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/*
poly1305 implementation using 64 bit * 64 bit = 128 bit multiplication and 128 bit addition
*/
#define POLY1305_IMPLEMENTATION_NAME "donna64"
#if defined(__SIZEOF_INT128__)
typedef unsigned __int128 uint128_t;
#else
typedef unsigned uint128_t __attribute__((mode(TI)));
#endif
#define MUL(out, x, y) out = ((uint128_t)x * y)
#define ADD(out, in) out += in
#define ADDLO(out, in) out += in
#define SHR(in, shift) (unsigned long long)(in >> (shift))
#define LO(in) (unsigned long long)(in)
#define POLY1305_NOINLINE __attribute__((noinline))
#define poly1305_block_size 16
/* 17 + sizeof(unsigned long long) + 8*sizeof(unsigned long long) */
typedef struct poly1305_state_internal_t {
unsigned long long r[3];
unsigned long long h[3];
unsigned long long pad[2];
unsigned long long leftover;
unsigned char buffer[poly1305_block_size];
unsigned char final;
} poly1305_state_internal_t;
/* interpret eight 8 bit unsigned integers as a 64 bit unsigned integer in little endian */
static unsigned long long
U8TO64(const unsigned char *p) {
return
(((unsigned long long)(p[0] & 0xff) ) |
((unsigned long long)(p[1] & 0xff) << 8) |
((unsigned long long)(p[2] & 0xff) << 16) |
((unsigned long long)(p[3] & 0xff) << 24) |
((unsigned long long)(p[4] & 0xff) << 32) |
((unsigned long long)(p[5] & 0xff) << 40) |
((unsigned long long)(p[6] & 0xff) << 48) |
((unsigned long long)(p[7] & 0xff) << 56));
}
/* store a 64 bit unsigned integer as eight 8 bit unsigned integers in little endian */
static void
U64TO8(unsigned char *p, unsigned long long v) {
p[0] = (v ) & 0xff;
p[1] = (v >> 8) & 0xff;
p[2] = (v >> 16) & 0xff;
p[3] = (v >> 24) & 0xff;
p[4] = (v >> 32) & 0xff;
p[5] = (v >> 40) & 0xff;
p[6] = (v >> 48) & 0xff;
p[7] = (v >> 56) & 0xff;
}
static void
poly1305_init(poly1305_context *ctx, const unsigned char key[32]) {
poly1305_state_internal_t *st = (poly1305_state_internal_t *)(void *)ctx;
unsigned long long t0,t1;
/* r &= 0xffffffc0ffffffc0ffffffc0fffffff */
t0 = U8TO64(&key[0]);
t1 = U8TO64(&key[8]);
st->r[0] = ( t0 ) & 0xffc0fffffff;
st->r[1] = ((t0 >> 44) | (t1 << 20)) & 0xfffffc0ffff;
st->r[2] = ((t1 >> 24) ) & 0x00ffffffc0f;
/* h = 0 */
st->h[0] = 0;
st->h[1] = 0;
st->h[2] = 0;
/* save pad for later */
st->pad[0] = U8TO64(&key[16]);
st->pad[1] = U8TO64(&key[24]);
st->leftover = 0;
st->final = 0;
}
static void
poly1305_blocks(poly1305_state_internal_t *st, const unsigned char *m, unsigned long long bytes) {
const unsigned long long hibit = (st->final) ? 0 : ((unsigned long long)1 << 40); /* 1 << 128 */
unsigned long long r0,r1,r2;
unsigned long long s1,s2;
unsigned long long h0,h1,h2;
unsigned long long c;
uint128_t 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 = r1 * (5 << 2);
s2 = r2 * (5 << 2);
while (bytes >= poly1305_block_size) {
unsigned long long t0,t1;
/* h += m[i] */
t0 = U8TO64(&m[0]);
t1 = U8TO64(&m[8]);
h0 += (( t0 ) & 0xfffffffffff);
h1 += (((t0 >> 44) | (t1 << 20)) & 0xfffffffffff);
h2 += (((t1 >> 24) ) & 0x3ffffffffff) | hibit;
/* h *= r */
MUL(d0, h0, r0); MUL(d, h1, s2); ADD(d0, d); MUL(d, h2, s1); ADD(d0, d);
MUL(d1, h0, r1); MUL(d, h1, r0); ADD(d1, d); MUL(d, h2, s2); ADD(d1, d);
MUL(d2, h0, r2); MUL(d, h1, r1); ADD(d2, d); MUL(d, h2, r0); ADD(d2, d);
/* (partial) h %= p */
c = SHR(d0, 44); h0 = LO(d0) & 0xfffffffffff;
ADDLO(d1, c); c = SHR(d1, 44); h1 = LO(d1) & 0xfffffffffff;
ADDLO(d2, c); c = SHR(d2, 42); h2 = LO(d2) & 0x3ffffffffff;
h0 += c * 5; c = (h0 >> 44); h0 = h0 & 0xfffffffffff;
h1 += c;
m += poly1305_block_size;
bytes -= poly1305_block_size;
}
st->h[0] = h0;
st->h[1] = h1;
st->h[2] = h2;
}
static POLY1305_NOINLINE void
poly1305_finish(poly1305_context *ctx, unsigned char mac[16]) {
poly1305_state_internal_t *st = (poly1305_state_internal_t *)(void *)ctx;
unsigned long long h0,h1,h2,c;
unsigned long long g0,g1,g2;
unsigned long long t0,t1;
/* process the remaining block */
if (st->leftover) {
unsigned long long i = st->leftover;
st->buffer[i] = 1;
for (i = i + 1; i < poly1305_block_size; i++)
st->buffer[i] = 0;
st->final = 1;
poly1305_blocks(st, st->buffer, poly1305_block_size);
}
/* 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 - ((unsigned long long)1 << 42);
/* select h if h < p, or h + -p if h >= p */
c = (g2 >> ((sizeof(unsigned long long) * 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 + pad) */
t0 = st->pad[0];
t1 = st->pad[1];
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));
U64TO8(&mac[0], h0);
U64TO8(&mac[8], h1);
/* zero out the state */
sodium_memzero((void *)st, sizeof *st);
}
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