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/rfc8452Signed-off-by: NNathan Huckleberry <nhuck@google.com>
Reviewed-by: NEric Biggers <ebiggers@google.com>
Reviewed-by: NArd Biesheuvel <ardb@kernel.org>
Signed-off-by: NHerbert Xu <herbert@gondor.apana.org.au>

crypto/Kconfig

@@ -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

@@ -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

+// 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

@@ -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

@@ -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,

crypto/testmgr.h

@@ -34944,4 +34944,175 @@ static const struct cipher_testvec aes_xctr_tv_template[] = {
 
 };
 
+/*
+ * Test vectors generated using https://github.com/google/hctr2
+ *
+ * To ensure compatibility with RFC 8452, some tests were sourced from
+ * https://datatracker.ietf.org/doc/html/rfc8452
+ */
+static const struct hash_testvec polyval_tv_template[] = {
+	{ // From RFC 8452
+		.key	= "\x31\x07\x28\xd9\x91\x1f\x1f\x38"
+			  "\x37\xb2\x43\x16\xc3\xfa\xb9\xa0",
+		.plaintext	= "\x65\x78\x61\x6d\x70\x6c\x65\x00"
+			  "\x00\x00\x00\x00\x00\x00\x00\x00"
+			  "\x48\x65\x6c\x6c\x6f\x20\x77\x6f"
+			  "\x72\x6c\x64\x00\x00\x00\x00\x00"
+			  "\x38\x00\x00\x00\x00\x00\x00\x00"
+			  "\x58\x00\x00\x00\x00\x00\x00\x00",
+		.digest	= "\xad\x7f\xcf\x0b\x51\x69\x85\x16"
+			  "\x62\x67\x2f\x3c\x5f\x95\x13\x8f",
+		.psize	= 48,
+		.ksize	= 16,
+	},
+	{ // From RFC 8452
+		.key	= "\xd9\xb3\x60\x27\x96\x94\x94\x1a"
+			  "\xc5\xdb\xc6\x98\x7a\xda\x73\x77",
+		.plaintext	= "\x00\x00\x00\x00\x00\x00\x00\x00"
+			  "\x00\x00\x00\x00\x00\x00\x00\x00",
+		.digest	= "\x00\x00\x00\x00\x00\x00\x00\x00"
+			  "\x00\x00\x00\x00\x00\x00\x00\x00",
+		.psize	= 16,
+		.ksize	= 16,
+	},
+	{ // From RFC 8452
+		.key	= "\xd9\xb3\x60\x27\x96\x94\x94\x1a"
+			  "\xc5\xdb\xc6\x98\x7a\xda\x73\x77",
+		.plaintext	= "\x01\x00\x00\x00\x00\x00\x00\x00"
+			  "\x00\x00\x00\x00\x00\x00\x00\x00"
+			  "\x00\x00\x00\x00\x00\x00\x00\x00"
+			  "\x40\x00\x00\x00\x00\x00\x00\x00",
+		.digest	= "\xeb\x93\xb7\x74\x09\x62\xc5\xe4"
+			  "\x9d\x2a\x90\xa7\xdc\x5c\xec\x74",
+		.psize	= 32,
+		.ksize	= 16,
+	},
+	{ // From RFC 8452
+		.key	= "\xd9\xb3\x60\x27\x96\x94\x94\x1a"
+			  "\xc5\xdb\xc6\x98\x7a\xda\x73\x77",
+		.plaintext	= "\x01\x00\x00\x00\x00\x00\x00\x00"
+			  "\x00\x00\x00\x00\x00\x00\x00\x00"
+			  "\x02\x00\x00\x00\x00\x00\x00\x00"
+			  "\x00\x00\x00\x00\x00\x00\x00\x00"
+			  "\x03\x00\x00\x00\x00\x00\x00\x00"
+			  "\x00\x00\x00\x00\x00\x00\x00\x00"
+			  "\x00\x00\x00\x00\x00\x00\x00\x00"
+			  "\x80\x01\x00\x00\x00\x00\x00\x00",
+		.digest	= "\x81\x38\x87\x46\xbc\x22\xd2\x6b"
+			  "\x2a\xbc\x3d\xcb\x15\x75\x42\x22",
+		.psize	= 64,
+		.ksize	= 16,
+	},
+	{ // From RFC 8452
+		.key	= "\xd9\xb3\x60\x27\x96\x94\x94\x1a"
+			  "\xc5\xdb\xc6\x98\x7a\xda\x73\x77",
+		.plaintext	= "\x01\x00\x00\x00\x00\x00\x00\x00"
+			  "\x00\x00\x00\x00\x00\x00\x00\x00"
+			  "\x02\x00\x00\x00\x00\x00\x00\x00"
+			  "\x00\x00\x00\x00\x00\x00\x00\x00"
+			  "\x03\x00\x00\x00\x00\x00\x00\x00"
+			  "\x00\x00\x00\x00\x00\x00\x00\x00"
+			  "\x04\x00\x00\x00\x00\x00\x00\x00"
+			  "\x00\x00\x00\x00\x00\x00\x00\x00"
+			  "\x00\x00\x00\x00\x00\x00\x00\x00"
+			  "\x00\x02\x00\x00\x00\x00\x00\x00",
+		.digest	= "\x1e\x39\xb6\xd3\x34\x4d\x34\x8f"
+			  "\x60\x44\xf8\x99\x35\xd1\xcf\x78",
+		.psize	= 80,
+		.ksize	= 16,
+	},
+	{ // From RFC 8452
+		.key	= "\xd9\xb3\x60\x27\x96\x94\x94\x1a"
+			  "\xc5\xdb\xc6\x98\x7a\xda\x73\x77",
+		.plaintext	= "\x01\x00\x00\x00\x00\x00\x00\x00"
+			  "\x00\x00\x00\x00\x00\x00\x00\x00"
+			  "\x02\x00\x00\x00\x00\x00\x00\x00"
+			  "\x00\x00\x00\x00\x00\x00\x00\x00"
+			  "\x03\x00\x00\x00\x00\x00\x00\x00"
+			  "\x00\x00\x00\x00\x00\x00\x00\x00"
+			  "\x04\x00\x00\x00\x00\x00\x00\x00"
+			  "\x00\x00\x00\x00\x00\x00\x00\x00"
+			  "\x05\x00\x00\x00\x00\x00\x00\x00"
+			  "\x00\x00\x00\x00\x00\x00\x00\x00"
+			  "\x08\x00\x00\x00\x00\x00\x00\x00"
+			  "\x00\x02\x00\x00\x00\x00\x00\x00",
+		.digest	= "\xff\xcd\x05\xd5\x77\x0f\x34\xad"
+			  "\x92\x67\xf0\xa5\x99\x94\xb1\x5a",
+		.psize	= 96,
+		.ksize	= 16,
+	},
+	{ // Random ( 1)
+		.key	= "\x90\xcc\xac\xee\xba\xd7\xd4\x68"
+			  "\x98\xa6\x79\x70\xdf\x66\x15\x6c",
+		.plaintext	= "",
+		.digest	= "\x00\x00\x00\x00\x00\x00\x00\x00"
+			  "\x00\x00\x00\x00\x00\x00\x00\x00",
+		.psize	= 0,
+		.ksize	= 16,
+	},
+	{ // Random ( 1)
+		.key	= "\xc1\x45\x71\xf0\x30\x07\x94\xe7"
+			  "\x3a\xdd\xe4\xc6\x19\x2d\x02\xa2",
+		.plaintext	= "\xc1\x5d\x47\xc7\x4c\x7c\x5e\x07"
+			  "\x85\x14\x8f\x79\xcc\x73\x83\xf7"
+			  "\x35\xb8\xcb\x73\x61\xf0\x53\x31"
+			  "\xbf\x84\xde\xb6\xde\xaf\xb0\xb8"
+			  "\xb7\xd9\x11\x91\x89\xfd\x1e\x4c"
+			  "\x84\x4a\x1f\x2a\x87\xa4\xaf\x62"
+			  "\x8d\x7d\x58\xf6\x43\x35\xfc\x53"
+			  "\x8f\x1a\xf6\x12\xe1\x13\x3f\x66"
+			  "\x91\x4b\x13\xd6\x45\xfb\xb0\x7a"
+			  "\xe0\x8b\x8e\x99\xf7\x86\x46\x37"
+			  "\xd1\x22\x9e\x52\xf3\x3f\xd9\x75"
+			  "\x2c\x2c\xc6\xbb\x0e\x08\x14\x29"
+			  "\xe8\x50\x2f\xd8\xbe\xf4\xe9\x69"
+			  "\x4a\xee\xf7\xae\x15\x65\x35\x1e",
+		.digest	= "\x00\x4f\x5d\xe9\x3b\xc0\xd6\x50"
+			  "\x3e\x38\x73\x86\xc6\xda\xca\x7f",
+		.psize	= 112,
+		.ksize	= 16,
+	},
+	{ // Random ( 1)
+		.key	= "\x37\xbe\x68\x16\x50\xb9\x4e\xb0"
+			  "\x47\xde\xe2\xbd\xde\xe4\x48\x09",
+		.plaintext	= "\x87\xfc\x68\x9f\xff\xf2\x4a\x1e"
+			  "\x82\x3b\x73\x8f\xc1\xb2\x1b\x7a"
+			  "\x6c\x4f\x81\xbc\x88\x9b\x6c\xa3"
+			  "\x9c\xc2\xa5\xbc\x14\x70\x4c\x9b"
+			  "\x0c\x9f\x59\x92\x16\x4b\x91\x3d"
+			  "\x18\x55\x22\x68\x12\x8c\x63\xb2"
+			  "\x51\xcb\x85\x4b\xd2\xae\x0b\x1c"
+			  "\x5d\x28\x9d\x1d\xb1\xc8\xf0\x77"
+			  "\xe9\xb5\x07\x4e\x06\xc8\xee\xf8"
+			  "\x1b\xed\x72\x2a\x55\x7d\x16\xc9"
+			  "\xf2\x54\xe7\xe9\xe0\x44\x5b\x33"
+			  "\xb1\x49\xee\xff\x43\xfb\x82\xcd"
+			  "\x4a\x70\x78\x81\xa4\x34\x36\xe8"
+			  "\x4c\x28\x54\xa6\x6c\xc3\x6b\x78"
+			  "\xe7\xc0\x5d\xc6\x5d\x81\xab\x70"
+			  "\x08\x86\xa1\xfd\xf4\x77\x55\xfd"
+			  "\xa3\xe9\xe2\x1b\xdf\x99\xb7\x80"
+			  "\xf9\x0a\x4f\x72\x4a\xd3\xaf\xbb"
+			  "\xb3\x3b\xeb\x08\x58\x0f\x79\xce"
+			  "\xa5\x99\x05\x12\x34\xd4\xf4\x86"
+			  "\x37\x23\x1d\xc8\x49\xc0\x92\xae"
+			  "\xa6\xac\x9b\x31\x55\xed\x15\xc6"
+			  "\x05\x17\x37\x8d\x90\x42\xe4\x87"
+			  "\x89\x62\x88\x69\x1c\x6a\xfd\xe3"
+			  "\x00\x2b\x47\x1a\x73\xc1\x51\xc2"
+			  "\xc0\x62\x74\x6a\x9e\xb2\xe5\x21"
+			  "\xbe\x90\xb5\xb0\x50\xca\x88\x68"
+			  "\xe1\x9d\x7a\xdf\x6c\xb7\xb9\x98"
+			  "\xee\x28\x62\x61\x8b\xd1\x47\xf9"
+			  "\x04\x7a\x0b\x5d\xcd\x2b\x65\xf5"
+			  "\x12\xa3\xfe\x1a\xaa\x2c\x78\x42"
+			  "\xb8\xbe\x7d\x74\xeb\x59\xba\xba",
+		.digest	= "\xae\x11\xd4\x60\x2a\x5f\x9e\x42"
+			  "\x89\x04\xc2\x34\x8d\x55\x94\x0a",
+		.psize	= 256,
+		.ksize	= 16,
+	},
+
+};
+
 #endif	/* _CRYPTO_TESTMGR_H */

include/crypto/polyval.h

+/* SPDX-License-Identifier: GPL-2.0 */
+/*
+ * Common values for the Polyval hash algorithm
+ *
+ * Copyright 2021 Google LLC
+ */
+
+#ifndef _CRYPTO_POLYVAL_H
+#define _CRYPTO_POLYVAL_H
+
+#include <linux/types.h>
+#include <linux/crypto.h>
+
+#define POLYVAL_BLOCK_SIZE	16
+#define POLYVAL_DIGEST_SIZE	16
+
+#endif