ref: d2089f949edd71626e2391672b723aa2d9fbcb9b
dir: /sys/src/libsec/port/poly1305.c/
#include "os.h"
#include <libsec.h>
/*
poly1305 implementation using 32 bit * 32 bit = 64 bit multiplication and 64 bit addition
derived from http://github.com/floodberry/poly1305-donna
*/
#define U8TO32(p) ((u32int)(p)[0] | (u32int)(p)[1]<<8 | (u32int)(p)[2]<<16 | (u32int)(p)[3]<<24)
#define U32TO8(p, v) (p)[0]=(v), (p)[1]=(v)>>8, (p)[2]=(v)>>16, (p)[3]=(v)>>24
/* (r,s) = (key[0:15],key[16:31]), the one time key */
DigestState*
poly1305(uchar *m, ulong len, uchar *key, ulong klen, uchar *digest, DigestState *s)
{
u32int r0,r1,r2,r3,r4, s1,s2,s3,s4, h0,h1,h2,h3,h4, g0,g1,g2,g3,g4;
u64int d0,d1,d2,d3,d4, f;
u32int hibit, mask, c;
if(s == nil){
s = malloc(sizeof(*s));
if(s == nil)
return nil;
memset(s, 0, sizeof(*s));
s->malloced = 1;
}
if(s->seeded == 0){
assert(klen == 32);
/* r &= 0xffffffc0ffffffc0ffffffc0fffffff */
s->state[0] = (U8TO32(&key[ 0]) ) & 0x3ffffff;
s->state[1] = (U8TO32(&key[ 3]) >> 2) & 0x3ffff03;
s->state[2] = (U8TO32(&key[ 6]) >> 4) & 0x3ffc0ff;
s->state[3] = (U8TO32(&key[ 9]) >> 6) & 0x3f03fff;
s->state[4] = (U8TO32(&key[12]) >> 8) & 0x00fffff;
/* h = 0 */
s->state[5] = 0;
s->state[6] = 0;
s->state[7] = 0;
s->state[8] = 0;
s->state[9] = 0;
/* save pad for later */
s->state[10] = U8TO32(&key[16]);
s->state[11] = U8TO32(&key[20]);
s->state[12] = U8TO32(&key[24]);
s->state[13] = U8TO32(&key[28]);
s->seeded = 1;
}
if(s->blen){
c = 16 - s->blen;
if(c > len)
c = len;
memmove(s->buf + s->blen, m, c);
len -= c, m += c;
s->blen += c;
if(s->blen == 16){
s->blen = 0;
poly1305(s->buf, 16, key, klen, nil, s);
} else if(len == 0){
m = s->buf;
len = s->blen;
s->blen = 0;
}
}
r0 = s->state[0];
r1 = s->state[1];
r2 = s->state[2];
r3 = s->state[3];
r4 = s->state[4];
h0 = s->state[5];
h1 = s->state[6];
h2 = s->state[7];
h3 = s->state[8];
h4 = s->state[9];
s1 = r1 * 5;
s2 = r2 * 5;
s3 = r3 * 5;
s4 = r4 * 5;
hibit = 1<<24; /* 1<<128 */
while(len >= 16){
Block:
/* h += m[i] */
h0 += (U8TO32(&m[0]) ) & 0x3ffffff;
h1 += (U8TO32(&m[3]) >> 2) & 0x3ffffff;
h2 += (U8TO32(&m[6]) >> 4) & 0x3ffffff;
h3 += (U8TO32(&m[9]) >> 6) & 0x3ffffff;
h4 += (U8TO32(&m[12])>> 8) | hibit;
/* h *= r */
d0 = ((u64int)h0 * r0) + ((u64int)h1 * s4) + ((u64int)h2 * s3) + ((u64int)h3 * s2) + ((u64int)h4 * s1);
d1 = ((u64int)h0 * r1) + ((u64int)h1 * r0) + ((u64int)h2 * s4) + ((u64int)h3 * s3) + ((u64int)h4 * s2);
d2 = ((u64int)h0 * r2) + ((u64int)h1 * r1) + ((u64int)h2 * r0) + ((u64int)h3 * s4) + ((u64int)h4 * s3);
d3 = ((u64int)h0 * r3) + ((u64int)h1 * r2) + ((u64int)h2 * r1) + ((u64int)h3 * r0) + ((u64int)h4 * s4);
d4 = ((u64int)h0 * r4) + ((u64int)h1 * r3) + ((u64int)h2 * r2) + ((u64int)h3 * r1) + ((u64int)h4 * r0);
/* (partial) h %= p */
c = (u32int)(d0 >> 26); h0 = (u32int)d0 & 0x3ffffff;
d1 += c; c = (u32int)(d1 >> 26); h1 = (u32int)d1 & 0x3ffffff;
d2 += c; c = (u32int)(d2 >> 26); h2 = (u32int)d2 & 0x3ffffff;
d3 += c; c = (u32int)(d3 >> 26); h3 = (u32int)d3 & 0x3ffffff;
d4 += c; c = (u32int)(d4 >> 26); h4 = (u32int)d4 & 0x3ffffff;
h0 += c * 5; c = (h0 >> 26); h0 = h0 & 0x3ffffff;
h1 += c;
len -= 16, m += 16;
}
if(len){
s->blen = len;
memmove(s->buf, m, len);
}
if(digest == nil){
s->state[5] = h0;
s->state[6] = h1;
s->state[7] = h2;
s->state[8] = h3;
s->state[9] = h4;
return s;
}
if(len){
m = s->buf;
m[len++] = 1;
while(len < 16)
m[len++] = 0;
hibit = 0;
goto Block;
}
c = h1 >> 26; h1 = h1 & 0x3ffffff;
h2 += c; c = h2 >> 26; h2 = h2 & 0x3ffffff;
h3 += c; c = h3 >> 26; h3 = h3 & 0x3ffffff;
h4 += c; c = h4 >> 26; h4 = h4 & 0x3ffffff;
h0 += c * 5; c = h0 >> 26; h0 = h0 & 0x3ffffff;
h1 += c;
/* compute h + -p */
g0 = h0 + 5; c = g0 >> 26; g0 &= 0x3ffffff;
g1 = h1 + c; c = g1 >> 26; g1 &= 0x3ffffff;
g2 = h2 + c; c = g2 >> 26; g2 &= 0x3ffffff;
g3 = h3 + c; c = g3 >> 26; g3 &= 0x3ffffff;
g4 = h4 + c - (1 << 26);
/* select h if h < p, or h + -p if h >= p */
mask = (g4 >> 31) - 1;
g0 &= mask;
g1 &= mask;
g2 &= mask;
g3 &= mask;
g4 &= mask;
mask = ~mask;
h0 = (h0 & mask) | g0;
h1 = (h1 & mask) | g1;
h2 = (h2 & mask) | g2;
h3 = (h3 & mask) | g3;
h4 = (h4 & mask) | g4;
/* h = h % (2^128) */
h0 = (h0 ) | (h1 << 26);
h1 = (h1 >> 6) | (h2 << 20);
h2 = (h2 >> 12) | (h3 << 14);
h3 = (h3 >> 18) | (h4 << 8);
/* digest = (h + pad) % (2^128) */
f = (u64int)h0 + s->state[10] ; h0 = (u32int)f;
f = (u64int)h1 + s->state[11] + (f >> 32); h1 = (u32int)f;
f = (u64int)h2 + s->state[12] + (f >> 32); h2 = (u32int)f;
f = (u64int)h3 + s->state[13] + (f >> 32); h3 = (u32int)f;
U32TO8(&digest[0], h0);
U32TO8(&digest[4], h1);
U32TO8(&digest[8], h2);
U32TO8(&digest[12], h3);
if(s->malloced){
memset(s, 0, sizeof(*s));
free(s);
return nil;
}
memset(s, 0, sizeof(*s));
return nil;
}