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/*
* Copyright 2016 The OpenSSL Project Authors. All Rights Reserved.
*
* Licensed under the OpenSSL license (the "License"). You may not use
* this file except in compliance with the License. You can obtain a copy
* in the file LICENSE in the source distribution or at
* https://www.openssl.org/source/license.html
*/
/*
* This module is meant to be used as template for base 2^44 assembly
* implementation[s]. On side note compiler-generated code is not
* slower than compiler-generated base 2^64 code on [high-end] x86_64,
* even though amount of multiplications is 50% higher. Go figure...
*/
#include <stdlib.h>
typedef unsigned char u8;
typedef unsigned int u32;
typedef unsigned long u64;
typedef unsigned __int128 u128;
typedef struct {
u64 h[3];
u64 s[2];
u64 r[3];
} poly1305_internal;
#define POLY1305_BLOCK_SIZE 16
/* pick 64-bit unsigned integer in little endian order */
static u64 U8TOU64(const unsigned char *p)
{
return (((u64)(p[0] & 0xff)) |
((u64)(p[1] & 0xff) << 8) |
((u64)(p[2] & 0xff) << 16) |
((u64)(p[3] & 0xff) << 24) |
((u64)(p[4] & 0xff) << 32) |
((u64)(p[5] & 0xff) << 40) |
((u64)(p[6] & 0xff) << 48) |
((u64)(p[7] & 0xff) << 56));
}
/* store a 64-bit unsigned integer in little endian */
static void U64TO8(unsigned char *p, u64 v)
{
p[0] = (unsigned char)((v) & 0xff);
p[1] = (unsigned char)((v >> 8) & 0xff);
p[2] = (unsigned char)((v >> 16) & 0xff);
p[3] = (unsigned char)((v >> 24) & 0xff);
p[4] = (unsigned char)((v >> 32) & 0xff);
p[5] = (unsigned char)((v >> 40) & 0xff);
p[6] = (unsigned char)((v >> 48) & 0xff);
p[7] = (unsigned char)((v >> 56) & 0xff);
}
int poly1305_init(void *ctx, const unsigned char key[16])
{
poly1305_internal *st = (poly1305_internal *)ctx;
u64 r0, r1;
/* h = 0 */
st->h[0] = 0;
st->h[1] = 0;
st->h[2] = 0;
r0 = U8TOU64(&key[0]) & 0x0ffffffc0fffffff;
r1 = U8TOU64(&key[8]) & 0x0ffffffc0ffffffc;
/* break r1:r0 to three 44-bit digits, masks are 1<<44-1 */
st->r[0] = r0 & 0x0fffffffffff;
st->r[1] = ((r0 >> 44) | (r1 << 20)) & 0x0fffffffffff;
st->r[2] = (r1 >> 24);
st->s[0] = (st->r[1] + (st->r[1] << 2)) << 2;
st->s[1] = (st->r[2] + (st->r[2] << 2)) << 2;
return 0;
}
void poly1305_blocks(void *ctx, const unsigned char *inp, size_t len,
u32 padbit)
{
poly1305_internal *st = (poly1305_internal *)ctx;
u64 r0, r1, r2;
u64 s1, s2;
u64 h0, h1, h2, c;
u128 d0, d1, d2;
u64 pad = (u64)padbit << 40;
r0 = st->r[0];
r1 = st->r[1];
r2 = st->r[2];
s1 = st->s[0];
s2 = st->s[1];
h0 = st->h[0];
h1 = st->h[1];
h2 = st->h[2];
while (len >= POLY1305_BLOCK_SIZE) {
u64 m0, m1;
m0 = U8TOU64(inp + 0);
m1 = U8TOU64(inp + 8);
/* h += m[i], m[i] is broken to 44-bit digits */
h0 += m0 & 0x0fffffffffff;
h1 += ((m0 >> 44) | (m1 << 20)) & 0x0fffffffffff;
h2 += (m1 >> 24) + pad;
/* h *= r "%" p, where "%" stands for "partial remainder" */
d0 = ((u128)h0 * r0) + ((u128)h1 * s2) + ((u128)h2 * s1);
d1 = ((u128)h0 * r1) + ((u128)h1 * r0) + ((u128)h2 * s2);
d2 = ((u128)h0 * r2) + ((u128)h1 * r1) + ((u128)h2 * r0);
/* "lazy" reduction step */
h0 = (u64)d0 & 0x0fffffffffff;
h1 = (u64)(d1 += (u64)(d0 >> 44)) & 0x0fffffffffff;
h2 = (u64)(d2 += (u64)(d1 >> 44)) & 0x03ffffffffff; /* last 42 bits */
c = (d2 >> 42);
h0 += c + (c << 2);
inp += POLY1305_BLOCK_SIZE;
len -= POLY1305_BLOCK_SIZE;
}
st->h[0] = h0;
st->h[1] = h1;
st->h[2] = h2;
}
void poly1305_emit(void *ctx, unsigned char mac[16], const u32 nonce[4])
{
poly1305_internal *st = (poly1305_internal *) ctx;
u64 h0, h1, h2;
u64 g0, g1, g2;
u128 t;
u64 mask;
h0 = st->h[0];
h1 = st->h[1];
h2 = st->h[2];
/* after "lazy" reduction, convert 44+bit digits to 64-bit ones */
h0 = (u64)(t = (u128)h0 + (h1 << 44)); h1 >>= 20;
h1 = (u64)(t = (u128)h1 + (h2 << 24) + (t >> 64)); h2 >>= 40;
h2 += (u64)(t >> 64);
/* compare to modulus by computing h + -p */
g0 = (u64)(t = (u128)h0 + 5);
g1 = (u64)(t = (u128)h1 + (t >> 64));
g2 = h2 + (u64)(t >> 64);
/* if there was carry into 131st bit, h1:h0 = g1:g0 */
mask = 0 - (g2 >> 2);
g0 &= mask;
g1 &= mask;
mask = ~mask;
h0 = (h0 & mask) | g0;
h1 = (h1 & mask) | g1;
/* mac = (h + nonce) % (2^128) */
h0 = (u64)(t = (u128)h0 + nonce[0] + ((u64)nonce[1]<<32));
h1 = (u64)(t = (u128)h1 + nonce[2] + ((u64)nonce[3]<<32) + (t >> 64));
U64TO8(mac + 0, h0);
U64TO8(mac + 8, h1);
}
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