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|
/* $OpenBSD: rnd.c,v 1.190 2016/10/18 13:40:59 deraadt Exp $ */
/*
* Copyright (c) 2011 Theo de Raadt.
* Copyright (c) 2008 Damien Miller.
* Copyright (c) 1996, 1997, 2000-2002 Michael Shalayeff.
* Copyright (c) 2013 Markus Friedl.
* Copyright Theodore Ts'o, 1994, 1995, 1996, 1997, 1998, 1999.
* 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.
*/
/*
* Computers are very predictable devices. Hence it is extremely hard
* to produce truly random numbers on a computer --- as opposed to
* pseudo-random numbers, which can be easily generated by using an
* 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. Instead, we must try to
* gather "environmental noise" from the computer's environment, which
* must be hard for outside attackers to observe and use 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 is
* added to the "rnd states" queue; this is used as much of the
* source material which is mixed on occasion using a CRC-like function
* into the "entropy pool". This is not cryptographically strong, but
* it is adequate assuming the randomness is not chosen maliciously,
* and it is very fast because the interrupt-time event is only to add
* a small random token to the "rnd states" queue.
*
* When random bytes are desired, they are obtained by pulling from
* the entropy pool and running a SHA512 hash. The SHA512 hash avoids
* exposing the internal state of the entropy pool. Even if it is
* possible to analyze SHA512 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 SHA512 hash will continue to generate
* output since there is no true risk because the SHA512 output is not
* exported outside this subsystem. It is next used as input to seed a
* ChaCha20 stream cipher, which is re-seeded from time to time. This
* design provides very high amounts of output data from a potentially
* small entropy base, at high enough speeds to encourage use of random
* numbers in nearly any situation. Before OpenBSD 5.5, the RC4 stream
* cipher (also known as ARC4) was used instead of ChaCha20.
*
* The output of this single ChaCha20 engine is then shared amongst many
* consumers in the kernel and userland via a few interfaces:
* arc4random_buf(), arc4random(), arc4random_uniform(), randomread()
* for the set of /dev/random nodes and the system call getentropy(),
* which provides seeds for process-context pseudorandom generators.
*
* Acknowledgements:
* =================
*
* Ideas for constructing this random number generator were derived
* from Pretty Good Privacy's random number generator, and from private
* discussions with Phil Karn. Colin Plumb provided a faster random
* number generator, which speeds up the mixing function of the entropy
* pool, taken from PGPfone. Dale Worley has also contributed many
* useful ideas and suggestions to improve this driver.
*
* Any flaws in the design are solely my responsibility, and should
* not be attributed to the Phil, Colin, or any of the authors of PGP.
*
* Further background information on this topic may be obtained from
* RFC 1750, "Randomness Recommendations for Security", by Donald
* Eastlake, Steve Crocker, and Jeff Schiller.
*
* Using a RC4 stream cipher as 2nd stage after the MD5 (now SHA512) output
* is the result of work by David Mazieres.
*/
#include <sys/param.h>
#include <sys/systm.h>
#include <sys/disk.h>
#include <sys/event.h>
#include <sys/limits.h>
#include <sys/time.h>
#include <sys/ioctl.h>
#include <sys/malloc.h>
#include <sys/fcntl.h>
#include <sys/timeout.h>
#include <sys/mutex.h>
#include <sys/task.h>
#include <sys/msgbuf.h>
#include <sys/mount.h>
#include <sys/syscallargs.h>
#include <crypto/sha2.h>
#define KEYSTREAM_ONLY
#include <crypto/chacha_private.h>
#include <dev/rndvar.h>
#include <uvm/uvm_param.h>
#include <uvm/uvm_extern.h>
/*
* For the purposes of better mixing, we use the CRC-32 polynomial as
* well to make a twisted Generalized Feedback Shift Register
*
* (See M. Matsumoto & Y. Kurita, 1992. Twisted GFSR generators. ACM
* Transactions on Modeling and Computer Simulation 2(3):179-194.
* Also see M. Matsumoto & Y. Kurita, 1994. Twisted GFSR generators
* II. ACM Transactions on Mdeling and Computer Simulation 4:254-266)
*
* Thanks to Colin Plumb for suggesting this.
*
* We have not analyzed the resultant polynomial to prove it primitive;
* in fact it almost certainly isn't. Nonetheless, the irreducible factors
* of a random large-degree polynomial over GF(2) are more than large enough
* that periodicity is not a concern.
*
* The input hash is much less sensitive than the output hash. All
* we want from it is to be a good non-cryptographic hash -
* i.e. to not produce collisions when fed "random" data of the sort
* we expect to see. As long as the pool state differs for different
* inputs, we have preserved the input entropy and done a good job.
* The fact that an intelligent attacker can construct inputs that
* will produce controlled alterations to the pool's state is not
* important because we don't consider such inputs to contribute any
* randomness. The only property we need with respect to them is that
* the attacker can't increase his/her knowledge of the pool's state.
* Since all additions are reversible (knowing the final state and the
* input, you can reconstruct the initial state), if an attacker has
* any uncertainty about the initial state, he/she can only shuffle
* that uncertainty about, but never cause any collisions (which would
* decrease the uncertainty).
*
* The chosen system lets the state of the pool be (essentially) the input
* modulo the generator polynomial. Now, for random primitive polynomials,
* this is a universal class of hash functions, meaning that the chance
* of a collision is limited by the attacker's knowledge of the generator
* polynomial, so if it is chosen at random, an attacker can never force
* a collision. Here, we use a fixed polynomial, but we *can* assume that
* ###--> it is unknown to the processes generating the input entropy. <-###
* Because of this important property, this is a good, collision-resistant
* hash; hash collisions will occur no more often than chance.
*/
/*
* Stirring polynomials over GF(2) for various pool sizes. Used in
* add_entropy_words() below.
*
* The polynomial terms are chosen to be evenly spaced (minimum RMS
* distance from evenly spaced; except for the last tap, which is 1 to
* get the twisting happening as fast as possible.
*
* The reultant polynomial is:
* 2^POOLWORDS + 2^POOL_TAP1 + 2^POOL_TAP2 + 2^POOL_TAP3 + 2^POOL_TAP4 + 1
*/
#define POOLWORDS 2048
#define POOLBYTES (POOLWORDS*4)
#define POOLMASK (POOLWORDS - 1)
#define POOL_TAP1 1638
#define POOL_TAP2 1231
#define POOL_TAP3 819
#define POOL_TAP4 411
struct mutex entropylock = MUTEX_INITIALIZER(IPL_HIGH);
/*
* Raw entropy collection from device drivers; at interrupt context or not.
* add_*_randomness() provide data which is put into the entropy queue.
* Almost completely under the entropylock.
*/
#define QEVLEN (1024 / sizeof(struct rand_event))
#define QEVSLOW (QEVLEN * 3 / 4) /* yet another 0.75 for 60-minutes hour /-; */
#define QEVSBITS 10
#define KEYSZ 32
#define IVSZ 8
#define BLOCKSZ 64
#define RSBUFSZ (16*BLOCKSZ)
#define EBUFSIZE KEYSZ + IVSZ
struct rand_event {
u_int re_time;
u_int re_val;
} rnd_event_space[QEVLEN];
/* index of next free slot */
u_int rnd_event_idx;
struct timeout rnd_timeout;
static u_int32_t entropy_pool[POOLWORDS];
static const u_int32_t entropy_pool0[POOLWORDS] __attribute__((section(".openbsd.randomdata")));
u_int entropy_add_ptr;
u_char entropy_input_rotate;
void dequeue_randomness(void *);
void add_entropy_words(const u_int32_t *, u_int);
void extract_entropy(u_int8_t *)
__attribute__((__bounded__(__minbytes__,1,EBUFSIZE)));
int filt_randomread(struct knote *, long);
void filt_randomdetach(struct knote *);
int filt_randomwrite(struct knote *, long);
static void _rs_seed(u_char *, size_t);
static void _rs_clearseed(const void *p, size_t s);
struct filterops randomread_filtops =
{ 1, NULL, filt_randomdetach, filt_randomread };
struct filterops randomwrite_filtops =
{ 1, NULL, filt_randomdetach, filt_randomwrite };
static __inline struct rand_event *
rnd_get(void)
{
if (rnd_event_idx == 0)
return NULL;
/* if it wrapped around, start dequeuing at the end */
if (rnd_event_idx > QEVLEN)
rnd_event_idx = QEVLEN;
return &rnd_event_space[--rnd_event_idx];
}
static __inline struct rand_event *
rnd_put(void)
{
u_int idx = rnd_event_idx++;
/* allow wrapping. caller will use xor. */
idx = idx % QEVLEN;
return &rnd_event_space[idx];
}
static __inline u_int
rnd_qlen(void)
{
return rnd_event_idx;
}
/*
* 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 "val" is also added to the pool - it should somehow describe
* the type of event which just happened. Currently the values of 0-255
* are for keyboard scan codes, 256 and upwards - for interrupts.
*/
void
enqueue_randomness(u_int state, u_int val)
{
struct rand_event *rep;
struct timespec ts;
#ifdef DIAGNOSTIC
if (state >= RND_SRC_NUM)
return;
#endif
if (timeout_initialized(&rnd_timeout))
nanotime(&ts);
val += state << 13;
mtx_enter(&entropylock);
rep = rnd_put();
rep->re_time += ts.tv_nsec ^ (ts.tv_sec << 20);
rep->re_val += val;
if (rnd_qlen() > QEVSLOW/2 && timeout_initialized(&rnd_timeout) &&
!timeout_pending(&rnd_timeout))
timeout_add(&rnd_timeout, 1);
mtx_leave(&entropylock);
}
/*
* 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 polynomial of degree POOLWORDS over GF(2);
* see POOL_TAP[1-4] above
*
* Rotate the input word by a changing number of bits, to help assure
* that all bits in the entropy get toggled. Otherwise, if the pool
* is consistently fed small numbers (such as keyboard scan codes)
* then the upper bits of the entropy pool will frequently remain
* untouched.
*/
void
add_entropy_words(const u_int32_t *buf, u_int n)
{
/* derived from IEEE 802.3 CRC-32 */
static const u_int32_t twist_table[8] = {
0x00000000, 0x3b6e20c8, 0x76dc4190, 0x4db26158,
0xedb88320, 0xd6d6a3e8, 0x9b64c2b0, 0xa00ae278
};
for (; n--; buf++) {
u_int32_t w = (*buf << entropy_input_rotate) |
(*buf >> ((32 - entropy_input_rotate) & 31));
u_int i = entropy_add_ptr =
(entropy_add_ptr - 1) & POOLMASK;
/*
* Normally, we add 7 bits of rotation to the pool.
* At the beginning of the pool, add an extra 7 bits
* rotation, so that successive passes spread the
* input bits across the pool evenly.
*/
entropy_input_rotate =
(entropy_input_rotate + (i ? 7 : 14)) & 31;
/* XOR pool contents corresponding to polynomial terms */
w ^= entropy_pool[(i + POOL_TAP1) & POOLMASK] ^
entropy_pool[(i + POOL_TAP2) & POOLMASK] ^
entropy_pool[(i + POOL_TAP3) & POOLMASK] ^
entropy_pool[(i + POOL_TAP4) & POOLMASK] ^
entropy_pool[(i + 1) & POOLMASK] ^
entropy_pool[i]; /* + 2^POOLWORDS */
entropy_pool[i] = (w >> 3) ^ twist_table[w & 7];
}
}
/*
* Pulls entropy out of the queue and throws merges it into the pool
* with the CRC.
*/
/* ARGSUSED */
void
dequeue_randomness(void *v)
{
struct rand_event *rep;
u_int32_t buf[2];
mtx_enter(&entropylock);
if (timeout_initialized(&rnd_timeout))
timeout_del(&rnd_timeout);
while ((rep = rnd_get())) {
buf[0] = rep->re_time;
buf[1] = rep->re_val;
mtx_leave(&entropylock);
add_entropy_words(buf, 2);
mtx_enter(&entropylock);
}
mtx_leave(&entropylock);
}
/*
* Grabs a chunk from the entropy_pool[] and slams it through SHA512 when
* requested.
*/
void
extract_entropy(u_int8_t *buf)
{
static u_int32_t extract_pool[POOLWORDS];
u_char digest[SHA512_DIGEST_LENGTH];
SHA2_CTX shactx;
#if SHA512_DIGEST_LENGTH < EBUFSIZE
#error "need more bigger hash output"
#endif
/*
* INTENTIONALLY not protected by entropylock. Races during
* memcpy() result in acceptable input data; races during
* SHA512Update() would create nasty data dependencies. We
* do not rely on this as a benefit, but if it happens, cool.
*/
memcpy(extract_pool, entropy_pool, sizeof(extract_pool));
/* Hash the pool to get the output */
SHA512Init(&shactx);
SHA512Update(&shactx, (u_int8_t *)extract_pool, sizeof(extract_pool));
SHA512Final(digest, &shactx);
/* Copy data to destination buffer */
memcpy(buf, digest, EBUFSIZE);
/* Modify pool so next hash will produce different results */
add_timer_randomness(EBUFSIZE);
dequeue_randomness(NULL);
/* Wipe data from memory */
explicit_bzero(extract_pool, sizeof(extract_pool));
explicit_bzero(digest, sizeof(digest));
}
/* random keystream by ChaCha */
void arc4_reinit(void *v); /* timeout to start reinit */
void arc4_init(void *); /* actually do the reinit */
struct mutex rndlock = MUTEX_INITIALIZER(IPL_HIGH);
struct timeout arc4_timeout;
struct task arc4_task = TASK_INITIALIZER(arc4_init, NULL);
static chacha_ctx rs; /* chacha context for random keystream */
/* keystream blocks (also chacha seed from boot) */
static u_char rs_buf[RSBUFSZ];
static const u_char rs_buf0[RSBUFSZ] __attribute__((section(".openbsd.randomdata")));
static size_t rs_have; /* valid bytes at end of rs_buf */
static size_t rs_count; /* bytes till reseed */
void
suspend_randomness(void)
{
struct timespec ts;
getnanotime(&ts);
add_true_randomness(ts.tv_sec);
add_true_randomness(ts.tv_nsec);
dequeue_randomness(NULL);
rs_count = 0;
arc4random_buf(entropy_pool, sizeof(entropy_pool));
}
void
resume_randomness(char *buf, size_t buflen)
{
struct timespec ts;
if (buf && buflen)
_rs_seed(buf, buflen);
getnanotime(&ts);
add_true_randomness(ts.tv_sec);
add_true_randomness(ts.tv_nsec);
dequeue_randomness(NULL);
rs_count = 0;
}
static inline void _rs_rekey(u_char *dat, size_t datlen);
static inline void
_rs_init(u_char *buf, size_t n)
{
KASSERT(n >= KEYSZ + IVSZ);
chacha_keysetup(&rs, buf, KEYSZ * 8);
chacha_ivsetup(&rs, buf + KEYSZ, NULL);
}
static void
_rs_seed(u_char *buf, size_t n)
{
_rs_rekey(buf, n);
/* invalidate rs_buf */
rs_have = 0;
memset(rs_buf, 0, RSBUFSZ);
rs_count = 1600000;
}
static void
_rs_stir(int do_lock)
{
struct timespec ts;
u_int8_t buf[EBUFSIZE], *p;
int i;
/*
* Use SHA512 PRNG data and a system timespec; early in the boot
* process this is the best we can do -- some architectures do
* not collect entropy very well during this time, but may have
* clock information which is better than nothing.
*/
extract_entropy(buf);
nanotime(&ts);
for (p = (u_int8_t *)&ts, i = 0; i < sizeof(ts); i++)
buf[i] ^= p[i];
if (do_lock)
mtx_enter(&rndlock);
_rs_seed(buf, sizeof(buf));
if (do_lock)
mtx_leave(&rndlock);
explicit_bzero(buf, sizeof(buf));
}
static inline void
_rs_stir_if_needed(size_t len)
{
static int rs_initialized;
if (!rs_initialized) {
memcpy(entropy_pool, entropy_pool0, sizeof entropy_pool);
memcpy(rs_buf, rs_buf0, sizeof rs_buf);
/* seeds cannot be cleaned yet, random_start() will do so */
_rs_init(rs_buf, KEYSZ + IVSZ);
rs_count = 1024 * 1024 * 1024; /* until main() runs */
rs_initialized = 1;
} else if (rs_count <= len)
_rs_stir(0);
else
rs_count -= len;
}
static void
_rs_clearseed(const void *p, size_t s)
{
struct kmem_dyn_mode kd_avoidalias;
vaddr_t va = trunc_page((vaddr_t)p);
vsize_t off = (vaddr_t)p - va;
vsize_t len;
vaddr_t rwva;
paddr_t pa;
while (s > 0) {
pmap_extract(pmap_kernel(), va, &pa);
memset(&kd_avoidalias, 0, sizeof kd_avoidalias);
kd_avoidalias.kd_prefer = pa;
kd_avoidalias.kd_waitok = 1;
rwva = (vaddr_t)km_alloc(PAGE_SIZE, &kv_any, &kp_none,
&kd_avoidalias);
if (!rwva)
panic("_rs_clearseed");
pmap_kenter_pa(rwva, pa, PROT_READ | PROT_WRITE);
pmap_update(pmap_kernel());
len = MIN(s, PAGE_SIZE - off);
explicit_bzero((void *)(rwva + off), len);
pmap_kremove(rwva, PAGE_SIZE);
km_free((void *)rwva, PAGE_SIZE, &kv_any, &kp_none);
va += PAGE_SIZE;
s -= len;
off = 0;
}
}
static inline void
_rs_rekey(u_char *dat, size_t datlen)
{
#ifndef KEYSTREAM_ONLY
memset(rs_buf, 0, RSBUFSZ);
#endif
/* fill rs_buf with the keystream */
chacha_encrypt_bytes(&rs, rs_buf, rs_buf, RSBUFSZ);
/* mix in optional user provided data */
if (dat) {
size_t i, m;
m = MIN(datlen, KEYSZ + IVSZ);
for (i = 0; i < m; i++)
rs_buf[i] ^= dat[i];
}
/* immediately reinit for backtracking resistance */
_rs_init(rs_buf, KEYSZ + IVSZ);
memset(rs_buf, 0, KEYSZ + IVSZ);
rs_have = RSBUFSZ - KEYSZ - IVSZ;
}
static inline void
_rs_random_buf(void *_buf, size_t n)
{
u_char *buf = (u_char *)_buf;
size_t m;
_rs_stir_if_needed(n);
while (n > 0) {
if (rs_have > 0) {
m = MIN(n, rs_have);
memcpy(buf, rs_buf + RSBUFSZ - rs_have, m);
memset(rs_buf + RSBUFSZ - rs_have, 0, m);
buf += m;
n -= m;
rs_have -= m;
}
if (rs_have == 0)
_rs_rekey(NULL, 0);
}
}
static inline void
_rs_random_u32(u_int32_t *val)
{
_rs_stir_if_needed(sizeof(*val));
if (rs_have < sizeof(*val))
_rs_rekey(NULL, 0);
memcpy(val, rs_buf + RSBUFSZ - rs_have, sizeof(*val));
memset(rs_buf + RSBUFSZ - rs_have, 0, sizeof(*val));
rs_have -= sizeof(*val);
return;
}
/* Return one word of randomness from a ChaCha20 generator */
u_int32_t
arc4random(void)
{
u_int32_t ret;
mtx_enter(&rndlock);
_rs_random_u32(&ret);
mtx_leave(&rndlock);
return ret;
}
/*
* Fill a buffer of arbitrary length with ChaCha20-derived randomness.
*/
void
arc4random_buf(void *buf, size_t n)
{
mtx_enter(&rndlock);
_rs_random_buf(buf, n);
mtx_leave(&rndlock);
}
/*
* Calculate a uniformly distributed random number less than upper_bound
* avoiding "modulo bias".
*
* Uniformity is achieved by generating new random numbers until the one
* returned is outside the range [0, 2**32 % upper_bound). This
* guarantees the selected random number will be inside
* [2**32 % upper_bound, 2**32) which maps back to [0, upper_bound)
* after reduction modulo upper_bound.
*/
u_int32_t
arc4random_uniform(u_int32_t upper_bound)
{
u_int32_t r, min;
if (upper_bound < 2)
return 0;
/* 2**32 % x == (2**32 - x) % x */
min = -upper_bound % upper_bound;
/*
* This could theoretically loop forever but each retry has
* p > 0.5 (worst case, usually far better) of selecting a
* number inside the range we need, so it should rarely need
* to re-roll.
*/
for (;;) {
r = arc4random();
if (r >= min)
break;
}
return r % upper_bound;
}
/* ARGSUSED */
void
arc4_init(void *null)
{
_rs_stir(1);
}
/*
* Called by timeout to mark arc4 for stirring,
*/
void
arc4_reinit(void *v)
{
task_add(systq, &arc4_task);
/* 10 minutes, per dm@'s suggestion */
timeout_add_sec(&arc4_timeout, 10 * 60);
}
/*
* Start periodic services inside the random subsystem, which pull
* entropy forward, hash it, and re-seed the random stream as needed.
*/
void
random_start(void)
{
#if !defined(NO_PROPOLICE)
extern long __guard_local;
if (__guard_local == 0)
printf("warning: no entropy supplied by boot loader\n");
#endif
_rs_clearseed(entropy_pool0, sizeof entropy_pool0);
_rs_clearseed(rs_buf0, sizeof rs_buf0);
/* Message buffer may contain data from previous boot */
if (msgbufp->msg_magic == MSG_MAGIC)
add_entropy_words((u_int32_t *)msgbufp->msg_bufc,
msgbufp->msg_bufs / sizeof(u_int32_t));
dequeue_randomness(NULL);
arc4_init(NULL);
timeout_set(&arc4_timeout, arc4_reinit, NULL);
arc4_reinit(NULL);
timeout_set(&rnd_timeout, dequeue_randomness, NULL);
}
int
randomopen(dev_t dev, int flag, int mode, struct proc *p)
{
return 0;
}
int
randomclose(dev_t dev, int flag, int mode, struct proc *p)
{
return 0;
}
/*
* Maximum number of bytes to serve directly from the main ChaCha
* pool. Larger requests are served from a discrete ChaCha instance keyed
* from the main pool.
*/
#define ARC4_MAIN_MAX_BYTES 2048
int
randomread(dev_t dev, struct uio *uio, int ioflag)
{
u_char lbuf[KEYSZ+IVSZ];
chacha_ctx lctx;
size_t total = uio->uio_resid;
u_char *buf;
int myctx = 0, ret = 0;
if (uio->uio_resid == 0)
return 0;
buf = malloc(POOLBYTES, M_TEMP, M_WAITOK);
if (total > ARC4_MAIN_MAX_BYTES) {
arc4random_buf(lbuf, sizeof(lbuf));
chacha_keysetup(&lctx, lbuf, KEYSZ * 8);
chacha_ivsetup(&lctx, lbuf + KEYSZ, NULL);
explicit_bzero(lbuf, sizeof(lbuf));
myctx = 1;
}
while (ret == 0 && uio->uio_resid > 0) {
size_t n = ulmin(POOLBYTES, uio->uio_resid);
if (myctx) {
#ifndef KEYSTREAM_ONLY
memset(buf, 0, n);
#endif
chacha_encrypt_bytes(&lctx, buf, buf, n);
} else
arc4random_buf(buf, n);
ret = uiomove(buf, n, uio);
if (ret == 0 && uio->uio_resid > 0)
yield();
}
if (myctx)
explicit_bzero(&lctx, sizeof(lctx));
explicit_bzero(buf, POOLBYTES);
free(buf, M_TEMP, POOLBYTES);
return ret;
}
int
randomwrite(dev_t dev, struct uio *uio, int flags)
{
int ret = 0, newdata = 0;
u_int32_t *buf;
if (uio->uio_resid == 0)
return 0;
buf = malloc(POOLBYTES, M_TEMP, M_WAITOK);
while (ret == 0 && uio->uio_resid > 0) {
size_t n = ulmin(POOLBYTES, uio->uio_resid);
ret = uiomove(buf, n, uio);
if (ret != 0)
break;
while (n % sizeof(u_int32_t))
((u_int8_t *)buf)[n++] = 0;
add_entropy_words(buf, n / 4);
if (uio->uio_resid > 0)
yield();
newdata = 1;
}
if (newdata)
arc4_init(NULL);
explicit_bzero(buf, POOLBYTES);
free(buf, M_TEMP, POOLBYTES);
return ret;
}
int
randomkqfilter(dev_t dev, struct knote *kn)
{
switch (kn->kn_filter) {
case EVFILT_READ:
kn->kn_fop = &randomread_filtops;
break;
case EVFILT_WRITE:
kn->kn_fop = &randomwrite_filtops;
break;
default:
return (EINVAL);
}
return (0);
}
void
filt_randomdetach(struct knote *kn)
{
}
int
filt_randomread(struct knote *kn, long hint)
{
kn->kn_data = ARC4_MAIN_MAX_BYTES;
return (1);
}
int
filt_randomwrite(struct knote *kn, long hint)
{
kn->kn_data = POOLBYTES;
return (1);
}
int
randomioctl(dev_t dev, u_long cmd, caddr_t data, int flag, struct proc *p)
{
switch (cmd) {
case FIOASYNC:
/* No async flag in softc so this is a no-op. */
break;
case FIONBIO:
/* Handled in the upper FS layer. */
break;
default:
return ENOTTY;
}
return 0;
}
int
sys_getentropy(struct proc *p, void *v, register_t *retval)
{
struct sys_getentropy_args /* {
syscallarg(void *) buf;
syscallarg(size_t) nbyte;
} */ *uap = v;
char buf[256];
int error;
if (SCARG(uap, nbyte) > sizeof(buf))
return (EIO);
arc4random_buf(buf, SCARG(uap, nbyte));
if ((error = copyout(buf, SCARG(uap, buf), SCARG(uap, nbyte))) != 0)
return (error);
explicit_bzero(buf, sizeof(buf));
retval[0] = 0;
return (0);
}
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