Commit f3c923a0 authored by Nathan Huckleberry's avatar Nathan Huckleberry Committed by Herbert Xu
Browse files

crypto: polyval - Add POLYVAL support 

Add support for POLYVAL, an ε-Δ-universal hash function similar to
GHASH.  This patch only uses POLYVAL as a component to implement HCTR2
mode.  It should be noted that POLYVAL was originally specified for use
in AES-GCM-SIV (RFC 8452), but the kernel does not currently support
this mode.

POLYVAL is implemented as an shash algorithm.  The implementation is
modified from ghash-generic.c.

For more information on POLYVAL see:
Length-preserving encryption with HCTR2:
  https://eprint.iacr.org/2021/1441.pdf
AES-GCM-SIV: Nonce Misuse-Resistant Authenticated Encryption:
  https://datatracker.ietf.org/doc/html/rfc8452



Signed-off-by: default avatarNathan Huckleberry <nhuck@google.com>
Reviewed-by: default avatarEric Biggers <ebiggers@google.com>
Reviewed-by: default avatarArd Biesheuvel <ardb@kernel.org>
Signed-off-by: default avatarHerbert Xu <herbert@gondor.apana.org.au>
parent 17fee07a

crypto/Kconfig

+8 −0
Original line number Diff line number Diff line
@@ -773,6 +773,14 @@ config CRYPTO_GHASH 
	  GHASH is the hash function used in GCM (Galois/Counter Mode).

	  It is not a general-purpose cryptographic hash function.



config CRYPTO_POLYVAL

	tristate

	select CRYPTO_GF128MUL

	select CRYPTO_HASH

	help

	  POLYVAL is the hash function used in HCTR2.  It is not a general-purpose

	  cryptographic hash function.



config CRYPTO_POLY1305

	tristate "Poly1305 authenticator algorithm"

	select CRYPTO_HASH

crypto/Makefile

+1 −0
Original line number Diff line number Diff line
@@ -172,6 +172,7 @@ UBSAN_SANITIZE_jitterentropy.o = n 
jitterentropy_rng-y := jitterentropy.o jitterentropy-kcapi.o

obj-$(CONFIG_CRYPTO_TEST) += tcrypt.o

obj-$(CONFIG_CRYPTO_GHASH) += ghash-generic.o

obj-$(CONFIG_CRYPTO_POLYVAL) += polyval-generic.o

obj-$(CONFIG_CRYPTO_USER_API) += af_alg.o

obj-$(CONFIG_CRYPTO_USER_API_HASH) += algif_hash.o

obj-$(CONFIG_CRYPTO_USER_API_SKCIPHER) += algif_skcipher.o

crypto/polyval-generic.c

0 → 100644
+205 −0
Original line number Diff line number Diff line 
// SPDX-License-Identifier: GPL-2.0-only

/*

 * POLYVAL: hash function for HCTR2.

 *

 * Copyright (c) 2007 Nokia Siemens Networks - Mikko Herranen <mh1@iki.fi>

 * Copyright (c) 2009 Intel Corp.

 *   Author: Huang Ying <ying.huang@intel.com>

 * Copyright 2021 Google LLC

 */



/*

 * Code based on crypto/ghash-generic.c

 *

 * POLYVAL is a keyed hash function similar to GHASH. POLYVAL uses a different

 * modulus for finite field multiplication which makes hardware accelerated

 * implementations on little-endian machines faster. POLYVAL is used in the

 * kernel to implement HCTR2, but was originally specified for AES-GCM-SIV

 * (RFC 8452).

 *

 * For more information see:

 * Length-preserving encryption with HCTR2:

 *   https://eprint.iacr.org/2021/1441.pdf

 * AES-GCM-SIV: Nonce Misuse-Resistant Authenticated Encryption:

 *   https://datatracker.ietf.org/doc/html/rfc8452

 *

 * Like GHASH, POLYVAL is not a cryptographic hash function and should

 * not be used outside of crypto modes explicitly designed to use POLYVAL.

 *

 * This implementation uses a convenient trick involving the GHASH and POLYVAL

 * fields. This trick allows multiplication in the POLYVAL field to be

 * implemented by using multiplication in the GHASH field as a subroutine. An

 * element of the POLYVAL field can be converted to an element of the GHASH

 * field by computing x*REVERSE(a), where REVERSE reverses the byte-ordering of

 * a. Similarly, an element of the GHASH field can be converted back to the

 * POLYVAL field by computing REVERSE(x^{-1}*a). For more information, see:

 * https://datatracker.ietf.org/doc/html/rfc8452#appendix-A

 *

 * By using this trick, we do not need to implement the POLYVAL field for the

 * generic implementation.

 *

 * Warning: this generic implementation is not intended to be used in practice

 * and is not constant time. For practical use, a hardware accelerated

 * implementation of POLYVAL should be used instead.

 *

 */



#include <asm/unaligned.h>

#include <crypto/algapi.h>

#include <crypto/gf128mul.h>

#include <crypto/polyval.h>

#include <crypto/internal/hash.h>

#include <linux/crypto.h>

#include <linux/init.h>

#include <linux/kernel.h>

#include <linux/module.h>



struct polyval_tfm_ctx {

	struct gf128mul_4k *gf128;

};



struct polyval_desc_ctx {

	union {

		u8 buffer[POLYVAL_BLOCK_SIZE];

		be128 buffer128;

	};

	u32 bytes;

};



static void copy_and_reverse(u8 dst[POLYVAL_BLOCK_SIZE],

			     const u8 src[POLYVAL_BLOCK_SIZE])

{

	u64 a = get_unaligned((const u64 *)&src[0]);

	u64 b = get_unaligned((const u64 *)&src[8]);



	put_unaligned(swab64(a), (u64 *)&dst[8]);

	put_unaligned(swab64(b), (u64 *)&dst[0]);

}



static int polyval_setkey(struct crypto_shash *tfm,

			  const u8 *key, unsigned int keylen)

{

	struct polyval_tfm_ctx *ctx = crypto_shash_ctx(tfm);

	be128 k;



	if (keylen != POLYVAL_BLOCK_SIZE)

		return -EINVAL;



	gf128mul_free_4k(ctx->gf128);



	BUILD_BUG_ON(sizeof(k) != POLYVAL_BLOCK_SIZE);

	copy_and_reverse((u8 *)&k, key);

	gf128mul_x_lle(&k, &k);



	ctx->gf128 = gf128mul_init_4k_lle(&k);

	memzero_explicit(&k, POLYVAL_BLOCK_SIZE);



	if (!ctx->gf128)

		return -ENOMEM;



	return 0;

}



static int polyval_init(struct shash_desc *desc)

{

	struct polyval_desc_ctx *dctx = shash_desc_ctx(desc);



	memset(dctx, 0, sizeof(*dctx));



	return 0;

}



static int polyval_update(struct shash_desc *desc,

			 const u8 *src, unsigned int srclen)

{

	struct polyval_desc_ctx *dctx = shash_desc_ctx(desc);

	const struct polyval_tfm_ctx *ctx = crypto_shash_ctx(desc->tfm);

	u8 *pos;

	u8 tmp[POLYVAL_BLOCK_SIZE];

	int n;



	if (dctx->bytes) {

		n = min(srclen, dctx->bytes);

		pos = dctx->buffer + dctx->bytes - 1;



		dctx->bytes -= n;

		srclen -= n;



		while (n--)

			*pos-- ^= *src++;



		if (!dctx->bytes)

			gf128mul_4k_lle(&dctx->buffer128, ctx->gf128);

	}



	while (srclen >= POLYVAL_BLOCK_SIZE) {

		copy_and_reverse(tmp, src);

		crypto_xor(dctx->buffer, tmp, POLYVAL_BLOCK_SIZE);

		gf128mul_4k_lle(&dctx->buffer128, ctx->gf128);

		src += POLYVAL_BLOCK_SIZE;

		srclen -= POLYVAL_BLOCK_SIZE;

	}



	if (srclen) {

		dctx->bytes = POLYVAL_BLOCK_SIZE - srclen;

		pos = dctx->buffer + POLYVAL_BLOCK_SIZE - 1;

		while (srclen--)

			*pos-- ^= *src++;

	}



	return 0;

}



static int polyval_final(struct shash_desc *desc, u8 *dst)

{

	struct polyval_desc_ctx *dctx = shash_desc_ctx(desc);

	const struct polyval_tfm_ctx *ctx = crypto_shash_ctx(desc->tfm);



	if (dctx->bytes)

		gf128mul_4k_lle(&dctx->buffer128, ctx->gf128);

	copy_and_reverse(dst, dctx->buffer);

	return 0;

}



static void polyval_exit_tfm(struct crypto_tfm *tfm)

{

	struct polyval_tfm_ctx *ctx = crypto_tfm_ctx(tfm);



	gf128mul_free_4k(ctx->gf128);

}



static struct shash_alg polyval_alg = {

	.digestsize	= POLYVAL_DIGEST_SIZE,

	.init		= polyval_init,

	.update		= polyval_update,

	.final		= polyval_final,

	.setkey		= polyval_setkey,

	.descsize	= sizeof(struct polyval_desc_ctx),

	.base		= {

		.cra_name		= "polyval",

		.cra_driver_name	= "polyval-generic",

		.cra_priority		= 100,

		.cra_blocksize		= POLYVAL_BLOCK_SIZE,

		.cra_ctxsize		= sizeof(struct polyval_tfm_ctx),

		.cra_module		= THIS_MODULE,

		.cra_exit		= polyval_exit_tfm,

	},

};



static int __init polyval_mod_init(void)

{

	return crypto_register_shash(&polyval_alg);

}



static void __exit polyval_mod_exit(void)

{

	crypto_unregister_shash(&polyval_alg);

}



subsys_initcall(polyval_mod_init);

module_exit(polyval_mod_exit);



MODULE_LICENSE("GPL");

MODULE_DESCRIPTION("POLYVAL hash function");

MODULE_ALIAS_CRYPTO("polyval");

MODULE_ALIAS_CRYPTO("polyval-generic");

crypto/tcrypt.c

+4 −0
Original line number Diff line number Diff line
@@ -1730,6 +1730,10 @@ static int do_test(const char *alg, u32 type, u32 mask, int m, u32 num_mb) 
		ret += tcrypt_test("ccm(sm4)");

		break;



	case 57:

		ret += tcrypt_test("polyval");

		break;



	case 100:

		ret += tcrypt_test("hmac(md5)");

		break;

crypto/testmgr.c

+6 −0
Original line number Diff line number Diff line
@@ -5342,6 +5342,12 @@ static const struct alg_test_desc alg_test_descs[] = { 
		.suite = {

			.hash = __VECS(poly1305_tv_template)

		}

	}, {

		.alg = "polyval",

		.test = alg_test_hash,

		.suite = {

			.hash = __VECS(polyval_tv_template)

		}

	}, {

		.alg = "rfc3686(ctr(aes))",

		.test = alg_test_skcipher,