/* * random.c -- A strong random number generator * * Copyright Matt Mackall , 2003, 2004, 2005 * * 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 General 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, ALL OF * WHICH ARE HEREBY 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 NOT 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 randomly distributed 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 implement a truly random distribution on a computer --- as * opposed to a pseudo-random distribution, which can easily * implemented by an algorithm. Unfortunately, it is sometimes * possible for attackers to guess the output sequence of * pseudo-random generators, and for some applications this is not * acceptable. So instead, we must try to gather "noise" from the * computer's environment, i.e. signals that contain an element of * actual entropy, and that are hard for outside attackers to observe, * and use that to generate randomly-distributed numbers. * Environmental sources that are available to the kernel include * inter-keyboard timings, inter-interrupt timings from some * interrupts, and similar events. Again, these must be both (a) * non-deterministic and (b) hard for an outside observer to measure. * Operation of this device is centered on four "pools". The four * pools are similar in structure but serve different purposes. * Here is a block diagram: * * fast events --> fast pool --\ /--> blocking pool * --> input pool -- * slower, larger events ------/ \--> nonblocking pool * The fast pool is similar in function to the input pool, as * described below. It handles events that occur frequently but * contain little entropy. It is fast enough that the overhead of * doing it on every interrupt is affordable. It is similar in * structure to the input pool, but much smaller. After accumulating * a modest amount of entropy, it passes the entropy on to the input * pool. * The input pool is serves as both a concentrator and as the main * storage area. The entropy that is available as input to the input * pool commonly has an entropy density of much less than 8 bits per * byte. This is mixed into the input pool, which is mixed using a * CRC-like function. The mixing is not cryptographically strong, but * should be adequate if the randomness is not chosen maliciously. As * bytes are mixed into this pool, the routines keep an *estimate* of * how many bits of entropy are contained in the pool. * When randomly-distributed bytes are desired, they can be extracted * from the input pool by taking the SHA hash of the pool contents. * This avoids exposing the internal state of the pool. It is * believed to be computationally infeasible to derive any useful * information about the input of SHA from its output. Even if it is * possible to analyze SHA in some clever way, as long as the amount * of data extracted in this way is less than the entropy content of * the the input pool, the extracted data is totally unpredictable. * For this reason, the routine decreases its internal estimate of how * many bits of "true randomness" (aka entropy) are contained in the * input pool whenever data is extracted. * The blocking pool is associated with /dev/random. It is similar in * structure to the input pool, but its purpose is different. It * takes its input from the input pool, so the input has a high * entropy density (8 bits per byte) so no concentration is necessary. * Therefore this pool serves primarily as a fifo. If the amount of * entropy stored in the blocking pool is insufficient to meet the * demand, and no more entropy can be pulled from the input pool, any * read to /dev/random will block. * The nonblocking pool is associated with the /dev/urandom device, * and with the get_random_bytes() function used by the kernel * internally. This pool is similar in structure, but its function is * quite different from the other pools. It functions primarily as a * PRNG i.e. pseudo ranomness generator. Specifically, it functions * as hash function operated in counter mode. The PRNG is reseeded * from time to time, using entropy from the input pool. An attacker * may (at least in theory) be able to infer the future output of the * PRNG from prior outputs. This requires successful cryptanalysis of * SHA, which is not believed to be feasible, but there is a remote * possibility. Nonetheless, a pseudorandom distribution of numbers * should be useful for a wide range 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 bytes, and place * it them 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 on hand (as estimated by the random number * generator). * The /dev/urandom device will never block, and will return as many * bytes as are requested. It is a PRNG. It is reseeded from time to * time. The resulting distribution of numbers is cryptographically * strong, but not in principle unbreakable. For many applications, * however, this is acceptable. * Exported interfaces ---- input * ============================== * * The current exported interfaces for gathering environmental noise * from the devices are: * * void add_device_randomness(const void *buf, unsigned int size); * void add_input_randomness(unsigned int type, unsigned int code, * unsigned int value); * void add_interrupt_randomness(int irq, int irq_flags); * void add_disk_randomness(struct gendisk *disk); * * add_device_randomness() is for adding data to the random pool that * is likely to differ between two devices (or possibly even per boot). * This would be things like MAC addresses or serial numbers, or the * read-out of the RTC. This does *not* add any actual entropy to the * pool, but it initializes the pool to different values for devices * that might otherwise be identical and have very little entropy * available to them (particularly common in the embedded world). * * add_input_randomness() uses the input layer interrupt timing, as well as * the event type information from the hardware. * * add_interrupt_randomness() uses the interrupt timing as random * inputs to the fast pool. Using the cycle counters and the irq source * as inputs, it feeds the randomness roughly once a second. * * add_disk_randomness() uses what amounts to the seek time of block * layer request events, on a per-disk_devt basis, as input to the * fast pool. Note that high-speed solid state drives with very low * seek times do not make for good sources of entropy, as their seek * times are usually fairly consistent. * * 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. * Exported interfaces ---- sysctl * =============================== * /proc/sys/kernel/random/poolsize (read only) reports the size of * the input pool. Since 2.6.12 this is measured in bits. Previously * it was measured in bytes. Note that the blocking pool and the * nonblocking pool are 4x smaller than the input pool. * /proc/sys/kernel/random/entropy_avail (read only) reports the total * amount of stored entropy, measured in bits. This includes entropy * stored in both the input pool and the blocking pool. * 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. * There is likely to be virtually zero real entropy available. * However, we still need the /dev/urandom and get_random_bytes() * interfaces to be usable at startup, and to have some semblance of * security. Therefore, it helps to store a seed that can be used to * re-seed the PRNG, and to carry this seed across shut-downs and * start-ups. To do this, put the following lines an appropriate * script which is run during the boot sequence: * The byte count of 512 is overkill at present, since we * only use it to reseed pools that are 4x smaller than that, * but we preserve it because (a) it is traditional, and (b) * we might put it to good use in future versions. * echo "Initializing random number generator..." * random_seed=/var/run/random-seed * # Carry a random seed from start-up to start-up * # Load and then save the whole nonblocking pool * if [ -f $random_seed ]; then * cat $random_seed >/dev/urandom * else * touch $random_seed * fi * chmod 600 $random_seed * dd if=/dev/urandom of=$random_seed count=1 bs=512 * * 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 the whole nonblocking pool * echo "Saving random seed..." * random_seed=/var/run/random-seed * touch $random_seed * chmod 600 $random_seed * dd if=/dev/urandom of=$random_seed count=1 bs=512 * For example, on most modern systems using the System V init * scripts, such code fragments would be found in * /etc/rc.d/init.d/random. On older Linux systems, the correct script * location might be in /etc/rcb.d/rc.local or /etc/rc.d/rc.0. * Effectively, these commands cause the contents of the nonblocking * pool to be saved at shut-down time and then used to initialize the * nonblocking pool -- and the blocking pool -- at start-up. (The * seed is saved by the bootup script, not only by the shutdown * script, 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 output pools requires knowledge of the previous * history of the system. * Note that writing to /dev/urandom affects only the blocking pool * and nonblocking pool (not the input pool or fast pool). * Writing to /dev/random is identical to writing to /dev/urandom. * 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. * * Further background information on this topic may be obtained from * RFC 1750, "Randomness Recommendations for Security", by Donald * Eastlake, Steve Crocker, and Jeff Schiller. */ // TODO: Scatter/gather, to reduce the number of files under /proc. #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #ifdef CONFIG_GENERIC_HARDIRQS # include #endif #include #include #include #include #include #define CREATE_TRACE_POINTS #include /* * Configuration information. * Here, a "word" is of type __u32 */ #define INPUT_POOL_WORDS 128 #define OUTPUT_POOL_WORDS 32 #define SEC_XFER_SIZE 512 #define EXTRACT_SIZE 10 /* Choose 160 bits. Seems reasonable. Recommended in the Yarrow paper. */ #define RESEED_BATCH 160 /* bits */ /* Saturation point of extraction subttl counters; large round number: */ #define SUBTTL_SAT 1000000000000000000LL typedef unsigned long long int ulonglong; #if defined __SIZEOF_LONG_LONG__ && __SIZEOF_LONG_LONG__ == 8 /* This is how we expect things to be when using gcc * on both Intel x86_32 and Intel 64 architectures. * I don't know how to extrapolate to other architectures * or other compilers ... * but at least we are being clear about the assumptions being made. */ #else #error Broken assumption: __SIZEOF_LONG_LONG__ should be defined and equal to 8 #endif #define LONGS(x) (((x) + sizeof(unsigned long) - 1)/sizeof(unsigned long)) #define W2BYTE(X) ((X)*4) /* convert #words to #bytes */ #define W2BIT(X) ((X)*32) /* convert #words to #bits */ #define BIT2BYTE(X) ((X)/8) /* convert #bits to #bytes */ #define BYTE2BIT(X) ((X)*8) /* convert #bytes to #bits */ /* * The minimum number of bits of entropy before we wake up a read on * /dev/random. * Can be changed at runtime via /proc/. * The minimum value is RESEED_BATCH; enforced at runtime. */ static int random_read_wakeup_thresh = RESEED_BATCH; /* * If the entropy count falls under this number of bits, then we * should wake up processes which are selecting or polling on write * access to /dev/random. */ static int random_write_wakeup_thresh = 128; /* * When the input pool goes over trickle_thresh, start dropping most * samples to avoid wasting CPU time and reduce lock contention. */ static int trickle_thresh __read_mostly = INPUT_POOL_WORDS * 28; static DEFINE_PER_CPU(int, trickle_count); /* * A pool of size .poolwords is stirred with a primitive polynomial * of degree .poolwords over GF(2). The taps for various sizes are * defined below. They are chosen to be evenly spaced (minimum RMS * distance from evenly spaced; the numbers in the comments are a * scaled squared error sum) except for the last tap, which is 1 to * get the twisting happening as fast as possible. */ static struct poolinfo { int poolwords; int tap1, tap2, tap3, tap4, tap5; } poolinfo_table[] = { /* x^128 + x^103 + x^76 + x^51 +x^25 + x + 1 -- 105 */ { 128, 103, 76, 51, 25, 1 }, /* x^32 + x^26 + x^20 + x^14 + x^7 + x + 1 -- 15 */ { 32, 26, 20, 14, 7, 1 }, #if 0 /* x^2048 + x^1638 + x^1231 + x^819 + x^411 + x + 1 -- 115 */ { 2048, 1638, 1231, 819, 411, 1 }, /* x^1024 + x^817 + x^615 + x^412 + x^204 + x + 1 -- 290 */ { 1024, 817, 615, 412, 204, 1 }, /* x^1024 + x^819 + x^616 + x^410 + x^207 + x^2 + 1 -- 115 */ { 1024, 819, 616, 410, 207, 2 }, /* x^512 + x^411 + x^308 + x^208 + x^104 + x + 1 -- 225 */ { 512, 411, 308, 208, 104, 1 }, /* x^512 + x^409 + x^307 + x^206 + x^102 + x^2 + 1 -- 95 */ { 512, 409, 307, 206, 102, 2 }, /* x^512 + x^409 + x^309 + x^205 + x^103 + x^2 + 1 -- 95 */ { 512, 409, 309, 205, 103, 2 }, /* x^256 + x^205 + x^155 + x^101 + x^52 + x + 1 -- 125 */ { 256, 205, 155, 101, 52, 1 }, /* x^128 + x^103 + x^78 + x^51 + x^27 + x^2 + 1 -- 70 */ { 128, 103, 78, 51, 27, 2 }, /* x^64 + x^52 + x^39 + x^26 + x^14 + x + 1 -- 15 */ { 64, 52, 39, 26, 14, 1 }, #endif }; #define POOLBITS poolwords*32 #define POOLBYTES poolwords*4 /* * 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 hash in the sense that it * not produce collisions when fed "random" data of the sort we expect * to see. It need not be a cryptographically-strong hash. 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 * 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. */ /* * Static global variables */ static DECLARE_WAIT_QUEUE_HEAD(random_read_wait); static DECLARE_WAIT_QUEUE_HEAD(random_write_wait); static struct fasync_struct *fasync; static bool debug = 0; module_param(debug, bool, 0644); #define DEBUG_ENT(fmt, arg...) do { \ if (debug) \ printk(KERN_DEBUG "random %04d %04d %04d: " \ fmt,\ input_pool.entropy_count,\ devrand_pool.entropy_count,\ prng_pool.entropy_count,\ ## arg); } while (0) /********************************************************************** * * OS independent pool. Here are the functions which handle * entropy storage, mixing, concentration, and PRNG counter mode. * **********************************************************************/ struct Pool; struct Pool { /* read-only data: */ struct poolinfo *poolinfo; __u32 *pooldata; const char *name; struct Pool *pull; int blockable; /* read-write data: */ spinlock_t lock; unsigned add_ptr; unsigned input_rotate; int entropy_count; int entropy_total; /* entropy input; used only during initialization */ ulonglong extracted_subttl; ulonglong extracted_total; unsigned int initialized:1; bool last_data_init; __u8 last_data[EXTRACT_SIZE]; }; static __u32 input_pool_data[INPUT_POOL_WORDS]; #ifdef OVERCOMPLICATED static __u32 devrand_pool_data[OUTPUT_POOL_WORDS]; #endif static __u32 prng_pool_data[OUTPUT_POOL_WORDS]; static struct Pool input_pool = { .poolinfo = &poolinfo_table[0], .name = "input", .blockable = 1, .lock = __SPIN_LOCK_UNLOCKED(input_pool.lock), .pooldata = input_pool_data }; #ifdef OVERCOMPLICATED static struct Pool devrand_pool = { .poolinfo = &poolinfo_table[1], .name = "blocking", .blockable = 1, .pull = &input_pool, .lock = __SPIN_LOCK_UNLOCKED(devrand_pool.lock), .pooldata = devrand_pool_data }; #else #define devrand_pool input_pool #endif static struct Pool prng_pool = { .poolinfo = &poolinfo_table[1], .name = "nonblocking", .pull = &input_pool, .lock = __SPIN_LOCK_UNLOCKED(prng_pool.lock), .pooldata = prng_pool_data }; static __u32 const twist_table[8] = { 0x00000000, 0x3b6e20c8, 0x76dc4190, 0x4db26158, 0xedb88320, 0xd6d6a3e8, 0x9b64c2b0, 0xa00ae278 }; /* * This function adds bytes into the entropy "pool". It does not * update the entropy estimate. The caller should call * credit_entropy_bits if this is appropriate. * * The pool is stirred with a primitive polynomial of the appropriate * degree, and then twisted. We twist by three bits at a time because * it's cheap to do so and helps slightly in the expected case where * the entropy is concentrated in the low-order bits. */ static void _mix_pool_bytes(struct Pool *r, const void *in, int nbytes, __u8 out[64]) { unsigned long i, j, tap1, tap2, tap3, tap4, tap5; int input_rotate; int wordmask = r->poolinfo->poolwords - 1; const char *bytes = in; __u32 w; tap1 = r->poolinfo->tap1; tap2 = r->poolinfo->tap2; tap3 = r->poolinfo->tap3; tap4 = r->poolinfo->tap4; tap5 = r->poolinfo->tap5; smp_rmb(); input_rotate = ACCESS_ONCE(r->input_rotate); i = ACCESS_ONCE(r->add_ptr); /* mix one byte at a time to simplify size handling and churn faster */ while (nbytes--) { w = rol32(*bytes++, input_rotate & 31); i = (i - 1) & wordmask; /* XOR in the various taps */ w ^= r->pooldata[i]; w ^= r->pooldata[(i + tap1) & wordmask]; w ^= r->pooldata[(i + tap2) & wordmask]; w ^= r->pooldata[(i + tap3) & wordmask]; w ^= r->pooldata[(i + tap4) & wordmask]; w ^= r->pooldata[(i + tap5) & wordmask]; /* Mix the result back in with a twist */ r->pooldata[i] = (w >> 3) ^ twist_table[w & 7]; /* * 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. */ input_rotate += i ? 7 : 14; } ACCESS_ONCE(r->input_rotate) = input_rotate; ACCESS_ONCE(r->add_ptr) = i; smp_wmb(); if (out) for (j = 0; j < 16; j++) ((__u32 *)out)[j] = r->pooldata[(i - j) & wordmask]; } static void __mix_pool_bytes(struct Pool *r, const void *in, int nbytes, __u8 out[64]) { trace_mix_pool_bytes_nolock(r->name, nbytes, _RET_IP_); _mix_pool_bytes(r, in, nbytes, out); } static void mix_pool_bytes(struct Pool *r, const void *in, int nbytes, __u8 out[64]) { unsigned long flags; trace_mix_pool_bytes(r->name, nbytes, _RET_IP_); spin_lock_irqsave(&r->lock, flags); _mix_pool_bytes(r, in, nbytes, out); spin_unlock_irqrestore(&r->lock, flags); } struct fast_pool { __u32 pooldata[4]; unsigned long last; unsigned short count; unsigned char rotate; unsigned char last_timer_intr; }; /* * This is a fast mixing routine used by the interrupt randomness * collector. It's hardcoded for an 128 bit pool and assumes that any * locks that might be needed are taken by the caller. */ static void fast_mix(struct fast_pool *f, const void *in, int nbytes) { const char *bytes = in; __u32 w; unsigned i = f->count; unsigned input_rotate = f->rotate; while (nbytes--) { w = rol32(*bytes++, input_rotate & 31) ^ f->pooldata[i & 3] ^ f->pooldata[(i + 1) & 3]; f->pooldata[i & 3] = (w >> 3) ^ twist_table[w & 7]; input_rotate += (i++ & 3) ? 7 : 14; } f->count = i; f->rotate = input_rotate; } /* * Credit the pool with n bits of entropy. * Normally n is positive. * Sufficiently large n will wake up a blocked reader. * Negative n values are allowed, but the resulting behavior * might not be what you wanted. */ static void credit_entropy_bits(struct Pool *r, int nbits) { int entropy_count, orig; if (!nbits) return; DEBUG_ENT("added %d entropy credits to %s\n", nbits, r->name); retry: entropy_count = orig = ACCESS_ONCE(r->entropy_count); entropy_count += nbits; if (entropy_count < 0) { DEBUG_ENT("negative entropy/overflow\n"); entropy_count = 0; } else if (entropy_count > r->poolinfo->POOLBITS) entropy_count = r->poolinfo->POOLBITS; if (cmpxchg(&r->entropy_count, orig, entropy_count) != orig) goto retry; if (!r->initialized && nbits > 0) { r->entropy_total += nbits; if (r->entropy_total > 128) r->initialized = 1; } trace_credit_entropy_bits(r->name, nbits, entropy_count, r->entropy_total, _RET_IP_); /* should we wake readers? */ if (r == &input_pool && entropy_count >= random_read_wakeup_thresh) { wake_up_interruptible(&random_read_wait); kill_fasync(&fasync, SIGIO, POLL_IN); } } /********************************************************************* * * Entropy input management * *********************************************************************/ /* There is one of these per entropy source */ struct timer_rand_state { cycles_t last_time; long last_delta, last_delta2; unsigned dont_count_entropy:1; }; /* * Add device- or boot-specific data to the input and nonblocking * pools to help initialize them to unique values. * * None of this adds any entropy, it is meant to avoid the * problem of the nonblocking pool having similar initial state * across largely identical devices. */ void add_device_randomness(const void *buf, unsigned int size) { unsigned long time = get_cycles() ^ jiffies; mix_pool_bytes(&input_pool, buf, size, NULL); mix_pool_bytes(&input_pool, &time, sizeof(time), NULL); mix_pool_bytes(&prng_pool, buf, size, NULL); mix_pool_bytes(&prng_pool, &time, sizeof(time), NULL); } EXPORT_SYMBOL(add_device_randomness); static struct timer_rand_state input_timer_state; /* * This function adds entropy to the input 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. * */ static void add_timer_randomness(struct timer_rand_state *state, unsigned num) { struct { long jiffies; unsigned cycles; unsigned num; } sample; long delta, delta2, delta3; preempt_disable(); /* if over the trickle threshold, use only 1 in 4096 samples */ if (input_pool.entropy_count > trickle_thresh && ((__this_cpu_inc_return(trickle_count) - 1) & 0xfff)) goto out; sample.jiffies = jiffies; sample.cycles = get_cycles(); sample.num = num; mix_pool_bytes(&input_pool, &sample, sizeof(sample), NULL); /* * Calculate number of bits of randomness we probably added. * We take into account the first, second and third-order deltas * in order to make our estimate. */ if (!state->dont_count_entropy) { delta = sample.jiffies - state->last_time; state->last_time = sample.jiffies; delta2 = delta - state->last_delta; state->last_delta = delta; delta3 = delta2 - state->last_delta2; state->last_delta2 = 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; /* * delta is now minimum absolute delta. * Round down by 1 bit on general principles, * and limit entropy entimate to 12 bits. */ credit_entropy_bits(&input_pool, min_t(int, fls(delta>>1), 11)); } out: preempt_enable(); } void add_input_randomness(unsigned int type, unsigned int code, unsigned int value) { static unsigned char last_value; /* ignore autorepeat and the like */ if (value == last_value) return; DEBUG_ENT("input event\n"); last_value = value; add_timer_randomness(&input_timer_state, (type << 4) ^ code ^ (code >> 4) ^ value); } EXPORT_SYMBOL_GPL(add_input_randomness); static DEFINE_PER_CPU(struct fast_pool, irq_randomness); void add_interrupt_randomness(int irq, int irq_flags) { struct Pool *r; struct fast_pool *fast_pool = &__get_cpu_var(irq_randomness); struct pt_regs *regs = get_irq_regs(); unsigned long now = jiffies; __u32 input[4], cycles = get_cycles(); input[0] = cycles ^ jiffies; input[1] = irq; if (regs) { __u64 ip = instruction_pointer(regs); input[2] = ip; input[3] = ip >> 32; } fast_mix(fast_pool, input, sizeof(input)); if ((fast_pool->count & 1023) && !time_after(now, fast_pool->last + HZ)) return; fast_pool->last = now; r = prng_pool.initialized ? &input_pool : &prng_pool; __mix_pool_bytes(r, &fast_pool->pooldata, sizeof(fast_pool->pooldata), NULL); /* * If we don't have a valid cycle counter, and we see * back-to-back timer interrupts, then skip giving credit for * any entropy. */ if (cycles == 0) { if (irq_flags & __IRQF_TIMER) { if (fast_pool->last_timer_intr) return; fast_pool->last_timer_intr = 1; } else fast_pool->last_timer_intr = 0; } credit_entropy_bits(r, 1); } #ifdef CONFIG_BLOCK void add_disk_randomness(struct gendisk *disk) { if (!disk || !disk->random) return; /* first major is 1, so we get >= 0x200 here */ DEBUG_ENT("disk event %d:%d\n", MAJOR(disk_devt(disk)), MINOR(disk_devt(disk))); add_timer_randomness(disk->random, 0x100 + disk_devt(disk)); } #endif /********************************************************************* * * Extraction routines. * These routines extract bytes from the pools. The extracted bytes * exhibit a random distribution, possibly "random" in the sense of * pseudorandom, or possibly "random" in the sense of actual entropy. * Since the latter is not guaranteed, please do not call them * "entropy" extraction routines. * Specifically, in the case of the PRNG, i.e. the nonblocking pool, * the extracted bytes may have an entropy density that is vastly less * than 8 bits per byte, orders of magnitude less. * ********************************************************************/ /* Forward reference */ static ssize_t extract_rnd(struct Pool *r, void *buf, size_t nbytes, int min, int rsvd); /* * This function is responsible for filling this pool (r) * to an appropriate level, by pulling from the upstream * pool (r->pull), if any, if necessary. * * We enforce the requirement that any contribution to the * nonblocking PRNG be large enough to be "significant" to any attacker. * * In principle, this would cascade, pulling from other pools * even farther upstream, but as it stands there are only two * pools, so no cascade. * * It is conceivable that the caller's want_level could exceed * POOL_BYTES, and this would not be ridiculous. * Mild fixme: Handling of this case needs more thought. */ static void fill_pool( struct Pool *r, size_t want_level /* measured in BYTES */ ){ __u32 tmp[OUTPUT_POOL_WORDS]; int rsvd; /* measured in bits */ int txbits; int mybatch; int actual; /* measured in BYTES */ int headspace = r->poolinfo->POOLBITS - r->entropy_count; if (!r->pull) return; /* no upstream pool to pull from */ if (r->blockable) { /* Here if we are blockable i.e. /dev/random i.e. TRNG. */ int pullhead = r->pull->poolinfo->POOLBITS - r->pull->entropy_count; /* Only the top 500 bits are free for extraloading: */ int extraload = 500 - pullhead; /* Don't extraload more than needed to fill the headspace: */ extraload = min_t(int, extraload, headspace); txbits = BYTE2BIT(want_level) - r->entropy_count; /* Load what is actually requested, or extraload whatever is freely available: */ txbits = max_t(int, txbits, extraload); if (txbits <= 0) return; /* already have all we want */ mybatch = rsvd = 0; } else { /* * Here if we are non-blocking i.e. urandom i.e. PRNG. * Reserve a suitable amount of entropy in the input pool, on a * sliding scale based on how desperately we need to be reseeded. * * Ignore the caller's want_level. Entropy level doesn't mean much * for a PRNG. The only thing the PRNG ever requests is RESEED_BATCH. * * The dilution factor ranges from 819 to 1 (at appetite=0) * to 858,993,459 to 1 (at appetite=20) */ int appetite = fls64(r->extracted_subttl) - 18; if (appetite < 0) return; /* 128k bits maps to appetite 0 */ /* The largest rsvd that makes any sense: */ rsvd = W2BIT(r->pull->poolinfo->poolwords) - RESEED_BATCH; /* When the appetite gets to 20, rsvd goes to zero: */ rsvd = rsvd - appetite*rsvd/20; if (rsvd < 0) rsvd = 0; /* * For the PRNG, make the request big enough to be * "significant" to any attacker: */ mybatch = txbits = RESEED_BATCH; } /* Don't request more than fits in our buffer: */ txbits = min_t(int, txbits, 8*sizeof(tmp)); DEBUG_ENT("About to reseed %s adding %d bits;" " caller want_level: %zu prev level: %d" " batch: %d rsvd: %d\n", r->name, txbits, want_level * 8, r->entropy_count, BIT2BYTE(mybatch), BIT2BYTE(rsvd)); if (txbits < 0) return; /* already full enough */ actual = extract_rnd(r->pull, tmp, BIT2BYTE(txbits), BIT2BYTE(mybatch), BIT2BYTE(rsvd)); mix_pool_bytes(r, tmp, actual, NULL); credit_entropy_bits(r, actual*8); /* * The subtotal starts over every time we transfer a * sufficiently-large batch. Super-important for PRNG; * probably not significant for TRNG. */ if (BYTE2BIT(actual) >= RESEED_BATCH) { r->extracted_subttl = 0; } } /* * General note, applying to several of the following routines: * * The /min/ parameter specifies the minimum amount we are allowed to pull; * otherwise we pull nothing. The PRNG uses this when reseeding, * to make sure the pull is "significant" to any attacker. * * The /reserved/ parameter indicates how much entropy we must leave * in the pool after each pull to avoid starving other readers. */ /* * Debit the entropy estimate for pool r. * Usually done right before an extract_buf(). * The return value is the amount to extract. */ static size_t debit(struct Pool *r, size_t nbytes, int min, int reserved) { unsigned long flags; int wakeup_write = 0; /* Hold lock while accounting */ spin_lock_irqsave(&r->lock, flags); BUG_ON(r->entropy_count > r->poolinfo->POOLBITS); DEBUG_ENT("trying to debit %zu bits from %s\n", nbytes * 8, r->name); /* If there's not enough available, don't extract anything. */ if (r->entropy_count / 8 < min + reserved) { nbytes = 0; } else { int entropy_count, orig; retry: entropy_count = orig = ACCESS_ONCE(r->entropy_count); /* If blockable, never pull more than available */ if (r->blockable && nbytes + reserved >= entropy_count / 8) nbytes = entropy_count/8 - reserved; if (entropy_count / 8 >= nbytes + reserved) { entropy_count -= nbytes*8; if (cmpxchg(&r->entropy_count, orig, entropy_count) != orig) goto retry; } else { entropy_count = reserved; if (cmpxchg(&r->entropy_count, orig, entropy_count) != orig) goto retry; } if (entropy_count < random_write_wakeup_thresh) wakeup_write = 1; } DEBUG_ENT("debiting %zu entropy credits from %s%s\n", nbytes * 8, r->name, r->blockable ? "" : " (nonblocking)"); spin_unlock_irqrestore(&r->lock, flags); if (wakeup_write) { wake_up_interruptible(&random_write_wait); kill_fasync(&fasync, SIGIO, POLL_OUT); } return nbytes; } /* * Extract randomness from the specified pool (r) and return it in a buffer. * Probably should always be preceded by debit(...). */ static void extract_buf(struct Pool *r, __u8 *out) { int i; union { __u32 w[5]; unsigned long l[LONGS(EXTRACT_SIZE)]; } hash; __u32 workspace[SHA_WORKSPACE_WORDS]; __u8 extract[64]; unsigned long flags; /* Generate a hash across the pool, 16 words (512 bits) at a time */ sha_init(hash.w); spin_lock_irqsave(&r->lock, flags); for (i = 0; i < r->poolinfo->poolwords; i += 16) sha_transform(hash.w, (__u8 *)(r->pooldata + i), workspace); /* * We mix the hash back into the pool to prevent backtracking * attacks (where the attacker knows the state of the pool * plus the current outputs, and attempts to find previous * ouputs), unless the hash function can be inverted. By * mixing at least a SHA1 worth of hash data back, we make * brute-forcing the feedback as hard as brute-forcing the * hash. */ __mix_pool_bytes(r, hash.w, sizeof(hash.w), extract); spin_unlock_irqrestore(&r->lock, flags); /* * To avoid duplicates, we atomically extract a portion of the * pool while mixing, and hash one final time. */ sha_transform(hash.w, extract, workspace); memset(extract, 0, sizeof(extract)); memset(workspace, 0, sizeof(workspace)); /* * In case the hash function has some recognizable output * pattern, we fold it in half. Thus, we always feed back * twice as much data as we output. */ hash.w[0] ^= hash.w[3]; hash.w[1] ^= hash.w[4]; hash.w[2] ^= rol32(hash.w[2], 16); /* * If we have a architectural hardware random number * generator, mix that in, too. */ for (i = 0; i < LONGS(EXTRACT_SIZE); i++) { unsigned long v; if (!arch_get_random_long(&v)) break; hash.l[i] ^= v; } memcpy(out, &hash, EXTRACT_SIZE); memset(&hash, 0, sizeof(hash)); } /* * Note: Here we assume that .poolwords is a multiple of 16 words. * * We return the actual number of bytes extracted. */ static ssize_t extract_rnd(struct Pool *r, void *buf, size_t txbytes, int min, int reserved) { ssize_t ret = 0, i; __u8 tmp[EXTRACT_SIZE]; unsigned long flags; /* if last_data isn't primed, we need EXTRACT_SIZE extra bytes */ if (fips_enabled) { spin_lock_irqsave(&r->lock, flags); if (!r->last_data_init) { r->last_data_init = true; spin_unlock_irqrestore(&r->lock, flags); trace_extract_rnd(r->name, EXTRACT_SIZE, r->entropy_count, _RET_IP_); fill_pool(r, EXTRACT_SIZE); /* FIXME: */ /* why is there no debit() associated with this extract_buf()? */ extract_buf(r, tmp); spin_lock_irqsave(&r->lock, flags); memcpy(r->last_data, tmp, EXTRACT_SIZE); } spin_unlock_irqrestore(&r->lock, flags); } trace_extract_rnd(r->name, txbytes, r->entropy_count, _RET_IP_); /* * We want our pool (r) to have enough entropy, if possible. * So pull it up to a level (txbits) that will cover the * extraction we are about to do. */ fill_pool(r, txbytes); /* This pool (r) has already been credited for the fill-in we just did. */ /* Debit this pool for the extraction we are about to do. */ txbytes = debit(r, txbytes, min, reserved); while (txbytes) { extract_buf(r, tmp); if (fips_enabled) { spin_lock_irqsave(&r->lock, flags); if (!memcmp(tmp, r->last_data, EXTRACT_SIZE)) panic("Hardware RNG duplicated output!\n"); memcpy(r->last_data, tmp, EXTRACT_SIZE); spin_unlock_irqrestore(&r->lock, flags); } i = min_t(int, txbytes, EXTRACT_SIZE); memcpy(buf, tmp, i); txbytes -= i; buf += i; ret += i; } /* Wipe data just returned from memory */ memset(tmp, 0, sizeof(tmp)); if (ret > 0) { /* Subttl does not overflow; it saturates at a user-friendly round number: */ r->extracted_subttl += BYTE2BIT(ret); if (r->extracted_subttl > SUBTTL_SAT) r->extracted_subttl = SUBTTL_SAT; /* Total does not saturate; it just overflows and wraps around. */ r->extracted_total += BYTE2BIT(ret); } return ret; } static ssize_t extract_rnd_user(struct Pool *r, void __user *buf, size_t nbytes) { ssize_t ret = 0, i; __u8 tmp[EXTRACT_SIZE]; trace_extract_rnd_user(r->name, nbytes, r->entropy_count, _RET_IP_); fill_pool(r, nbytes); /* Debit the estimate, according to the extraction we are about to do: */ nbytes = debit(r, nbytes, 0, 0); while (nbytes) { if (need_resched()) { if (signal_pending(current)) { if (ret == 0) ret = -ERESTARTSYS; break; } schedule(); } extract_buf(r, tmp); i = min_t(int, nbytes, EXTRACT_SIZE); if (copy_to_user(buf, tmp, i)) { ret = -EFAULT; break; } nbytes -= i; buf += i; ret += i; } /* Wipe data just returned from memory */ memset(tmp, 0, sizeof(tmp)); if (ret > 0) { r->extracted_subttl += BYTE2BIT(ret); r->extracted_total += BYTE2BIT(ret); } return ret; } /* * This function is the exported kernel interface. It returns some * number of good pseudorandomly distributed numbers, suitable for key * generation, seeding TCP sequence numbers, etc. It does not use the * hw random number generator, if available; use * get_random_bytes_arch() for that. */ void get_random_bytes(void *buf, int nbytes) { extract_rnd(&prng_pool, buf, nbytes, 0, 0); } EXPORT_SYMBOL(get_random_bytes); /* * This function will use the architecture-specific hardware random * number generator if it is available. The arch-specific hw RNG will * almost certainly be faster than what we can do in software, but it * is impossible to verify that it is implemented securely (as * opposed, to, say, the AES encryption of a sequence number using a * key known by the NSA). So it's useful if we need the speed, but * only if we're willing to trust the hardware manufacturer not to * have put in a back door. */ void get_random_bytes_arch(void *buf, int nbytes) { char *p = buf; trace_get_random_bytes(nbytes, _RET_IP_); while (nbytes) { unsigned long v; int chunk = min(nbytes, (int)sizeof(unsigned long)); if (!arch_get_random_long(&v)) break; memcpy(p, &v, chunk); p += chunk; nbytes -= chunk; } if (nbytes) extract_rnd(&prng_pool, p, nbytes, 0, 0); } EXPORT_SYMBOL(get_random_bytes_arch); /* * init_std_data - initialize pool with system data * * @r: pool to initialize * * This function clears the pool's entropy count and mixes some system * data into the pool to prepare it for use. The pool is not cleared * as that can only decrease the entropy in the pool. */ static void init_std_data(struct Pool *r) { int i; ktime_t now = ktime_get_real(); unsigned long rv; r->entropy_count = 0; r->entropy_total = 0; r->extracted_subttl = 0; r->extracted_total = 0; r->last_data_init = false; mix_pool_bytes(r, &now, sizeof(now), NULL); for (i = r->poolinfo->POOLBYTES; i > 0; i -= sizeof(rv)) { if (!arch_get_random_long(&rv)) break; mix_pool_bytes(r, &rv, sizeof(rv), NULL); } mix_pool_bytes(r, utsname(), sizeof(*(utsname())), NULL); } /* * Note that setup_arch() may call add_device_randomness() * long before we get here. This allows seeding of the pools * with some platform dependent data very early in the boot * process. But it limits our options here. We must use * statically allocated structures that already have all * initializations complete at compile time. We should also * take care not to overwrite the precious per platform data * we were given. */ static int rand_initialize(void) { init_std_data(&input_pool); init_std_data(&devrand_pool); init_std_data(&prng_pool); return 0; } module_init(rand_initialize); #ifdef CONFIG_BLOCK void rand_initialize_disk(struct gendisk *disk) { struct timer_rand_state *state; /* * If kzalloc returns null, we just won't use that entropy * source. */ state = kzalloc(sizeof(struct timer_rand_state), GFP_KERNEL); if (state) disk->random = state; } #endif /* * Interface used by the actual /dev/random. * * This is the only place where the process can block. * It blocks if /dev/random wants to read more bits than are available. */ static ssize_t random_read(struct file *file, char __user *buf, size_t nbytes, loff_t *ppos) { ssize_t n, retval = 0, count = 0; /* * Kludge: zero-byte read: Fill the pool from upstream sources. */ if (nbytes == 0){ fill_pool(&devrand_pool, 0); return 0; } while (nbytes > 0) { n = nbytes; if (n > SEC_XFER_SIZE) n = SEC_XFER_SIZE; DEBUG_ENT("reading %zu bits\n", n*8); n = extract_rnd_user(&devrand_pool, buf, n); if (n < 0) { retval = n; break; } DEBUG_ENT("read got %zd bits (%zd still needed)\n", n*8, (nbytes-n)*8); if (n == 0) { if (file->f_flags & O_NONBLOCK) { retval = -EAGAIN; break; } DEBUG_ENT("sleeping?\n"); wait_event_interruptible(random_read_wait, input_pool.entropy_count >= random_read_wakeup_thresh); DEBUG_ENT("awake\n"); if (signal_pending(current)) { retval = -ERESTARTSYS; break; } continue; } count += n; buf += n; nbytes -= n; break; /* This break makes the device work */ /* like a named pipe */ } return (count ? count : retval); } static ssize_t urandom_read(struct file *file, char __user *buf, size_t nbytes, loff_t *ppos) { return extract_rnd_user(&prng_pool, buf, nbytes); } static unsigned int random_poll(struct file *file, poll_table * wait) { unsigned int mask; poll_wait(file, &random_read_wait, wait); poll_wait(file, &random_write_wait, wait); mask = 0; if (input_pool.entropy_count >= random_read_wakeup_thresh) mask |= POLLIN | POLLRDNORM; if (input_pool.entropy_count < random_write_wakeup_thresh) mask |= POLLOUT | POLLWRNORM; return mask; } static int write_pool(struct Pool *r, const char __user *buffer, size_t count) { size_t bytes; __u32 buf[16]; const char __user *p = buffer; while (count > 0) { bytes = min(count, sizeof(buf)); if (copy_from_user(&buf, p, bytes)) return -EFAULT; count -= bytes; p += bytes; mix_pool_bytes(r, buf, bytes, NULL); cond_resched(); } return 0; } static ssize_t random_write(struct file *file, const char __user *buffer, size_t count, loff_t *ppos) { size_t ret; ret = write_pool(&devrand_pool, buffer, count); if (ret) return ret; /* some error */ ret = write_pool(&prng_pool, buffer, count); if (ret) return ret; /* some error */ return (ssize_t)count; } static long random_ioctl(struct file *f, unsigned int cmd, unsigned long arg) { int size, ent_count; int __user *p = (int __user *)arg; int retval; switch (cmd) { case RNDGETENTCNT: /* inherently racy, no point locking */ if (put_user(input_pool.entropy_count + devrand_pool.entropy_count + prng_pool.entropy_count, p)) return -EFAULT; return 0; case RNDADDTOENTCNT: if (!capable(CAP_SYS_ADMIN)) return -EPERM; if (get_user(ent_count, p)) return -EFAULT; credit_entropy_bits(&input_pool, ent_count); return 0; case RNDADDENTROPY: if (!capable(CAP_SYS_ADMIN)) return -EPERM; if (get_user(ent_count, p++)) return -EFAULT; if (ent_count < 0) return -EINVAL; if (get_user(size, p++)) return -EFAULT; retval = write_pool(&input_pool, (const char __user *)p, size); if (retval < 0) return retval; credit_entropy_bits(&input_pool, ent_count); return 0; case RNDZAPENTCNT: case RNDCLEARPOOL: /* Clear the entropy estimates. */ if (!capable(CAP_SYS_ADMIN)) return -EPERM; rand_initialize(); return 0; default: return -EINVAL; } } static int random_fasync(int fd, struct file *filp, int on) { return fasync_helper(fd, filp, on, &fasync); } const struct file_operations random_fops = { .read = random_read, .write = random_write, .poll = random_poll, .unlocked_ioctl = random_ioctl, .fasync = random_fasync, .llseek = noop_llseek, }; const struct file_operations urandom_fops = { .read = urandom_read, .write = random_write, .unlocked_ioctl = random_ioctl, .fasync = random_fasync, .llseek = noop_llseek, }; /*************************************************************** * Random UUID interface * * Used here for a Boot ID, but can be useful for other kernel * drivers. ***************************************************************/ /* * Generate randomly-distributed UUID */ void generate_random_uuid(unsigned char uuid_out[16]) { get_random_bytes(uuid_out, 16); /* Set UUID version to 4 --- truly random generation */ uuid_out[6] = (uuid_out[6] & 0x0F) | 0x40; /* Set the UUID variant to DCE */ uuid_out[8] = (uuid_out[8] & 0x3F) | 0x80; } EXPORT_SYMBOL(generate_random_uuid); /******************************************************************** * * Sysctl interface * ********************************************************************/ #ifdef CONFIG_SYSCTL #include static int min_read_thresh = RESEED_BATCH; static int min_write_thresh; /* shouldn't this have a value? */ static int max_read_thresh = INPUT_POOL_WORDS * 32; static int max_write_thresh = INPUT_POOL_WORDS * 32; static char sysctl_bootid[16]; /* * These functions is used to return both the bootid UUID, and random * UUID. The difference is in whether table->data is NULL; if it is, * then a new UUID is generated and returned to the user. * * If the user accesses this via the proc interface, it will be returned * as an ASCII string in the standard UUID format. If accesses via the * sysctl system call, it is returned as 16 bytes of binary data. */ static int proc_do_uuid(struct ctl_table *table, int write, void __user *buffer, size_t *lenp, loff_t *ppos) { struct ctl_table fake_table; unsigned char buf[64], tmp_uuid[16], *uuid; uuid = table->data; if (!uuid) { uuid = tmp_uuid; generate_random_uuid(uuid); } else { static DEFINE_SPINLOCK(bootid_spinlock); spin_lock(&bootid_spinlock); if (!uuid[8]) generate_random_uuid(uuid); spin_unlock(&bootid_spinlock); } sprintf(buf, "%pU", uuid); fake_table.data = buf; fake_table.maxlen = sizeof(buf); return proc_dostring(&fake_table, write, buffer, lenp, ppos); } static int total_entropy_count; static int sum_entropy_count(struct ctl_table *table, int write, void __user *buffer, size_t *lenp, loff_t *ppos){ total_entropy_count = input_pool.entropy_count #ifdef OVERCOMPLICATED + devrand_pool.entropy_count #endif + prng_pool.entropy_count; return proc_dointvec(table, write, buffer, lenp, ppos); } static int sysctl_poolsize = INPUT_POOL_WORDS * 32; extern struct ctl_table random_table[]; struct ctl_table random_table[] = { { .procname = "poolsize", .data = &sysctl_poolsize, .maxlen = sizeof(int), .mode = 0444, .proc_handler = proc_dointvec, }, { .procname = "entropy_avail", .maxlen = sizeof(int), .mode = 0444, .proc_handler = sum_entropy_count, .data = &total_entropy_count, }, { .procname = "entropy_avail_inp", .maxlen = sizeof(int), .mode = 0444, .proc_handler = proc_dointvec, .data = &input_pool.entropy_count, }, { .procname = "entropy_avail_r", .maxlen = sizeof(int), .mode = 0444, .proc_handler = proc_dointvec, .data = &devrand_pool.entropy_count, }, { .procname = "entropy_avail_ur", .maxlen = sizeof(int), .mode = 0444, .proc_handler = proc_dointvec, .data = &prng_pool.entropy_count, }, { .procname = "extracted_total_inp", .maxlen = sizeof(ulonglong), .mode = 0644, .proc_handler = proc_doulonglongvec_minmax, .data = &input_pool.extracted_total, }, { .procname = "extracted_total_r", .maxlen = sizeof(ulonglong), .mode = 0644, .proc_handler = proc_doulonglongvec_minmax, .data = &devrand_pool.extracted_total, }, { .procname = "extracted_total_ur", .maxlen = sizeof(ulonglong), .mode = 0644, .proc_handler = proc_doulonglongvec_minmax, .data = &prng_pool.extracted_total, }, { .procname = "extracted_subttl_inp", .maxlen = sizeof(ulonglong), .mode = 0644, .proc_handler = proc_doulonglongvec_minmax, .data = &input_pool.extracted_subttl, }, { .procname = "extracted_subttl_r", .maxlen = sizeof(ulonglong), .mode = 0644, .proc_handler = proc_doulonglongvec_minmax, .data = &devrand_pool.extracted_subttl, }, { .procname = "extracted_subttl_ur", .maxlen = sizeof(ulonglong), .mode = 0644, .proc_handler = proc_doulonglongvec_minmax, .data = &prng_pool.extracted_subttl, }, { .procname = "read_wakeup_threshold", .data = &random_read_wakeup_thresh, .maxlen = sizeof(int), .mode = 0644, .proc_handler = proc_dointvec_minmax, .extra1 = &min_read_thresh, .extra2 = &max_read_thresh, }, { .procname = "write_wakeup_threshold", .data = &random_write_wakeup_thresh, .maxlen = sizeof(int), .mode = 0644, .proc_handler = proc_dointvec_minmax, .extra1 = &min_write_thresh, .extra2 = &max_write_thresh, }, { .procname = "boot_id", .data = &sysctl_bootid, .maxlen = 16, .mode = 0444, .proc_handler = proc_do_uuid, }, { .procname = "uuid", .maxlen = 16, .mode = 0444, .proc_handler = proc_do_uuid, }, { } }; #endif /* CONFIG_SYSCTL */ static u32 random_int_secret[MD5_MESSAGE_BYTES / 4] ____cacheline_aligned; static int __init random_int_secret_init(void) { get_random_bytes(random_int_secret, sizeof(random_int_secret)); return 0; } late_initcall(random_int_secret_init); /* * Get a word from a random distribution, for internal kernel use * only. Similar to urandom but with the goal of minimal consumption * of entropy. As a result, the random distribution is not * cryptographically secure but for several uses the cost of depleting * entropy is too high. * Presumably no longer needed, now that /dev/urandom * no longer consumes entropy so rapaciously. */ static DEFINE_PER_CPU(__u32 [MD5_DIGEST_WORDS], get_random_int_hash); unsigned int get_random_int(void) { __u32 *hash; unsigned int ret; if (arch_get_random_int(&ret)) return ret; hash = get_cpu_var(get_random_int_hash); hash[0] += current->pid + jiffies + get_cycles(); md5_transform(hash, random_int_secret); ret = hash[0]; put_cpu_var(get_random_int_hash); return ret; } EXPORT_SYMBOL(get_random_int); /* * randomize_range() returns a start address such that * * [...... .....] * start end * * a with size "len" starting at the return value is inside in the * area defined by [start, end], but is otherwise randomized. */ unsigned long randomize_range(unsigned long start, unsigned long end, unsigned long len) { unsigned long range = end - len - start; if (end <= start + len) return 0; return PAGE_ALIGN(get_random_int() % range + start); }