ttssh2/ttxssh/poly1305.c

/* Imported from OpenSSH-8.5p1, TeraTerm Project */

/* 
 * Public Domain poly1305 from Andrew Moon
 * poly1305-donna-unrolled.c from https://github.com/floodyberry/poly1305-donna
 */

/* $OpenBSD: poly1305.c,v 1.3 2013/12/19 22:57:13 djm Exp $ */

// #include "includes.h"

#include <sys/types.h>
#ifdef HAVE_STDINT_H
# include <stdint.h>
#endif

#include "poly1305.h"

#define mul32x32_64(a,b) ((uint64_t)(a) * (b))

#define U8TO32_LE(p) \
        (((uint32_t)((p)[0])) | \
         ((uint32_t)((p)[1]) <<  8) | \
         ((uint32_t)((p)[2]) << 16) | \
         ((uint32_t)((p)[3]) << 24))

#define U32TO8_LE(p, v) \
        do { \
                (p)[0] = (uint8_t)((v)); \
                (p)[1] = (uint8_t)((v) >>  8); \
                (p)[2] = (uint8_t)((v) >> 16); \
                (p)[3] = (uint8_t)((v) >> 24); \
        } while (0)

void
poly1305_auth(unsigned char out[POLY1305_TAGLEN], const unsigned char *m, size_t inlen, const unsigned char key[POLY1305_KEYLEN]) {
        uint32_t t0,t1,t2,t3;
        uint32_t h0,h1,h2,h3,h4;
        uint32_t r0,r1,r2,r3,r4;
        uint32_t s1,s2,s3,s4;
        uint32_t b, nb;
        size_t j;
        uint64_t t[5];
        uint64_t f0,f1,f2,f3;
        uint32_t g0,g1,g2,g3,g4;
        uint64_t c;
        unsigned char mp[16];

        /* clamp key */
        t0 = U8TO32_LE(key+0);
        t1 = U8TO32_LE(key+4);
        t2 = U8TO32_LE(key+8);
        t3 = U8TO32_LE(key+12);

        /* precompute multipliers */
        r0 = t0 & 0x3ffffff; t0 >>= 26; t0 |= t1 << 6;
        r1 = t0 & 0x3ffff03; t1 >>= 20; t1 |= t2 << 12;
        r2 = t1 & 0x3ffc0ff; t2 >>= 14; t2 |= t3 << 18;
        r3 = t2 & 0x3f03fff; t3 >>= 8;
        r4 = t3 & 0x00fffff;

        s1 = r1 * 5;
        s2 = r2 * 5;
        s3 = r3 * 5;
        s4 = r4 * 5;

        /* init state */
        h0 = 0;
        h1 = 0;
        h2 = 0;
        h3 = 0;
        h4 = 0;

        /* full blocks */
        if (inlen < 16) goto poly1305_donna_atmost15bytes;
poly1305_donna_16bytes:
        m += 16;
        inlen -= 16;

        t0 = U8TO32_LE(m-16);
        t1 = U8TO32_LE(m-12);
        t2 = U8TO32_LE(m-8);
        t3 = U8TO32_LE(m-4);

        h0 += t0 & 0x3ffffff;
        h1 += ((((uint64_t)t1 << 32) | t0) >> 26) & 0x3ffffff;
        h2 += ((((uint64_t)t2 << 32) | t1) >> 20) & 0x3ffffff;
        h3 += ((((uint64_t)t3 << 32) | t2) >> 14) & 0x3ffffff;
        h4 += (t3 >> 8) | (1 << 24);


poly1305_donna_mul:
        t[0]  = mul32x32_64(h0,r0) + mul32x32_64(h1,s4) + mul32x32_64(h2,s3) + mul32x32_64(h3,s2) + mul32x32_64(h4,s1);
        t[1]  = mul32x32_64(h0,r1) + mul32x32_64(h1,r0) + mul32x32_64(h2,s4) + mul32x32_64(h3,s3) + mul32x32_64(h4,s2);
        t[2]  = mul32x32_64(h0,r2) + mul32x32_64(h1,r1) + mul32x32_64(h2,r0) + mul32x32_64(h3,s4) + mul32x32_64(h4,s3);
        t[3]  = mul32x32_64(h0,r3) + mul32x32_64(h1,r2) + mul32x32_64(h2,r1) + mul32x32_64(h3,r0) + mul32x32_64(h4,s4);
        t[4]  = mul32x32_64(h0,r4) + mul32x32_64(h1,r3) + mul32x32_64(h2,r2) + mul32x32_64(h3,r1) + mul32x32_64(h4,r0);

                        h0 = (uint32_t)t[0] & 0x3ffffff; c =           (t[0] >> 26);
        t[1] += c;      h1 = (uint32_t)t[1] & 0x3ffffff; b = (uint32_t)(t[1] >> 26);
        t[2] += b;      h2 = (uint32_t)t[2] & 0x3ffffff; b = (uint32_t)(t[2] >> 26);
        t[3] += b;      h3 = (uint32_t)t[3] & 0x3ffffff; b = (uint32_t)(t[3] >> 26);
        t[4] += b;      h4 = (uint32_t)t[4] & 0x3ffffff; b = (uint32_t)(t[4] >> 26);
        h0 += b * 5;

        if (inlen >= 16) goto poly1305_donna_16bytes;

        /* final bytes */
poly1305_donna_atmost15bytes:
        if (!inlen) goto poly1305_donna_finish;

        for (j = 0; j < inlen; j++) mp[j] = m[j];
        mp[j++] = 1;
        for (; j < 16; j++)     mp[j] = 0;
        inlen = 0;

        t0 = U8TO32_LE(mp+0);
        t1 = U8TO32_LE(mp+4);
        t2 = U8TO32_LE(mp+8);
        t3 = U8TO32_LE(mp+12);

        h0 += t0 & 0x3ffffff;
        h1 += ((((uint64_t)t1 << 32) | t0) >> 26) & 0x3ffffff;
        h2 += ((((uint64_t)t2 << 32) | t1) >> 20) & 0x3ffffff;
        h3 += ((((uint64_t)t3 << 32) | t2) >> 14) & 0x3ffffff;
        h4 += (t3 >> 8);

        goto poly1305_donna_mul;

poly1305_donna_finish:
                     b = h0 >> 26; h0 = h0 & 0x3ffffff;
        h1 +=     b; b = h1 >> 26; h1 = h1 & 0x3ffffff;
        h2 +=     b; b = h2 >> 26; h2 = h2 & 0x3ffffff;
        h3 +=     b; b = h3 >> 26; h3 = h3 & 0x3ffffff;
        h4 +=     b; b = h4 >> 26; h4 = h4 & 0x3ffffff;
        h0 += b * 5; b = h0 >> 26; h0 = h0 & 0x3ffffff;
        h1 +=     b;

        g0 = h0 + 5; b = g0 >> 26; g0 &= 0x3ffffff;
        g1 = h1 + b; b = g1 >> 26; g1 &= 0x3ffffff;
        g2 = h2 + b; b = g2 >> 26; g2 &= 0x3ffffff;
        g3 = h3 + b; b = g3 >> 26; g3 &= 0x3ffffff;
        g4 = h4 + b - (1 << 26);

        b = (g4 >> 31) - 1;
        nb = ~b;
        h0 = (h0 & nb) | (g0 & b);
        h1 = (h1 & nb) | (g1 & b);
        h2 = (h2 & nb) | (g2 & b);
        h3 = (h3 & nb) | (g3 & b);
        h4 = (h4 & nb) | (g4 & b);

        f0 = ((h0      ) | (h1 << 26)) + (uint64_t)U8TO32_LE(&key[16]);
        f1 = ((h1 >>  6) | (h2 << 20)) + (uint64_t)U8TO32_LE(&key[20]);
        f2 = ((h2 >> 12) | (h3 << 14)) + (uint64_t)U8TO32_LE(&key[24]);
        f3 = ((h3 >> 18) | (h4 <<  8)) + (uint64_t)U8TO32_LE(&key[28]);

        U32TO8_LE(&out[ 0], f0); f1 += (f0 >> 32);
        U32TO8_LE(&out[ 4], f1); f2 += (f1 >> 32);
        U32TO8_LE(&out[ 8], f2); f3 += (f2 >> 32);
        U32TO8_LE(&out[12], f3);
}