From: Eric Biggers <ebiggers@kernel.org>
To: "David C.C.M. Gall" <david.ccm.gall@googlemail.com>
Cc: Lukas Wunner <lukas@wunner.de>, Ignat Korchagin <ignat@linux.win>,
Herbert Xu <herbert@gondor.apana.org.au>,
"David S. Miller" <davem@davemloft.net>,
linux-crypto@vger.kernel.org, linux-kernel@vger.kernel.org,
gregkh@linuxfoundation.org
Subject: Re: [PATCH] crypto: rsassa-pkcs1: use constant-time comparison for digest and signature verification
Date: Fri, 10 Jul 2026 17:37:18 -0400 [thread overview]
Message-ID: <20260710213718.GD1911@quark> (raw)
In-Reply-To: <alEr_e-G0L2nxxv-@fudgebox>
On Fri, Jul 10, 2026 at 07:29:33PM +0200, David C.C.M. Gall wrote:
> Replace memcmp() with crypto_memneq() for cryptographic digest and
> signature comparisons to prevent timing side-channel attacks.
>
> crypto/rsassa-pkcs1.c: RSA signature digest verification used memcmp
> which can leak valid prefix length via timing analysis, user data
> could reach the leaky comparison via the digest argument to verify.
>
> Assisted-by: gregkh_clanker_t1000
> Signed-off-by: David C.C.M. Gall <david.ccm.gall@googlemail.com>
While we should use crypto_memneq() on MACs, auth tags, and other secret
data, I don't think we should let it creep into domains where it is
clearly not needed, like public key signature verification.
- Eric
next prev parent reply other threads:[~2026-07-10 21:37 UTC|newest]
Thread overview: 6+ messages / expand[flat|nested] mbox.gz Atom feed top
2026-07-10 17:29 [PATCH] crypto: rsassa-pkcs1: use constant-time comparison for digest and signature verification David C.C.M. Gall
2026-07-10 21:37 ` Eric Biggers [this message]
2026-07-11 5:19 ` Greg KH
2026-07-11 8:00 ` Ignat Korchagin
2026-07-11 11:23 ` David Gall
2026-07-11 15:17 ` Lukas Wunner
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=20260710213718.GD1911@quark \
--to=ebiggers@kernel.org \
--cc=davem@davemloft.net \
--cc=david.ccm.gall@googlemail.com \
--cc=gregkh@linuxfoundation.org \
--cc=herbert@gondor.apana.org.au \
--cc=ignat@linux.win \
--cc=linux-crypto@vger.kernel.org \
--cc=linux-kernel@vger.kernel.org \
--cc=lukas@wunner.de \
/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 an external index of several public inboxes,
see mirroring instructions on how to clone and mirror
all data and code used by this external index.