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#include "u.h"
#include "../port/lib.h"
#include "mem.h"
#include "dat.h"
#include "fns.h"
#include "../port/error.h"
#include <libsec.h>
/* machine specific hardware random number generator */
void (*hwrandbuf)(void*, ulong) = nil;
static struct
{
QLock;
Chachastate;
} *rs;
typedef struct Seedbuf Seedbuf;
struct Seedbuf
{
ulong randomcount;
uchar buf[64];
uchar nbuf;
uchar next;
ushort bits;
SHA2_512state ds;
};
static void
randomsample(Ureg*, Timer *t)
{
Seedbuf *s = t->ta;
if(s->randomcount == 0 || s->nbuf >= sizeof(s->buf))
return;
s->bits = (s->bits<<2) ^ s->randomcount;
s->randomcount = 0;
if(++s->next < 8/2)
return;
s->next = 0;
s->buf[s->nbuf++] ^= s->bits;
}
static void
randomseed(void*)
{
Seedbuf *s;
s = secalloc(sizeof(Seedbuf));
if(hwrandbuf != nil)
(*hwrandbuf)(s->buf, sizeof(s->buf));
/* Frequency close but not equal to HZ */
up->tns = (vlong)(MS2HZ+3)*1000000LL;
up->tmode = Tperiodic;
up->tt = nil;
up->ta = s;
up->tf = randomsample;
timeradd(up);
while(s->nbuf < sizeof(s->buf)){
if(++s->randomcount <= 100000)
continue;
if(anyhigher())
sched();
}
timerdel(up);
sha2_512(s->buf, sizeof(s->buf), s->buf, &s->ds);
setupChachastate(rs, s->buf, 32, s->buf+32, 12, 20);
qunlock(rs);
secfree(s);
pexit("", 1);
}
void
randominit(void)
{
rs = secalloc(sizeof(*rs));
qlock(rs); /* randomseed() unlocks once seeded */
kproc("randomseed", randomseed, nil);
}
ulong
randomread(void *p, ulong n)
{
Chachastate c;
ulong b;
if(n == 0)
return 0;
if(hwrandbuf != nil)
(*hwrandbuf)(p, n);
/* copy chacha state and advance block counter */
qlock(rs);
c = *rs;
b = rs->input[12];
rs->input[12] += (n + ChachaBsize-1)/ChachaBsize;
if(rs->input[12] < b) rs->input[13]++;
qunlock(rs);
/* encrypt the buffer, can fault */
chacha_encrypt((uchar*)p, n, &c);
/* prevent state leakage */
memset(&c, 0, sizeof(c));
return n;
}
/* used by fastrand() */
void
genrandom(uchar *p, int n)
{
randomread(p, n);
}
/* used by rand(),nrand() */
long
lrand(void)
{
/* xoroshiro128+ algorithm */
static int seeded = 0;
static uvlong s[2];
static Lock lk;
ulong r;
if(seeded == 0){
randomread(s, sizeof(s));
seeded = (s[0] | s[1]) != 0;
}
lock(&lk);
r = (s[0] + s[1]) >> 33;
s[1] ^= s[0];
s[0] = (s[0] << 55 | s[0] >> 9) ^ s[1] ^ (s[1] << 14);
s[1] = (s[1] << 36 | s[1] >> 28);
unlock(&lk);
return r;
}
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