From: Jarkko Sakkinen <jarkko@kernel.org>
To: "Mickaël Salaün" <mic@digikod.net>
Cc: "Thomas Weißschuh" <linux@weissschuh.net>,
"David Howells" <dhowells@redhat.com>,
"David Woodhouse" <dwmw2@infradead.org>,
keyrings@vger.kernel.org, linux-kernel@vger.kernel.org,
"Mark Pearson" <markpearson@lenovo.com>,
"Eric Snowberg" <eric.snowberg@oracle.com>,
linux-integrity@vger.kernel.org,
linux-security-module@vger.kernel.org
Subject: Re: [PATCH] certs: Prevent spurious errors on repeated blacklisting
Date: Wed, 16 Nov 2022 01:57:22 +0200 [thread overview]
Message-ID: <Y3QnYhJGIkWCm4LQ@kernel.org> (raw)
In-Reply-To: <e2909fe5-7fc4-c73a-b33a-e65fed1d837f@digikod.net>
On Mon, Nov 07, 2022 at 08:40:09PM +0100, Mickaël Salaün wrote:
>
> On 07/11/2022 17:35, Thomas Weißschuh wrote:
> > On 2022-11-07 17:20+0100, Mickaël Salaün wrote:
> > > On 07/11/2022 16:55, Thomas Weißschuh wrote:
> > > > On 2022-11-07 14:12+0100, Mickaël Salaün wrote:
> > > > > This is a follow-up of
> > > > > https://lore.kernel.org/r/c8c65713-5cda-43ad-8018-20f2e32e4432@t-8ch.de
> > > > >
> > > > > Added Jarkko, Mark Pearson, Eric Snowberg and more ML in Cc.
> > > > >
> > > > >
> > > > > On 04/11/2022 02:47, Thomas Weißschuh wrote:
> > > > > > When the blacklist keyring was changed to allow updates from the root
> > > > > > user it gained an ->update() function that disallows all updates.
> > > > > > When the a hash is blacklisted multiple times from the builtin or
> > > > > > firmware-provided blacklist this spams prominent logs during boot:
> > > > > >
> > > > > > [ 0.890814] blacklist: Problem blacklisting hash (-13)
> > > > > >
> > > > > > As all these repeated calls to mark_raw_hash_blacklisted() would create
> > > > > > the same keyring entry again anyways these errors can be safely ignored.
> > > > >
> > > > > These errors can indeed be safely ignored, however they highlight issues
> > > > > with some firmware vendors not checking nor optimizing their blocked hashes.
> > > > > This raises security concerns, and it should be fixed by firmware vendors.
> > > >
> > > > Thanks, I was not aware that these are worth fixing.
> > > >
> > > > > > Fixes: 6364d106e041 ("certs: Allow root user to append signed hashes to the blacklist keyring")
> > > > > > Signed-off-by: Thomas Weißschuh <linux@weissschuh.net>
> > > > > > ---
> > > > > > certs/blacklist.c | 4 +++-
> > > > > > 1 file changed, 3 insertions(+), 1 deletion(-)
> > > > > >
> > > > > > diff --git a/certs/blacklist.c b/certs/blacklist.c
> > > > > > index 41f10601cc72..5f7f2882ced7 100644
> > > > > > --- a/certs/blacklist.c
> > > > > > +++ b/certs/blacklist.c
> > > > > > @@ -191,7 +191,9 @@ static int mark_raw_hash_blacklisted(const char *hash)
> > > > > > BLACKLIST_KEY_PERM,
> > > > > > KEY_ALLOC_NOT_IN_QUOTA |
> > > > > > KEY_ALLOC_BUILT_IN);
> > > > > > - if (IS_ERR(key)) {
> > > > > > +
> > > > > > + /* Blacklisting the same hash twice fails but would be idempotent */
> > > > > > + if (IS_ERR(key) && PTR_ERR(key) != -EACCES) {
> > > > >
> > > > > We should not hide EACCES errors. This logs issues, which is correct for
> > > > > duplicate hashes, and can help firmware vendors to fix their database. I'd
> > > > > really like to see a different log message instead: change the duplicate
> > > > > entry error code from EACCES to EEXIST, and call pr_warn for this specific
> > > > > case.
> > > >
> > > > Returning EACCES would require some deeper changes to how the keyring is set up
> > >
> > > I guess you meant EEXIST?
> >
> > Indeed, sorry.
> >
> > > > or even changes to the keyring core itself to introduce a key_create() (without
> > > > update) function.
> > > >
> > > > Is this something you would take a look at, or should I try to do it?
> > > > (I have no previous knowledge about the keyring subsystem)
> > >
> > > Please take a look. I think it should not be too complex.
> >
> > Will do.
> >
> > My plan is to create a new function key_create() that does takes the core logic
> > of key_create_or_update() and fails with EEXIST if needed.
> >
> > > > In any case it probably would also be good to log the problematic hashes
> > > > themselves, so users can properly report the issue to their firmware vendors.
> > >
> > > Agree
> >
> > I'll send a patch for that, too.
>
> Good!
>
> Jarkko, David, any though?
I'm happy to review a patch once it is available.
BR, Jarkko
next prev parent reply other threads:[~2022-11-15 23:57 UTC|newest]
Thread overview: 8+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-11-04 1:47 [PATCH] certs: Prevent spurious errors on repeated blacklisting Thomas Weißschuh
2022-11-07 13:12 ` Mickaël Salaün
2022-11-07 15:55 ` Thomas Weißschuh
2022-11-07 16:20 ` Mickaël Salaün
2022-11-07 16:35 ` Thomas Weißschuh
2022-11-07 19:40 ` Mickaël Salaün
2022-11-15 23:57 ` Jarkko Sakkinen [this message]
2022-11-09 15:50 ` Eric Snowberg
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=Y3QnYhJGIkWCm4LQ@kernel.org \
--to=jarkko@kernel.org \
--cc=dhowells@redhat.com \
--cc=dwmw2@infradead.org \
--cc=eric.snowberg@oracle.com \
--cc=keyrings@vger.kernel.org \
--cc=linux-integrity@vger.kernel.org \
--cc=linux-kernel@vger.kernel.org \
--cc=linux-security-module@vger.kernel.org \
--cc=linux@weissschuh.net \
--cc=markpearson@lenovo.com \
--cc=mic@digikod.net \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).