mirror of https://github.com/postgres/postgres
440 lines
8.9 KiB
C
440 lines
8.9 KiB
C
/*
|
|
* fortuna.c
|
|
* Fortuna-like PRNG.
|
|
*
|
|
* Copyright (c) 2005 Marko Kreen
|
|
* All rights reserved.
|
|
*
|
|
* Redistribution and use in source and binary forms, with or without
|
|
* modification, are permitted provided that the following conditions
|
|
* are met:
|
|
* 1. Redistributions of source code must retain the above copyright
|
|
* notice, this list of conditions and the following disclaimer.
|
|
* 2. 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.
|
|
*
|
|
* THIS SOFTWARE IS PROVIDED BY THE AUTHOR 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 AUTHOR 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.
|
|
*
|
|
* $PostgreSQL: pgsql/contrib/pgcrypto/fortuna.c,v 1.5 2005/10/15 02:49:06 momjian Exp $
|
|
*/
|
|
|
|
#include "postgres.h"
|
|
|
|
#include <sys/time.h>
|
|
#include <time.h>
|
|
|
|
#include "rijndael.h"
|
|
#include "sha2.h"
|
|
#include "fortuna.h"
|
|
|
|
|
|
/*
|
|
* Why Fortuna-like: There does not seem to be any definitive reference
|
|
* on Fortuna in the net. Instead this implementation is based on
|
|
* following references:
|
|
*
|
|
* http://en.wikipedia.org/wiki/Fortuna_(PRNG)
|
|
* - Wikipedia article
|
|
* http://jlcooke.ca/random/
|
|
* - Jean-Luc Cooke Fortuna-based /dev/random driver for Linux.
|
|
*/
|
|
|
|
/*
|
|
* There is some confusion about whether and how to carry forward
|
|
* the state of the pools. Seems like original Fortuna does not
|
|
* do it, resetting hash after each request. I guess expecting
|
|
* feeding to happen more often that requesting. This is absolutely
|
|
* unsuitable for pgcrypto, as nothing asynchronous happens here.
|
|
*
|
|
* J.L. Cooke fixed this by feeding previous hash to new re-initialized
|
|
* hash context.
|
|
*
|
|
* Fortuna predecessor Yarrow requires ability to query intermediate
|
|
* 'final result' from hash, without affecting it.
|
|
*
|
|
* This implementation uses the Yarrow method - asking intermediate
|
|
* results, but continuing with old state.
|
|
*/
|
|
|
|
|
|
/*
|
|
* Algorithm parameters
|
|
*/
|
|
|
|
/*
|
|
* How many pools.
|
|
*
|
|
* Original Fortuna uses 32 pools, that means 32'th pool is
|
|
* used not earlier than in 13th year. This is a waste in
|
|
* pgcrypto, as we have very low-frequancy seeding. Here
|
|
* is preferable to have all entropy usable in reasonable time.
|
|
*
|
|
* With 23 pools, 23th pool is used after 9 days which seems
|
|
* more sane.
|
|
*
|
|
* In our case the minimal cycle time would be bit longer
|
|
* than the system-randomness feeding frequency.
|
|
*/
|
|
#define NUM_POOLS 23
|
|
|
|
/* in microseconds */
|
|
#define RESEED_INTERVAL 100000 /* 0.1 sec */
|
|
|
|
/* for one big request, reseed after this many bytes */
|
|
#define RESEED_BYTES (1024*1024)
|
|
|
|
/*
|
|
* Skip reseed if pool 0 has less than this many
|
|
* bytes added since last reseed.
|
|
*/
|
|
#define POOL0_FILL (256/8)
|
|
|
|
/*
|
|
* Algorithm constants
|
|
*/
|
|
|
|
/* Both cipher key size and hash result size */
|
|
#define BLOCK 32
|
|
|
|
/* cipher block size */
|
|
#define CIPH_BLOCK 16
|
|
|
|
/* for internal wrappers */
|
|
#define MD_CTX SHA256_CTX
|
|
#define CIPH_CTX rijndael_ctx
|
|
|
|
struct fortuna_state
|
|
{
|
|
uint8 counter[CIPH_BLOCK];
|
|
uint8 result[CIPH_BLOCK];
|
|
uint8 key[BLOCK];
|
|
MD_CTX pool[NUM_POOLS];
|
|
CIPH_CTX ciph;
|
|
unsigned reseed_count;
|
|
struct timeval last_reseed_time;
|
|
unsigned pool0_bytes;
|
|
unsigned rnd_pos;
|
|
int counter_init;
|
|
};
|
|
typedef struct fortuna_state FState;
|
|
|
|
|
|
/*
|
|
* Use our own wrappers here.
|
|
* - Need to get intermediate result from digest, without affecting it.
|
|
* - Need re-set key on a cipher context.
|
|
* - Algorithms are guaranteed to exist.
|
|
* - No memory allocations.
|
|
*/
|
|
|
|
static void
|
|
ciph_init(CIPH_CTX * ctx, const uint8 *key, int klen)
|
|
{
|
|
rijndael_set_key(ctx, (const uint32 *) key, klen, 1);
|
|
}
|
|
|
|
static void
|
|
ciph_encrypt(CIPH_CTX * ctx, const uint8 *in, uint8 *out)
|
|
{
|
|
rijndael_encrypt(ctx, (const uint32 *) in, (uint32 *) out);
|
|
}
|
|
|
|
static void
|
|
md_init(MD_CTX * ctx)
|
|
{
|
|
SHA256_Init(ctx);
|
|
}
|
|
|
|
static void
|
|
md_update(MD_CTX * ctx, const uint8 *data, int len)
|
|
{
|
|
SHA256_Update(ctx, data, len);
|
|
}
|
|
|
|
static void
|
|
md_result(MD_CTX * ctx, uint8 *dst)
|
|
{
|
|
SHA256_CTX tmp;
|
|
|
|
memcpy(&tmp, ctx, sizeof(*ctx));
|
|
SHA256_Final(dst, &tmp);
|
|
memset(&tmp, 0, sizeof(tmp));
|
|
}
|
|
|
|
/*
|
|
* initialize state
|
|
*/
|
|
static void
|
|
init_state(FState * st)
|
|
{
|
|
int i;
|
|
|
|
memset(st, 0, sizeof(*st));
|
|
for (i = 0; i < NUM_POOLS; i++)
|
|
md_init(&st->pool[i]);
|
|
}
|
|
|
|
/*
|
|
* Endianess does not matter.
|
|
* It just needs to change without repeating.
|
|
*/
|
|
static void
|
|
inc_counter(FState * st)
|
|
{
|
|
uint32 *val = (uint32 *) st->counter;
|
|
|
|
if (++val[0])
|
|
return;
|
|
if (++val[1])
|
|
return;
|
|
if (++val[2])
|
|
return;
|
|
++val[3];
|
|
}
|
|
|
|
/*
|
|
* This is called 'cipher in counter mode'.
|
|
*/
|
|
static void
|
|
encrypt_counter(FState * st, uint8 *dst)
|
|
{
|
|
ciph_encrypt(&st->ciph, st->counter, dst);
|
|
inc_counter(st);
|
|
}
|
|
|
|
|
|
/*
|
|
* The time between reseed must be at least RESEED_INTERVAL
|
|
* microseconds.
|
|
*/
|
|
static int
|
|
too_often(FState * st)
|
|
{
|
|
int ok;
|
|
struct timeval tv;
|
|
struct timeval *last = &st->last_reseed_time;
|
|
|
|
gettimeofday(&tv, NULL);
|
|
|
|
ok = 0;
|
|
if (tv.tv_sec != last->tv_sec)
|
|
ok = 1;
|
|
else if (tv.tv_usec - last->tv_usec >= RESEED_INTERVAL)
|
|
ok = 1;
|
|
|
|
memcpy(last, &tv, sizeof(tv));
|
|
memset(&tv, 0, sizeof(tv));
|
|
|
|
return ok;
|
|
}
|
|
|
|
/*
|
|
* generate new key from all the pools
|
|
*/
|
|
static void
|
|
reseed(FState * st)
|
|
{
|
|
unsigned k;
|
|
unsigned n;
|
|
MD_CTX key_md;
|
|
uint8 buf[BLOCK];
|
|
|
|
/* set pool as empty */
|
|
st->pool0_bytes = 0;
|
|
|
|
/*
|
|
* Both #0 and #1 reseed would use only pool 0. Just skip #0 then.
|
|
*/
|
|
n = ++st->reseed_count;
|
|
|
|
/*
|
|
* The goal: use k-th pool only 1/(2^k) of the time.
|
|
*/
|
|
md_init(&key_md);
|
|
for (k = 0; k < NUM_POOLS; k++)
|
|
{
|
|
md_result(&st->pool[k], buf);
|
|
md_update(&key_md, buf, BLOCK);
|
|
|
|
if (n & 1 || !n)
|
|
break;
|
|
n >>= 1;
|
|
}
|
|
|
|
/* add old key into mix too */
|
|
md_update(&key_md, st->key, BLOCK);
|
|
|
|
/* now we have new key */
|
|
md_result(&key_md, st->key);
|
|
|
|
/* use new key */
|
|
ciph_init(&st->ciph, st->key, BLOCK);
|
|
|
|
memset(&key_md, 0, sizeof(key_md));
|
|
memset(buf, 0, BLOCK);
|
|
}
|
|
|
|
/*
|
|
* Pick a random pool. This uses key bytes as random source.
|
|
*/
|
|
static unsigned
|
|
get_rand_pool(FState * st)
|
|
{
|
|
unsigned rnd;
|
|
|
|
/*
|
|
* This slightly prefers lower pools - thats OK.
|
|
*/
|
|
rnd = st->key[st->rnd_pos] % NUM_POOLS;
|
|
|
|
st->rnd_pos++;
|
|
if (st->rnd_pos >= BLOCK)
|
|
st->rnd_pos = 0;
|
|
|
|
return rnd;
|
|
}
|
|
|
|
/*
|
|
* update pools
|
|
*/
|
|
static void
|
|
add_entropy(FState * st, const uint8 *data, unsigned len)
|
|
{
|
|
unsigned pos;
|
|
uint8 hash[BLOCK];
|
|
MD_CTX md;
|
|
|
|
/* hash given data */
|
|
md_init(&md);
|
|
md_update(&md, data, len);
|
|
md_result(&md, hash);
|
|
|
|
/*
|
|
* Make sure the pool 0 is initialized, then update randomly.
|
|
*/
|
|
if (st->reseed_count == 0 && st->pool0_bytes < POOL0_FILL)
|
|
pos = 0;
|
|
else
|
|
pos = get_rand_pool(st);
|
|
md_update(&st->pool[pos], hash, BLOCK);
|
|
|
|
if (pos == 0)
|
|
st->pool0_bytes += len;
|
|
|
|
memset(hash, 0, BLOCK);
|
|
memset(&md, 0, sizeof(md));
|
|
}
|
|
|
|
/*
|
|
* Just take 2 next blocks as new key
|
|
*/
|
|
static void
|
|
rekey(FState * st)
|
|
{
|
|
encrypt_counter(st, st->key);
|
|
encrypt_counter(st, st->key + CIPH_BLOCK);
|
|
ciph_init(&st->ciph, st->key, BLOCK);
|
|
}
|
|
|
|
/*
|
|
* Fortuna relies on AES standing known-plaintext attack.
|
|
* In case it does not, slow down the attacker by initialising
|
|
* the couter to random value.
|
|
*/
|
|
static void
|
|
init_counter(FState * st)
|
|
{
|
|
/* Use next block as counter. */
|
|
encrypt_counter(st, st->counter);
|
|
|
|
/* Hide the key. */
|
|
rekey(st);
|
|
|
|
/* The counter can be shuffled only once. */
|
|
st->counter_init = 1;
|
|
}
|
|
|
|
static void
|
|
extract_data(FState * st, unsigned count, uint8 *dst)
|
|
{
|
|
unsigned n;
|
|
unsigned block_nr = 0;
|
|
|
|
/* Can we reseed? */
|
|
if (st->pool0_bytes >= POOL0_FILL && !too_often(st))
|
|
reseed(st);
|
|
|
|
/* Is counter initialized? */
|
|
if (!st->counter_init)
|
|
init_counter(st);
|
|
|
|
while (count > 0)
|
|
{
|
|
/* produce bytes */
|
|
encrypt_counter(st, st->result);
|
|
|
|
/* copy result */
|
|
if (count > CIPH_BLOCK)
|
|
n = CIPH_BLOCK;
|
|
else
|
|
n = count;
|
|
memcpy(dst, st->result, n);
|
|
dst += n;
|
|
count -= n;
|
|
|
|
/* must not give out too many bytes with one key */
|
|
block_nr++;
|
|
if (block_nr > (RESEED_BYTES / CIPH_BLOCK))
|
|
{
|
|
rekey(st);
|
|
block_nr = 0;
|
|
}
|
|
}
|
|
/* Set new key for next request. */
|
|
rekey(st);
|
|
}
|
|
|
|
/*
|
|
* public interface
|
|
*/
|
|
|
|
static FState main_state;
|
|
static int init_done = 0;
|
|
|
|
void
|
|
fortuna_add_entropy(const uint8 *data, unsigned len)
|
|
{
|
|
if (!init_done)
|
|
{
|
|
init_state(&main_state);
|
|
init_done = 1;
|
|
}
|
|
if (!data || !len)
|
|
return;
|
|
add_entropy(&main_state, data, len);
|
|
}
|
|
|
|
void
|
|
fortuna_get_bytes(unsigned len, uint8 *dst)
|
|
{
|
|
if (!init_done)
|
|
{
|
|
init_state(&main_state);
|
|
init_done = 1;
|
|
}
|
|
if (!dst || !len)
|
|
return;
|
|
extract_data(&main_state, len, dst);
|
|
}
|