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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)[3]<<8) | (p)[2])<<8) | (p)[1])<<8 | (p)[0])
#define PUT4(p, v) (((p)[0]=v), (v>>=8), ((p)[1]=v), (v>>=8), ((p)[2]=v), (v>>=8), ((p)[3]=v))
#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 != 96/8 && ivlen != 64/8)
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->ivwords = ivlen/sizeof(u32int);
s->input[12] = 0;
s->input[13] = 0;
if(iv == nil){
s->input[14] = 0;
s->input[15] = 0;
}else
chacha_setiv(s, iv);
}
void
chacha_setiv(Chachastate *s, uchar *iv)
{
load(&s->input[16 - s->ivwords], iv, s->ivwords);
}
void
chacha_setblock(Chachastate *s, u64int blockno)
{
s->input[12] = blockno;
if(s->ivwords == 2)
s->input[13] = blockno>>32;
}
static void
encryptblock(Chachastate *s, uchar *src, uchar *dst)
{
u32int x[Blockwords];
int i, rounds;
rounds = s->rounds;
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];
for(i = rounds; i > 0; i -= 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)
}
#ifdef FULL_UNROLL
ENCRYPT(src+0*4, x[0], s->input[0], dst+0*4);
ENCRYPT(src+1*4, x[1], s->input[1], dst+1*4);
ENCRYPT(src+2*4, x[2], s->input[2], dst+2*4);
ENCRYPT(src+3*4, x[3], s->input[3], dst+3*4);
ENCRYPT(src+4*4, x[4], s->input[4], dst+4*4);
ENCRYPT(src+5*4, x[5], s->input[5], dst+5*4);
ENCRYPT(src+6*4, x[6], s->input[6], dst+6*4);
ENCRYPT(src+7*4, x[7], s->input[7], dst+7*4);
ENCRYPT(src+8*4, x[8], s->input[8], dst+8*4);
ENCRYPT(src+9*4, x[9], s->input[9], dst+9*4);
ENCRYPT(src+10*4, x[10], s->input[10], dst+10*4);
ENCRYPT(src+11*4, x[11], s->input[11], dst+11*4);
ENCRYPT(src+12*4, x[12], s->input[12], dst+12*4);
ENCRYPT(src+13*4, x[13], s->input[13], dst+13*4);
ENCRYPT(src+14*4, x[14], s->input[14], dst+14*4);
ENCRYPT(src+15*4, x[15], s->input[15], dst+15*4);
#else
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;
}
#endif
if(++s->input[12] == 0 && s->ivwords == 2)
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);
}
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