/*-
* 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
*/
#if !defined(SOLARIS2)
# include <sys/cdefs.h>
#endif
#include <sys/types.h>
#include <sys/param.h>
#ifdef __FreeBSD__
# include <sys/kernel.h>
#endif
# include <sys/random.h>
#ifdef __FreeBSD__
# include <sys/libkern.h>
#endif
#include <sys/lock.h>
# include <sys/mutex.h>
#include <sys/time.h>
#include <sys/socket.h>
#include <net/if.h>
#include <netinet/in.h>
#include <netinet/ip.h>
#include "netinet/ip_compat.h"
#ifdef HAS_SYS_MD5_H
# include <sys/md5.h>
#else
# include "md5.h"
#endif
#ifdef NEED_LOCAL_RAND
#if !defined(__GNUC__)
# define __inline
#endif
#define ARC4_RESEED_BYTES 65536
#define ARC4_RESEED_SECONDS 300
#define ARC4_KEYBYTES (256 / 8)
static u_int8_t arc4_i, arc4_j;
static int arc4_numruns = 0;
static u_int8_t arc4_sbox[256];
static time_t arc4_t_reseed;
static ipfmutex_t arc4_mtx;
static MD5_CTX md5ctx;
static u_int8_t arc4_randbyte(void);
static int ipf_read_random(void *dest, int length);
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;
struct timeval tv_now;
/*
* XXX read_random() returns unsafe numbers if the entropy
* device is not loaded -- MarkM.
*/
r = ipf_read_random(key, ARC4_KEYBYTES);
GETKTIME(&tv_now);
MUTEX_ENTER(&arc4_mtx);
/* 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]);
}
/* Reset for next reseed cycle. */
arc4_t_reseed = tv_now.tv_sec + ARC4_RESEED_SECONDS;
arc4_numruns = 0;
/*
* Throw away the first N words of output, as suggested in the
* paper "Weaknesses in the Key Scheduling Algorithm of RC4"
* by Fluher, Mantin, and Shamir. (N = 768 in our case.)
*/
for (n = 0; n < 768*4; n++)
arc4_randbyte();
MUTEX_EXIT(&arc4_mtx);
}
/*
* Initialize our S-box to its beginning defaults.
*/
static void
arc4_init(void)
{
int n;
MD5Init(&md5ctx);
MUTEX_INIT(&arc4_mtx, "arc4_mtx");
arc4_i = arc4_j = 0;
for (n = 0; n < 256; n++)
arc4_sbox[n] = (u_int8_t) n;
arc4_t_reseed = 0;
}
/*
* 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];
}
/*
* MPSAFE
*/
void
arc4rand(void *ptr, u_int len, int reseed)
{
u_int8_t *p;
struct timeval tv;
GETKTIME(&tv);
if (reseed ||
(arc4_numruns > ARC4_RESEED_BYTES) ||
(tv.tv_sec > arc4_t_reseed))
arc4_randomstir();
MUTEX_ENTER(&arc4_mtx);
arc4_numruns += len;
p = ptr;
while (len--)
*p++ = arc4_randbyte();
MUTEX_EXIT(&arc4_mtx);
}
uint32_t
ipf_random(void)
{
uint32_t ret;
arc4rand(&ret, sizeof ret, 0);
return ret;
}
static u_char pot[ARC4_RESEED_BYTES];
static u_char *pothead = pot, *pottail = pot;
static int inpot = 0;
/*
* This is not very strong, and this is understood, but the aim isn't to
* be cryptographically strong - it is just to make up something that is
* pseudo random.
*/
void
ipf_rand_push(void *src, int length)
{
static int arc4_inited = 0;
u_char *nsrc;
int mylen;
if (arc4_inited == 0) {
arc4_init();
arc4_inited = 1;
}
if (length < 64) {
MD5Update(&md5ctx, src, length);
return;
}
nsrc = src;
mylen = length;
#if defined(_SYS_MD5_H) && defined(SOLARIS2)
# define buf buf_un.buf8
#endif
MUTEX_ENTER(&arc4_mtx);
while ((mylen > 64) && (sizeof(pot) - inpot > sizeof(md5ctx.buf))) {
MD5Update(&md5ctx, nsrc, 64);
mylen -= 64;
nsrc += 64;
if (pottail + sizeof(md5ctx.buf) > pot + sizeof(pot)) {
int left, numbytes;
numbytes = pot + sizeof(pot) - pottail;
bcopy(md5ctx.buf, pottail, numbytes);
left = sizeof(md5ctx.buf) - numbytes;
pottail = pot;
bcopy(md5ctx.buf + sizeof(md5ctx.buf) - left,
pottail, left);
pottail += left;
} else {
bcopy(md5ctx.buf, pottail, sizeof(md5ctx.buf));
pottail += sizeof(md5ctx.buf);
}
inpot += 64;
}
MUTEX_EXIT(&arc4_mtx);
#if defined(_SYS_MD5_H) && defined(SOLARIS2)
# undef buf
#endif
}
static int
ipf_read_random(void *dest, int length)
{
if (length > inpot)
return 0;
MUTEX_ENTER(&arc4_mtx);
if (pothead + length > pot + sizeof(pot)) {
int left, numbytes;
left = length;
numbytes = pot + sizeof(pot) - pothead;
bcopy(pothead, dest, numbytes);
left -= numbytes;
pothead = pot;
bcopy(pothead, dest + length - left, left);
pothead += left;
} else {
bcopy(pothead, dest, length);
pothead += length;
}
inpot -= length;
if (inpot == 0)
pothead = pottail = pot;
MUTEX_EXIT(&arc4_mtx);
return length;
}
#endif /* NEED_LOCAL_RAND */
