// SPDX-License-Identifier: GPL-2.0 OR MIT
/*
 * Copyright (C) 2015-2019 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.
 */

#include <crypto/internal/poly1305.h>
#include <linux/export.h>
#include <linux/kernel.h>
#include <linux/unaligned.h>

void poly1305_core_setkey(struct poly1305_core_key *key,
                          const u8 raw_key[POLY1305_BLOCK_SIZE])
{
        u64 t0, t1;

        /* r &= 0xffffffc0ffffffc0ffffffc0fffffff */
        t0 = get_unaligned_le64(&raw_key[0]);
        t1 = get_unaligned_le64(&raw_key[8]);

        key->key.r64[0] = t0 & 0xffc0fffffffULL;
        key->key.r64[1] = ((t0 >> 44) | (t1 << 20)) & 0xfffffc0ffffULL;
        key->key.r64[2] = ((t1 >> 24)) & 0x00ffffffc0fULL;

        /* s = 20*r */
        key->precomputed_s.r64[0] = key->key.r64[1] * 20;
        key->precomputed_s.r64[1] = key->key.r64[2] * 20;
}
EXPORT_SYMBOL(poly1305_core_setkey);

void poly1305_core_blocks(struct poly1305_state *state,
                          const struct poly1305_core_key *key, const void *src,
                          unsigned int nblocks, u32 hibit)
{
        const u8 *input = src;
        u64 hibit64;
        u64 r0, r1, r2;
        u64 s1, s2;
        u64 h0, h1, h2;
        u64 c;
        u128 d0, d1, d2, d;

        if (!nblocks)
                return;

        hibit64 = ((u64)hibit) << 40;

        r0 = key->key.r64[0];
        r1 = key->key.r64[1];
        r2 = key->key.r64[2];

        h0 = state->h64[0];
        h1 = state->h64[1];
        h2 = state->h64[2];

        s1 = key->precomputed_s.r64[0];
        s2 = key->precomputed_s.r64[1];

        do {
                u64 t0, t1;

                /* h += m[i] */
                t0 = get_unaligned_le64(&input[0]);
                t1 = get_unaligned_le64(&input[8]);

                h0 += t0 & 0xfffffffffffULL;
                h1 += ((t0 >> 44) | (t1 << 20)) & 0xfffffffffffULL;
                h2 += (((t1 >> 24)) & 0x3ffffffffffULL) | hibit64;

                /* 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 & 0xfffffffffffULL;
                d1 += c;
                c = (u64)(d1 >> 44);
                h1 = (u64)d1 & 0xfffffffffffULL;
                d2 += c;
                c = (u64)(d2 >> 42);
                h2 = (u64)d2 & 0x3ffffffffffULL;
                h0 += c * 5;
                c = h0 >> 44;
                h0 = h0 & 0xfffffffffffULL;
                h1 += c;

                input += POLY1305_BLOCK_SIZE;
        } while (--nblocks);

        state->h64[0] = h0;
        state->h64[1] = h1;
        state->h64[2] = h2;
}
EXPORT_SYMBOL(poly1305_core_blocks);

void poly1305_core_emit(const struct poly1305_state *state, const u32 nonce[4],
                        void *dst)
{
        u8 *mac = dst;
        u64 h0, h1, h2, c;
        u64 g0, g1, g2;
        u64 t0, t1;

        /* fully carry h */
        h0 = state->h64[0];
        h1 = state->h64[1];
        h2 = state->h64[2];

        c = h1 >> 44;
        h1 &= 0xfffffffffffULL;
        h2 += c;
        c = h2 >> 42;
        h2 &= 0x3ffffffffffULL;
        h0 += c * 5;
        c = h0 >> 44;
        h0 &= 0xfffffffffffULL;
        h1 += c;
        c = h1 >> 44;
        h1 &= 0xfffffffffffULL;
        h2 += c;
        c = h2 >> 42;
        h2 &= 0x3ffffffffffULL;
        h0 += c * 5;
        c = h0 >> 44;
        h0 &= 0xfffffffffffULL;
        h1 += c;

        /* compute h + -p */
        g0 = h0 + 5;
        c  = g0 >> 44;
        g0 &= 0xfffffffffffULL;
        g1 = h1 + c;
        c  = g1 >> 44;
        g1 &= 0xfffffffffffULL;
        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;

        if (likely(nonce)) {
                /* h = (h + nonce) */
                t0 = ((u64)nonce[1] << 32) | nonce[0];
                t1 = ((u64)nonce[3] << 32) | nonce[2];

                h0 += t0 & 0xfffffffffffULL;
                c = h0 >> 44;
                h0 &= 0xfffffffffffULL;
                h1 += (((t0 >> 44) | (t1 << 20)) & 0xfffffffffffULL) + c;
                c = h1 >> 44;
                h1 &= 0xfffffffffffULL;
                h2 += (((t1 >> 24)) & 0x3ffffffffffULL) + c;
                h2 &= 0x3ffffffffffULL;
        }

        /* 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]);
}
EXPORT_SYMBOL(poly1305_core_emit);