linux-kernel - Re: How to add additional blacklist entries?

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Date:	Tue, 09 Feb 2016 10:42:39 +0000
From:	David Howells <dhowells@...hat.com>
To:	Mimi Zohar <zohar@...ux.vnet.ibm.com>
Cc:	dhowells@...hat.com, linux-security-module@...r.kernel.org,
	keyrings@...r.kernel.org, petkan@...-labs.com,
	linux-kernel@...r.kernel.org
Subject: Re: How to add additional blacklist entries?

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

> > You can link from any key you have LINK permission on.  Further, add_key()
> > can add directly.
> 
> Oh, for some reason I thought the system blacklist keyring was limited
> to the new key type with just a description.   I was able to add, but
> also remove a key from the system blacklist.   I guess the KEY_FLAG_KEEP
> is not set on the system blacklist.

With patch 18 you can.  Prior to that it's not possible to modify it from
userspace at all.

> The keys being added to the IMA keyring are signed x509 certs (eg.
> openssl ca -ss_cert).  It would be nice to be able to include the skid
> in the description, without a payload, and sign that.  I have no idea if
> that Is possible or if it makes sense.  I'm open to suggestions.

I think we need a new keyctl or syscall for this.

We need to run through the X.509 parser, but we don't actually want to keep
any of the payload - and, in fact, we don't even necessarily want to create an
asymmetric-type key, though it's not a complete loss if we do that and create
one with a blacklist subtype.  The blacklist subtype would just return an
error from all operation points, but would otherwise be handled as normal.

David