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Diffstat (limited to 'drivers/char')
| -rw-r--r-- | drivers/char/random.c | 1515 |
1 files changed, 1515 insertions, 0 deletions
diff --git a/drivers/char/random.c b/drivers/char/random.c new file mode 100644 index 0000000..0d91fe5 --- /dev/null +++ b/drivers/char/random.c @@ -0,0 +1,1515 @@ +/* + * random.c -- A strong random number generator + * + * Copyright Matt Mackall <mpm@selenic.com>, 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 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 SHA + * hash of the contents of the "entropy pool". The SHA 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 SHA from its output. Even if it is possible to + * analyze SHA 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 SHA, 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_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 entropy 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 + * entropy 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. + * + * 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..." + * random_seed=/var/run/random-seed + * # Carry a random seed from start-up to start-up + * # Load and then save the whole entropy 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 entropy 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 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. + * + * 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 <linux/utsname.h> +#include <linux/module.h> +#include <linux/kernel.h> +#include <linux/major.h> +#include <linux/string.h> +#include <linux/fcntl.h> +#include <linux/slab.h> +#include <linux/random.h> +#include <linux/poll.h> +#include <linux/init.h> +#include <linux/fs.h> +#include <linux/genhd.h> +#include <linux/interrupt.h> +#include <linux/mm.h> +#include <linux/spinlock.h> +#include <linux/percpu.h> +#include <linux/cryptohash.h> +#include <linux/fips.h> +#include <linux/ptrace.h> +#include <linux/kmemcheck.h> + +#ifdef CONFIG_GENERIC_HARDIRQS +# include <linux/irq.h> +#endif + +#include <asm/processor.h> +#include <asm/uaccess.h> +#include <asm/irq.h> +#include <asm/irq_regs.h> +#include <asm/io.h> + +#define CREATE_TRACE_POINTS +#include <trace/events/random.h> + +/* + * Configuration information + */ +#define INPUT_POOL_WORDS 128 +#define OUTPUT_POOL_WORDS 32 +#define SEC_XFER_SIZE 512 +#define EXTRACT_SIZE 10 + +#define LONGS(x) (((x) + sizeof(unsigned long) - 1)/sizeof(unsigned long)) + +/* + * The minimum number of bits of entropy before we wake up a read on + * /dev/random. Should be enough to do a significant reseed. + */ +static int random_read_wakeup_thresh = 64; + +/* + * 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 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. + */ + +/* + * 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; +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,\ + blocking_pool.entropy_count,\ + nonblocking_pool.entropy_count,\ + ## arg); } while (0) + +/********************************************************************** + * + * OS independent entropy store. Here are the functions which handle + * storing entropy in an entropy pool. + * + **********************************************************************/ + +struct entropy_store; +struct entropy_store { + /* read-only data: */ + struct poolinfo *poolinfo; + __u32 *pool; + const char *name; + struct entropy_store *pull; + int limit; + + /* read-write data: */ + spinlock_t lock; + unsigned add_ptr; + unsigned input_rotate; + int entropy_count; + int entropy_total; + unsigned int initialized:1; + bool last_data_init; + __u8 last_data[EXTRACT_SIZE]; +}; + +static __u32 input_pool_data[INPUT_POOL_WORDS]; +static __u32 blocking_pool_data[OUTPUT_POOL_WORDS]; +static __u32 nonblocking_pool_data[OUTPUT_POOL_WORDS]; + +static struct entropy_store input_pool = { + .poolinfo = &poolinfo_table[0], + .name = "input", + .limit = 1, + .lock = __SPIN_LOCK_UNLOCKED(input_pool.lock), + .pool = input_pool_data +}; + +static struct entropy_store blocking_pool = { + .poolinfo = &poolinfo_table[1], + .name = "blocking", + .limit = 1, + .pull = &input_pool, + .lock = __SPIN_LOCK_UNLOCKED(blocking_pool.lock), + .pool = blocking_pool_data +}; + +static struct entropy_store nonblocking_pool = { + .poolinfo = &poolinfo_table[1], + .name = "nonblocking", + .pull = &input_pool, + .lock = __SPIN_LOCK_UNLOCKED(nonblocking_pool.lock), + .pool = nonblocking_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 entropy_store *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->pool[i]; + w ^= r->pool[(i + tap1) & wordmask]; + w ^= r->pool[(i + tap2) & wordmask]; + w ^= r->pool[(i + tap3) & wordmask]; + w ^= r->pool[(i + tap4) & wordmask]; + w ^= r->pool[(i + tap5) & wordmask]; + + /* Mix the result back in with a twist */ + r->pool[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->pool[(i - j) & wordmask]; +} + +static void __mix_pool_bytes(struct entropy_store *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 entropy_store *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 pool[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->pool[i & 3] ^ + f->pool[(i + 1) & 3]; + f->pool[i & 3] = (w >> 3) ^ twist_table[w & 7]; + input_rotate += (i++ & 3) ? 7 : 14; + } + f->count = i; + f->rotate = input_rotate; +} + +/* + * Credit (or debit) the entropy store with n bits of entropy + */ +static void credit_entropy_bits(struct entropy_store *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(&nonblocking_pool, buf, size, NULL); + mix_pool_bytes(&nonblocking_pool, &time, sizeof(time), NULL); +} +EXPORT_SYMBOL(add_device_randomness); + +static struct timer_rand_state input_timer_state; + +/* + * 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. + * + */ +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 entropy_store *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 = nonblocking_pool.initialized ? &input_pool : &nonblocking_pool; + __mix_pool_bytes(r, &fast_pool->pool, sizeof(fast_pool->pool), 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 + +/********************************************************************* + * + * Entropy extraction routines + * + *********************************************************************/ + +static ssize_t extract_entropy(struct entropy_store *r, void *buf, + size_t nbytes, int min, int rsvd); + +/* + * This utility inline function is responsible for transferring entropy + * from the primary pool to the secondary extraction pool. We make + * sure we pull enough for a 'catastrophic reseed'. + */ +static void xfer_secondary_pool(struct entropy_store *r, size_t nbytes) +{ + __u32 tmp[OUTPUT_POOL_WORDS]; + + if (r->pull && r->entropy_count < nbytes * 8 && + r->entropy_count < r->poolinfo->POOLBITS) { + /* If we're limited, always leave two wakeup worth's BITS */ + int rsvd = r->limit ? 0 : random_read_wakeup_thresh/4; + int bytes = nbytes; + + /* pull at least as many as BYTES as wakeup BITS */ + bytes = max_t(int, bytes, random_read_wakeup_thresh / 8); + /* but never more than the buffer size */ + bytes = min_t(int, bytes, sizeof(tmp)); + + DEBUG_ENT("going to reseed %s with %d bits " + "(%zu of %d requested)\n", + r->name, bytes * 8, nbytes * 8, r->entropy_count); + + bytes = extract_entropy(r->pull, tmp, bytes, + random_read_wakeup_thresh / 8, rsvd); + mix_pool_bytes(r, tmp, bytes, NULL); + credit_entropy_bits(r, bytes*8); + } +} + +/* + * These functions extracts randomness from the "entropy pool", and + * returns it in a buffer. + * + * The min parameter specifies the minimum amount we can pull before + * failing to avoid races that defeat catastrophic reseeding while the + * reserved parameter indicates how much entropy we must leave in the + * pool after each pull to avoid starving other readers. + * + * Note: extract_entropy() assumes that .poolwords is a multiple of 16 words. + */ + +static size_t account(struct entropy_store *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 extract %zu bits from %s\n", + nbytes * 8, r->name); + + /* Can we pull enough? */ + if (r->entropy_count / 8 < min + reserved) { + nbytes = 0; + } else { + int entropy_count, orig; +retry: + entropy_count = orig = ACCESS_ONCE(r->entropy_count); + /* If limited, never pull more than available */ + if (r->limit && 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->limit ? "" : " (unlimited)"); + + spin_unlock_irqrestore(&r->lock, flags); + + if (wakeup_write) { + wake_up_interruptible(&random_write_wait); + kill_fasync(&fasync, SIGIO, POLL_OUT); + } + + return nbytes; +} + +static void extract_buf(struct entropy_store *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->pool + 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)); +} + +static ssize_t extract_entropy(struct entropy_store *r, void *buf, + size_t nbytes, 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_entropy(r->name, EXTRACT_SIZE, + r->entropy_count, _RET_IP_); + xfer_secondary_pool(r, EXTRACT_SIZE); + 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_entropy(r->name, nbytes, r->entropy_count, _RET_IP_); + xfer_secondary_pool(r, nbytes); + nbytes = account(r, nbytes, min, reserved); + + while (nbytes) { + 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, nbytes, EXTRACT_SIZE); + memcpy(buf, tmp, i); + nbytes -= i; + buf += i; + ret += i; + } + + /* Wipe data just returned from memory */ + memset(tmp, 0, sizeof(tmp)); + + return ret; +} + +static ssize_t extract_entropy_user(struct entropy_store *r, void __user *buf, + size_t nbytes) +{ + ssize_t ret = 0, i; + __u8 tmp[EXTRACT_SIZE]; + + trace_extract_entropy_user(r->name, nbytes, r->entropy_count, _RET_IP_); + xfer_secondary_pool(r, nbytes); + nbytes = account(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)); + + return ret; +} + +/* + * This function is the exported kernel interface. It returns some + * number of good random 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_entropy(&nonblocking_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_entropy(&nonblocking_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 entropy_store *r) +{ + int i; + ktime_t now = ktime_get_real(); + unsigned long rv; + + r->entropy_count = 0; + r->entropy_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(&blocking_pool); + init_std_data(&nonblocking_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 + +static ssize_t +random_read(struct file *file, char __user *buf, size_t nbytes, loff_t *ppos) +{ + ssize_t n, retval = 0, count = 0; + + if (nbytes == 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_entropy_user(&blocking_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_entropy_user(&nonblocking_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 entropy_store *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(&blocking_pool, buffer, count); + if (ret) + return ret; + ret = write_pool(&nonblocking_pool, buffer, count); + if (ret) + return ret; + + 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, 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 pool counters. */ + 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 random 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 <linux/sysctl.h> + +static int min_read_thresh = 8, min_write_thresh; +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 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 = proc_dointvec, + .data = &input_pool.entropy_count, + }, + { + .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 random word for internal kernel use only. Similar to urandom but + * with the goal of minimal entropy pool depletion. As a result, the random + * value is not cryptographically secure but for several uses the cost of + * depleting entropy is too high + */ +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 + * + * [...... <range> .....] + * start end + * + * a <range> 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); +} |