freebsd-dev/sys/kern/kern_random.c
Matthew Dillon 3e1ce344ba Load the current timecounter into tc. The timecounter global can change
at any time and we do not want to call one timercounter's function with
another timecounter's structural pointer.

MFC after:	3 days
2002-02-18 19:49:30 +00:00

398 lines
11 KiB
C

/*
* kern_random.c -- A strong random number generator
*
* $FreeBSD$
*
* 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/md5.h>
#include <sys/poll.h>
#include <sys/random.h>
#include <sys/systm.h>
#include <sys/select.h>
#include <sys/timetc.h>
#include <machine/ipl.h>
#include <machine/mutex.h>
#ifdef __i386__
#include <i386/isa/icu.h>
#endif
#ifdef __alpha__
/*
XXX the below should be used. However there is too much "16"
hardcodeing in kern_random.c right now. -- obrien
#include <machine/ipl.h>
#if NHWI > 0
#define ICU_LEN (NHWI)
#else
#define ICU_LEN (NSWI)
#endif
*/
#define ICU_LEN 16
#endif
#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;
struct timecounter *tc = timecounter; /* can change at any time */
num ^= tc->tc_get_timecount(tc) << 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 revents = 0;
mtx_enter_sched_quick();
if (events & (POLLIN | POLLRDNORM)) {
if (random_state.entropy_count >= 8)
revents |= events & (POLLIN | POLLRDNORM);
else
selrecord(p, &random_state.rsel);
}
mtx_exit_sched_quick();
if (events & (POLLOUT | POLLWRNORM))
revents |= events & (POLLOUT | POLLWRNORM); /* heh */
return (revents);
}