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Linux/crypto/nhpoly1305.c

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  1 // SPDX-License-Identifier: GPL-2.0
  2 /*
  3  * NHPoly1305 - ε-almost-∆-universal hash function for Adiantum
  4  *
  5  * Copyright 2018 Google LLC
  6  */
  7 
  8 /*
  9  * "NHPoly1305" is the main component of Adiantum hashing.
 10  * Specifically, it is the calculation
 11  *
 12  *      H_L ← Poly1305_{K_L}(NH_{K_N}(pad_{128}(L)))
 13  *
 14  * from the procedure in section 6.4 of the Adiantum paper [1].  It is an
 15  * ε-almost-∆-universal (ε-∆U) hash function for equal-length inputs over
 16  * Z/(2^{128}Z), where the "∆" operation is addition.  It hashes 1024-byte
 17  * chunks of the input with the NH hash function [2], reducing the input length
 18  * by 32x.  The resulting NH digests are evaluated as a polynomial in
 19  * GF(2^{130}-5), like in the Poly1305 MAC [3].  Note that the polynomial
 20  * evaluation by itself would suffice to achieve the ε-∆U property; NH is used
 21  * for performance since it's over twice as fast as Poly1305.
 22  *
 23  * This is *not* a cryptographic hash function; do not use it as such!
 24  *
 25  * [1] Adiantum: length-preserving encryption for entry-level processors
 26  *     (https://eprint.iacr.org/2018/720.pdf)
 27  * [2] UMAC: Fast and Secure Message Authentication
 28  *     (https://fastcrypto.org/umac/umac_proc.pdf)
 29  * [3] The Poly1305-AES message-authentication code
 30  *     (https://cr.yp.to/mac/poly1305-20050329.pdf)
 31  */
 32 
 33 #include <asm/unaligned.h>
 34 #include <crypto/algapi.h>
 35 #include <crypto/internal/hash.h>
 36 #include <crypto/internal/poly1305.h>
 37 #include <crypto/nhpoly1305.h>
 38 #include <linux/crypto.h>
 39 #include <linux/kernel.h>
 40 #include <linux/module.h>
 41 
 42 static void nh_generic(const u32 *key, const u8 *message, size_t message_len,
 43                        __le64 hash[NH_NUM_PASSES])
 44 {
 45         u64 sums[4] = { 0, 0, 0, 0 };
 46 
 47         BUILD_BUG_ON(NH_PAIR_STRIDE != 2);
 48         BUILD_BUG_ON(NH_NUM_PASSES != 4);
 49 
 50         while (message_len) {
 51                 u32 m0 = get_unaligned_le32(message + 0);
 52                 u32 m1 = get_unaligned_le32(message + 4);
 53                 u32 m2 = get_unaligned_le32(message + 8);
 54                 u32 m3 = get_unaligned_le32(message + 12);
 55 
 56                 sums[0] += (u64)(u32)(m0 + key[ 0]) * (u32)(m2 + key[ 2]);
 57                 sums[1] += (u64)(u32)(m0 + key[ 4]) * (u32)(m2 + key[ 6]);
 58                 sums[2] += (u64)(u32)(m0 + key[ 8]) * (u32)(m2 + key[10]);
 59                 sums[3] += (u64)(u32)(m0 + key[12]) * (u32)(m2 + key[14]);
 60                 sums[0] += (u64)(u32)(m1 + key[ 1]) * (u32)(m3 + key[ 3]);
 61                 sums[1] += (u64)(u32)(m1 + key[ 5]) * (u32)(m3 + key[ 7]);
 62                 sums[2] += (u64)(u32)(m1 + key[ 9]) * (u32)(m3 + key[11]);
 63                 sums[3] += (u64)(u32)(m1 + key[13]) * (u32)(m3 + key[15]);
 64                 key += NH_MESSAGE_UNIT / sizeof(key[0]);
 65                 message += NH_MESSAGE_UNIT;
 66                 message_len -= NH_MESSAGE_UNIT;
 67         }
 68 
 69         hash[0] = cpu_to_le64(sums[0]);
 70         hash[1] = cpu_to_le64(sums[1]);
 71         hash[2] = cpu_to_le64(sums[2]);
 72         hash[3] = cpu_to_le64(sums[3]);
 73 }
 74 
 75 /* Pass the next NH hash value through Poly1305 */
 76 static void process_nh_hash_value(struct nhpoly1305_state *state,
 77                                   const struct nhpoly1305_key *key)
 78 {
 79         BUILD_BUG_ON(NH_HASH_BYTES % POLY1305_BLOCK_SIZE != 0);
 80 
 81         poly1305_core_blocks(&state->poly_state, &key->poly_key, state->nh_hash,
 82                              NH_HASH_BYTES / POLY1305_BLOCK_SIZE, 1);
 83 }
 84 
 85 /*
 86  * Feed the next portion of the source data, as a whole number of 16-byte
 87  * "NH message units", through NH and Poly1305.  Each NH hash is taken over
 88  * 1024 bytes, except possibly the final one which is taken over a multiple of
 89  * 16 bytes up to 1024.  Also, in the case where data is passed in misaligned
 90  * chunks, we combine partial hashes; the end result is the same either way.
 91  */
 92 static void nhpoly1305_units(struct nhpoly1305_state *state,
 93                              const struct nhpoly1305_key *key,
 94                              const u8 *src, unsigned int srclen, nh_t nh_fn)
 95 {
 96         do {
 97                 unsigned int bytes;
 98 
 99                 if (state->nh_remaining == 0) {
100                         /* Starting a new NH message */
101                         bytes = min_t(unsigned int, srclen, NH_MESSAGE_BYTES);
102                         nh_fn(key->nh_key, src, bytes, state->nh_hash);
103                         state->nh_remaining = NH_MESSAGE_BYTES - bytes;
104                 } else {
105                         /* Continuing a previous NH message */
106                         __le64 tmp_hash[NH_NUM_PASSES];
107                         unsigned int pos;
108                         int i;
109 
110                         pos = NH_MESSAGE_BYTES - state->nh_remaining;
111                         bytes = min(srclen, state->nh_remaining);
112                         nh_fn(&key->nh_key[pos / 4], src, bytes, tmp_hash);
113                         for (i = 0; i < NH_NUM_PASSES; i++)
114                                 le64_add_cpu(&state->nh_hash[i],
115                                              le64_to_cpu(tmp_hash[i]));
116                         state->nh_remaining -= bytes;
117                 }
118                 if (state->nh_remaining == 0)
119                         process_nh_hash_value(state, key);
120                 src += bytes;
121                 srclen -= bytes;
122         } while (srclen);
123 }
124 
125 int crypto_nhpoly1305_setkey(struct crypto_shash *tfm,
126                              const u8 *key, unsigned int keylen)
127 {
128         struct nhpoly1305_key *ctx = crypto_shash_ctx(tfm);
129         int i;
130 
131         if (keylen != NHPOLY1305_KEY_SIZE)
132                 return -EINVAL;
133 
134         poly1305_core_setkey(&ctx->poly_key, key);
135         key += POLY1305_BLOCK_SIZE;
136 
137         for (i = 0; i < NH_KEY_WORDS; i++)
138                 ctx->nh_key[i] = get_unaligned_le32(key + i * sizeof(u32));
139 
140         return 0;
141 }
142 EXPORT_SYMBOL(crypto_nhpoly1305_setkey);
143 
144 int crypto_nhpoly1305_init(struct shash_desc *desc)
145 {
146         struct nhpoly1305_state *state = shash_desc_ctx(desc);
147 
148         poly1305_core_init(&state->poly_state);
149         state->buflen = 0;
150         state->nh_remaining = 0;
151         return 0;
152 }
153 EXPORT_SYMBOL(crypto_nhpoly1305_init);
154 
155 int crypto_nhpoly1305_update_helper(struct shash_desc *desc,
156                                     const u8 *src, unsigned int srclen,
157                                     nh_t nh_fn)
158 {
159         struct nhpoly1305_state *state = shash_desc_ctx(desc);
160         const struct nhpoly1305_key *key = crypto_shash_ctx(desc->tfm);
161         unsigned int bytes;
162 
163         if (state->buflen) {
164                 bytes = min(srclen, (int)NH_MESSAGE_UNIT - state->buflen);
165                 memcpy(&state->buffer[state->buflen], src, bytes);
166                 state->buflen += bytes;
167                 if (state->buflen < NH_MESSAGE_UNIT)
168                         return 0;
169                 nhpoly1305_units(state, key, state->buffer, NH_MESSAGE_UNIT,
170                                  nh_fn);
171                 state->buflen = 0;
172                 src += bytes;
173                 srclen -= bytes;
174         }
175 
176         if (srclen >= NH_MESSAGE_UNIT) {
177                 bytes = round_down(srclen, NH_MESSAGE_UNIT);
178                 nhpoly1305_units(state, key, src, bytes, nh_fn);
179                 src += bytes;
180                 srclen -= bytes;
181         }
182 
183         if (srclen) {
184                 memcpy(state->buffer, src, srclen);
185                 state->buflen = srclen;
186         }
187         return 0;
188 }
189 EXPORT_SYMBOL(crypto_nhpoly1305_update_helper);
190 
191 int crypto_nhpoly1305_update(struct shash_desc *desc,
192                              const u8 *src, unsigned int srclen)
193 {
194         return crypto_nhpoly1305_update_helper(desc, src, srclen, nh_generic);
195 }
196 EXPORT_SYMBOL(crypto_nhpoly1305_update);
197 
198 int crypto_nhpoly1305_final_helper(struct shash_desc *desc, u8 *dst, nh_t nh_fn)
199 {
200         struct nhpoly1305_state *state = shash_desc_ctx(desc);
201         const struct nhpoly1305_key *key = crypto_shash_ctx(desc->tfm);
202 
203         if (state->buflen) {
204                 memset(&state->buffer[state->buflen], 0,
205                        NH_MESSAGE_UNIT - state->buflen);
206                 nhpoly1305_units(state, key, state->buffer, NH_MESSAGE_UNIT,
207                                  nh_fn);
208         }
209 
210         if (state->nh_remaining)
211                 process_nh_hash_value(state, key);
212 
213         poly1305_core_emit(&state->poly_state, NULL, dst);
214         return 0;
215 }
216 EXPORT_SYMBOL(crypto_nhpoly1305_final_helper);
217 
218 int crypto_nhpoly1305_final(struct shash_desc *desc, u8 *dst)
219 {
220         return crypto_nhpoly1305_final_helper(desc, dst, nh_generic);
221 }
222 EXPORT_SYMBOL(crypto_nhpoly1305_final);
223 
224 static struct shash_alg nhpoly1305_alg = {
225         .base.cra_name          = "nhpoly1305",
226         .base.cra_driver_name   = "nhpoly1305-generic",
227         .base.cra_priority      = 100,
228         .base.cra_ctxsize       = sizeof(struct nhpoly1305_key),
229         .base.cra_module        = THIS_MODULE,
230         .digestsize             = POLY1305_DIGEST_SIZE,
231         .init                   = crypto_nhpoly1305_init,
232         .update                 = crypto_nhpoly1305_update,
233         .final                  = crypto_nhpoly1305_final,
234         .setkey                 = crypto_nhpoly1305_setkey,
235         .descsize               = sizeof(struct nhpoly1305_state),
236 };
237 
238 static int __init nhpoly1305_mod_init(void)
239 {
240         return crypto_register_shash(&nhpoly1305_alg);
241 }
242 
243 static void __exit nhpoly1305_mod_exit(void)
244 {
245         crypto_unregister_shash(&nhpoly1305_alg);
246 }
247 
248 subsys_initcall(nhpoly1305_mod_init);
249 module_exit(nhpoly1305_mod_exit);
250 
251 MODULE_DESCRIPTION("NHPoly1305 ε-almost-∆-universal hash function");
252 MODULE_LICENSE("GPL v2");
253 MODULE_AUTHOR("Eric Biggers <ebiggers@google.com>");
254 MODULE_ALIAS_CRYPTO("nhpoly1305");
255 MODULE_ALIAS_CRYPTO("nhpoly1305-generic");
256 

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