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/*
* util/random.c - thread safe random generator, which is reasonably secure.
*
* Copyright (c) 2007, NLnet Labs. All rights reserved.
*
* This software is open source.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions
* are met:
*
* Redistributions of source code must retain the above copyright notice,
* this list of conditions and the following disclaimer.
*
* Redistributions in binary form must reproduce the above copyright notice,
* this list of conditions and the following disclaimer in the documentation
* and/or other materials provided with the distribution.
*
* Neither the name of the NLNET LABS nor the names of its contributors may
* be used to endorse or promote products derived from this software without
* specific prior written permission.
*
* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
* "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED
* TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
* PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE
* LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
* CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
* SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
* INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
* CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
* ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
* POSSIBILITY OF SUCH DAMAGE.
*/
/**
* \file
* Thread safe random functions. Similar to arc4random() with an explicit
* initialisation routine.
*
* The code in this file is based on arc4random from
* openssh-4.0p1/openbsd-compat/bsd-arc4random.c
* That code is also BSD licensed. Here is their statement:
*
* Copyright (c) 1996, David Mazieres <dm@uun.org>
* Copyright (c) 2008, Damien Miller <djm@openbsd.org>
*
* Permission to use, copy, modify, and distribute this software for any
* purpose with or without fee is hereby granted, provided that the above
* copyright notice and this permission notice appear in all copies.
*
* THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
* WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
* MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
* ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
* WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
* ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
* OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
*/
#include "config.h"
#include "util/random.h"
#include "util/log.h"
#include <openssl/rand.h>
#include <openssl/rc4.h>
#include <openssl/err.h>
/**
* Struct with per-thread random state.
* Keeps SSL types away from the header file.
*/
struct ub_randstate {
/** key used for arc4random generation */
RC4_KEY rc4;
/** keeps track of key usage */
int rc4_ready;
};
/** Size of key to use (must be multiple of 8) */
#define SEED_SIZE 24
/**
* Max random value. Similar to RAND_MAX, but more portable
* (mingw uses only 15 bits random).
*/
#define MAX_VALUE 0x7fffffff
/** Number of bytes to reseed after */
#define REKEY_BYTES (1 << 24)
/* (re)setup system seed */
void
ub_systemseed(unsigned int seed)
{
/* RAND_ is threadsafe, by the way */
if(!RAND_status()) {
/* try to seed it */
unsigned char buf[256];
unsigned int v = seed;
size_t i;
for(i=0; i<256/sizeof(seed); i++) {
memmove(buf+i*sizeof(seed), &v, sizeof(seed));
v = v*seed + (unsigned int)i;
}
RAND_seed(buf, 256);
if(!RAND_status()) {
log_err("Random generator has no entropy "
"(error %ld)", ERR_get_error());
} else {
verbose(VERB_OPS, "openssl has no entropy, "
"seeding with time and pid");
}
}
}
/** reseed random generator */
static void
ub_arc4random_stir(struct ub_randstate* s, struct ub_randstate* from)
{
/* not as unsigned char, but longerint so that it is
aligned properly on alignment sensitive platforms */
uint64_t rand_buf[SEED_SIZE/sizeof(uint64_t)];
int i;
memset(&s->rc4, 0, sizeof(s->rc4));
memset(rand_buf, 0xc, sizeof(rand_buf));
if (from) {
uint8_t* rbuf = (uint8_t*)rand_buf;
for(i=0; i<SEED_SIZE; i++)
rbuf[i] = (uint8_t)ub_random(from);
} else {
if(!RAND_status())
ub_systemseed((unsigned)getpid()^(unsigned)time(NULL));
if (RAND_bytes((unsigned char*)rand_buf,
(int)sizeof(rand_buf)) <= 0) {
/* very unlikely that this happens, since we seeded
* above, if it does; complain and keep going */
log_err("Couldn't obtain random bytes (error %ld)",
ERR_get_error());
s->rc4_ready = 256;
return;
}
}
RC4_set_key(&s->rc4, SEED_SIZE, (unsigned char*)rand_buf);
/*
* Discard early keystream, as per recommendations in:
* http://www.wisdom.weizmann.ac.il/~itsik/RC4/Papers/Rc4_ksa.ps
*/
for(i = 0; i <= 256; i += sizeof(rand_buf))
RC4(&s->rc4, sizeof(rand_buf), (unsigned char*)rand_buf,
(unsigned char*)rand_buf);
memset(rand_buf, 0, sizeof(rand_buf));
s->rc4_ready = REKEY_BYTES;
}
struct ub_randstate*
ub_initstate(unsigned int seed, struct ub_randstate* from)
{
struct ub_randstate* s = (struct ub_randstate*)calloc(1, sizeof(*s));
if(!s) {
log_err("malloc failure in random init");
return NULL;
}
ub_systemseed(seed);
ub_arc4random_stir(s, from);
return s;
}
long int
ub_random(struct ub_randstate* s)
{
unsigned int r = 0;
if (s->rc4_ready <= 0) {
ub_arc4random_stir(s, NULL);
}
RC4(&s->rc4, sizeof(r),
(unsigned char *)&r, (unsigned char *)&r);
s->rc4_ready -= sizeof(r);
return (long int)((r) % (((unsigned)MAX_VALUE + 1)));
}
long int
ub_random_max(struct ub_randstate* state, long int x)
{
/* make sure we fetch in a range that is divisible by x. ignore
* values from d .. MAX_VALUE, instead draw a new number */
long int d = MAX_VALUE - (MAX_VALUE % x); /* d is divisible by x */
long int v = ub_random(state);
while(d <= v)
v = ub_random(state);
return (v % x);
}
void
ub_randfree(struct ub_randstate* s)
{
if(s)
free(s);
/* user app must do RAND_cleanup(); */
}
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