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/*
Adapted from chacha-merged.c version 20080118
D. J. Bernstein
Public domain.
modified for use in Plan 9 and Inferno (no algorithmic changes),
and including the changes to block number and nonce defined in RFC7539
*/
#include "os.h"
#include <libsec.h>
enum{
Blockwords= ChachaBsize/sizeof(u32int)
};
/* little-endian data order */
#define GET4(p) ((p)[0]|((p)[1]<<8)|((p)[2]<<16)|((p)[3]<<24))
#define PUT4(p,v) (p)[0]=(v);(p)[1]=(v)>>8;(p)[2]=(v)>>16;(p)[3]=(v)>>24
#define ROTATE(v,c) ((u32int)((v) << (c)) | ((v) >> (32 - (c))))
#define QUARTERROUND(ia,ib,ic,id) { \
u32int a, b, c, d, t; \
a = x[ia]; b = x[ib]; c = x[ic]; d = x[id]; \
a += b; t = d^a; d = ROTATE(t,16); \
c += d; t = b^c; b = ROTATE(t,12); \
a += b; t = d^a; d = ROTATE(t, 8); \
c += d; t = b^c; b = ROTATE(t, 7); \
x[ia] = a; x[ib] = b; x[ic] = c; x[id] = d; \
}
#define ENCRYPT(s, x, y, d) {\
u32int v; \
uchar *sp, *dp; \
sp = (s); \
v = GET4(sp); \
v ^= (x)+(y); \
dp = (d); \
PUT4(dp, v); \
}
static uchar sigma[16] = "expand 32-byte k";
static uchar tau[16] = "expand 16-byte k";
static void
load(u32int *d, uchar *s, int nw)
{
int i;
for(i = 0; i < nw; i++, s+=4)
d[i] = GET4(s);
}
void
setupChachastate(Chachastate *s, uchar *key, ulong keylen, uchar *iv, ulong ivlen, int rounds)
{
if(keylen != 256/8 && keylen != 128/8)
sysfatal("invalid chacha key length");
if(ivlen != 64/8 && ivlen != 96/8
&& ivlen != 128/8 && ivlen != 192/8) /* hchacha, xchacha */
sysfatal("invalid chacha iv length");
if(rounds == 0)
rounds = 20;
s->rounds = rounds;
if(keylen == 256/8) { /* recommended */
load(&s->input[0], sigma, 4);
load(&s->input[4], key, 8);
}else{
load(&s->input[0], tau, 4);
load(&s->input[4], key, 4);
load(&s->input[8], key, 4);
}
s->xkey[0] = s->input[4];
s->xkey[1] = s->input[5];
s->xkey[2] = s->input[6];
s->xkey[3] = s->input[7];
s->xkey[4] = s->input[8];
s->xkey[5] = s->input[9];
s->xkey[6] = s->input[10];
s->xkey[7] = s->input[11];
s->ivwords = ivlen/4;
s->input[12] = 0;
s->input[13] = 0;
if(iv == nil){
s->input[14] = 0;
s->input[15] = 0;
}else
chacha_setiv(s, iv);
}
static void
dorounds(u32int x[Blockwords], int rounds)
{
for(; rounds > 0; rounds -= 2) {
QUARTERROUND(0, 4, 8,12)
QUARTERROUND(1, 5, 9,13)
QUARTERROUND(2, 6,10,14)
QUARTERROUND(3, 7,11,15)
QUARTERROUND(0, 5,10,15)
QUARTERROUND(1, 6,11,12)
QUARTERROUND(2, 7, 8,13)
QUARTERROUND(3, 4, 9,14)
}
}
static void
hchachablock(uchar h[32], Chachastate *s)
{
u32int x[16];
x[0] = s->input[0];
x[1] = s->input[1];
x[2] = s->input[2];
x[3] = s->input[3];
x[4] = s->input[4];
x[5] = s->input[5];
x[6] = s->input[6];
x[7] = s->input[7];
x[8] = s->input[8];
x[9] = s->input[9];
x[10] = s->input[10];
x[11] = s->input[11];
x[12] = s->input[12];
x[13] = s->input[13];
x[14] = s->input[14];
x[15] = s->input[15];
dorounds(x, s->rounds);
PUT4(h+0*4, x[0]);
PUT4(h+1*4, x[1]);
PUT4(h+2*4, x[2]);
PUT4(h+3*4, x[3]);
PUT4(h+4*4, x[12]);
PUT4(h+5*4, x[13]);
PUT4(h+6*4, x[14]);
PUT4(h+7*4, x[15]);
}
void
chacha_setiv(Chachastate *s, uchar *iv)
{
if(s->ivwords == 192/32){
/* xchacha with 192-bit iv */
u32int counter[2];
uchar h[32];
s->input[4] = s->xkey[0];
s->input[5] = s->xkey[1];
s->input[6] = s->xkey[2];
s->input[7] = s->xkey[3];
s->input[8] = s->xkey[4];
s->input[9] = s->xkey[5];
s->input[10] = s->xkey[6];
s->input[11] = s->xkey[7];
counter[0] = s->input[12];
counter[1] = s->input[13];
load(&s->input[12], iv, 4);
hchachablock(h, s);
load(&s->input[4], h, 8);
memset(h, 0, 32);
s->input[12] = counter[0];
s->input[13] = counter[1];
load(&s->input[14], iv+16, 2);
return;
}
load(&s->input[16 - s->ivwords], iv, s->ivwords);
}
void
chacha_setblock(Chachastate *s, u64int blockno)
{
s->input[12] = blockno;
if(s->ivwords != 3)
s->input[13] = blockno>>32;
}
static void
encryptblock(Chachastate *s, uchar *src, uchar *dst)
{
u32int x[Blockwords];
int i;
x[0] = s->input[0];
x[1] = s->input[1];
x[2] = s->input[2];
x[3] = s->input[3];
x[4] = s->input[4];
x[5] = s->input[5];
x[6] = s->input[6];
x[7] = s->input[7];
x[8] = s->input[8];
x[9] = s->input[9];
x[10] = s->input[10];
x[11] = s->input[11];
x[12] = s->input[12];
x[13] = s->input[13];
x[14] = s->input[14];
x[15] = s->input[15];
dorounds(x, s->rounds);
for(i=0; i<nelem(x); i+=4){
ENCRYPT(src, x[i], s->input[i], dst);
ENCRYPT(src+4, x[i+1], s->input[i+1], dst+4);
ENCRYPT(src+8, x[i+2], s->input[i+2], dst+8);
ENCRYPT(src+12, x[i+3], s->input[i+3], dst+12);
src += 16;
dst += 16;
}
if(++s->input[12] == 0 && s->ivwords != 3)
s->input[13]++;
}
void
chacha_encrypt2(uchar *src, uchar *dst, ulong bytes, Chachastate *s)
{
uchar tmp[ChachaBsize];
for(; bytes >= ChachaBsize; bytes -= ChachaBsize){
encryptblock(s, src, dst);
src += ChachaBsize;
dst += ChachaBsize;
}
if(bytes > 0){
memmove(tmp, src, bytes);
encryptblock(s, tmp, tmp);
memmove(dst, tmp, bytes);
}
}
void
chacha_encrypt(uchar *buf, ulong bytes, Chachastate *s)
{
chacha_encrypt2(buf, buf, bytes, s);
}
void
hchacha(uchar h[32], uchar *key, ulong keylen, uchar nonce[16], int rounds)
{
Chachastate s[1];
setupChachastate(s, key, keylen, nonce, 16, rounds);
hchachablock(h, s);
memset(s, 0, sizeof(s));
}
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