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crypto: authencesn - reject short ahash digests during instance creation

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authencesn requires either a zero authsize or an authsize of at least
4 bytes because the ESN encrypt/decrypt paths always move 4 bytes of
high-order sequence number data at the end of the authenticated data.

While crypto_authenc_esn_setauthsize() already rejects explicit
non-zero authsizes in the range 1..3, crypto_authenc_esn_create()
still copied auth->digestsize into inst->alg.maxauthsize without
validating it.  The AEAD core then initialized the tfm's default
authsize from that value.

As a result, selecting an ahash with digest size 1..3, such as
cbcmac(cipher_null), exposed authencesn instances whose default
authsize was invalid even though setauthsize() would have rejected the
same value.  AF_ALG could then trigger the ESN tail handling with a
too-short tag and hit an out-of-bounds access.

Reject authencesn instances whose ahash digest size is in the invalid
non-zero range 1..3 so that no tfm can inherit an unsupported default
authsize.

Fixes: f15f05b0a5 ("crypto: ccm - switch to separate cbcmac driver")
Cc: stable@kernel.org
Reported-by: Yifan Wu <yifanwucs@gmail.com>
Reported-by: Juefei Pu <tomapufckgml@gmail.com>
Co-developed-by: Yuan Tan <yuantan098@gmail.com>
Signed-off-by: Yuan Tan <yuantan098@gmail.com>
Suggested-by: Xin Liu <bird@lzu.edu.cn>
Tested-by: Yuhang Zheng <z1652074432@gmail.com>
Reviewed-by: Eric Biggers <ebiggers@kernel.org>
Signed-off-by: Yucheng Lu <kanolyc@gmail.com>
Signed-off-by: Ren Wei <n05ec@lzu.edu.cn>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>
This commit is contained in:
Yucheng Lu 2026-04-22 21:45:04 +08:00 committed by Herbert Xu
parent 3bfbf5f0a9
commit 5db6ef9847
1 changed files with 5 additions and 0 deletions
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5
crypto/authencesn.c
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@ -390,6 +390,11 @@ static int crypto_authenc_esn_create(struct crypto_template *tmpl,
auth = crypto_spawn_ahash_alg(&ctx->auth);
auth_base = &auth->base;
if (auth->digestsize > 0 && auth->digestsize < 4) {
err = -EINVAL;
goto err_free_inst;
}
err = crypto_grab_skcipher(&ctx->enc, aead_crypto_instance(inst),
crypto_attr_alg_name(tb[2]), 0, mask);
if (err)