KEYCTL_PKEY_VERIFY lets an unprivileged caller supply a zero-length
digest (in_len == 0). keyctl_pkey_params_get_2() accepts the zero
length and the request reaches pkcs1pad_verify(), where the empty
digest is rejected but only after being passed through
WARN_ON(!digest_size). The warning is therefore directly
user-triggerable, and on kernels built with panic_on_warn=1 an
unprivileged process can panic the machine -- a local denial of
service. Reproduced as UID 65534 in a setuid sandbox.
Keep rejecting the invalid request with -EINVAL, but do not emit a
warning for the user-controlled length.
Mainline does not contain this code path; commit 1e562deace
("crypto: rsassa-pkcs1 - Migrate to sig_alg backend") removed
pkcs1pad_verify() in v6.13-rc1. This is a minimal fix for the
affected stable branches. It applies as-is to 6.1.y, 6.6.y and
6.12.y (identical pkcs1pad_verify); the 5.10.y/5.15.y form is sent
as a separate patch due to the older req->dst_len spelling.
Found by 0sec automated security-research tooling (https://0sec.ai).
Fixes: c7381b0128 ("crypto: akcipher - new verify API for public key algorithms")
Cc: stable@vger.kernel.org
Assisted-by: 0sec:multi-model
Signed-off-by: Doruk Tan Ozturk <doruk@0sec.ai>
Reviewed-by: Lukas Wunner <lukas@wunner.de>
Signed-off-by: Sasha Levin <sashal@kernel.org>
Doruk Tan Ozturk
7dc44840ca