linux-kernel - authenc methods vs FIPS in light of unencrypted associated data

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Date:	Thu, 2 Jun 2016 18:01:04 +0200
From:	Marcus Meissner <meissner@...e.de>
To:	herbert@...dor.apana.org.au, davem@...emloft.net,
	linux-crypto@...r.kernel.org, linux-kernel@...r.kernel.org,
	smueller@...onox.de
Subject: authenc methods vs FIPS in light of unencrypted associated data

Hi,

In February I already tagged some authenc ciphers for FIPS compatibility.

I currently revisit this to get testmgr running all the tests in strict FIPS mode.

The authenc() class is troublesome.

There is a HASH + ENC part of this method, but you can also add associated data,
which is not encrypted. (using the ctx->null cipher in crypto/authenc.c)

But in FIPS mode the crypto_authenc_init_tfm does:

	null = crypto_get_default_null_skcipher();

which results in error, as the crypto_alloc_blkcipher("ecb(cipher_null)", 0, 0);
results in failure due to "ecb(cipher_null)" not FIPS compliant.

How to handle this?

I think GCM also does not encrypt, just hashes, the associated data, it just does
copy the content itself and does not use a virtual cipher.

Ciao, Marcus