/* $MirOS: src/sys/dev/rnd.c,v 1.75 2014/02/20 00:30:24 tg Exp $ */ /*- * rnd.c -- A strong random number generator * * Copyright (c) 2000, 2002, 2003, 2004, 2005, 2006, 2007, 2008, 2009, * 2010, 2013, 2014 * Thorsten Glaser * Copyright (c) 1996, 1997, 2000-2002 Michael Shalayeff. * * 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. */ /*- * (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 * desirable 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 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 "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 content 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 * believed to be not feasible, but there is a remote possibility. * Nonetheless, these numbers should be useful for the vast majority * of purposes. * * Exported interfaces ---- output * =============================== * * There are three exported interfaces. * The first one is designed to be used from within the kernel: * * void get_random_bytes(void *buf, size_t nbytes); * * This interface will return the requested number of random bytes, * and place it in the requested buffer. * * 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 were requested. As more and more random bytes * 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. * * On OpenBSD and MirBSD, the /dev/arandom device will return the * output of an arcfour stream cipher, which is periodically reseeded * from the kernel pool. All applications are strongly encouraged to * use the /dev/arandom device for all their entropy needs instead, * as it will never deplete the kernel's entropy pool. * * On OpenBSD and MirBSD, the /dev/prandom device will return numbers * from random() calls, which, while not secure or random at all, are * blazingly fast. Do not use. * * On MirBSD, /dev/wrandom (with the same minor number as /dev/prandom) * exports a user-writable, non-privileged interface to get entropic * bytes from userspace into the kernel. See /sys/crypto/random.c for * more information on this. * * Exported interfaces ---- input * ============================== * * The current exported interfaces for gathering environmental noise * from the devices are: * * void add_true_randomness(int data); * void add_timer_randomness(int data); * void add_mouse_randomness(int mouse_data); * void add_tty_randomness(int c); * void add_disk_randomness(int n); * void add_net_randomness(int isr); * void add_auvis_randomness(int n); * void add_imacs_randomness(int data); * * add_true_randomness() uses true random number generators present * on some cryptographic and system chipsets. Entropy accounting * is not quitable, no timing is done, supplied 32 bits of pure entropy * are hashed into the pool plain and blindly, increasing the counter. * * add_timer_randomness() uses the random driver itselves timing, * measuring extract_entropy() and rndioctl() execution times. * * add_mouse_randomness() uses the mouse interrupt timing, as well as * the reported position of the mouse from the hardware. * * add_net_randomness() times the finishing time of net input. * * add_tty_randomness() uses the inter-keypress timing, as well as the * character as random inputs into the entropy pool. * * add_disk_randomness() times the finishing time of disk requests as well * as feeding both xfer size & time into the entropy pool. * * add_auvis_randomness() times the finishing of audio/video codec dma * requests for both recording and playback, apparently supplies quite * a lot of entropy. I'd blame it on low resolution audio clock generators. * * add_imacs_randomness() is called from keyboard drivers in order * to be able to use things that won't end up as tty randomness, * such as (local) meta/alt/ctrl/shift key events. * * All of these routines (except for add_true_randomness() of course) * try to estimate how many bits of randomness are in a particular * randomness source. They do this by keeping track of the first and * second order deltas of the event timings. * * Ensuring unpredictability at system startup * ============================================ * * When any operating system starts up, it will go through a sequence * of actions that are fairly predictable by an adversary, especially * if the start-up does not involve interaction with a human operator. * This reduces the actual number of bits of unpredictability in the * entropy pool below the value in entropy_count. In order to * counteract this effect, it helps to carry information in the * entropy pool across shut-downs and start-ups. To do this, put the * following lines in appropriate script which is run during the boot * sequence: * * echo "Initializing random number generator..." * # Carry a random seed from start-up to start-up * # Load and then save 512 bytes, which is the size of the entropy pool * if [ -f /etc/random-seed ]; then * cat /etc/random-seed >/dev/urandom * fi * dd if=/dev/urandom of=/etc/random-seed count=1 * * and the following lines in appropriate script which is run when * the system is shutting down: * * # Carry a random seed from shut-down to start-up * # Save 512 bytes, which is the size of the entropy pool * echo "Saving random seed..." * dd if=/dev/urandom of=/etc/random-seed count=1 * * On a MirBSD system, /etc/rc does this in a slightly more * sophisticated way. The kernel also contains a seed. * * Effectively, these commands cause the contents of the entropy pool * to be saved at shutdown time and reloaded into the entropy pool at * start-up. (The 'dd' in the addition to the bootup script is to * make sure that /etc/random-seed is different for every start-up, * even if the system crashes without executing rc.shutdown) Even with * complete knowledge of the start-up activities, predicting the state * of the entropy pool requires knowledge of the previous history of * the system. * * Configuring the random(4) driver under MirBSD * ============================================= * * The special files for the random(4) driver should have been created * during the installation process. However, if your system does not have * /dev/random and /dev/[s|u|p|a|w]random created already, they can be * created by using the MAKEDEV(8) script in /dev: * * /dev/MAKEDEV random * * Check MAKEDEV for information about major and minor numbers. * * 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. */ #include #include #include #include #include #include #include #include #include #include #include #include #include #include /* * 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) #define POOLBYTES (POOLWORDS*4) #if POOLWORDS == 2048 #define TAP1 1638 #define TAP2 1231 #define TAP3 819 #define TAP4 411 #define TAP5 1 #elif POOLWORDS == 1024 /* also (819, 616, 410, 207, 2) */ #define TAP1 817 #define TAP2 615 #define TAP3 412 #define TAP4 204 #define TAP5 1 #elif POOLWORDS == 512 /* also (409,307,206,102,2), (409,309,205,103,2) */ #define TAP1 411 #define TAP2 308 #define TAP3 208 #define TAP4 104 #define TAP5 1 #elif POOLWORDS == 256 #define TAP1 205 #define TAP2 155 #define TAP3 101 #define TAP4 52 #define TAP5 1 #elif POOLWORDS == 128 /* also (103, 78, 51, 27, 2) */ #define TAP1 103 #define TAP2 76 #define TAP3 51 #define TAP4 25 #define TAP5 1 #elif POOLWORDS == 64 #define TAP1 52 #define TAP2 39 #define TAP3 26 #define TAP4 14 #define TAP5 1 #elif POOLWORDS == 32 #define TAP1 26 #define TAP2 20 #define TAP3 14 #define TAP4 7 #define TAP5 1 #else #error No primitive polynomial available for chosen POOLWORDS #endif /*- * 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. */ /* pIII/333 reported to have some drops w/ these numbers */ #define QEVLEN (1024 / sizeof(struct rand_event)) #define QEVSLOW (QEVLEN * 3 / 4) /* yet another 0.75 for 60-minutes hour /-; */ #define QEVSBITS 10 /* There is one of these per entropy source */ struct timer_rand_state { u_int last_time; u_int last_delta; u_int last_delta2; u_int dont_count_entropy : 1; u_int max_entropy : 1; }; struct rand_event { struct timer_rand_state *re_state; u_int re_nbits; u_int re_time; u_int re_val; }; struct timeout rnd_timeout; struct timer_rand_state rnd_states[RND_SRC_NUM]; struct rand_event rnd_event_space[QEVLEN]; struct rand_event *rnd_event_head = rnd_event_space; struct rand_event *rnd_event_tail = rnd_event_space; struct selinfo rnd_rsel, rnd_wsel; void filt_rndrdetach(struct knote *kn); int filt_rndread(struct knote *kn, long hint); struct filterops rndread_filtops = { 1, NULL, filt_rndrdetach, filt_rndread}; void filt_rndwdetach(struct knote *kn); int filt_rndwrite(struct knote *kn, long hint); struct filterops rndwrite_filtops = { 1, NULL, filt_rndwdetach, filt_rndwrite}; struct rndstats rndstats; static __inline u_int32_t roll(u_int32_t w, int i) { #ifdef i386 __asm ("roll %%cl, %0" : "+r" (w) : "c" (i)); #else w = (w << i) | (w >> (32 - i)); #endif return w; } /* must be called at a proper spl, returns ptr to the next event */ static __inline struct rand_event * rnd_get(void) { struct rand_event *p = rnd_event_tail; if (p == rnd_event_head) return NULL; if (p + 1 >= &rnd_event_space[QEVLEN]) rnd_event_tail = rnd_event_space; else rnd_event_tail++; return p; } /* must be called at a proper spl, returns next available item */ static __inline struct rand_event * rnd_put(void) { struct rand_event *p = rnd_event_head + 1; if (p >= &rnd_event_space[QEVLEN]) p = rnd_event_space; if (p == rnd_event_tail) return NULL; return rnd_event_head = p; } /* must be called at a proper spl, returns number of items in the queue */ static __inline int rnd_qlen(void) { int len = rnd_event_head - rnd_event_tail; return (len < 0)? -len : len; } void dequeue_randomness(void *); static void add_entropy_words(const u_int32_t *, u_int n); void extract_entropy(register u_int8_t *, int); void rndpool_init(void) { timeout_set(&rnd_timeout, dequeue_randomness, NULL); random_state.add_ptr = 0; random_state.entropy_count = 0; rnd_states[RND_SRC_TIMER].dont_count_entropy = 1; rnd_states[RND_SRC_TRUE].dont_count_entropy = 1; rnd_states[RND_SRC_TRUE].max_entropy = 1; bzero(&rndstats, sizeof(rndstats)); bzero(&rnd_event_space, sizeof(rnd_event_space)); } int randomopen(dev_t dev, int flag, int mode, struct proc *p) { return (minor(dev) < RND_NODEV ? 0 : ENXIO); } int randomclose(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 void add_entropy_words(buf, n) const u_int32_t *buf; u_int n; { static const u_int32_t twist_table[8] = { 0x00000000, 0x3b6e20c8, 0x76dc4190, 0x4db26158, 0xedb88320, 0xd6d6a3e8, 0x9b64c2b0, 0xa00ae278 }; for (; n--; buf++) { register u_int32_t w = roll(*buf, random_state.input_rotate); register u_int i = random_state.add_ptr = (random_state.add_ptr - 1) & (POOLWORDS - 1); /* * 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. */ random_state.input_rotate = (random_state.input_rotate + (i? 7 : 14)) & 31; /* XOR in the various taps */ w ^= random_state.pool[(i+TAP1) & (POOLWORDS-1)] ^ random_state.pool[(i+TAP2) & (POOLWORDS-1)] ^ random_state.pool[(i+TAP3) & (POOLWORDS-1)] ^ random_state.pool[(i+TAP4) & (POOLWORDS-1)] ^ random_state.pool[(i+TAP5) & (POOLWORDS-1)] ^ random_state.pool[i]; random_state.pool[i] = (w >> 3) ^ twist_table[w & 7]; } } /* * 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. * On the i386, this is assumed to be at most 16 bits, and the high bits * are used for a high-resolution timer. * */ void enqueue_randomness(int state, int val) { register struct timer_rand_state *p; register struct rand_event *rep; int s; struct { struct timeval tv; int val, state, delta2, delta3; u_int d_time_, d_nbits; #define time_ drop.d_time_ #define nbits drop.d_nbits struct timer_rand_state p; char why[sizeof(val) == 4 ? 1 : -1]; } drop; drop.val = val; if ((drop.state = state) == RND_SRC_LPC) state = RND_SRC_TRUE; /* we sometimes get here before randomattach() */ if (!rnd_attached) { /* cache, since we get a *lot* of information here, early */ drop.why[0] = 1; rnd_lopool_addh(&drop, sizeof(drop)); return; } #define rndebugtmp(x) drop.state == RND_SRC_ ## x ? #x : RNDEBUG(RD_ENQUEUE, "rnd: enqueue(%s, %u)\n", rndebugtmp(TRUE) rndebugtmp(TIMER) rndebugtmp(MOUSE) rndebugtmp(TTY) rndebugtmp(DISK) rndebugtmp(NET) rndebugtmp(AUVIS) rndebugtmp(IMACS) rndebugtmp(LPC) "unknown", val); #undef rndebugtmp #ifdef DIAGNOSTIC if (state < 0 || state >= RND_SRC_NUM) return; #endif p = &rnd_states[state]; val += state << 13; microtime(&drop.tv); time_ = drop.tv.tv_usec + (drop.tv.tv_sec << 20); nbits = 0; /* * Calculate the number of bits of randomness that we probably * added. We take into account the first and second order * deltas in order to make our estimate. */ if (!p->dont_count_entropy) { register int delta, delta2, delta3; delta = time_ - p->last_time; delta2 = delta - p->last_delta; delta3 = delta2 - p->last_delta2; if (delta < 0) delta = -delta; if (delta2 < 0) delta2 = -delta2; if (delta3 < 0) delta3 = -delta3; if (delta > delta2) delta = delta2; if (delta > delta3) delta = delta3; delta3 = delta >>= 1; /* * delta &= 0xfff; * we don't do it since our time sheet is different from linux */ if (delta & 0xffff0000) { nbits = 16; delta >>= 16; } if (delta & 0xff00) { nbits += 8; delta >>= 8; } if (delta & 0xf0) { nbits += 4; delta >>= 4; } if (delta & 0xc) { nbits += 2; delta >>= 2; } if (delta & 2) { nbits += 1; delta >>= 1; } if (delta & 1) nbits++; #ifdef DIAGNOSTIC if (nbits >= 32) { /* sanity check, shouldn’t happen */ RNDEBUG(RD_ALWAYS, "rnd: nbits (%u) >= 32", nbits); drop.why[0] = 4; goto do_a_drop_with_delta; } #endif /* * the logic is to drop low-entropy entries, * in hope for dequeuing to be more randomfull */ if (rnd_qlen() > QEVSLOW && nbits < QEVSBITS) { rndstats.rnd_drople++; drop.why[0] = 2; #ifdef DIAGNOSTIC do_a_drop_with_delta: #endif drop.delta2 = delta2; drop.delta3 = delta3; goto do_a_drop; } p->last_time = time_; p->last_delta = delta3; p->last_delta2 = delta2; } else if (p->max_entropy) /* 31 = (8 * sizeof(val) - 1) see assertion in struct{}drop */ nbits = drop.state == RND_SRC_LPC ? 24 : 31; s = splhigh(); if ((rep = rnd_put()) == NULL) { rndstats.rnd_drops++; splx(s); drop.why[0] = 3; do_a_drop: /* if we have a drop, put the randomfull[sic!]ness to use */ drop.p = *p; rnd_lopool_add(&drop, sizeof(drop)); return; } rep->re_state = p; rep->re_nbits = nbits; rep->re_time = time_; rep->re_val = val; rndstats.rnd_enqs++; rndstats.rnd_ed[nbits]++; rndstats.rnd_sc[state]++; rndstats.rnd_sb[state] += nbits; if (rnd_qlen() > QEVSLOW/2 && !random_state.tmo) { random_state.tmo++; timeout_add(&rnd_timeout, 1); } splx(s); #undef time_ #undef nbits } void dequeue_randomness(void *v __unused) { register struct rand_event *rep; u_int32_t buf[2]; u_int nbits; int s; timeout_del(&rnd_timeout); rndstats.rnd_deqs++; s = splhigh(); while ((rep = rnd_get())) { buf[0] = rep->re_time; buf[1] = rep->re_val; nbits = rep->re_nbits; splx(s); add_entropy_words(buf, 2); rndstats.rnd_total += nbits; random_state.entropy_count += nbits; if (random_state.entropy_count > POOLBITS) random_state.entropy_count = POOLBITS; if (random_state.asleep && random_state.entropy_count > 8) { RNDEBUG(RD_WAIT, "rnd: wakeup[%u]{%u}\n", random_state.asleep, random_state.entropy_count); random_state.asleep--; wakeup((void *)&random_state.asleep); selwakeup(&rnd_rsel); KNOTE(&rnd_rsel.si_note, 0); } s = splhigh(); } random_state.tmo = 0; splx(s); } #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. */ void extract_entropy(buf, nbytes) register u_int8_t *buf; int nbytes; { u_char buffer[16]; MD5_CTX tmp; u_int i; int s; add_timer_randomness(nbytes); while (nbytes) { if (nbytes < sizeof(buffer) / 2) i = nbytes; else i = sizeof(buffer) / 2; /* Hash the pool to get the output */ MD5Init(&tmp); s = splhigh(); MD5Update(&tmp, (void *)random_state.pool, sizeof(random_state.pool)); if (random_state.entropy_count / 8 > i) random_state.entropy_count -= i * 8; else random_state.entropy_count = 0; splx(s); MD5Final(buffer, &tmp); /* * In case the hash function has some recognizable * output pattern, we fold it in half. */ buffer[0] ^= buffer[15]; buffer[1] ^= buffer[14]; buffer[2] ^= buffer[13]; buffer[3] ^= buffer[12]; buffer[4] ^= buffer[11]; buffer[5] ^= buffer[10]; buffer[6] ^= buffer[ 9]; buffer[7] ^= buffer[ 8]; /* Copy data to destination buffer */ bcopy(buffer, buf, i); nbytes -= i; buf += i; /* Modify pool so next hash will produce different results */ add_timer_randomness(nbytes); dequeue_randomness(&random_state); } /* Wipe data from memory */ bzero(&tmp, sizeof(tmp)); bzero(buffer, sizeof(buffer)); } /* * 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((u_int8_t *) buf, nbytes); rndstats.rnd_used += nbytes * 8; } int randomread(dev_t dev, struct uio *uio, int ioflag) { size_t n; int rv = 0; uint16_t *buf; if (uio->uio_resid == 0) return (0); MALLOC(buf, uint16_t *, POOLBYTES, M_TEMP, M_WAITOK); add_timer_randomness((u_long)dev ^ (u_long)uio ^ (u_long)buf); while (rv == 0 && uio->uio_resid > 0) { n = min(uio->uio_resid, POOLBYTES); switch (minor(dev)) { case RND_SRND: /* * check if we have enough entropy left in the * rndpool to answer a request (partially) */ if (random_state.entropy_count < 16 * 8) { if (ioflag & IO_NDELAY) { rv = EWOULDBLOCK; break; } RNDEBUG(RD_WAIT, "rnd: sleep[%u]\n", random_state.asleep); ++random_state.asleep; ++rndstats.rnd_waits; rv = tsleep(&random_state.asleep, PWAIT | PCATCH, "rndrd", 0); RNDEBUG(RD_WAIT, "rnd: awakened(%d)\n", rv); if (rv) break; } /* check how much entropy we have left */ if (n > random_state.entropy_count / 8) n = random_state.entropy_count / 8; ++rndstats.rnd_reads; /* FALLTHROUGH */ case RND_URND: /* deplete the rndpool, no matter what */ RNDEBUG(RD_OUTPUT, "rnd: %lu bytes output\n", (u_long)n); get_random_bytes(buf, n); break; case RND_RND: /* * Originally intended as direct interface to * a HW RNG, which we will never do; map this * to read from arc4random and write to lopool * for compat with other OSes. */ case RND_PRND: /* * This is /dev/prandom on read (old, but now * mapped to arc4random) and /dev/wrandom on * write (mapped to the lopool), and always * writable, even for regulat users. */ case RND_ARND: arc4random_buf(buf, n); break; default: rv = ENXIO; } if (rv == 0 && n > 0) rv = uiomove((caddr_t)buf, n, uio); /* yield here on SMP */ } add_timer_randomness((u_long)dev ^ (u_long)uio ^ (u_long)buf); FREE(buf, M_TEMP); return (rv); } int randompoll(dev, events, p) dev_t dev; int events; struct proc *p; { int revents; revents = events & (POLLOUT | POLLWRNORM); /* always writable */ if (events & (POLLIN | POLLRDNORM)) { if (minor(dev) == RND_SRND && random_state.entropy_count <= 0) selrecord(p, &rnd_rsel); else revents |= events & (POLLIN | POLLRDNORM); } return (revents); } int randomkqfilter(dev_t dev, struct knote *kn) { struct klist *klist; int s; switch (kn->kn_filter) { case EVFILT_READ: klist = &rnd_rsel.si_note; kn->kn_fop = &rndread_filtops; break; case EVFILT_WRITE: klist = &rnd_wsel.si_note; kn->kn_fop = &rndwrite_filtops; break; default: return (1); } kn->kn_hook = (void *)&random_state; s = splhigh(); SLIST_INSERT_HEAD(klist, kn, kn_selnext); splx(s); return (0); } void filt_rndrdetach(struct knote *kn) { int s = splhigh(); SLIST_REMOVE(&rnd_rsel.si_note, kn, knote, kn_selnext); splx(s); } int filt_rndread(struct knote *kn, long hint) { /* this is a singleton, thus we don't use kn->kn_hook */ kn->kn_data = random_state.entropy_count; return (random_state.entropy_count > 0); } void filt_rndwdetach(struct knote *kn) { int s = splhigh(); SLIST_REMOVE(&rnd_wsel.si_note, kn, knote, kn_selnext); splx(s); } int filt_rndwrite(kn, hint) struct knote *kn; long hint; { return (1); } int randomwrite(dev_t dev, struct uio *uio, int flags) { size_t n; int rv = 0; uint8_t *buf; int newdata = 0; /* see randomread() for some explanations */ if (securelevel > 1) switch (minor(dev)) { case RND_RND: case RND_PRND: break; default: return (EPERM); } if (uio->uio_resid == 0) return (0); MALLOC(buf, uint8_t *, POOLBYTES, M_TEMP, M_WAITOK); add_timer_randomness((u_long)dev ^ (u_long)uio ^ (u_long)buf); while (rv == 0 && uio->uio_resid > 0) { n = min(uio->uio_resid, POOLBYTES); if ((rv = uiomove((caddr_t)buf, n, uio))) break; switch (minor(dev)) { case RND_RND: case RND_PRND: rnd_lopool_add(buf, n); break; default: if (n % sizeof(uint32_t)) { uint32_t v = arc4random(); while (n % sizeof(uint32_t)) { buf[n++] = v & 0xFF; v >>= 8; } } add_entropy_words((void *)buf, n / sizeof(uint32_t)); newdata = 1; break; } } if (newdata && minor(dev) == RND_ARND) arc4random_reinit(NULL); add_timer_randomness((u_long)dev ^ (u_long)uio ^ (u_long)buf); FREE(buf, M_TEMP); return (rv); } int randomioctl(dev_t dev, u_long cmd, caddr_t data, int flag, struct proc *p) { int rv = 0, s; u_int cnt; switch (cmd) { case RNDADDRNDNESS: case RNDADDTOENTCNT: case RNDZAPENTCNT: case RNDSTIRARC4: if (securelevel > 1) rv = EPERM; else /* FALLTHROUGH */ case RNDCLRSTATS: if (suser(p, 0) != 0) rv = EPERM; break; } if (!rv) switch (cmd) { case FIOASYNC: /* rnd has no async flag in softc so this is really a no-op */ case FIONBIO: /* handled in the upper FS layer */ break; case RNDGETENTCNT: s = splhigh(); cnt = random_state.entropy_count; splx(s); memcpy(data, &cnt, sizeof(u_int)); break; case RNDADDTOENTCNT: memcpy(&cnt, data, sizeof(u_int)); s = splhigh(); if ((random_state.entropy_count += cnt) > POOLBITS) random_state.entropy_count = POOLBITS; splx(s); break; case RNDZAPENTCNT: s = splhigh(); random_state.entropy_count = 0; splx(s); break; case RNDSTIRARC4: if (p->p_pid == 1) { RNDEBUG(RD_ALWAYS, "rnd: init called, "); rnd_flush(); } else if (random_state.entropy_count < 80) rv = EAGAIN; else arc4random_reinit(NULL); break; case RNDCLRSTATS: s = splhigh(); bzero(&rndstats, sizeof(rndstats)); splx(s); break; case RNDADDRNDNESS: { const struct rnd_add_randomness *sar = (const void *)data; size_t i = sar->count; if (i > sizeof(sar->buf) / sizeof(sar->buf[0])) rv = EINVAL; else if (sar->source == 0) /* just add; i==0 will be caught */ add_entropy_words(sar->buf, i); else if (i > 0) while (i--) enqueue_randomness(sar->source, sar->buf[i]); break; } default: rv = ENOTTY; } return (rv); }