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/*
* The ISAAC CSPRNG plus interface.
* Slightly modified readable.c from Bob Jenkins 1996.
*/
#include <stdio.h>
#include <stddef.h>
#include <string.h>
#include "ptypes.h"
#include "isaac.h"
/* Ensure big-endian and little-endian get the same results */
#if __LITTLE_ENDIAN__ || (defined(BYTEORDER) && (BYTEORDER == 0x1234 || BYTEORDER == 0x12345678))
#define SWAPRSL(rsl, num) { }
#define COPYRSL(data, rsl, start, bytes) \
memcpy(data, (unsigned char*) (rsl+start), bytes);
#else
#if !defined(__x86_64__)
#undef U8TO32_LE
#undef U32TO8_LE
#endif
#ifndef U32TO8_LE
#define U32TO8_LE(p, v) \
do { uint32_t _v = v; \
(p)[0] = (((_v) ) & 0xFFU); \
(p)[1] = (((_v) >> 8) & 0xFFU); \
(p)[2] = (((_v) >> 16) & 0xFFU); \
(p)[3] = (((_v) >> 24) & 0xFFU); } while (0)
#endif
#define SWAPRSL(rsl, num) \
{ unsigned char* rsc = (unsigned char*) rsl; \
uint32_t i; \
for (i = 0; i < num; i++) \
U32TO8_LE(rsc+4*i, rsl[i]); \
}
#define COPYRSL(data, rsl, start, bytes) \
{ \
unsigned char swapbuf[256*4]; \
uint32_t i; \
for (i = 0; i < (bytes+3)/4; i++) \
{ U32TO8_LE(swapbuf+4*i, rsl[start+i]); } \
memcpy(data, swapbuf, bytes); \
}
#endif
static uint32_t randrsl[256];
static uint32_t randcnt;
static int good_seed = 0;
/* internal state */
static uint32_t mm[256];
static uint32_t aa = 0, bb = 0, cc = 0;
static void isaac(void)
{
uint32_t i,x,y;
cc = cc + 1; /* cc just gets incremented once per 256 results */
bb = bb + cc; /* then combined with bb */
for (i=0; i<256; ++i)
{
x = mm[i];
switch (i%4) {
case 0: aa = aa^(aa<<13); break;
case 1: aa = aa^(aa>>6); break;
case 2: aa = aa^(aa<<2); break;
case 3: aa = aa^(aa>>16); break;
}
aa = mm[(i+128)%256] + aa;
mm[i] = y = mm[(x>>2)%256] + aa + bb;
randrsl[i] = bb = mm[(y>>10)%256] + x;
}
randcnt = 0;
}
#define mix(a,b,c,d,e,f,g,h) \
{ \
a^=b<<11; d+=a; b+=c; \
b^=c>>2; e+=b; c+=d; \
c^=d<<8; f+=c; d+=e; \
d^=e>>16; g+=d; e+=f; \
e^=f<<10; h+=e; f+=g; \
f^=g>>4; a+=f; g+=h; \
g^=h<<8; b+=g; h+=a; \
h^=a>>9; c+=h; a+=b; \
}
static void randinit(void) {
int i;
uint32_t a,b,c,d,e,f,g,h;
aa=bb=cc=0;
a=b=c=d=e=f=g=h=0x9e3779b9; /* the golden ratio */
for (i=0; i<4; ++i) /* scramble it */
{
mix(a,b,c,d,e,f,g,h);
}
for (i=0; i<256; i+=8) /* fill in mm[] with messy stuff */
{
a+=randrsl[i ]; b+=randrsl[i+1]; c+=randrsl[i+2]; d+=randrsl[i+3];
e+=randrsl[i+4]; f+=randrsl[i+5]; g+=randrsl[i+6]; h+=randrsl[i+7];
mix(a,b,c,d,e,f,g,h);
mm[i ]=a; mm[i+1]=b; mm[i+2]=c; mm[i+3]=d;
mm[i+4]=e; mm[i+5]=f; mm[i+6]=g; mm[i+7]=h;
}
{ /* do a second pass to make all of the seed affect all of mm */
for (i=0; i<256; i+=8)
{
a+=mm[i ]; b+=mm[i+1]; c+=mm[i+2]; d+=mm[i+3];
e+=mm[i+4]; f+=mm[i+5]; g+=mm[i+6]; h+=mm[i+7];
mix(a,b,c,d,e,f,g,h);
mm[i ]=a; mm[i+1]=b; mm[i+2]=c; mm[i+3]=d;
mm[i+4]=e; mm[i+5]=f; mm[i+6]=g; mm[i+7]=h;
}
}
isaac(); /* fill in the first set of results */
randcnt=256; /* first use will run isaac() again */
}
void isaac_init(uint32_t bytes, const unsigned char* data)
{
memset(mm, 0, 4*256);
memset(randrsl, 0, 4*256);
if (bytes > 0 && data != 0) {
/* Replicate supplied seed as recommended by Bob Jenkins. */
unsigned char* rdata = (unsigned char*) randrsl;
uint32_t n_fill_bytes = 1024;
while (n_fill_bytes > 0) {
uint32_t n_copy_bytes = (bytes > n_fill_bytes) ? n_fill_bytes : bytes;
memcpy(rdata, data, n_copy_bytes);
rdata += n_copy_bytes;
n_fill_bytes -= n_copy_bytes;
}
SWAPRSL(randrsl, 256);
}
randinit();
good_seed = (bytes >= 16);
}
int isaac_seeded(void) { return good_seed; }
void isaac_rand_bytes(uint32_t bytes, unsigned char* data)
{
if ( 4*(256-randcnt) >= bytes) {
/* We have enough data, just copy it and leave */
COPYRSL(data, randrsl, randcnt, bytes);
randcnt += (bytes+3)/4;
} else {
/* Loop copying up to 1024 bytes at a time */
uint32_t n_rand_bytes, n_copy_bytes;
while (bytes > 0) {
if (randcnt > 255)
isaac();
n_rand_bytes = 4 * (256-randcnt);
n_copy_bytes = (n_rand_bytes > bytes) ? bytes : n_rand_bytes;
COPYRSL(data, randrsl, randcnt, n_copy_bytes);
data += n_copy_bytes;
randcnt += (n_copy_bytes+3)/4;
bytes -= n_copy_bytes;
}
}
}
uint32_t isaac_rand32(void)
{
if (randcnt > 255) isaac();
return randrsl[randcnt++];
}
/* Return rand 32-bit integer between 0 to n-1 inclusive */
uint32_t isaac_rand(uint32_t n)
{
uint32_t r, rmin;
if (n <= 1) return 0;
rmin = -n % n;
while (1) {
r = isaac_rand32();
if (r >= rmin)
break;
}
return r % n;
}
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