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|
/* $OpenBSD: rnd.c,v 1.3 1996/04/24 21:26:41 mickey Exp $ */
/*
* Copyright (c) 1996 Michael Shalayeff.
*
* This software derived from one contributed by Theodore Ts'o.
*
* 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.
* 3. All advertising materials mentioning features or use of this software
* must display the following acknowledgement:
* This product includes software developed by Theodore Ts'o.
* 4. Neither the name of the University nor of the Laboratory may be used
* to endorse or promote products derived from this software without
* specific prior written permission.
*
* THIS SOFTWARE IS PROVIDED BY THE REGENTS 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.
*
*
*
* random.c -- A strong random number generator
*
* Version 0.96, last modified 29-Dec-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.
*/
/*
* (now, with legal B.S. out of the way.....)
*
* This routine gathers environmental noise from device drivers, etc.,
* and returns good random numbers, suitable for cryptographic use.
* Besides the obvious cryptographic uses, these numbers are also good
* for seeding TCP sequence numbers, and other places where it is
* desireable to have numbers which are not only random, but hard to
* predict by an attacker.
*
* Theory of operation
* ===================
*
* Computers are very predictable devices. Hence it is extremely hard
* to produce truely random numbers on a computer --- as opposed to
* pseudo-random numbers, which can easily generated by using a
* algorithm. Unfortunately, it is very easy for attackers to guess
* the sequence of pseudo-random number generators, and for some
* applications this is not acceptable. So instead, we must try to
* gather "environmental noise" from the computer's environment, which
* must be hard for outside attackers to observe, and use that to
* generate random numbers. In a Unix environment, this is best done
* from inside the kernel.
*
* Sources of randomness from the environment include inter-keyboard
* timings, inter-interrupt timings from some interrupts, and other
* events which are both (a) non-deterministic and (b) hard for an
* outside observer to measure. Randomness from these sources are
* added to an "entropy pool", which is mixed using a CRC-like function.
* This is not cryptographically strong, but it is adequate assuming
* the randomness is not chosen maliciously, and it is fast enough that
* the overhead of doing it on every interrupt is very reasonable.
* As random bytes are mixed into the entropy pool, the routines keep
* an *estimate* of how many bits of randomness have been stored into
* the random number generator's internal state.
*
* When random bytes are desired, they are obtained by taking the MD5
* hash of the contents of the "entropy pool". The MD5 hash avoids
* exposing the internal state of the entropy pool. It is believed to
* be computationally infeasible to derive any useful information
* about the input of MD5 from its output. Even if it is possible to
* analyze MD5 in some clever way, as long as the amount of data
* returned from the generator is less than the inherent entropy in
* the pool, the output data is totally unpredictable. For this
* reason, the routine decreases its internal estimate of how many
* bits of "true randomness" are contained in the entropy pool as it
* outputs random numbers.
*
* If this estimate goes to zero, the routine can still generate
* random numbers; however, an attacker may (at least in theory) be
* able to infer the future output of the generator from prior
* outputs. This requires successful cryptanalysis of MD5, which is
* not believed to be feasible, but there is a remote possiblility.
* Nonetheless, these numbers should be useful for the vast majority
* of purposes.
*
* Exported interfaces ---- output
* ===============================
*
* There are three exported interfaces; the first is one designed to
* be used from within the kernel:
*
* void get_random_bytes(void *buf, int nbytes);
*
* This interface will return the requested number of random bytes,
* and place it in the requested buffer.
*
* The two other interfaces are two character devices /dev/random and
* /dev/urandom. /dev/random is suitable for use when very high
* quality randomness is desired (for example, for key generation or
* one-time pads), as it will only return a maximum of the number of
* bits of randomness (as estimated by the random number generator)
* contained in the entropy pool.
*
* The /dev/urandom device does not have this limit, and will return
* as many bytes as are requested. As more and more random bytes are
* requested without giving time for the entropy pool to recharge,
* this will result in random numbers that are merely cryptographically
* strong. For many applications, however, this is acceptable.
*
* Exported interfaces ---- input
* ==============================
*
* The current exported interfaces for gathering environmental noise
* from the devices are:
*
* void add_keyboard_randomness(u_char scancode);
* void add_mouse_randomness(u_int32_t mouse_data);
* void add_interrupt_randomness(int irq);
* void add_blkdev_randomness(dev_t dev);
*
* add_keyboard_randomness() uses the inter-keypress timing, as well as the
* scancode as random inputs into the "entropy pool".
*
* add_mouse_randomness() uses the mouse interrupt timing, as well as
* the reported position of the mouse from the hardware.
*
* add_interrupt_randomness() uses the inter-interrupt timing as random
* inputs to the entropy pool. Note that not all interrupts are good
* sources of randomness! For example, the timer interrupts is not a
* good choice, because the periodicity of the interrupts is to
* regular, and hence predictable to an attacker. Disk interrupts are
* a better measure, since the timing of the disk interrupts are more
* unpredictable.
*
* add_blkdev_randomness() times the finishing time of block requests.
*
* All of these routines try to estimate how many bits of randomness a
* particular randomness source. They do this by keeping track of the
* first and second order deltas of the event timings.
*
* Acknowledgements:
* =================
*
* Ideas for constructing this random number generator were derived
* from the Pretty Good Privacy's random number generator, and from
* private discussions with Phil Karn. Colin Plumb provided a faster
* random number generator, which speed up the mixing function of the
* entropy pool, taken from PGP 3.0 (under development). It has since
* been modified by myself to provide better mixing in the case where
* the input values to add_entropy_word() are mostly small numbers.
*
* Any flaws in the design are solely my responsibility, and should
* not be attributed to the Phil, Colin, or any of authors of PGP.
*
*/
#include "rnd.h"
#if NRND > 0
#include <sys/param.h>
#include <sys/types.h>
#include <sys/systm.h>
#include <sys/kernel.h>
#include <sys/conf.h>
#include <sys/device.h>
#include <sys/ioctl.h>
#include <sys/malloc.h>
#include <sys/proc.h>
#include <sys/user.h>
#include <sys/fcntl.h>
#include <sys/vnode.h>
#include <net/netisr.h>
#include <dev/rndvar.h>
#include <dev/rndioctl.h>
#ifdef DEBUG
int rnd_debug = 0x0000;
#define RD_INPUT 0x000f /* input data */
#define RD_OUTPUT 0x00f0 /* output data */
#define RD_WAIT 0x0100 /* sleep/wakeup for good data */
#endif
/*
* 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 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
/* 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;
};
/* There is one of these per entropy source */
struct timer_rand_state {
u_long last_time;
int last_delta;
int dont_count_entropy:1;
};
/* tags for different random sources */
#define ENT_NET 0x100
#define ENT_BLKDEV 0x200
#define ENT_TTY 0x300
/* device functions prototypes: XXX move em to dev_conf.h */
cdev_decl(rnd);
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 mouse_timer_state;
static struct timer_rand_state extract_timer_state;
static struct timer_rand_state net_timer_state[32]; /* XXX */
static struct timer_rand_state *blkdev_timer_state;
static struct timer_rand_state *tty_timer_state;
static int rnd_sleep = 0;
#ifndef MIN
#define MIN(a,b) (((a) < (b)) ? (a) : (b))
#endif
void
rndattach(num)
int num;
{
if (num > 1)
panic("no more than one rnd device");
random_state.add_ptr = 0;
random_state.entropy_count = 0;
random_state.pool = random_pool;
blkdev_timer_state = malloc(nblkdev*sizeof(*blkdev_timer_state),
M_DEVBUF, M_WAITOK);
bzero(blkdev_timer_state, nblkdev*sizeof(*blkdev_timer_state));
tty_timer_state = malloc(nchrdev*sizeof(*tty_timer_state),
M_DEVBUF, M_WAITOK);
bzero(tty_timer_state, nchrdev*sizeof(*tty_timer_state));
extract_timer_state.dont_count_entropy = 1;
}
int
rndopen(dev, flag, mode, p)
dev_t dev;
int flag;
int mode;
struct proc *p;
{
return 0;
}
int
rndclose(dev, flag, mode, p)
dev_t dev;
int flag;
int mode;
struct proc *p;
{
return 0;
}
/*
* This function adds a byte 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 jiffies 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(r, input)
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 many 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(r, state, num)
struct random_bucket *r;
struct timer_rand_state *state;
u_int num;
{
int delta, delta2;
u_int nbits;
u_int32_t time;
{
struct timeval tv;
microtime(&tv);
time = tv.tv_usec ^ tv.tv_sec;
}
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.
*/
if (!state->dont_count_entropy) {
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 && rnd_sleep != 0) {
rnd_sleep--;
#ifdef DEBUG
if (rnd_debug & RD_WAIT)
printf("rnd: wakeup[%d]{%u}\n",
rnd_sleep, r->entropy_count);
#endif
wakeup(&rnd_sleep);
}
}
void
add_keyboard_randomness(scancode)
u_char scancode;
{
#ifdef DEBUG
if (rnd_debug & RD_INPUT)
printf("rnd: adding %02x from kbd\n", scancode);
#endif
add_timer_randomness(&random_state, &keyboard_timer_state, scancode);
}
void
add_mouse_randomness(mouse_data)
u_int32_t mouse_data;
{
add_timer_randomness(&random_state, &mouse_timer_state, mouse_data);
}
void
add_net_randomness(isr)
int isr;
{
if (isr >= sizeof(net_timer_state)/sizeof(*net_timer_state))
return;
add_timer_randomness(&random_state, &net_timer_state[isr],
ENT_NET + isr);
}
void
add_blkdev_randomness(dev)
dev_t dev;
{
if (major(dev) <= nblkdev || blkdev_timer_state == NULL)
return;
add_timer_randomness(&random_state, &blkdev_timer_state[major(dev)],
ENT_BLKDEV + major(dev));
}
void
add_tty_randomness(dev, c)
dev_t dev;
int c;
{
if (major(dev) <= nchrdev || tty_timer_state == NULL)
return;
add_timer_randomness(&random_state, &tty_timer_state[major(dev)],
ENT_TTY + c);
}
#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(r, buf, nbytes)
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 */
MD5Init(tmp);
for (i = 0; i < POOLWORDS; i += 16)
MD5Transform(tmp, 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, r->pool);
/* Copy data to destination buffer */
i = MIN(nbytes, 16);
bcopy((caddr_t)tmp, buf, i);
nbytes -= i;
buf += i;
}
/* Wipe data from memory */
bzero(tmp, sizeof(tmp));
return ret;
}
/*
* 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(buf, nbytes)
void *buf;
size_t nbytes;
{
extract_entropy(&random_state, (char *) buf, nbytes, 0);
}
int
rndread(dev, uio, ioflag)
dev_t dev;
struct uio *uio;
int ioflag;
{
int ret = 0;
int s;
if (uio->uio_resid == 0)
return 0;
while (!ret && uio->uio_resid > 0) {
u_int32_t buf[ POOLWORDS ];
int n = min(sizeof(buf), uio->uio_resid);
s = splhigh();
switch(minor(dev))
{
case RND_RND:
break;
case RND_SRND:
if (random_state.entropy_count < 8) {
if (ioflag & IO_NDELAY) {
ret = EWOULDBLOCK;
break;
}
#ifdef DEBUG
if (rnd_debug & RD_WAIT)
printf("rnd: sleep[%d]\n",
rnd_sleep);
#endif
rnd_sleep++;
ret = tsleep(&rnd_sleep, PWAIT | PCATCH,
"rndrd", 0);
#ifdef DEBUG
if (rnd_debug & RD_WAIT)
printf("rnd: awakened(%d)\n",
ret);
#endif
if (ret)
break;
}
n = min(n, random_state.entropy_count / 8);
#ifdef DEBUG
if (rnd_debug & RD_OUTPUT)
printf("rnd: %u possible output\n",
n );
#endif
case RND_URND:
n = extract_entropy(&random_state, buf, n);
#ifdef DEBUG
if (rnd_debug & RD_OUTPUT)
printf("rnd: %u bytes for output\n",
n );
#endif
break;
case RND_PRND:
{
int i = (n + 3) / 4;
while(i--)
buf[i] = random();
}
break;
}
splx(s);
if (n != 0 && ret == 0)
ret = uiomove((caddr_t)buf, n, uio);
}
return ret;
}
int
rndselect(dev, rw, p)
dev_t dev;
int rw;
struct proc *p;
{
switch (rw) {
case FREAD:
return random_state.entropy_count > 0;
case FWRITE:
return 1;
}
return 0;
}
int
rndwrite(dev, uio, flags)
dev_t dev;
struct uio *uio;
int flags;
{
int ret = 0;
if (minor(dev) == RND_RND || minor(dev) == RND_PRND)
return ENXIO;
if (uio->uio_resid == 0)
return 0;
while (!ret && uio->uio_resid > 0) {
u_int32_t buf[ POOLWORDS ];
u_short n = min(sizeof(buf),uio->uio_resid);
ret = uiomove((caddr_t)buf, n, uio);
if (!ret) {
int i;
while (n % sizeof(u_int32_t))
buf[n++] = 0;
for (i = 0; i < n; i++)
add_entropy_word(&random_state, buf[i]);
}
}
return ret;
}
int
rndioctl(dev, cmd, data, flag, p)
dev_t dev;
u_long cmd;
caddr_t data;
int flag;
struct proc *p;
{
int ret;
switch (cmd) {
case RNDGETENTCNT:
ret = copyout(&random_state.entropy_count, data,
sizeof(random_state.entropy_count));
break;
case RNDADDTOENTCNT:
if (suser(p->p_ucred, &p->p_acflag) != 0)
return EPERM;
{
u_int cnt;
copyin(&cnt, data, sizeof(cnt));
random_state.entropy_count += cnt;
}
if (random_state.entropy_count > POOLBITS)
random_state.entropy_count = POOLBITS;
break;
case RNDZAPENTCNT:
if (suser(p->p_ucred, &p->p_acflag) != 0)
return EPERM;
random_state.entropy_count = 0;
break;
default:
ret = EINVAL;
}
return ret;
}
#endif
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