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+// 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_L ← Poly1305_{K_L}(NH_{K_N}(pad_{128}(L)))
+ *
+ * from the procedure in section 6.4 of the Adiantum paper [1]. It is an
+ * ε-almost-∆-universal (ε-∆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 ε-∆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");