Message-ID: <20251109234726.638437-8-ebiggers@kernel.org>
Date: Sun,  9 Nov 2025 15:47:22 -0800
From: Eric Biggers <ebiggers@...nel.org>
To: linux-crypto@...r.kernel.org
Cc: linux-kernel@...r.kernel.org,
	Ard Biesheuvel <ardb@...nel.org>,
	"Jason A . Donenfeld" <Jason@...c4.com>,
	Herbert Xu <herbert@...dor.apana.org.au>,
	linux-arm-kernel@...ts.infradead.org,
	x86@...nel.org,
	Eric Biggers <ebiggers@...nel.org>
Subject: [PATCH 7/9] crypto: polyval - Remove the polyval crypto_shash

Remove polyval support from crypto_shash.  It no longer has any user now
that the HCTR2 code uses the POLYVAL library instead.

Signed-off-by: Eric Biggers <ebiggers@...nel.org>
---
 crypto/Kconfig           |  10 --
 crypto/Makefile          |   1 -
 crypto/polyval-generic.c | 205 ---------------------------------------
 3 files changed, 216 deletions(-)
 delete mode 100644 crypto/polyval-generic.c

diff --git a/crypto/Kconfig b/crypto/Kconfig
index 805172f75bf1..bf8b8a60a0c0 100644
--- a/crypto/Kconfig
+++ b/crypto/Kconfig
@@ -946,20 +946,10 @@ config CRYPTO_MICHAEL_MIC
 	  known as WPA (Wif-Fi Protected Access).
 
 	  This algorithm is required for TKIP, but it should not be used for
 	  other purposes because of the weakness of the algorithm.
 
-config CRYPTO_POLYVAL
-	tristate
-	select CRYPTO_HASH
-	select CRYPTO_LIB_GF128MUL
-	help
-	  POLYVAL hash function for HCTR2
-
-	  This is used in HCTR2.  It is not a general-purpose
-	  cryptographic hash function.
-
 config CRYPTO_RMD160
 	tristate "RIPEMD-160"
 	select CRYPTO_HASH
 	help
 	  RIPEMD-160 hash function (ISO/IEC 10118-3)
diff --git a/crypto/Makefile b/crypto/Makefile
index 0388ff8d219d..093c56a45d3f 100644
--- a/crypto/Makefile
+++ b/crypto/Makefile
@@ -170,11 +170,10 @@ KASAN_SANITIZE_jitterentropy.o = n
 UBSAN_SANITIZE_jitterentropy.o = n
 jitterentropy_rng-y := jitterentropy.o jitterentropy-kcapi.o
 obj-$(CONFIG_CRYPTO_JITTERENTROPY_TESTINTERFACE) += jitterentropy-testing.o
 obj-$(CONFIG_CRYPTO_BENCHMARK) += 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-$(CONFIG_CRYPTO_USER_API_SKCIPHER) += algif_skcipher.o
 obj-$(CONFIG_CRYPTO_USER_API_RNG) += algif_rng.o
 obj-$(CONFIG_CRYPTO_USER_API_AEAD) += algif_aead.o
diff --git a/crypto/polyval-generic.c b/crypto/polyval-generic.c
deleted file mode 100644
index fe5b01a4000d..000000000000
--- a/crypto/polyval-generic.c
+++ /dev/null
@@ -1,205 +0,0 @@
-// SPDX-License-Identifier: GPL-2.0-only
-/*
- * POLYVAL: hash function for HCTR2.
- *
- * Copyright (c) 2007 Nokia Siemens Networks - Mikko Herranen <mh1@....fi>
- * Copyright (c) 2009 Intel Corp.
- *   Author: Huang Ying <ying.huang@...el.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 <crypto/gf128mul.h>
-#include <crypto/internal/hash.h>
-#include <crypto/polyval.h>
-#include <crypto/utils.h>
-#include <linux/errno.h>
-#include <linux/kernel.h>
-#include <linux/module.h>
-#include <linux/string.h>
-#include <linux/unaligned.h>
-
-struct polyval_tfm_ctx {
-	struct gf128mul_4k *gf128;
-};
-
-struct polyval_desc_ctx {
-	union {
-		u8 buffer[POLYVAL_BLOCK_SIZE];
-		be128 buffer128;
-	};
-};
-
-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_generic_init(struct shash_desc *desc)
-{
-	struct polyval_desc_ctx *dctx = shash_desc_ctx(desc);
-
-	memset(dctx, 0, sizeof(*dctx));
-
-	return 0;
-}
-
-static int polyval_generic_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 tmp[POLYVAL_BLOCK_SIZE];
-
-	do {
-		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;
-	} while (srclen >= POLYVAL_BLOCK_SIZE);
-
-	return srclen;
-}
-
-static int polyval_finup(struct shash_desc *desc, const u8 *src,
-			 unsigned int len, u8 *dst)
-{
-	struct polyval_desc_ctx *dctx = shash_desc_ctx(desc);
-
-	if (len) {
-		u8 tmp[POLYVAL_BLOCK_SIZE] = {};
-
-		memcpy(tmp, src, len);
-		polyval_generic_update(desc, tmp, POLYVAL_BLOCK_SIZE);
-	}
-	copy_and_reverse(dst, dctx->buffer);
-	return 0;
-}
-
-static int polyval_export(struct shash_desc *desc, void *out)
-{
-	struct polyval_desc_ctx *dctx = shash_desc_ctx(desc);
-
-	copy_and_reverse(out, dctx->buffer);
-	return 0;
-}
-
-static int polyval_import(struct shash_desc *desc, const void *in)
-{
-	struct polyval_desc_ctx *dctx = shash_desc_ctx(desc);
-
-	copy_and_reverse(dctx->buffer, in);
-	return 0;
-}
-
-static void polyval_exit_tfm(struct crypto_shash *tfm)
-{
-	struct polyval_tfm_ctx *ctx = crypto_shash_ctx(tfm);
-
-	gf128mul_free_4k(ctx->gf128);
-}
-
-static struct shash_alg polyval_alg = {
-	.digestsize	= POLYVAL_DIGEST_SIZE,
-	.init		= polyval_generic_init,
-	.update		= polyval_generic_update,
-	.finup		= polyval_finup,
-	.setkey		= polyval_setkey,
-	.export		= polyval_export,
-	.import		= polyval_import,
-	.exit_tfm	= polyval_exit_tfm,
-	.statesize	= sizeof(struct polyval_desc_ctx),
-	.descsize	= sizeof(struct polyval_desc_ctx),
-	.base		= {
-		.cra_name		= "polyval",
-		.cra_driver_name	= "polyval-generic",
-		.cra_priority		= 100,
-		.cra_flags		= CRYPTO_AHASH_ALG_BLOCK_ONLY,
-		.cra_blocksize		= POLYVAL_BLOCK_SIZE,
-		.cra_ctxsize		= sizeof(struct polyval_tfm_ctx),
-		.cra_module		= THIS_MODULE,
-	},
-};
-
-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);
-}
-
-module_init(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");
-- 
2.51.2

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