From: Peter Jones <pjones-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org>
To: Ard Biesheuvel <ard.biesheuvel-QSEj5FYQhm4dnm+yROfE0A@public.gmane.org>
Cc: Josh Boyer
<jwboyer-rxtnV0ftBwyoClj4AeEUq9i2O/JbrIOy@public.gmane.org>,
David Howells <dhowells-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org>,
keyrings-u79uwXL29TY76Z2rM5mHXA@public.gmane.org,
Matthew Garrett
<matthew.garrett-05XSO3Yj/JvQT0dZR+AlfA@public.gmane.org>,
"linux-efi-u79uwXL29TY76Z2rM5mHXA@public.gmane.org"
<linux-efi-u79uwXL29TY76Z2rM5mHXA@public.gmane.org>,
"linux-kernel-u79uwXL29TY76Z2rM5mHXA@public.gmane.org"
<linux-kernel-u79uwXL29TY76Z2rM5mHXA@public.gmane.org>,
linux-security-module
<linux-security-module-u79uwXL29TY76Z2rM5mHXA@public.gmane.org>
Subject: Re: [PATCH 9/9] MODSIGN: Allow the "db" UEFI variable to be suppressed
Date: Mon, 21 Nov 2016 14:05:32 -0500 [thread overview]
Message-ID: <20161121190531.dcha3soohybzaqr6@redhat.com> (raw)
In-Reply-To: <CAKv+Gu__wAnOawWZWVF6NF3En0suuFTBrFwwZ5KosqBU8LVHMA-JsoAwUIsXosN+BqQ9rBEUg@public.gmane.org>
On Mon, Nov 21, 2016 at 04:42:45PM +0000, Ard Biesheuvel wrote:
> On 21 November 2016 at 16:26, Josh Boyer <jwboyer-rxtnV0ftBwyoClj4AeEUq9i2O/JbrIOy@public.gmane.org> wrote:
> > On Mon, Nov 21, 2016 at 11:18 AM, Ard Biesheuvel
> > <ard.biesheuvel-QSEj5FYQhm4dnm+yROfE0A@public.gmane.org> wrote:
> >> On 16 November 2016 at 18:11, David Howells <dhowells-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org> wrote:
> >>> From: Josh Boyer <jwboyer-rxtnV0ftBwyoClj4AeEUq9i2O/JbrIOy@public.gmane.org>
> >>>
> >>> If a user tells shim to not use the certs/hashes in the UEFI db variable
> >>> for verification purposes, shim will set a UEFI variable called
> >>> MokIgnoreDB. Have the uefi import code look for this and ignore the db
> >>> variable if it is found.
> >>>
> >>
> >> Similar concern as in the previous patch: it appears to me that you
> >> can DoS a machine by setting MokIgnoreDB if, e.g., its modules are
> >> signed against a cert that resides in db, and shim/mokmanager are not
> >> being used.
> >
> > If shim/mokmanager aren't used, then you can't actually modify
> > MokIgnoreDB. Again, it requires physical access and a reboot into
> > mokmanager to actually take effect.
> >
>
> This does the trick as well
>
> printf "\x07\x00\x00\x00\x01" >
> /sys/firmware/efi/efivars/MokIgnoreDB-605dab50-e046-4300-abb6-3dd810dd8b23
So that really means two things. First, kernel should only honor any of
the Mok* variables if they're Boot Services-only variables. Second, to
avoid the DoS, shim should create them all as Boot Services-only the
first time it boots. That'll prevent them from being created post-boot.
--
Peter
next prev parent reply other threads:[~2016-11-21 19:05 UTC|newest]
Thread overview: 40+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-11-16 18:10 [PATCH 0/9] KEYS: Blacklisting & UEFI database load David Howells
2016-11-16 18:10 ` [PATCH 1/9] KEYS: Add a system blacklist keyring David Howells
2016-11-16 18:10 ` [PATCH 2/9] X.509: Allow X.509 certs to be blacklisted David Howells
2016-11-16 18:11 ` [PATCH 3/9] PKCS#7: Handle blacklisted certificates David Howells
2016-11-16 18:11 ` [PATCH 4/9] KEYS: Allow unrestricted boot-time addition of keys to secondary keyring David Howells
2016-11-17 6:41 ` Petko Manolov
2016-11-17 9:56 ` David Howells
2016-11-17 11:18 ` David Howells
[not found] ` <26349.1479376560-S6HVgzuS8uM4Awkfq6JHfwNdhmdF6hFW@public.gmane.org>
2016-11-17 10:22 ` Petko Manolov
2016-11-21 14:04 ` Mimi Zohar
2016-11-21 15:17 ` David Howells
2016-11-21 16:24 ` Mimi Zohar
2016-11-16 18:11 ` [PATCH 5/9] efi: Add SHIM and image security database GUID definitions David Howells
2016-11-21 16:07 ` Ard Biesheuvel
2016-11-16 18:11 ` [PATCH 6/9] efi: Add EFI signature data types David Howells
2016-11-16 23:43 ` Mat Martineau
[not found] ` <alpine.OSX.2.20.1611161535590.67352-zaFMaa3cLiZe6KzckbbZvYT4S9po1h25@public.gmane.org>
2016-11-17 9:44 ` David Howells
[not found] ` <26198.1479375840-S6HVgzuS8uM4Awkfq6JHfwNdhmdF6hFW@public.gmane.org>
2016-11-21 16:08 ` Ard Biesheuvel
2016-11-16 18:11 ` [PATCH 7/9] efi: Add an EFI signature blob parser David Howells
2016-11-16 18:11 ` [PATCH 8/9] MODSIGN: Import certificates from UEFI Secure Boot David Howells
2016-11-21 16:16 ` Ard Biesheuvel
[not found] ` <CAKv+Gu_QVyd1Jx7ZdnBzYmZzUnH4ZuhQgiGO-zx-JPViWosjXQ-JsoAwUIsXosN+BqQ9rBEUg@public.gmane.org>
2016-11-21 16:25 ` Josh Boyer
[not found] ` <CA+5PVA6dWw-p3q9SBmJwQvuru4k7JZAraRZeb2=VDf8E=c=SmA-JsoAwUIsXosN+BqQ9rBEUg@public.gmane.org>
2016-11-24 19:22 ` James Bottomley
2016-11-24 19:17 ` James Bottomley
2016-12-02 18:57 ` James Bottomley
2016-12-02 20:18 ` Mimi Zohar
2016-11-16 18:11 ` [PATCH 9/9] MODSIGN: Allow the "db" UEFI variable to be suppressed David Howells
[not found] ` <147931990959.16460.3038875071067540418.stgit-S6HVgzuS8uM4Awkfq6JHfwNdhmdF6hFW@public.gmane.org>
2016-11-21 16:18 ` Ard Biesheuvel
[not found] ` <CAKv+Gu96ihE7pHrCCeCpy78man-r821b3Vs4Tn_RsYyzY4HV2Q-JsoAwUIsXosN+BqQ9rBEUg@public.gmane.org>
2016-11-21 16:26 ` Josh Boyer
[not found] ` <CA+5PVA7SivAegwxdxuiAFL41Apie4JLK5KbtGGHLr1fP0p3MsQ-JsoAwUIsXosN+BqQ9rBEUg@public.gmane.org>
2016-11-21 16:42 ` Ard Biesheuvel
[not found] ` <CAKv+Gu__wAnOawWZWVF6NF3En0suuFTBrFwwZ5KosqBU8LVHMA-JsoAwUIsXosN+BqQ9rBEUg@public.gmane.org>
2016-11-21 19:05 ` Peter Jones [this message]
2016-11-21 19:06 ` Ard Biesheuvel
2016-11-21 19:18 ` Peter Jones
2016-11-21 19:33 ` Ard Biesheuvel
2018-03-06 14:05 ` [PATCH 0/9] KEYS: Blacklisting & UEFI database load Jiri Slaby
2018-03-07 13:18 ` Mimi Zohar
2018-03-07 15:28 ` James Bottomley
2018-03-11 3:20 ` joeyli
2018-03-19 14:12 ` Mimi Zohar
2018-03-27 11:08 ` joeyli
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