5a9b5f7c13
entropy device is loaded or not. If the entropy device is NOT loaded, the the quality of perturbations supplied by this will suffer.
115 lines
1.9 KiB
C
115 lines
1.9 KiB
C
/*-
|
|
* THE BEER-WARE LICENSE
|
|
*
|
|
* <dan@FreeBSD.ORG> wrote this file. As long as you retain this notice you
|
|
* can do whatever you want with this stuff. If we meet some day, and you
|
|
* think this stuff is worth it, you can buy me a beer in return.
|
|
*
|
|
* Dan Moschuk
|
|
*
|
|
* $FreeBSD$
|
|
*/
|
|
|
|
#include <sys/types.h>
|
|
#include <sys/random.h>
|
|
#include <sys/libkern.h>
|
|
|
|
#define ARC4_MAXRUNS 64
|
|
|
|
static u_int8_t arc4_i, arc4_j;
|
|
static int arc4_initialized = 0;
|
|
static int arc4_numruns = 0;
|
|
static u_int8_t arc4_sbox[256];
|
|
|
|
static __inline void
|
|
arc4_swap(u_int8_t *a, u_int8_t *b)
|
|
{
|
|
u_int8_t c;
|
|
|
|
c = *a;
|
|
*a = *b;
|
|
*b = c;
|
|
}
|
|
|
|
/*
|
|
* Stir our S-box.
|
|
*/
|
|
static void
|
|
arc4_randomstir (void)
|
|
{
|
|
u_int8_t key[256];
|
|
int r, n;
|
|
|
|
/* XXX read_random() returns unsafe numbers if the entropy
|
|
* devce is not loaded - MarkM
|
|
*/
|
|
r = read_random(key, sizeof(key));
|
|
/* if r == 0 || -1, just use what was on the stack */
|
|
if (r > 0)
|
|
{
|
|
for (n = r; n < sizeof(key); n++)
|
|
key[n] = key[n % r];
|
|
}
|
|
|
|
for (n = 0; n < 256; n++)
|
|
{
|
|
arc4_j = (arc4_j + arc4_sbox[n] + key[n]) % 256;
|
|
arc4_swap(&arc4_sbox[n], &arc4_sbox[arc4_j]);
|
|
}
|
|
}
|
|
|
|
/*
|
|
* Initialize our S-box to its beginning defaults.
|
|
*/
|
|
static void
|
|
arc4_init(void)
|
|
{
|
|
int n;
|
|
|
|
arc4_i = arc4_j = 0;
|
|
for (n = 0; n < 256; n++)
|
|
arc4_sbox[n] = (u_int8_t) n;
|
|
|
|
arc4_randomstir();
|
|
arc4_initialized = 1;
|
|
}
|
|
|
|
/*
|
|
* Generate a random byte.
|
|
*/
|
|
static u_int8_t
|
|
arc4_randbyte(void)
|
|
{
|
|
u_int8_t arc4_t;
|
|
|
|
arc4_i = (arc4_i + 1) % 256;
|
|
arc4_j = (arc4_j + arc4_sbox[arc4_i]) % 256;
|
|
|
|
arc4_swap(&arc4_sbox[arc4_i], &arc4_sbox[arc4_j]);
|
|
|
|
arc4_t = (arc4_sbox[arc4_i] + arc4_sbox[arc4_j]) % 256;
|
|
return arc4_sbox[arc4_t];
|
|
}
|
|
|
|
u_int32_t
|
|
arc4random(void)
|
|
{
|
|
u_int32_t ret;
|
|
|
|
/* Initialize array if needed. */
|
|
if (!arc4_initialized)
|
|
arc4_init();
|
|
if (++arc4_numruns > ARC4_MAXRUNS)
|
|
{
|
|
arc4_randomstir();
|
|
arc4_numruns = 0;
|
|
}
|
|
|
|
ret = arc4_randbyte();
|
|
ret |= arc4_randbyte() << 8;
|
|
ret |= arc4_randbyte() << 16;
|
|
ret |= arc4_randbyte() << 24;
|
|
|
|
return ret;
|
|
}
|