// SPDX-License-Identifier: GPL-2.0
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/*
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* NHPoly1305 - ε-almost-∆-universal hash function for Adiantum
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*
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* Copyright 2018 Google LLC
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*/
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/*
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* "NHPoly1305" is the main component of Adiantum hashing.
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* Specifically, it is the calculation
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*
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* H_L ← Poly1305_{K_L}(NH_{K_N}(pad_{128}(L)))
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*
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* from the procedure in section 6.4 of the Adiantum paper [1]. It is an
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* ε-almost-∆-universal (ε-∆U) hash function for equal-length inputs over
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* Z/(2^{128}Z), where the "∆" operation is addition. It hashes 1024-byte
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* chunks of the input with the NH hash function [2], reducing the input length
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* by 32x. The resulting NH digests are evaluated as a polynomial in
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* GF(2^{130}-5), like in the Poly1305 MAC [3]. Note that the polynomial
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* evaluation by itself would suffice to achieve the ε-∆U property; NH is used
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* for performance since it's over twice as fast as Poly1305.
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*
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* This is *not* a cryptographic hash function; do not use it as such!
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*
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* [1] Adiantum: length-preserving encryption for entry-level processors
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* (https://eprint.iacr.org/2018/720.pdf)
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* [2] UMAC: Fast and Secure Message Authentication
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* (https://fastcrypto.org/umac/umac_proc.pdf)
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* [3] The Poly1305-AES message-authentication code
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* (https://cr.yp.to/mac/poly1305-20050329.pdf)
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*/
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#include <asm/unaligned.h>
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#include <crypto/algapi.h>
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#include <crypto/internal/hash.h>
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#include <crypto/internal/poly1305.h>
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#include <crypto/nhpoly1305.h>
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#include <linux/crypto.h>
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#include <linux/kernel.h>
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#include <linux/module.h>
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static void nh_generic(const u32 *key, const u8 *message, size_t message_len,
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__le64 hash[NH_NUM_PASSES])
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{
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u64 sums[4] = { 0, 0, 0, 0 };
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BUILD_BUG_ON(NH_PAIR_STRIDE != 2);
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BUILD_BUG_ON(NH_NUM_PASSES != 4);
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while (message_len) {
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u32 m0 = get_unaligned_le32(message + 0);
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u32 m1 = get_unaligned_le32(message + 4);
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u32 m2 = get_unaligned_le32(message + 8);
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u32 m3 = get_unaligned_le32(message + 12);
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sums[0] += (u64)(u32)(m0 + key[ 0]) * (u32)(m2 + key[ 2]);
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sums[1] += (u64)(u32)(m0 + key[ 4]) * (u32)(m2 + key[ 6]);
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sums[2] += (u64)(u32)(m0 + key[ 8]) * (u32)(m2 + key[10]);
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sums[3] += (u64)(u32)(m0 + key[12]) * (u32)(m2 + key[14]);
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sums[0] += (u64)(u32)(m1 + key[ 1]) * (u32)(m3 + key[ 3]);
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sums[1] += (u64)(u32)(m1 + key[ 5]) * (u32)(m3 + key[ 7]);
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sums[2] += (u64)(u32)(m1 + key[ 9]) * (u32)(m3 + key[11]);
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sums[3] += (u64)(u32)(m1 + key[13]) * (u32)(m3 + key[15]);
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key += NH_MESSAGE_UNIT / sizeof(key[0]);
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message += NH_MESSAGE_UNIT;
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message_len -= NH_MESSAGE_UNIT;
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}
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hash[0] = cpu_to_le64(sums[0]);
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hash[1] = cpu_to_le64(sums[1]);
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hash[2] = cpu_to_le64(sums[2]);
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hash[3] = cpu_to_le64(sums[3]);
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}
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/* Pass the next NH hash value through Poly1305 */
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static void process_nh_hash_value(struct nhpoly1305_state *state,
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const struct nhpoly1305_key *key)
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{
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BUILD_BUG_ON(NH_HASH_BYTES % POLY1305_BLOCK_SIZE != 0);
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poly1305_core_blocks(&state->poly_state, &key->poly_key, state->nh_hash,
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NH_HASH_BYTES / POLY1305_BLOCK_SIZE, 1);
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}
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/*
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* Feed the next portion of the source data, as a whole number of 16-byte
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* "NH message units", through NH and Poly1305. Each NH hash is taken over
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* 1024 bytes, except possibly the final one which is taken over a multiple of
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* 16 bytes up to 1024. Also, in the case where data is passed in misaligned
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* chunks, we combine partial hashes; the end result is the same either way.
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*/
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static void nhpoly1305_units(struct nhpoly1305_state *state,
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const struct nhpoly1305_key *key,
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const u8 *src, unsigned int srclen, nh_t nh_fn)
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{
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do {
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unsigned int bytes;
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if (state->nh_remaining == 0) {
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/* Starting a new NH message */
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bytes = min_t(unsigned int, srclen, NH_MESSAGE_BYTES);
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nh_fn(key->nh_key, src, bytes, state->nh_hash);
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state->nh_remaining = NH_MESSAGE_BYTES - bytes;
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} else {
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/* Continuing a previous NH message */
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__le64 tmp_hash[NH_NUM_PASSES];
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unsigned int pos;
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int i;
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pos = NH_MESSAGE_BYTES - state->nh_remaining;
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bytes = min(srclen, state->nh_remaining);
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nh_fn(&key->nh_key[pos / 4], src, bytes, tmp_hash);
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for (i = 0; i < NH_NUM_PASSES; i++)
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le64_add_cpu(&state->nh_hash[i],
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le64_to_cpu(tmp_hash[i]));
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state->nh_remaining -= bytes;
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}
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if (state->nh_remaining == 0)
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process_nh_hash_value(state, key);
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src += bytes;
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srclen -= bytes;
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} while (srclen);
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}
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int crypto_nhpoly1305_setkey(struct crypto_shash *tfm,
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const u8 *key, unsigned int keylen)
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{
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struct nhpoly1305_key *ctx = crypto_shash_ctx(tfm);
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int i;
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if (keylen != NHPOLY1305_KEY_SIZE)
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return -EINVAL;
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poly1305_core_setkey(&ctx->poly_key, key);
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key += POLY1305_BLOCK_SIZE;
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for (i = 0; i < NH_KEY_WORDS; i++)
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ctx->nh_key[i] = get_unaligned_le32(key + i * sizeof(u32));
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return 0;
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}
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EXPORT_SYMBOL(crypto_nhpoly1305_setkey);
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int crypto_nhpoly1305_init(struct shash_desc *desc)
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{
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struct nhpoly1305_state *state = shash_desc_ctx(desc);
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poly1305_core_init(&state->poly_state);
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state->buflen = 0;
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state->nh_remaining = 0;
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return 0;
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}
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EXPORT_SYMBOL(crypto_nhpoly1305_init);
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int crypto_nhpoly1305_update_helper(struct shash_desc *desc,
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const u8 *src, unsigned int srclen,
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nh_t nh_fn)
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{
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struct nhpoly1305_state *state = shash_desc_ctx(desc);
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const struct nhpoly1305_key *key = crypto_shash_ctx(desc->tfm);
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unsigned int bytes;
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if (state->buflen) {
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bytes = min(srclen, (int)NH_MESSAGE_UNIT - state->buflen);
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memcpy(&state->buffer[state->buflen], src, bytes);
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state->buflen += bytes;
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if (state->buflen < NH_MESSAGE_UNIT)
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return 0;
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nhpoly1305_units(state, key, state->buffer, NH_MESSAGE_UNIT,
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nh_fn);
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state->buflen = 0;
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src += bytes;
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srclen -= bytes;
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}
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if (srclen >= NH_MESSAGE_UNIT) {
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bytes = round_down(srclen, NH_MESSAGE_UNIT);
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nhpoly1305_units(state, key, src, bytes, nh_fn);
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src += bytes;
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srclen -= bytes;
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}
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if (srclen) {
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memcpy(state->buffer, src, srclen);
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state->buflen = srclen;
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}
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return 0;
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}
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EXPORT_SYMBOL(crypto_nhpoly1305_update_helper);
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int crypto_nhpoly1305_update(struct shash_desc *desc,
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const u8 *src, unsigned int srclen)
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{
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return crypto_nhpoly1305_update_helper(desc, src, srclen, nh_generic);
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}
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EXPORT_SYMBOL(crypto_nhpoly1305_update);
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int crypto_nhpoly1305_final_helper(struct shash_desc *desc, u8 *dst, nh_t nh_fn)
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{
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struct nhpoly1305_state *state = shash_desc_ctx(desc);
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const struct nhpoly1305_key *key = crypto_shash_ctx(desc->tfm);
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if (state->buflen) {
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memset(&state->buffer[state->buflen], 0,
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NH_MESSAGE_UNIT - state->buflen);
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nhpoly1305_units(state, key, state->buffer, NH_MESSAGE_UNIT,
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nh_fn);
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}
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if (state->nh_remaining)
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process_nh_hash_value(state, key);
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poly1305_core_emit(&state->poly_state, NULL, dst);
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return 0;
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}
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EXPORT_SYMBOL(crypto_nhpoly1305_final_helper);
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int crypto_nhpoly1305_final(struct shash_desc *desc, u8 *dst)
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{
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return crypto_nhpoly1305_final_helper(desc, dst, nh_generic);
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}
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EXPORT_SYMBOL(crypto_nhpoly1305_final);
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static struct shash_alg nhpoly1305_alg = {
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.base.cra_name = "nhpoly1305",
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.base.cra_driver_name = "nhpoly1305-generic",
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.base.cra_priority = 100,
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.base.cra_ctxsize = sizeof(struct nhpoly1305_key),
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.base.cra_module = THIS_MODULE,
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.digestsize = POLY1305_DIGEST_SIZE,
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.init = crypto_nhpoly1305_init,
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.update = crypto_nhpoly1305_update,
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.final = crypto_nhpoly1305_final,
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.setkey = crypto_nhpoly1305_setkey,
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.descsize = sizeof(struct nhpoly1305_state),
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};
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static int __init nhpoly1305_mod_init(void)
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{
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return crypto_register_shash(&nhpoly1305_alg);
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}
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static void __exit nhpoly1305_mod_exit(void)
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{
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crypto_unregister_shash(&nhpoly1305_alg);
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}
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subsys_initcall(nhpoly1305_mod_init);
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module_exit(nhpoly1305_mod_exit);
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MODULE_DESCRIPTION("NHPoly1305 ε-almost-∆-universal hash function");
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MODULE_LICENSE("GPL v2");
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MODULE_AUTHOR("Eric Biggers <ebiggers@google.com>");
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MODULE_ALIAS_CRYPTO("nhpoly1305");
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MODULE_ALIAS_CRYPTO("nhpoly1305-generic");
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