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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@suse.de>
Signed-off-by: Vladis Dronov <vdronov@redhat.com>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>

authored by

Nicolai Stange and committed by
Herbert Xu 1c4428b2 39a76cf1

+7
+7
include/crypto/xts.h
··· 35 35 if (keylen % 2) 36 36 return -EINVAL; 37 37 38 + /* 39 + * In FIPS mode only a combined key length of either 256 or 40 + * 512 bits is allowed, c.f. FIPS 140-3 IG C.I. 41 + */ 42 + if (fips_enabled && keylen != 32 && keylen != 64) 43 + return -EINVAL; 44 + 38 45 /* ensure that the AES and tweak key are not identical */ 39 46 if ((fips_enabled || (crypto_skcipher_get_flags(tfm) & 40 47 CRYPTO_TFM_REQ_FORBID_WEAK_KEYS)) &&