crypto: nhpoly1305 - add NHPoly1305 support

Add a generic implementation of NHPoly1305, an ε-almost-∆-universal hash
function used in the Adiantum encryption mode.

CONFIG_NHPOLY1305 is not selectable by itself since there won't be any
real reason to enable it without also enabling Adiantum support.

Signed-off-by: Eric Biggers <ebiggers@google.com>
Acked-by: Ard Biesheuvel <ard.biesheuvel@linaro.org>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>

1 files changed, 254 insertions, 0 deletions

diff --git a/crypto/nhpoly1305.c b/crypto/nhpoly1305.c
new file mode 100644
index 000000000000..c8385853f699
--- /dev/null
+++ b/crypto/nhpoly1305.c
@@ -0,0 +1,254 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * NHPoly1305 - ε-almost-∆-universal hash function for Adiantum
+ *
+ * Copyright 2018 Google LLC
+ */
+
+/*
+ * "NHPoly1305" is the main component of Adiantum hashing.
+ * Specifically, it is the calculation
+ *
+ *	H_M ← Poly1305_{K_M}(NH_{K_N}(pad_{128}(M)))
+ *
+ * from the procedure in section A.5 of the Adiantum paper [1].  It is an
+ * ε-almost-∆-universal (εA∆U) hash function for equal-length inputs over
+ * Z/(2^{128}Z), where the "∆" operation is addition.  It hashes 1024-byte
+ * chunks of the input with the NH hash function [2], reducing the input length
+ * by 32x.  The resulting NH digests are evaluated as a polynomial in
+ * GF(2^{130}-5), like in the Poly1305 MAC [3].  Note that the polynomial
+ * evaluation by itself would suffice to achieve the εA∆U property; NH is used
+ * for performance since it's over twice as fast as Poly1305.
+ *
+ * This is *not* a cryptographic hash function; do not use it as such!
+ *
+ * [1] Adiantum: length-preserving encryption for entry-level processors
+ *     (https://eprint.iacr.org/2018/720.pdf)
+ * [2] UMAC: Fast and Secure Message Authentication
+ *     (https://fastcrypto.org/umac/umac_proc.pdf)
+ * [3] The Poly1305-AES message-authentication code
+ *     (https://cr.yp.to/mac/poly1305-20050329.pdf)
+ */
+
+#include <asm/unaligned.h>
+#include <crypto/algapi.h>
+#include <crypto/internal/hash.h>
+#include <crypto/nhpoly1305.h>
+#include <linux/crypto.h>
+#include <linux/kernel.h>
+#include <linux/module.h>
+
+static void nh_generic(const u32 *key, const u8 *message, size_t message_len,
+		       __le64 hash[NH_NUM_PASSES])
+{
+	u64 sums[4] = { 0, 0, 0, 0 };
+
+	BUILD_BUG_ON(NH_PAIR_STRIDE != 2);
+	BUILD_BUG_ON(NH_NUM_PASSES != 4);
+
+	while (message_len) {
+		u32 m0 = get_unaligned_le32(message + 0);
+		u32 m1 = get_unaligned_le32(message + 4);
+		u32 m2 = get_unaligned_le32(message + 8);
+		u32 m3 = get_unaligned_le32(message + 12);
+
+		sums[0] += (u64)(u32)(m0 + key[ 0]) * (u32)(m2 + key[ 2]);
+		sums[1] += (u64)(u32)(m0 + key[ 4]) * (u32)(m2 + key[ 6]);
+		sums[2] += (u64)(u32)(m0 + key[ 8]) * (u32)(m2 + key[10]);
+		sums[3] += (u64)(u32)(m0 + key[12]) * (u32)(m2 + key[14]);
+		sums[0] += (u64)(u32)(m1 + key[ 1]) * (u32)(m3 + key[ 3]);
+		sums[1] += (u64)(u32)(m1 + key[ 5]) * (u32)(m3 + key[ 7]);
+		sums[2] += (u64)(u32)(m1 + key[ 9]) * (u32)(m3 + key[11]);
+		sums[3] += (u64)(u32)(m1 + key[13]) * (u32)(m3 + key[15]);
+		key += NH_MESSAGE_UNIT / sizeof(key[0]);
+		message += NH_MESSAGE_UNIT;
+		message_len -= NH_MESSAGE_UNIT;
+	}
+
+	hash[0] = cpu_to_le64(sums[0]);
+	hash[1] = cpu_to_le64(sums[1]);
+	hash[2] = cpu_to_le64(sums[2]);
+	hash[3] = cpu_to_le64(sums[3]);
+}
+
+/* Pass the next NH hash value through Poly1305 */
+static void process_nh_hash_value(struct nhpoly1305_state *state,
+				  const struct nhpoly1305_key *key)
+{
+	BUILD_BUG_ON(NH_HASH_BYTES % POLY1305_BLOCK_SIZE != 0);
+
+	poly1305_core_blocks(&state->poly_state, &key->poly_key, state->nh_hash,
+			     NH_HASH_BYTES / POLY1305_BLOCK_SIZE);
+}
+
+/*
+ * Feed the next portion of the source data, as a whole number of 16-byte
+ * "NH message units", through NH and Poly1305.  Each NH hash is taken over
+ * 1024 bytes, except possibly the final one which is taken over a multiple of
+ * 16 bytes up to 1024.  Also, in the case where data is passed in misaligned
+ * chunks, we combine partial hashes; the end result is the same either way.
+ */
+static void nhpoly1305_units(struct nhpoly1305_state *state,
+			     const struct nhpoly1305_key *key,
+			     const u8 *src, unsigned int srclen, nh_t nh_fn)
+{
+	do {
+		unsigned int bytes;
+
+		if (state->nh_remaining == 0) {
+			/* Starting a new NH message */
+			bytes = min_t(unsigned int, srclen, NH_MESSAGE_BYTES);
+			nh_fn(key->nh_key, src, bytes, state->nh_hash);
+			state->nh_remaining = NH_MESSAGE_BYTES - bytes;
+		} else {
+			/* Continuing a previous NH message */
+			__le64 tmp_hash[NH_NUM_PASSES];
+			unsigned int pos;
+			int i;
+
+			pos = NH_MESSAGE_BYTES - state->nh_remaining;
+			bytes = min(srclen, state->nh_remaining);
+			nh_fn(&key->nh_key[pos / 4], src, bytes, tmp_hash);
+			for (i = 0; i < NH_NUM_PASSES; i++)
+				le64_add_cpu(&state->nh_hash[i],
+					     le64_to_cpu(tmp_hash[i]));
+			state->nh_remaining -= bytes;
+		}
+		if (state->nh_remaining == 0)
+			process_nh_hash_value(state, key);
+		src += bytes;
+		srclen -= bytes;
+	} while (srclen);
+}
+
+int crypto_nhpoly1305_setkey(struct crypto_shash *tfm,
+			     const u8 *key, unsigned int keylen)
+{
+	struct nhpoly1305_key *ctx = crypto_shash_ctx(tfm);
+	int i;
+
+	if (keylen != NHPOLY1305_KEY_SIZE)
+		return -EINVAL;
+
+	poly1305_core_setkey(&ctx->poly_key, key);
+	key += POLY1305_BLOCK_SIZE;
+
+	for (i = 0; i < NH_KEY_WORDS; i++)
+		ctx->nh_key[i] = get_unaligned_le32(key + i * sizeof(u32));
+
+	return 0;
+}
+EXPORT_SYMBOL(crypto_nhpoly1305_setkey);
+
+int crypto_nhpoly1305_init(struct shash_desc *desc)
+{
+	struct nhpoly1305_state *state = shash_desc_ctx(desc);
+
+	poly1305_core_init(&state->poly_state);
+	state->buflen = 0;
+	state->nh_remaining = 0;
+	return 0;
+}
+EXPORT_SYMBOL(crypto_nhpoly1305_init);
+
+int crypto_nhpoly1305_update_helper(struct shash_desc *desc,
+				    const u8 *src, unsigned int srclen,
+				    nh_t nh_fn)
+{
+	struct nhpoly1305_state *state = shash_desc_ctx(desc);
+	const struct nhpoly1305_key *key = crypto_shash_ctx(desc->tfm);
+	unsigned int bytes;
+
+	if (state->buflen) {
+		bytes = min(srclen, (int)NH_MESSAGE_UNIT - state->buflen);
+		memcpy(&state->buffer[state->buflen], src, bytes);
+		state->buflen += bytes;
+		if (state->buflen < NH_MESSAGE_UNIT)
+			return 0;
+		nhpoly1305_units(state, key, state->buffer, NH_MESSAGE_UNIT,
+				 nh_fn);
+		state->buflen = 0;
+		src += bytes;
+		srclen -= bytes;
+	}
+
+	if (srclen >= NH_MESSAGE_UNIT) {
+		bytes = round_down(srclen, NH_MESSAGE_UNIT);
+		nhpoly1305_units(state, key, src, bytes, nh_fn);
+		src += bytes;
+		srclen -= bytes;
+	}
+
+	if (srclen) {
+		memcpy(state->buffer, src, srclen);
+		state->buflen = srclen;
+	}
+	return 0;
+}
+EXPORT_SYMBOL(crypto_nhpoly1305_update_helper);
+
+int crypto_nhpoly1305_update(struct shash_desc *desc,
+			     const u8 *src, unsigned int srclen)
+{
+	return crypto_nhpoly1305_update_helper(desc, src, srclen, nh_generic);
+}
+EXPORT_SYMBOL(crypto_nhpoly1305_update);
+
+int crypto_nhpoly1305_final_helper(struct shash_desc *desc, u8 *dst, nh_t nh_fn)
+{
+	struct nhpoly1305_state *state = shash_desc_ctx(desc);
+	const struct nhpoly1305_key *key = crypto_shash_ctx(desc->tfm);
+
+	if (state->buflen) {
+		memset(&state->buffer[state->buflen], 0,
+		       NH_MESSAGE_UNIT - state->buflen);
+		nhpoly1305_units(state, key, state->buffer, NH_MESSAGE_UNIT,
+				 nh_fn);
+	}
+
+	if (state->nh_remaining)
+		process_nh_hash_value(state, key);
+
+	poly1305_core_emit(&state->poly_state, dst);
+	return 0;
+}
+EXPORT_SYMBOL(crypto_nhpoly1305_final_helper);
+
+int crypto_nhpoly1305_final(struct shash_desc *desc, u8 *dst)
+{
+	return crypto_nhpoly1305_final_helper(desc, dst, nh_generic);
+}
+EXPORT_SYMBOL(crypto_nhpoly1305_final);
+
+static struct shash_alg nhpoly1305_alg = {
+	.base.cra_name		= "nhpoly1305",
+	.base.cra_driver_name	= "nhpoly1305-generic",
+	.base.cra_priority	= 100,
+	.base.cra_ctxsize	= sizeof(struct nhpoly1305_key),
+	.base.cra_module	= THIS_MODULE,
+	.digestsize		= POLY1305_DIGEST_SIZE,
+	.init			= crypto_nhpoly1305_init,
+	.update			= crypto_nhpoly1305_update,
+	.final			= crypto_nhpoly1305_final,
+	.setkey			= crypto_nhpoly1305_setkey,
+	.descsize		= sizeof(struct nhpoly1305_state),
+};
+
+static int __init nhpoly1305_mod_init(void)
+{
+	return crypto_register_shash(&nhpoly1305_alg);
+}
+
+static void __exit nhpoly1305_mod_exit(void)
+{
+	crypto_unregister_shash(&nhpoly1305_alg);
+}
+
+module_init(nhpoly1305_mod_init);
+module_exit(nhpoly1305_mod_exit);
+
+MODULE_DESCRIPTION("NHPoly1305 ε-almost-∆-universal hash function");
+MODULE_LICENSE("GPL v2");
+MODULE_AUTHOR("Eric Biggers <ebiggers@google.com>");
+MODULE_ALIAS_CRYPTO("nhpoly1305");
+MODULE_ALIAS_CRYPTO("nhpoly1305-generic");