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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 *xp, ulong n)
{
if(n == 0)
return 0;
if(hwrandbuf != nil)
(*hwrandbuf)(xp, n);
if(waserror()){
qunlock(rs);
nexterror();
}
qlock(rs);
chacha_encrypt((uchar*)xp, n, rs);
qunlock(rs);
poperror();
return n;
}
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