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/* SPDX-License-Identifier: GPL-2.0
*
* Copyright (C) 2015-2018 Jason A. Donenfeld <Jason@zx2c4.com>. All Rights Reserved.
*
* This is based in part on Andrew Moon's poly1305-donna, which is in the
* public domain.
*/
typedef __uint128_t u128;
struct poly1305_internal {
u64 r[3];
u64 h[3];
u64 s[2];
};
static void poly1305_init_generic(void *ctx, const u8 key[16])
{
struct poly1305_internal *st = (struct poly1305_internal *)ctx;
u64 t0, t1;
/* r &= 0xffffffc0ffffffc0ffffffc0fffffff */
t0 = get_unaligned_le64(&key[0]);
t1 = get_unaligned_le64(&key[8]);
st->r[0] = t0 & 0xffc0fffffff;
st->r[1] = ((t0 >> 44) | (t1 << 20)) & 0xfffffc0ffff;
st->r[2] = ((t1 >> 24)) & 0x00ffffffc0f;
/* s = 20*r */
st->s[0] = st->r[1] * 20;
st->s[1] = st->r[2] * 20;
/* h = 0 */
st->h[0] = 0;
st->h[1] = 0;
st->h[2] = 0;
}
static void poly1305_blocks_generic(void *ctx, const u8 *input, size_t len,
const u32 padbit)
{
struct poly1305_internal *st = (struct poly1305_internal *)ctx;
const u64 hibit = ((u64)padbit) << 40;
u64 r0, r1, r2;
u64 s1, s2;
u64 h0, h1, h2;
u64 c;
u128 d0, d1, d2, d;
r0 = st->r[0];
r1 = st->r[1];
r2 = st->r[2];
h0 = st->h[0];
h1 = st->h[1];
h2 = st->h[2];
s1 = st->s[0];
s2 = st->s[1];
while (len >= POLY1305_BLOCK_SIZE) {
u64 t0, t1;
/* h += m[i] */
t0 = get_unaligned_le64(&input[0]);
t1 = get_unaligned_le64(&input[8]);
h0 += t0 & 0xfffffffffff;
h1 += ((t0 >> 44) | (t1 << 20)) & 0xfffffffffff;
h2 += (((t1 >> 24)) & 0x3ffffffffff) | hibit;
/* h *= r */
d0 = (u128)h0 * r0;
d = (u128)h1 * s2;
d0 += d;
d = (u128)h2 * s1;
d0 += d;
d1 = (u128)h0 * r1;
d = (u128)h1 * r0;
d1 += d;
d = (u128)h2 * s2;
d1 += d;
d2 = (u128)h0 * r2;
d = (u128)h1 * r1;
d2 += d;
d = (u128)h2 * r0;
d2 += d;
/* (partial) h %= p */
c = (u64)(d0 >> 44);
h0 = (u64)d0 & 0xfffffffffff;
d1 += c;
c = (u64)(d1 >> 44);
h1 = (u64)d1 & 0xfffffffffff;
d2 += c;
c = (u64)(d2 >> 42);
h2 = (u64)d2 & 0x3ffffffffff;
h0 += c * 5;
c = h0 >> 44;
h0 = h0 & 0xfffffffffff;
h1 += c;
input += POLY1305_BLOCK_SIZE;
len -= POLY1305_BLOCK_SIZE;
}
st->h[0] = h0;
st->h[1] = h1;
st->h[2] = h2;
}
static void poly1305_emit_generic(void *ctx, u8 mac[16], const u32 nonce[4])
{
struct poly1305_internal *st = (struct poly1305_internal *)ctx;
u64 h0, h1, h2, c;
u64 g0, g1, g2;
u64 t0, t1;
/* fully carry h */
h0 = st->h[0];
h1 = st->h[1];
h2 = st->h[2];
c = h1 >> 44;
h1 &= 0xfffffffffff;
h2 += c;
c = h2 >> 42;
h2 &= 0x3ffffffffff;
h0 += c * 5;
c = h0 >> 44;
h0 &= 0xfffffffffff;
h1 += c;
c = h1 >> 44;
h1 &= 0xfffffffffff;
h2 += c;
c = h2 >> 42;
h2 &= 0x3ffffffffff;
h0 += c * 5;
c = h0 >> 44;
h0 &= 0xfffffffffff;
h1 += c;
/* compute h + -p */
g0 = h0 + 5;
c = g0 >> 44;
g0 &= 0xfffffffffff;
g1 = h1 + c;
c = g1 >> 44;
g1 &= 0xfffffffffff;
g2 = h2 + c - (1ULL << 42);
/* select h if h < p, or h + -p if h >= p */
c = (g2 >> ((sizeof(u64) * 8) - 1)) - 1;
g0 &= c;
g1 &= c;
g2 &= c;
c = ~c;
h0 = (h0 & c) | g0;
h1 = (h1 & c) | g1;
h2 = (h2 & c) | g2;
/* h = (h + nonce) */
t0 = ((u64)nonce[1] << 32) | nonce[0];
t1 = ((u64)nonce[3] << 32) | nonce[2];
h0 += t0 & 0xfffffffffff;
c = h0 >> 44;
h0 &= 0xfffffffffff;
h1 += (((t0 >> 44) | (t1 << 20)) & 0xfffffffffff) + c;
c = h1 >> 44;
h1 &= 0xfffffffffff;
h2 += (((t1 >> 24)) & 0x3ffffffffff) + c;
h2 &= 0x3ffffffffff;
/* mac = h % (2^128) */
h0 = h0 | (h1 << 44);
h1 = (h1 >> 20) | (h2 << 24);
put_unaligned_le64(h0, &mac[0]);
put_unaligned_le64(h1, &mac[8]);
}
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