Date: Thu, 5 Nov 2026 19:49:25 -0800
From: Eric Biggers <ebiggers@kernel.org>
To: Walter McKelvie <walt@mckelvie.org>
Cc: herbert@gondor.apana.org.au, davem@davemloft.net,
	linux-crypto@vger.kernel.org, stable@vger.kernel.org
Subject: Re: [PATCH] crypto: algif_aead - Allow gcm(aes) for privileged users
Message-ID: <20261106034925.GA3877@sol>
References: <20261106034150.1159818-1-walt@mckelvie.org>
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In-Reply-To: <20261106034150.1159818-1-walt@mckelvie.org>

On Thu, Nov 05, 2026 at 10:41:50PM -0500, Walter McKelvie wrote:
> iwd (via ell) implements TLS for the EAP-TLS/TTLS/PEAP authentication
> methods and uses AF_ALG for the AES-GCM AEAD of the
> TLS_*_WITH_AES_{128,256}_GCM_SHA{256,384} cipher suites.  With
> af_alg_restrict=1 these suites are silently dropped from the
> ClientHello, and authentication fails against RADIUS servers that only
> accept GCM suites (common for eduroam deployments).  This contradicts
> the stated intent of commit 2f204fe718f5 ("crypto: af_alg - Add
> af_alg_restrict sysctl, defaulting to 1"), which was to keep iwd
> working under the default restriction level.
> 
> iwd runs with CAP_NET_ADMIN, so add gcm(aes) to the privileged part of
> the AEAD allowlist, next to ccm(aes) which iwd also uses.
> 
> Fixes: 2f204fe718f5 ("crypto: af_alg - Add af_alg_restrict sysctl, defaulting to 1")
> Link: https://github.com/NixOS/nixpkgs/issues/583203
> Cc: stable@vger.kernel.org
> Signed-off-by: Walter McKelvie <walt@mckelvie.org>

Is this with upstream iwd, and do you have a source code reference?
"gcm(aes)" is L_AEAD_CIPHER_AES_GCM in libell, but iwd has no references
to L_AEAD_CIPHER_AES_GCM.  It didn't show up in the search before either
(https://lore.kernel.org/iwd/bcbbef00-5881-421b-8892-7be6c04b832d@gmail.com/),
and the iwd maintainer confirmed the full list without "gcm(aes)" on it.

- Eric