/*
* random_machdep.c -- A strong random number generator
*
* $Id: random_machdep.c,v 1.28 1998/06/18 15:32:07 bde Exp $
*
* Version 0.95, last modified 18-Oct-95
*
* Copyright Theodore Ts'o, 1994, 1995. 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, and the entire permission notice in its entirety,
* including the disclaimer of warranties.
* 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.
* 3. The name of the author may not be used to endorse or promote
* products derived from this software without specific prior
* written permission.
*
* ALTERNATIVELY, this product may be distributed under the terms of
* the GNU Public License, in which case the provisions of the GPL are
* required INSTEAD OF the above restrictions. (This clause is
* necessary due to a potential bad interaction between the GPL and
* the restrictions contained in a BSD-style copyright.)
*
* THIS SOFTWARE IS PROVIDED ``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 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.
*/
#include <sys/param.h>
#include <sys/systm.h>
#include <sys/kernel.h>
#include <sys/select.h>
#include <sys/poll.h>
#include <sys/md5.h>
#include <machine/random.h>
#include <i386/isa/icu.h>
#include <i386/isa/intr_machdep.h>
#define MAX_BLKDEV 4
/*
* The pool is stirred with a primitive polynomial of degree 128
* over GF(2), namely x^128 + x^99 + x^59 + x^31 + x^9 + x^7 + 1.
* For a pool of size 64, try x^64+x^62+x^38+x^10+x^6+x+1.
*/
#define POOLWORDS 128 /* Power of 2 - note that this is 32-bit words */
#define POOLBITS (POOLWORDS*32)
#if POOLWORDS == 128
#define TAP1 99 /* The polynomial taps */
#define TAP2 59
#define TAP3 31
#define TAP4 9
#define TAP5 7
#elif POOLWORDS == 64
#define TAP1 62 /* The polynomial taps */
#define TAP2 38
#define TAP3 10
#define TAP4 6
#define TAP5 1
#else
#error No primitive polynomial available for chosen POOLWORDS
#endif
#define WRITEBUFFER 512 /* size in bytes */
/* There is actually only one of these, globally. */
struct random_bucket {
u_int add_ptr;
u_int entropy_count;
int input_rotate;
u_int32_t *pool;
struct selinfo rsel;
};
/* There is one of these per entropy source */
struct timer_rand_state {
u_long last_time;
int last_delta;
int nbits;
};
static struct random_bucket random_state;
static u_int32_t random_pool[POOLWORDS];
static struct timer_rand_state keyboard_timer_state;
static struct timer_rand_state extract_timer_state;
static struct timer_rand_state irq_timer_state[ICU_LEN];
#ifdef notyet
static struct timer_rand_state blkdev_timer_state[MAX_BLKDEV];
#endif
static struct wait_queue *random_wait;
#ifndef MIN
#define MIN(a,b) (((a) < (b)) ? (a) : (b))
#endif
void
rand_initialize(void)
{
random_state.add_ptr = 0;
random_state.entropy_count = 0;
random_state.pool = random_pool;
random_wait = NULL;
random_state.rsel.si_flags = 0;
random_state.rsel.si_pid = 0;
}
/*
* This function adds an int into the entropy "pool". It does not
* update the entropy estimate. The caller must do this if appropriate.
*
* The pool is stirred with a primitive polynomial of degree 128
* over GF(2), namely x^128 + x^99 + x^59 + x^31 + x^9 + x^7 + 1.
* For a pool of size 64, try x^64+x^62+x^38+x^10+x^6+x+1.
*
* We rotate the input word by a changing number of bits, to help
* assure that all bits in the entropy get toggled. Otherwise, if we
* consistently feed the entropy pool small numbers (like ticks and
* scancodes, for example), the upper bits of the entropy pool don't
* get affected. --- TYT, 10/11/95
*/
static __inline void
add_entropy_word(struct random_bucket *r, const u_int32_t input)
{
u_int i;
u_int32_t w;
w = (input << r->input_rotate) | (input >> (32 - r->input_rotate));
i = r->add_ptr = (r->add_ptr - 1) & (POOLWORDS-1);
if (i)
r->input_rotate = (r->input_rotate + 7) & 31;
else
/*
* At the beginning of the pool, add an extra 7 bits
* rotation, so that successive passes spread the
* input bits across the pool evenly.
*/
r->input_rotate = (r->input_rotate + 14) & 31;
/* XOR in the various taps */
w ^= r->pool[(i+TAP1)&(POOLWORDS-1)];
w ^= r->pool[(i+TAP2)&(POOLWORDS-1)];
w ^= r->pool[(i+TAP3)&(POOLWORDS-1)];
w ^= r->pool[(i+TAP4)&(POOLWORDS-1)];
w ^= r->pool[(i+TAP5)&(POOLWORDS-1)];
w ^= r->pool[i];
/* Rotate w left 1 bit (stolen from SHA) and store */
r->pool[i] = (w << 1) | (w >> 31);
}
/*
* This function adds entropy to the entropy "pool" by using timing
* delays. It uses the timer_rand_state structure to make an estimate
* of how any bits of entropy this call has added to the pool.
*
* The number "num" is also added to the pool - it should somehow describe
* the type of event which just happened. This is currently 0-255 for
* keyboard scan codes, and 256 upwards for interrupts.
* On the i386, this is assumed to be at most 16 bits, and the high bits
* are used for a high-resolution timer.
*/
static void
add_timer_randomness(struct random_bucket *r, struct timer_rand_state *state,
u_int num)
{
int delta, delta2;
u_int nbits;
u_int32_t time;
num ^= timecounter->tc_get_timecount(timecounter) << 16;
r->entropy_count += 2;
time = ticks;
add_entropy_word(r, (u_int32_t) num);
add_entropy_word(r, time);
/*
* Calculate number of bits of randomness we probably
* added. We take into account the first and second order
* deltas in order to make our estimate.
*/
delta = time - state->last_time;
state->last_time = time;
delta2 = delta - state->last_delta;
state->last_delta = delta;
if (delta < 0) delta = -delta;
if (delta2 < 0) delta2 = -delta2;
delta = MIN(delta, delta2) >> 1;
for (nbits = 0; delta; nbits++)
delta >>= 1;
r->entropy_count += nbits;
/* Prevent overflow */
if (r->entropy_count > POOLBITS)
r->entropy_count = POOLBITS;
if (r->entropy_count >= 8)
selwakeup(&random_state.rsel);
}
void
add_keyboard_randomness(u_char scancode)
{
add_timer_randomness(&random_state, &keyboard_timer_state, scancode);
}
void
add_interrupt_randomness(void *vsc)
{
int intr;
struct random_softc *sc = vsc;
(sc->sc_handler)(sc->sc_arg);
intr = sc->sc_intr;
add_timer_randomness(&random_state, &irq_timer_state[intr], intr);
}
#ifdef notused
void
add_blkdev_randomness(int major)
{
if (major >= MAX_BLKDEV)
return;
add_timer_randomness(&random_state, &blkdev_timer_state[major],
0x200+major);
}
#endif /* notused */
#if POOLWORDS % 16
#error extract_entropy() assumes that POOLWORDS is a multiple of 16 words.
#endif
/*
* This function extracts randomness from the "entropy pool", and
* returns it in a buffer. This function computes how many remaining
* bits of entropy are left in the pool, but it does not restrict the
* number of bytes that are actually obtained.
*/
static __inline int
extract_entropy(struct random_bucket *r, char *buf, int nbytes)
{
int ret, i;
u_int32_t tmp[4];
add_timer_randomness(r, &extract_timer_state, nbytes);
/* Redundant, but just in case... */
if (r->entropy_count > POOLBITS)
r->entropy_count = POOLBITS;
/* Why is this here? Left in from Ted Ts'o. Perhaps to limit time. */
if (nbytes > 32768)
nbytes = 32768;
ret = nbytes;
if (r->entropy_count / 8 >= nbytes)
r->entropy_count -= nbytes*8;
else
r->entropy_count = 0;
while (nbytes) {
/* Hash the pool to get the output */
tmp[0] = 0x67452301;
tmp[1] = 0xefcdab89;
tmp[2] = 0x98badcfe;
tmp[3] = 0x10325476;
for (i = 0; i < POOLWORDS; i += 16)
MD5Transform(tmp, (char *)(r->pool+i));
/* Modify pool so next hash will produce different results */
add_entropy_word(r, tmp[0]);
add_entropy_word(r, tmp[1]);
add_entropy_word(r, tmp[2]);
add_entropy_word(r, tmp[3]);
/*
* Run the MD5 Transform one more time, since we want
* to add at least minimal obscuring of the inputs to
* add_entropy_word(). --- TYT
*/
MD5Transform(tmp, (char *)(r->pool));
/* Copy data to destination buffer */
i = MIN(nbytes, 16);
bcopy(tmp, buf, i);
nbytes -= i;
buf += i;
}
/* Wipe data from memory */
bzero(tmp, sizeof(tmp));
return ret;
}
#ifdef notused /* XXX NOT the exported kernel interface */
/*
* This function is the exported kernel interface. It returns some
* number of good random numbers, suitable for seeding TCP sequence
* numbers, etc.
*/
void
get_random_bytes(void *buf, u_int nbytes)
{
extract_entropy(&random_state, (char *) buf, nbytes);
}
#endif /* notused */
u_int
read_random(void *buf, u_int nbytes)
{
if ((nbytes * 8) > random_state.entropy_count)
nbytes = random_state.entropy_count / 8;
return extract_entropy(&random_state, (char *)buf, nbytes);
}
u_int
read_random_unlimited(void *buf, u_int nbytes)
{
return extract_entropy(&random_state, (char *)buf, nbytes);
}
#ifdef notused
u_int
write_random(const char *buf, u_int nbytes)
{
u_int i;
u_int32_t word, *p;
for (i = nbytes, p = (u_int32_t *)buf;
i >= sizeof(u_int32_t);
i-= sizeof(u_int32_t), p++)
add_entropy_word(&random_state, *p);
if (i) {
word = 0;
bcopy(p, &word, i);
add_entropy_word(&random_state, word);
}
return nbytes;
}
#endif /* notused */
int
random_poll(dev_t dev, int events, struct proc *p)
{
int s;
int revents = 0;
s = splhigh();
if (events & (POLLIN | POLLRDNORM))
if (random_state.entropy_count >= 8)
revents |= events & (POLLIN | POLLRDNORM);
else
selrecord(p, &random_state.rsel);
splx(s);
if (events & (POLLOUT | POLLWRNORM))
revents |= events & (POLLOUT | POLLWRNORM); /* heh */
return (revents);
}
