linux-kernel - [PATCH 1/4] crypto: xts - restrict key lengths to approved values in FIPS mode

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Message-Id: <20221108142025.13461-2-nstange@suse.de>
Date:   Tue,  8 Nov 2022 15:20:22 +0100
From:   Nicolai Stange <nstange@...e.de>
To:     Herbert Xu <herbert@...dor.apana.org.au>,
        "David S. Miller" <davem@...emloft.net>
Cc:     Vladis Dronov <vdronov@...hat.com>,
        Stephan Mueller <smueller@...onox.de>,
        linux-crypto@...r.kernel.org, linux-kernel@...r.kernel.org,
        Nicolai Stange <nstange@...e.de>
Subject: [PATCH 1/4] crypto: xts - restrict key lengths to approved values in FIPS mode

According to FIPS 140-3 IG C.I., only (total) key lengths of either
256 bits or 512 bits are allowed with xts(aes). Make xts_verify_key() to
reject anything else in FIPS mode.

As xts(aes) is the only approved xts() template instantiation in FIPS mode,
the new restriction implemented in xts_verify_key() effectively only
applies to this particular construction.

Signed-off-by: Nicolai Stange <nstange@...e.de>
---
 include/crypto/xts.h | 7 +++++++
 1 file changed, 7 insertions(+)

diff --git a/include/crypto/xts.h b/include/crypto/xts.h
index 0f8dba69feb4..a233c1054df2 100644
--- a/include/crypto/xts.h
+++ b/include/crypto/xts.h
@@ -35,6 +35,13 @@ static inline int xts_verify_key(struct crypto_skcipher *tfm,
 	if (keylen % 2)
 		return -EINVAL;
 
+	/*
+	 * In FIPS mode only a combined key length of either 256 or
+	 * 512 bits is allowed, c.f. FIPS 140-3 IG C.I.
+	 */
+	if (fips_enabled && keylen != 32 && keylen != 64)
+		return -EINVAL;
+
 	/* ensure that the AES and tweak key are not identical */
 	if ((fips_enabled || (crypto_skcipher_get_flags(tfm) &
 			      CRYPTO_TFM_REQ_FORBID_WEAK_KEYS)) &&
-- 
2.38.0