had neither AKID nor SKID, the symptoms of which show
> up as an attempt to load a certificate failing with -ERANGE or -EBADMSG.
> This is produced from the RSA module when the result of calculating "m =
> s^e mod n" is checked.

Oops - I forgot to change the patch description.

David
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