linux-kernel - [PATCH 2/8] crypto: user - reject requests for untested algorithms

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Message-Id: <20211003181413.12465-3-nstange@suse.de>
Date:   Sun,  3 Oct 2021 20:14:07 +0200
From:   Nicolai Stange <nstange@...e.de>
To:     Herbert Xu <herbert@...dor.apana.org.au>,
        "David S. Miller" <davem@...emloft.net>
Cc:     linux-crypto@...r.kernel.org, linux-kernel@...r.kernel.org,
        Stephan Müller <smueller@...onox.de>,
        Torsten Duwe <duwe@...e.de>, Nicolai Stange <nstange@...e.de>
Subject: [PATCH 2/8] crypto: user - reject requests for untested algorithms

Currently it's possible for userspace to specify any combination of
->cru_type and ->cru_mask with respect to CRYTPO_ALG_TESTED via the
CRYPTO_MSG_NEWALG crypto_user interface.

As these are passed onwards to crypto_larval_lookup() unmodified as
'mask' and 'type' parameters eventually, this can lead to the creation of
obscure lookup larvals like e.g. (mask & CRYTPO_ALG_TESTED) but not
(type & CRYTPO_ALG_TESTED) or the other way around.

Userspace should have no business in asking for untested algorithms. Make
crypto_user's crypto_add_alg() reject nonsensical combinations of
->cru_type and ->cru_mask with respect to CRYTPO_ALG_TESTED with -EINVAL.

Note that CRYTPO_ALG_TESTED not being set in either of mask and type is
considered equivalent to that flag being set in both and these two
combinations are the only ones supported as of now.

Signed-off-by: Nicolai Stange <nstange@...e.de>
---
 crypto/crypto_user_base.c | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/crypto/crypto_user_base.c b/crypto/crypto_user_base.c
index 3fa20f12989f..a9c06cd98a8c 100644
--- a/crypto/crypto_user_base.c
+++ b/crypto/crypto_user_base.c
@@ -352,6 +352,9 @@ static int crypto_add_alg(struct sk_buff *skb, struct nlmsghdr *nlh,
 	if (priority && !exact)
 		return -EINVAL;
 
+	if ((p->cru_type ^ p->cru_mask) & CRYPTO_ALG_TESTED)
+		return -EINVAL;
+
 	alg = crypto_alg_match(p, exact);
 	if (alg) {
 		crypto_mod_put(alg);
-- 
2.26.2