1// SPDX-License-Identifier: GPL-2.0 OR MIT
2/*
3 * Copyright (C) 2015-2019 Jason A. Donenfeld <Jason@zx2c4.com>. All Rights Reserved.
4 *
5 * This is based in part on Andrew Moon's poly1305-donna, which is in the
6 * public domain.
7 */
8
9#include <linux/kernel.h>
10#include <asm/unaligned.h>
11#include <crypto/internal/poly1305.h>
12
13void poly1305_core_setkey(struct poly1305_core_key *key,
14			  const u8 raw_key[POLY1305_BLOCK_SIZE])
15{
16	/* r &= 0xffffffc0ffffffc0ffffffc0fffffff */
17	key->key.r[0] = (get_unaligned_le32(&raw_key[0])) & 0x3ffffff;
18	key->key.r[1] = (get_unaligned_le32(&raw_key[3]) >> 2) & 0x3ffff03;
19	key->key.r[2] = (get_unaligned_le32(&raw_key[6]) >> 4) & 0x3ffc0ff;
20	key->key.r[3] = (get_unaligned_le32(&raw_key[9]) >> 6) & 0x3f03fff;
21	key->key.r[4] = (get_unaligned_le32(&raw_key[12]) >> 8) & 0x00fffff;
22
23	/* s = 5*r */
24	key->precomputed_s.r[0] = key->key.r[1] * 5;
25	key->precomputed_s.r[1] = key->key.r[2] * 5;
26	key->precomputed_s.r[2] = key->key.r[3] * 5;
27	key->precomputed_s.r[3] = key->key.r[4] * 5;
28}
29EXPORT_SYMBOL(poly1305_core_setkey);
30
31void poly1305_core_blocks(struct poly1305_state *state,
32			  const struct poly1305_core_key *key, const void *src,
33			  unsigned int nblocks, u32 hibit)
34{
35	const u8 *input = src;
36	u32 r0, r1, r2, r3, r4;
37	u32 s1, s2, s3, s4;
38	u32 h0, h1, h2, h3, h4;
39	u64 d0, d1, d2, d3, d4;
40	u32 c;
41
42	if (!nblocks)
43		return;
44
45	hibit <<= 24;
46
47	r0 = key->key.r[0];
48	r1 = key->key.r[1];
49	r2 = key->key.r[2];
50	r3 = key->key.r[3];
51	r4 = key->key.r[4];
52
53	s1 = key->precomputed_s.r[0];
54	s2 = key->precomputed_s.r[1];
55	s3 = key->precomputed_s.r[2];
56	s4 = key->precomputed_s.r[3];
57
58	h0 = state->h[0];
59	h1 = state->h[1];
60	h2 = state->h[2];
61	h3 = state->h[3];
62	h4 = state->h[4];
63
64	do {
65		/* h += m[i] */
66		h0 += (get_unaligned_le32(&input[0])) & 0x3ffffff;
67		h1 += (get_unaligned_le32(&input[3]) >> 2) & 0x3ffffff;
68		h2 += (get_unaligned_le32(&input[6]) >> 4) & 0x3ffffff;
69		h3 += (get_unaligned_le32(&input[9]) >> 6) & 0x3ffffff;
70		h4 += (get_unaligned_le32(&input[12]) >> 8) | hibit;
71
72		/* h *= r */
73		d0 = ((u64)h0 * r0) + ((u64)h1 * s4) +
74		     ((u64)h2 * s3) + ((u64)h3 * s2) +
75		     ((u64)h4 * s1);
76		d1 = ((u64)h0 * r1) + ((u64)h1 * r0) +
77		     ((u64)h2 * s4) + ((u64)h3 * s3) +
78		     ((u64)h4 * s2);
79		d2 = ((u64)h0 * r2) + ((u64)h1 * r1) +
80		     ((u64)h2 * r0) + ((u64)h3 * s4) +
81		     ((u64)h4 * s3);
82		d3 = ((u64)h0 * r3) + ((u64)h1 * r2) +
83		     ((u64)h2 * r1) + ((u64)h3 * r0) +
84		     ((u64)h4 * s4);
85		d4 = ((u64)h0 * r4) + ((u64)h1 * r3) +
86		     ((u64)h2 * r2) + ((u64)h3 * r1) +
87		     ((u64)h4 * r0);
88
89		/* (partial) h %= p */
90		c = (u32)(d0 >> 26);
91		h0 = (u32)d0 & 0x3ffffff;
92		d1 += c;
93		c = (u32)(d1 >> 26);
94		h1 = (u32)d1 & 0x3ffffff;
95		d2 += c;
96		c = (u32)(d2 >> 26);
97		h2 = (u32)d2 & 0x3ffffff;
98		d3 += c;
99		c = (u32)(d3 >> 26);
100		h3 = (u32)d3 & 0x3ffffff;
101		d4 += c;
102		c = (u32)(d4 >> 26);
103		h4 = (u32)d4 & 0x3ffffff;
104		h0 += c * 5;
105		c = (h0 >> 26);
106		h0 = h0 & 0x3ffffff;
107		h1 += c;
108
109		input += POLY1305_BLOCK_SIZE;
110	} while (--nblocks);
111
112	state->h[0] = h0;
113	state->h[1] = h1;
114	state->h[2] = h2;
115	state->h[3] = h3;
116	state->h[4] = h4;
117}
118EXPORT_SYMBOL(poly1305_core_blocks);
119
120void poly1305_core_emit(const struct poly1305_state *state, const u32 nonce[4],
121			void *dst)
122{
123	u8 *mac = dst;
124	u32 h0, h1, h2, h3, h4, c;
125	u32 g0, g1, g2, g3, g4;
126	u64 f;
127	u32 mask;
128
129	/* fully carry h */
130	h0 = state->h[0];
131	h1 = state->h[1];
132	h2 = state->h[2];
133	h3 = state->h[3];
134	h4 = state->h[4];
135
136	c = h1 >> 26;
137	h1 = h1 & 0x3ffffff;
138	h2 += c;
139	c = h2 >> 26;
140	h2 = h2 & 0x3ffffff;
141	h3 += c;
142	c = h3 >> 26;
143	h3 = h3 & 0x3ffffff;
144	h4 += c;
145	c = h4 >> 26;
146	h4 = h4 & 0x3ffffff;
147	h0 += c * 5;
148	c = h0 >> 26;
149	h0 = h0 & 0x3ffffff;
150	h1 += c;
151
152	/* compute h + -p */
153	g0 = h0 + 5;
154	c = g0 >> 26;
155	g0 &= 0x3ffffff;
156	g1 = h1 + c;
157	c = g1 >> 26;
158	g1 &= 0x3ffffff;
159	g2 = h2 + c;
160	c = g2 >> 26;
161	g2 &= 0x3ffffff;
162	g3 = h3 + c;
163	c = g3 >> 26;
164	g3 &= 0x3ffffff;
165	g4 = h4 + c - (1UL << 26);
166
167	/* select h if h < p, or h + -p if h >= p */
168	mask = (g4 >> ((sizeof(u32) * 8) - 1)) - 1;
169	g0 &= mask;
170	g1 &= mask;
171	g2 &= mask;
172	g3 &= mask;
173	g4 &= mask;
174	mask = ~mask;
175
176	h0 = (h0 & mask) | g0;
177	h1 = (h1 & mask) | g1;
178	h2 = (h2 & mask) | g2;
179	h3 = (h3 & mask) | g3;
180	h4 = (h4 & mask) | g4;
181
182	/* h = h % (2^128) */
183	h0 = ((h0) | (h1 << 26)) & 0xffffffff;
184	h1 = ((h1 >> 6) | (h2 << 20)) & 0xffffffff;
185	h2 = ((h2 >> 12) | (h3 << 14)) & 0xffffffff;
186	h3 = ((h3 >> 18) | (h4 << 8)) & 0xffffffff;
187
188	if (likely(nonce)) {
189		/* mac = (h + nonce) % (2^128) */
190		f = (u64)h0 + nonce[0];
191		h0 = (u32)f;
192		f = (u64)h1 + nonce[1] + (f >> 32);
193		h1 = (u32)f;
194		f = (u64)h2 + nonce[2] + (f >> 32);
195		h2 = (u32)f;
196		f = (u64)h3 + nonce[3] + (f >> 32);
197		h3 = (u32)f;
198	}
199
200	put_unaligned_le32(h0, &mac[0]);
201	put_unaligned_le32(h1, &mac[4]);
202	put_unaligned_le32(h2, &mac[8]);
203	put_unaligned_le32(h3, &mac[12]);
204}
205EXPORT_SYMBOL(poly1305_core_emit);
206