From: Jarkko Sakkinen <jarkko@kernel.org>
To: "Mickaël Salaün" <mic@digikod.net>
Cc: "David Howells" <dhowells@redhat.com>,
"David Woodhouse" <dwmw2@infradead.org>,
"David S . Miller" <davem@davemloft.net>,
"Herbert Xu" <herbert@gondor.apana.org.au>,
"James Morris" <jmorris@namei.org>,
"Mickaël Salaün" <mic@linux.microsoft.com>,
"Mimi Zohar" <zohar@linux.ibm.com>,
"Serge E . Hallyn" <serge@hallyn.com>,
keyrings@vger.kernel.org, linux-crypto@vger.kernel.org,
linux-integrity@vger.kernel.org, linux-kernel@vger.kernel.org,
linux-security-module@vger.kernel.org,
"Ben Boeckel" <mathstuf@gmail.com>
Subject: Re: [PATCH v3 02/10] certs: Fix blacklisted hexadecimal hash string check
Date: Thu, 21 Jan 2021 01:44:56 +0200 [thread overview]
Message-ID: <YAjAePytNXMC6HqX@kernel.org> (raw)
In-Reply-To: <05e3ce56-c27c-877d-8ebe-d088ba95f248@digikod.net>
On Wed, Jan 20, 2021 at 12:12:50PM +0100, Mickaël Salaün wrote:
>
> On 20/01/2021 04:43, Jarkko Sakkinen wrote:
> > On Thu, Jan 14, 2021 at 04:19:01PM +0100, Mickaël Salaün wrote:
> >> From: Mickaël Salaün <mic@linux.microsoft.com>
> >>
> >> When looking for a blacklisted hash, bin2hex() is used to transform a
> >> binary hash to an ascii (lowercase) hexadecimal string. This string is
> >> then search for in the description of the keys from the blacklist
> >> keyring. When adding a key to the blacklist keyring,
> >> blacklist_vet_description() checks the hash prefix and the hexadecimal
> >> string, but not that this string is lowercase. It is then valid to set
> >> hashes with uppercase hexadecimal, which will be silently ignored by the
> >> kernel.
> >>
> >> Add an additional check to blacklist_vet_description() to check that
> >> hexadecimal strings are in lowercase.
> >>
> >> Cc: David Woodhouse <dwmw2@infradead.org>
> >> Signed-off-by: Mickaël Salaün <mic@linux.microsoft.com>
> >> Signed-off-by: David Howells <dhowells@redhat.com>
> >> Reviewed-by: Ben Boeckel <mathstuf@gmail.com>
> >> ---
> >>
> >> Changes since v2:
> >> * Cherry-pick v1 patch from
> >> https://lore.kernel.org/lkml/2659836.1607940186@warthog.procyon.org.uk/
> >> to rebase on v5.11-rc3.
> >> * Rearrange Cc order.
> >> ---
> >> certs/blacklist.c | 2 +-
> >> 1 file changed, 1 insertion(+), 1 deletion(-)
> >>
> >> diff --git a/certs/blacklist.c b/certs/blacklist.c
> >> index 2719fb2fbc1c..a888b934a1cd 100644
> >> --- a/certs/blacklist.c
> >> +++ b/certs/blacklist.c
> >> @@ -37,7 +37,7 @@ static int blacklist_vet_description(const char *desc)
> >> found_colon:
> >> desc++;
> >> for (; *desc; desc++) {
> >> - if (!isxdigit(*desc))
> >> + if (!isxdigit(*desc) || isupper(*desc))
> >> return -EINVAL;
> >> n++;
> >> }
> >> --
> >> 2.30.0
> >>
> >
> > Shouldn't this rather convert the upper case to lower case? I don't like
> > the ABI break that this causes.
>
> It doesn't break the ABI because keys loaded in the blacklist keyring
> can only happen with builtin hashes. Moreover these builtin hashes will
> be checked by patch 10/10 at build time.
Right the patches are just out of order then.
/Jarkko
>
> This patch is also important to remove a false sense of security and
> warns about mis-blacklisted certificates or binaries:
> https://lore.kernel.org/lkml/c9664a67-61b7-6b4a-86d7-5aca9ff06fa5@digikod.net/
>
> Hot-patching keys doesn't seem a good idea, especially when these keys
> are signed. Moreover, it would bring additional complexity and will
> require to change the core of the key management.
>
> >
> > /Jarkko
> >
>
next prev parent reply other threads:[~2021-01-21 6:39 UTC|newest]
Thread overview: 33+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-01-14 15:18 [PATCH v3 00/10] Enable root to update the blacklist keyring Mickaël Salaün
2021-01-14 15:19 ` [PATCH v3 01/10] certs/blacklist: fix kernel doc interface issue Mickaël Salaün
2021-01-20 3:39 ` Jarkko Sakkinen
2021-01-14 15:19 ` [PATCH v3 02/10] certs: Fix blacklisted hexadecimal hash string check Mickaël Salaün
2021-01-20 3:43 ` Jarkko Sakkinen
2021-01-20 11:12 ` Mickaël Salaün
2021-01-20 23:44 ` Jarkko Sakkinen [this message]
2021-01-14 15:19 ` [PATCH v3 03/10] PKCS#7: Fix missing include Mickaël Salaün
2021-01-20 3:44 ` Jarkko Sakkinen
2021-01-14 15:19 ` [PATCH v3 04/10] certs: Fix blacklist flag type confusion Mickaël Salaün
2021-01-20 3:55 ` Jarkko Sakkinen
2021-01-20 11:15 ` Mickaël Salaün
2021-01-20 23:45 ` Jarkko Sakkinen
2021-01-14 15:19 ` [PATCH v3 05/10] certs: Replace K{U,G}IDT_INIT() with GLOBAL_ROOT_{U,G}ID Mickaël Salaün
2021-01-20 5:15 ` Jarkko Sakkinen
2021-01-20 11:17 ` Mickaël Salaün
2021-01-20 23:48 ` Jarkko Sakkinen
2021-01-14 15:19 ` [PATCH v3 06/10] certs: Make blacklist_vet_description() more strict Mickaël Salaün
2021-01-20 4:16 ` Jarkko Sakkinen
2021-01-20 11:23 ` Mickaël Salaün
2021-01-14 15:19 ` [PATCH v3 07/10] certs: Factor out the blacklist hash creation Mickaël Salaün
2021-01-14 15:19 ` [PATCH v3 08/10] certs: Check that builtin blacklist hashes are valid Mickaël Salaün
2021-01-20 5:19 ` Jarkko Sakkinen
2021-01-20 11:57 ` Mickaël Salaün
2021-01-20 23:53 ` Jarkko Sakkinen
2021-01-21 9:18 ` Mickaël Salaün
2021-01-21 15:21 ` Jarkko Sakkinen
2021-01-14 15:19 ` [PATCH v3 09/10] certs: Allow root user to append signed hashes to the blacklist keyring Mickaël Salaün
2021-01-15 13:06 ` Mimi Zohar
2021-01-20 5:23 ` Jarkko Sakkinen
2021-01-20 11:24 ` Mickaël Salaün
2021-01-14 15:19 ` [PATCH v3 10/10] tools/certs: Add print-cert-tbs-hash.sh Mickaël Salaün
2021-01-15 9:28 ` [PATCH v3 00/10] Enable root to update the blacklist keyring Jarkko Sakkinen
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