/* $OpenBSD: rnd.c,v 1.46 2001/01/17 01:59:50 mickey Exp $ */ /* * random.c -- A strong random number generator * * Copyright (c) 1996, 1997, 2000 Michael Shalayeff. * * Version 1.89, last modified 19-Sep-99 * * 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 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 possibility. * 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_true_randomness(int data); * void add_timer_randomness(int data); * void add_mouse_randomness(int mouse_data); * void add_net_randomness(int isr); * void add_tty_randomness(int c); * void add_disk_randomness(int n); * void add_audio_randomness(int n); * * 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_audio_randomness() times the finishing of audio codec dma * requests for both recording and playback, apparently supplies quite * a lot of entropy, i'd blame on low resolution audio clock generators. * * All of these routines (except for add_true_randomness() of course) * 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. * * 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 an 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 an appropriate script which is run as * the system is shutdown: * * # 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 * * For example, on many Linux systems, the appropriate scripts are * usually /etc/rc.d/rc.local and /etc/rc.d/rc.0, respectively. * * Effectively, these commands cause the contents of the entropy pool * to be saved at shut-down 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.0.) 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 /dev/random driver under Linux * ============================================== * * The /dev/random driver under Linux uses minor numbers 8 and 9 of * the /dev/mem major number (#1). So if your system does not have * /dev/random and /dev/urandom created already, they can be created * by using the commands: * * mknod /dev/random c 1 8 * mknod /dev/urandom c 1 9 * * 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 speed 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 authors of PGP. * * The code for SHA transform was taken from Peter Gutmann's * implementation, which has been placed in the public domain. * The code for MD5 transform was taken from Colin Plumb's * implementation, which has been placed in the public domain. * The MD5 cryptographic checksum was devised by Ronald Rivest, and is * documented in RFC 1321, "The MD5 Message Digest Algorithm". * * Further background information on this topic may be obtained from * RFC 1750, "Randomness Recommendations for Security", by Donald * Eastlake, Steve Crocker, and Jeff Schiller. */ #undef RNDEBUG #include #include #include #include #include #include #include #include #include #include #include #include #include #ifdef RNDEBUG 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 == 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 Reigster * * (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 * that we want of it is that it be a good non-cryptographic hash; * i.e. it 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 polymnomial. 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 * polynomail, 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 96 #define QEVSLOW 64 /* yet another 0.75 for 60-minutes hour /-; */ #define QEVSBITS 12 /* There is actually only one of these, globally. */ struct random_bucket { u_int add_ptr; u_int entropy_count; u_char input_rotate; u_int32_t pool[POOLWORDS]; u_int asleep; u_int queued; u_int tmo; }; /* 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_char dont_count_entropy : 1; u_char max_entropy : 1; }; struct arc4_stream { u_int8_t s[256]; u_int cnt; u_int8_t i; u_int8_t j; }; struct rand_event { struct rand_event *re_next; struct timer_rand_state *re_state; u_char re_nbits; u_int re_time; u_int re_val; }; struct timeout rnd_timeout, arc4_timeout; struct random_bucket random_state; struct arc4_stream arc4random_state; struct timer_rand_state rnd_states[RND_SRC_NUM]; struct rand_event rnd_event_space[QEVLEN]; struct rand_event *rnd_event_q; struct rand_event *rnd_event_free; int rnd_attached; int arc4random_initialized; 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; } void dequeue_randomness __P((void *)); static __inline void add_entropy_words __P((const u_int32_t *, u_int n)); static __inline void extract_entropy __P((register u_int8_t *, int)); static __inline u_int8_t arc4_getbyte __P((void)); void arc4_stir __P((void)); void arc4_reinit __P((void *v)); /* Arcfour random stream generator. This code is derived from section * 17.1 of Applied Cryptography, second edition, which describes a * stream cipher allegedly compatible with RSA Labs "RC4" cipher (the * actual description of which is a trade secret). The same algorithm * is used as a stream cipher called "arcfour" in Tatu Ylonen's ssh * package. * * The initialization function here has been modified not to discard * old state, and its input always includes the time of day in * microseconds. Moreover, bytes from the stream may at any point be * diverted to multiple processes or even kernel functions desiring * random numbers. This increases the strenght of the random stream, * but makes it impossible to use this code for encryption--There is * no way ever to reproduce the same stream of random bytes. * * RC4 is a registered trademark of RSA Laboratories. */ void arc4_stir(void) { u_int8_t buf[256]; register u_int8_t si; register int n, s; int len; microtime((struct timeval *) buf); len = random_state.entropy_count / 8; /* XXX maybe a half? */ if (len > sizeof(buf) - sizeof(struct timeval)) len = sizeof(buf) - sizeof(struct timeval); get_random_bytes(buf + sizeof (struct timeval), len); len += sizeof(struct timeval); s = splhigh(); arc4random_state.i--; for (n = 0; n < 256; n++) { arc4random_state.i++; si = arc4random_state.s[arc4random_state.i]; arc4random_state.j += si + buf[n % len]; arc4random_state.s[arc4random_state.i] = arc4random_state.s[arc4random_state.j]; arc4random_state.s[arc4random_state.j] = si; } arc4random_state.j = arc4random_state.i; arc4random_state.cnt = 0; rndstats.arc4_stirs += len; rndstats.arc4_nstirs++; splx(s); } static __inline u_int8_t arc4_getbyte(void) { register u_int8_t si, sj; rndstats.arc4_reads++; arc4random_state.cnt++; arc4random_state.i++; si = arc4random_state.s[arc4random_state.i]; arc4random_state.j += si; sj = arc4random_state.s[arc4random_state.j]; arc4random_state.s[arc4random_state.i] = sj; arc4random_state.s[arc4random_state.j] = si; return arc4random_state.s[(si + sj) & 0xff]; } static __inline void arc4maybeinit(void) { if (!arc4random_initialized) { arc4random_initialized++; arc4_stir(); } } void arc4_reinit(v) void *v; { extern int hz; arc4random_initialized = 0; timeout_add(&arc4_timeout, 10*60*hz); } int arc4random_8(void) { arc4maybeinit(); return arc4_getbyte(); } u_int32_t arc4random(void) { arc4maybeinit(); return ((arc4_getbyte() << 24) | (arc4_getbyte() << 16) | (arc4_getbyte() << 8) | arc4_getbyte()); } void randomattach(void) { int i; struct timeval tv; struct rand_event *rep; if (rnd_attached) { #ifdef RNDEBUG printf("random: second attach\n"); #endif return; } 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)); rnd_event_free = rnd_event_space; for (rep = rnd_event_space; rep < &rnd_event_space[QEVLEN-1]; rep++) rep->re_next = rep + 1; for (i = 0; i < 256; i++) arc4random_state.s[i] = i; microtime(&tv); timeout_set(&rnd_timeout, dequeue_randomness, NULL); timeout_set(&arc4_timeout, arc4_reinit, NULL); arc4_reinit(NULL); rnd_attached = 1; } int randomopen(dev, flag, mode, p) 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 __inline 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 }; u_int i; int new_rotate; u_int32_t w; for (; n--; buf++) { w = roll(*buf, random_state.input_rotate); 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. */ new_rotate = random_state.input_rotate + 14; if (i) new_rotate = random_state.input_rotate + 7; random_state.input_rotate = new_rotate & 31; /* XOR in the various taps */ w ^= random_state.pool[(i+TAP1)&(POOLWORDS-1)]; w ^= random_state.pool[(i+TAP2)&(POOLWORDS-1)]; w ^= random_state.pool[(i+TAP3)&(POOLWORDS-1)]; w ^= random_state.pool[(i+TAP4)&(POOLWORDS-1)]; w ^= random_state.pool[(i+TAP5)&(POOLWORDS-1)]; w ^= 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 "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. * */ void enqueue_randomness(state, val) int state, val; { struct timer_rand_state *p; struct timeval tv; register struct rand_event *rep; int s; u_int time, nbits; #ifdef DIAGNOSTIC if (state < 0 || state >= RND_SRC_NUM) return; #endif p = &rnd_states[state]; val += state << 13; microtime(&tv); time = tv.tv_usec ^ tv.tv_sec; nbits = 0; /* * 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 (!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++; /* * the logic is to drop low-entropy entries, * in hope for dequeuing to be more sourcefull */ if (random_state.queued > QEVSLOW && nbits < QEVSBITS) { rndstats.rnd_drople++; return; } p->last_time = time; p->last_delta = delta3; p->last_delta2 = delta2; } else if (p->max_entropy) nbits = 8 * sizeof(val) - 1; s = splhigh(); if ((rep = rnd_event_free) == NULL) { rndstats.rnd_drops++; splx(s); return; } rnd_event_free = rep->re_next; rep->re_state = p; rep->re_nbits = nbits; rep->re_time = time; rep->re_val = val; rep->re_next = rnd_event_q; rnd_event_q = rep; rep = rep->re_next; random_state.queued++; rndstats.rnd_enqs++; rndstats.rnd_ed[nbits]++; rndstats.rnd_sc[state]++; rndstats.rnd_sb[state] += nbits; if (++random_state.queued > QEVSLOW/2 && !random_state.tmo) { random_state.tmo++; timeout_add(&rnd_timeout, 1); } splx(s); } void dequeue_randomness(v) void *v; { register struct rand_event *rep; u_int32_t val, time; u_int nbits; int s; timeout_del(&rnd_timeout); rndstats.rnd_deqs++; do { s = splhigh(); if (rnd_event_q == NULL) { splx(s); break; } rep = rnd_event_q; rnd_event_q = rep->re_next; random_state.queued--; val = rep->re_val; time = rep->re_time; nbits = rep->re_nbits; rep->re_next = rnd_event_free; rnd_event_free = rep; splx(s); add_entropy_words(&val, 1); add_entropy_words(&time, 1); rndstats.rnd_total += nbits; random_state.entropy_count += nbits; if (random_state.entropy_count > POOLBITS) random_state.entropy_count = POOLBITS; if (random_state.entropy_count > 8 && random_state.asleep != 0) { #ifdef RNDEBUG if (rnd_debug & RD_WAIT) printf("rnd: wakeup[%u]{%u}\n", random_state.asleep, random_state.entropy_count); #endif random_state.asleep--; wakeup(&random_state.asleep); } } while(1); random_state.tmo = 0; } #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 void extract_entropy(buf, nbytes) register u_int8_t *buf; int nbytes; { MD5_CTX tmp; u_char buffer[16]; add_timer_randomness(nbytes); /* Redundant, but just in case... */ if (random_state.entropy_count > POOLBITS) random_state.entropy_count = POOLBITS; if (random_state.entropy_count / 8 > nbytes) random_state.entropy_count -= nbytes*8; else random_state.entropy_count = 0; while (nbytes) { register u_char *p = buf; register int i = sizeof(buffer); if (i > nbytes) { i = nbytes; p = buffer; } /* Hash the pool to get the output */ MD5Init(&tmp); MD5Update(&tmp, (u_int8_t*)random_state.pool, sizeof(random_state.pool)); MD5Final(p, &tmp); /* * In case the hash function has some recognizable * output pattern, we fold it in half. */ p[0] ^= p[15]; p[1] ^= p[14]; p[2] ^= p[13]; p[3] ^= p[12]; p[4] ^= p[11]; p[5] ^= p[10]; p[6] ^= p[ 9]; p[7] ^= p[ 8]; /* Modify pool so next hash will produce different results */ add_entropy_words((u_int32_t*)p, sizeof(buffer)/4); /* Copy data to destination buffer */ if (i < sizeof(buffer)) bcopy(buffer, buf, i); nbytes -= i; buf += i; add_timer_randomness(nbytes); } /* 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, uio, ioflag) dev_t dev; struct uio *uio; int ioflag; { int ret = 0; int s, i; 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: ret = EIO; /* no chip -- error */ break; case RND_SRND: if (random_state.entropy_count < 16 * 8) { if (ioflag & IO_NDELAY) { ret = EWOULDBLOCK; break; } #ifdef RNDEBUG if (rnd_debug & RD_WAIT) printf("rnd: sleep[%u]\n", random_state.asleep); #endif random_state.asleep++; rndstats.rnd_waits++; ret = tsleep(&random_state.asleep, PWAIT | PCATCH, "rndrd", 0); #ifdef RNDEBUG if (rnd_debug & RD_WAIT) printf("rnd: awakened(%d)\n", ret); #endif if (ret) break; } if (n > random_state.entropy_count / 8) n = random_state.entropy_count / 8; rndstats.rnd_reads++; #ifdef RNDEBUG if (rnd_debug & RD_OUTPUT) printf("rnd: %u possible output\n", n); #endif case RND_URND: get_random_bytes((char *)buf, n); #ifdef RNDEBUG if (rnd_debug & RD_OUTPUT) printf("rnd: %u bytes for output\n", n); #endif break; case RND_PRND: i = (n + 3) / 4; while (i--) buf[i] = random() << 16 | (random() & 0xFFFF); break; case RND_ARND: { u_int8_t *cp = (u_int8_t *) buf; u_int8_t *end = cp + n; while (cp < end) *cp++ = arc4random_8(); break; } default: ret = ENXIO; } splx(s); if (n != 0 && ret == 0) ret = uiomove((caddr_t)buf, n, uio); } return ret; } int randomselect(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 randomwrite(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) { while (n % sizeof(u_int32_t)) ((u_int8_t *) buf)[n++] = 0; add_entropy_words(buf, n / 4); } } if (minor(dev) == RND_ARND && !ret) arc4random_initialized = 0; return ret; } int randomioctl(dev, cmd, data, flag, p) dev_t dev; u_long cmd; caddr_t data; int flag; struct proc *p; { int s, ret = 0; u_int cnt; add_timer_randomness((u_long)p ^ (u_long)data ^ cmd); switch (cmd) { case FIOASYNC: /* rnd has no async flag in softc so this is really a no-op. */ break; case FIONBIO: /* Handled in the upper FS layer. */ break; case RNDGETENTCNT: s = splhigh(); *(u_int *)data = random_state.entropy_count; splx(s); break; case RNDADDTOENTCNT: if (suser(p->p_ucred, &p->p_acflag) != 0) ret = EPERM; else { cnt = *(u_int *)data; s = splhigh(); random_state.entropy_count += cnt; if (random_state.entropy_count > POOLBITS) random_state.entropy_count = POOLBITS; splx(s); } break; case RNDZAPENTCNT: if (suser(p->p_ucred, &p->p_acflag) != 0) ret = EPERM; else { s = splhigh(); random_state.entropy_count = 0; splx(s); } break; case RNDSTIRARC4: if (suser(p->p_ucred, &p->p_acflag) != 0) ret = EPERM; else if (random_state.entropy_count < 64) ret = EAGAIN; else { s = splhigh(); arc4random_initialized = 0; splx(s); } break; case RNDCLRSTATS: if (suser(p->p_ucred, &p->p_acflag) != 0) ret = EPERM; else { s = splhigh(); bzero(&rndstats, sizeof(rndstats)); splx(s); } break; default: ret = EINVAL; } add_timer_randomness((u_long)p ^ (u_long)data ^ cmd); return ret; }