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/*
* crypto-class pseudorandom number generator
* currently uses same algorithm as RC4(TM), from Schneier 2nd ed p397
* Copyright (C) 2002 Henry Spencer.
*
* This library is free software; you can redistribute it and/or modify it
* under the terms of the GNU Library General Public License as published by
* the Free Software Foundation; either version 2 of the License, or (at your
* option) any later version. See <http://www.fsf.org/copyleft/lgpl.txt>.
*
* This library is distributed in the hope that it will be useful, but
* WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY
* or FITNESS FOR A PARTICULAR PURPOSE. See the GNU Library General Public
* License for more details.
*/
#include "internal.h"
#include "freeswan.h"
/*
- prng_init - initialize PRNG from a key
*/
void
prng_init(prng, key, keylen)
struct prng *prng;
const unsigned char *key;
size_t keylen;
{
unsigned char k[256];
int i, j;
unsigned const char *p;
unsigned const char *keyend = key + keylen;
unsigned char t;
for (i = 0; i <= 255; i++)
prng->sbox[i] = i;
p = key;
for (i = 0; i <= 255; i++) {
k[i] = *p++;
if (p >= keyend)
p = key;
}
j = 0;
for (i = 0; i <= 255; i++) {
j = (j + prng->sbox[i] + k[i]) & 0xff;
t = prng->sbox[i];
prng->sbox[i] = prng->sbox[j];
prng->sbox[j] = t;
k[i] = 0; /* clear out key memory */
}
prng->i = 0;
prng->j = 0;
prng->count = 0;
}
/*
- prng_bytes - get some pseudorandom bytes from PRNG
*/
void
prng_bytes(prng, dst, dstlen)
struct prng *prng;
unsigned char *dst;
size_t dstlen;
{
int i, j, t;
unsigned char *p = dst;
size_t remain = dstlen;
# define MAX 4000000000ul
while (remain > 0) {
i = (prng->i + 1) & 0xff;
prng->i = i;
j = (prng->j + prng->sbox[i]) & 0xff;
prng->j = j;
t = prng->sbox[i];
prng->sbox[i] = prng->sbox[j];
prng->sbox[j] = t;
t = (t + prng->sbox[i]) & 0xff;
*p++ = prng->sbox[t];
remain--;
}
if (prng->count < MAX - dstlen)
prng->count += dstlen;
else
prng->count = MAX;
}
/*
- prnt_count - how many bytes have been extracted from PRNG so far?
*/
unsigned long
prng_count(prng)
struct prng *prng;
{
return prng->count;
}
/*
- prng_final - clear out PRNG to ensure nothing left in memory
*/
void
prng_final(prng)
struct prng *prng;
{
int i;
for (i = 0; i <= 255; i++)
prng->sbox[i] = 0;
prng->i = 0;
prng->j = 0;
prng->count = 0; /* just for good measure */
}
#ifdef PRNG_MAIN
#include <stdio.h>
void regress();
int
main(argc, argv)
int argc;
char *argv[];
{
struct prng pr;
unsigned char buf[100];
unsigned char *p;
size_t n;
if (argc < 2) {
fprintf(stderr, "Usage: %s {key|-r}\n", argv[0]);
exit(2);
}
if (strcmp(argv[1], "-r") == 0) {
regress();
fprintf(stderr, "regress() returned?!?\n");
exit(1);
}
prng_init(&pr, argv[1], strlen(argv[1]));
prng_bytes(&pr, buf, 32);
printf("0x");
for (p = buf, n = 32; n > 0; p++, n--)
printf("%02x", *p);
printf("\n%lu bytes\n", prng_count(&pr));
prng_final(&pr);
exit(0);
}
void
regress()
{
struct prng pr;
unsigned char buf[100];
unsigned char *p;
size_t n;
/* somewhat non-random sample key */
unsigned char key[] = "here we go gathering nuts in May";
/* first thirty bytes of output from that key */
unsigned char good[] = "\x3f\x02\x8e\x4a\x2a\xea\x23\x18\x92\x7c"
"\x09\x52\x83\x61\xaa\x26\xce\xbb\x9d\x71"
"\x71\xe5\x10\x22\xaf\x60\x54\x8d\x5b\x28";
int nzero, none;
int show = 0;
prng_init(&pr, key, strlen(key));
prng_bytes(&pr, buf, sizeof(buf));
for (p = buf, n = sizeof(buf); n > 0; p++, n--) {
if (*p == 0)
nzero++;
if (*p == 255)
none++;
}
if (nzero > 3 || none > 3) {
fprintf(stderr, "suspiciously non-random output!\n");
show = 1;
}
if (memcmp(buf, good, strlen(good)) != 0) {
fprintf(stderr, "incorrect output!\n");
show = 1;
}
if (show) {
fprintf(stderr, "0x");
for (p = buf, n = sizeof(buf); n > 0; p++, n--)
fprintf(stderr, "%02x", *p);
fprintf(stderr, "\n");
exit(1);
}
if (prng_count(&pr) != sizeof(buf)) {
fprintf(stderr, "got %u bytes, but count is %lu\n",
sizeof(buf), prng_count(&pr));
exit(1);
}
prng_final(&pr);
exit(0);
}
#endif /* PRNG_MAIN */
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