--- /dev/null
+/*
+ * 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/kthread.h>
+#include <linux/percpu.h>
+#include <linux/cryptohash.h>
+#include <linux/fips.h>
+#include <linux/ptrace.h>
+#include <linux/kmemcheck.h>
+#include <linux/workqueue.h>
+#include <linux/irq.h>
+#include <linux/syscalls.h>
+#include <linux/completion.h>
+
+#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>
+
+/* #define ADD_INTERRUPT_BENCH */
+
+/*
+ * Configuration information
+ */
+#define INPUT_POOL_SHIFT 12
+#define INPUT_POOL_WORDS (1 << (INPUT_POOL_SHIFT-5))
+#define OUTPUT_POOL_SHIFT 10
+#define OUTPUT_POOL_WORDS (1 << (OUTPUT_POOL_SHIFT-5))
+#define SEC_XFER_SIZE 512
+#define EXTRACT_SIZE 10
+
+#define DEBUG_RANDOM_BOOT 0
+
+#define LONGS(x) (((x) + sizeof(unsigned long) - 1)/sizeof(unsigned long))
+
+/*
+ * To allow fractional bits to be tracked, the entropy_count field is
+ * denominated in units of 1/8th bits.
+ *
+ * 2*(ENTROPY_SHIFT + log2(poolbits)) must <= 31, or the multiply in
+ * credit_entropy_bits() needs to be 64 bits wide.
+ */
+#define ENTROPY_SHIFT 3
+#define ENTROPY_BITS(r) ((r)->entropy_count >> ENTROPY_SHIFT)
+
+/*
+ * 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_bits = 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_bits = 28 * OUTPUT_POOL_WORDS;
+
+/*
+ * The minimum number of seconds between urandom pool reseeding. We
+ * do this to limit the amount of entropy that can be drained from the
+ * input pool even if there are heavy demands on /dev/urandom.
+ */
+static int random_min_urandom_seed = 60;
+
+/*
+ * Originally, we used a primitive polynomial of degree .poolwords
+ * over GF(2). The taps for various sizes are defined below. They
+ * were chosen to be evenly spaced except for the last tap, which is 1
+ * to get the twisting happening as fast as possible.
+ *
+ * For the purposes of better mixing, we use the CRC-32 polynomial as
+ * well to make a (modified) twisted Generalized Feedback Shift
+ * Register. (See M. Matsumoto & Y. Kurita, 1992. Twisted GFSR
+ * generators. ACM Transactions on Modeling and Computer Simulation
+ * 2(3):179-194. Also see M. Matsumoto & Y. Kurita, 1994. Twisted
+ * GFSR generators II. ACM Transactions on Modeling and Computer
+ * Simulation 4:254-266)
+ *
+ * Thanks to Colin Plumb for suggesting this.
+ *
+ * The mixing operation is much less sensitive than the output hash,
+ * where we use SHA-1. All that we want of mixing operation 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).
+ *
+ * Our mixing functions were analyzed by Lacharme, Roeck, Strubel, and
+ * Videau in their paper, "The Linux Pseudorandom Number Generator
+ * Revisited" (see: http://eprint.iacr.org/2012/251.pdf). In their
+ * paper, they point out that we are not using a true Twisted GFSR,
+ * since Matsumoto & Kurita used a trinomial feedback polynomial (that
+ * is, with only three taps, instead of the six that we are using).
+ * As a result, the resulting polynomial is neither primitive nor
+ * irreducible, and hence does not have a maximal period over
+ * GF(2**32). They suggest a slight change to the generator
+ * polynomial which improves the resulting TGFSR polynomial to be
+ * irreducible, which we have made here.
+ */
+static struct poolinfo {
+ int poolbitshift, poolwords, poolbytes, poolbits, poolfracbits;
+#define S(x) ilog2(x)+5, (x), (x)*4, (x)*32, (x) << (ENTROPY_SHIFT+5)
+ int tap1, tap2, tap3, tap4, tap5;
+} poolinfo_table[] = {
+ /* was: x^128 + x^103 + x^76 + x^51 +x^25 + x + 1 */
+ /* x^128 + x^104 + x^76 + x^51 +x^25 + x + 1 */
+ { S(128), 104, 76, 51, 25, 1 },
+ /* was: x^32 + x^26 + x^20 + x^14 + x^7 + x + 1 */
+ /* x^32 + x^26 + x^19 + x^14 + x^7 + x + 1 */
+ { S(32), 26, 19, 14, 7, 1 },
+#if 0
+ /* x^2048 + x^1638 + x^1231 + x^819 + x^411 + x + 1 -- 115 */
+ { S(2048), 1638, 1231, 819, 411, 1 },
+
+ /* x^1024 + x^817 + x^615 + x^412 + x^204 + x + 1 -- 290 */
+ { S(1024), 817, 615, 412, 204, 1 },
+
+ /* x^1024 + x^819 + x^616 + x^410 + x^207 + x^2 + 1 -- 115 */
+ { S(1024), 819, 616, 410, 207, 2 },
+
+ /* x^512 + x^411 + x^308 + x^208 + x^104 + x + 1 -- 225 */
+ { S(512), 411, 308, 208, 104, 1 },
+
+ /* x^512 + x^409 + x^307 + x^206 + x^102 + x^2 + 1 -- 95 */
+ { S(512), 409, 307, 206, 102, 2 },
+ /* x^512 + x^409 + x^309 + x^205 + x^103 + x^2 + 1 -- 95 */
+ { S(512), 409, 309, 205, 103, 2 },
+
+ /* x^256 + x^205 + x^155 + x^101 + x^52 + x + 1 -- 125 */
+ { S(256), 205, 155, 101, 52, 1 },
+
+ /* x^128 + x^103 + x^78 + x^51 + x^27 + x^2 + 1 -- 70 */
+ { S(128), 103, 78, 51, 27, 2 },
+
+ /* x^64 + x^52 + x^39 + x^26 + x^14 + x + 1 -- 15 */
+ { S(64), 52, 39, 26, 14, 1 },
+#endif
+};
+
+/*
+ * Static global variables
+ */
+static DECLARE_WAIT_QUEUE_HEAD(random_read_wait);
+static DECLARE_WAIT_QUEUE_HEAD(random_write_wait);
+static DECLARE_WAIT_QUEUE_HEAD(urandom_init_wait);
+static struct fasync_struct *fasync;
+
+/**********************************************************************
+ *
+ * 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: */
+ const struct poolinfo *poolinfo;
+ __u32 *pool;
+ const char *name;
+ struct entropy_store *pull;
+ struct work_struct push_work;
+
+ /* read-write data: */
+ unsigned long last_pulled;
+ spinlock_t lock;
+ unsigned short add_ptr;
+ unsigned short input_rotate;
+ int entropy_count;
+ int entropy_total;
+ unsigned int initialized:1;
+ unsigned int limit:1;
+ unsigned int last_data_init:1;
+ __u8 last_data[EXTRACT_SIZE];
+};
+
+static void push_to_pool(struct work_struct *work);
+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,
+ .push_work = __WORK_INITIALIZER(blocking_pool.push_work,
+ push_to_pool),
+};
+
+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,
+ .push_work = __WORK_INITIALIZER(nonblocking_pool.push_work,
+ push_to_pool),
+};
+
+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)
+{
+ unsigned long i, 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;
+
+ input_rotate = r->input_rotate;
+ i = r->add_ptr;
+
+ /* mix one byte at a time to simplify size handling and churn faster */
+ while (nbytes--) {
+ w = rol32(*bytes++, input_rotate);
+ 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 = (input_rotate + (i ? 7 : 14)) & 31;
+ }
+
+ r->input_rotate = input_rotate;
+ r->add_ptr = i;
+}
+
+static void __mix_pool_bytes(struct entropy_store *r, const void *in,
+ int nbytes)
+{
+ trace_mix_pool_bytes_nolock(r->name, nbytes, _RET_IP_);
+ _mix_pool_bytes(r, in, nbytes);
+}
+
+static void mix_pool_bytes(struct entropy_store *r, const void *in,
+ int nbytes)
+{
+ unsigned long flags;
+
+ trace_mix_pool_bytes(r->name, nbytes, _RET_IP_);
+ spin_lock_irqsave(&r->lock, flags);
+ _mix_pool_bytes(r, in, nbytes);
+ spin_unlock_irqrestore(&r->lock, flags);
+}
+
+struct fast_pool {
+ __u32 pool[4];
+ unsigned long last;
+ unsigned short reg_idx;
+ unsigned char count;
+};
+
+/*
+ * 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)
+{
+ __u32 a = f->pool[0], b = f->pool[1];
+ __u32 c = f->pool[2], d = f->pool[3];
+
+ a += b; c += d;
+ b = rol32(b, 6); d = rol32(d, 27);
+ d ^= a; b ^= c;
+
+ a += b; c += d;
+ b = rol32(b, 16); d = rol32(d, 14);
+ d ^= a; b ^= c;
+
+ a += b; c += d;
+ b = rol32(b, 6); d = rol32(d, 27);
+ d ^= a; b ^= c;
+
+ a += b; c += d;
+ b = rol32(b, 16); d = rol32(d, 14);
+ d ^= a; b ^= c;
+
+ f->pool[0] = a; f->pool[1] = b;
+ f->pool[2] = c; f->pool[3] = d;
+ f->count++;
+}
+
+/*
+ * Credit (or debit) the entropy store with n bits of entropy.
+ * Use credit_entropy_bits_safe() if the value comes from userspace
+ * or otherwise should be checked for extreme values.
+ */
+static void credit_entropy_bits(struct entropy_store *r, int nbits)
+{
+ int entropy_count, orig;
+ const int pool_size = r->poolinfo->poolfracbits;
+ int nfrac = nbits << ENTROPY_SHIFT;
+
+ if (!nbits)
+ return;
+
+retry:
+ entropy_count = orig = ACCESS_ONCE(r->entropy_count);
+ if (nfrac < 0) {
+ /* Debit */
+ entropy_count += nfrac;
+ } else {
+ /*
+ * Credit: we have to account for the possibility of
+ * overwriting already present entropy. Even in the
+ * ideal case of pure Shannon entropy, new contributions
+ * approach the full value asymptotically:
+ *
+ * entropy <- entropy + (pool_size - entropy) *
+ * (1 - exp(-add_entropy/pool_size))
+ *
+ * For add_entropy <= pool_size/2 then
+ * (1 - exp(-add_entropy/pool_size)) >=
+ * (add_entropy/pool_size)*0.7869...
+ * so we can approximate the exponential with
+ * 3/4*add_entropy/pool_size and still be on the
+ * safe side by adding at most pool_size/2 at a time.
+ *
+ * The use of pool_size-2 in the while statement is to
+ * prevent rounding artifacts from making the loop
+ * arbitrarily long; this limits the loop to log2(pool_size)*2
+ * turns no matter how large nbits is.
+ */
+ int pnfrac = nfrac;
+ const int s = r->poolinfo->poolbitshift + ENTROPY_SHIFT + 2;
+ /* The +2 corresponds to the /4 in the denominator */
+
+ do {
+ unsigned int anfrac = min(pnfrac, pool_size/2);
+ unsigned int add =
+ ((pool_size - entropy_count)*anfrac*3) >> s;
+
+ entropy_count += add;
+ pnfrac -= anfrac;
+ } while (unlikely(entropy_count < pool_size-2 && pnfrac));
+ }
+
+ if (unlikely(entropy_count < 0)) {
+ pr_warn("random: negative entropy/overflow: pool %s count %d\n",
+ r->name, entropy_count);
+ WARN_ON(1);
+ entropy_count = 0;
+ } else if (entropy_count > pool_size)
+ entropy_count = pool_size;
+ if (cmpxchg(&r->entropy_count, orig, entropy_count) != orig)
+ goto retry;
+
+ r->entropy_total += nbits;
+ if (!r->initialized && r->entropy_total > 128) {
+ r->initialized = 1;
+ r->entropy_total = 0;
+ if (r == &nonblocking_pool) {
+ prandom_reseed_late();
+ wake_up_interruptible(&urandom_init_wait);
+ pr_notice("random: %s pool is initialized\n", r->name);
+ }
+ }
+
+ trace_credit_entropy_bits(r->name, nbits,
+ entropy_count >> ENTROPY_SHIFT,
+ r->entropy_total, _RET_IP_);
+
+ if (r == &input_pool) {
+ int entropy_bits = entropy_count >> ENTROPY_SHIFT;
+
+ /* should we wake readers? */
+ if (entropy_bits >= random_read_wakeup_bits) {
+ wake_up_interruptible(&random_read_wait);
+ kill_fasync(&fasync, SIGIO, POLL_IN);
+ }
+ /* If the input pool is getting full, send some
+ * entropy to the two output pools, flipping back and
+ * forth between them, until the output pools are 75%
+ * full.
+ */
+ if (entropy_bits > random_write_wakeup_bits &&
+ r->initialized &&
+ r->entropy_total >= 2*random_read_wakeup_bits) {
+ static struct entropy_store *last = &blocking_pool;
+ struct entropy_store *other = &blocking_pool;
+
+ if (last == &blocking_pool)
+ other = &nonblocking_pool;
+ if (other->entropy_count <=
+ 3 * other->poolinfo->poolfracbits / 4)
+ last = other;
+ if (last->entropy_count <=
+ 3 * last->poolinfo->poolfracbits / 4) {
+ schedule_work(&last->push_work);
+ r->entropy_total = 0;
+ }
+ }
+ }
+}
+
+static void credit_entropy_bits_safe(struct entropy_store *r, int nbits)
+{
+ const int nbits_max = (int)(~0U >> (ENTROPY_SHIFT + 1));
+
+ /* Cap the value to avoid overflows */
+ nbits = min(nbits, nbits_max);
+ nbits = max(nbits, -nbits_max);
+
+ credit_entropy_bits(r, nbits);
+}
+
+/*********************************************************************
+ *
+ * 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;
+};
+
+#define INIT_TIMER_RAND_STATE { INITIAL_JIFFIES, };
+
+/*
+ * 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 = random_get_entropy() ^ jiffies;
+ unsigned long flags;
+
+ trace_add_device_randomness(size, _RET_IP_);
+ spin_lock_irqsave(&input_pool.lock, flags);
+ _mix_pool_bytes(&input_pool, buf, size);
+ _mix_pool_bytes(&input_pool, &time, sizeof(time));
+ spin_unlock_irqrestore(&input_pool.lock, flags);
+
+ spin_lock_irqsave(&nonblocking_pool.lock, flags);
+ _mix_pool_bytes(&nonblocking_pool, buf, size);
+ _mix_pool_bytes(&nonblocking_pool, &time, sizeof(time));
+ spin_unlock_irqrestore(&nonblocking_pool.lock, flags);
+}
+EXPORT_SYMBOL(add_device_randomness);
+
+static struct timer_rand_state input_timer_state = INIT_TIMER_RAND_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 entropy_store *r;
+ struct {
+ long jiffies;
+ unsigned cycles;
+ unsigned num;
+ } sample;
+ long delta, delta2, delta3;
+
+ sample.jiffies = jiffies;
+ sample.cycles = random_get_entropy();
+ sample.num = num;
+ r = nonblocking_pool.initialized ? &input_pool : &nonblocking_pool;
+ mix_pool_bytes(r, &sample, sizeof(sample));
+
+ /*
+ * 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(r, min_t(int, fls(delta>>1), 11));
+ }
+}
+
+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;
+
+ last_value = value;
+ add_timer_randomness(&input_timer_state,
+ (type << 4) ^ code ^ (code >> 4) ^ value);
+ trace_add_input_randomness(ENTROPY_BITS(&input_pool));
+}
+EXPORT_SYMBOL_GPL(add_input_randomness);
+
+static DEFINE_PER_CPU(struct fast_pool, irq_randomness);
+
+#ifdef ADD_INTERRUPT_BENCH
+static unsigned long avg_cycles, avg_deviation;
+
+#define AVG_SHIFT 8 /* Exponential average factor k=1/256 */
+#define FIXED_1_2 (1 << (AVG_SHIFT-1))
+
+static void add_interrupt_bench(cycles_t start)
+{
+ long delta = random_get_entropy() - start;
+
+ /* Use a weighted moving average */
+ delta = delta - ((avg_cycles + FIXED_1_2) >> AVG_SHIFT);
+ avg_cycles += delta;
+ /* And average deviation */
+ delta = abs(delta) - ((avg_deviation + FIXED_1_2) >> AVG_SHIFT);
+ avg_deviation += delta;
+}
+#else
+#define add_interrupt_bench(x)
+#endif
+
+static __u32 get_reg(struct fast_pool *f, struct pt_regs *regs)
+{
+ __u32 *ptr = (__u32 *) regs;
+
+ if (regs == NULL)
+ return 0;
+ if (f->reg_idx >= sizeof(struct pt_regs) / sizeof(__u32))
+ f->reg_idx = 0;
+ return *(ptr + f->reg_idx++);
+}
+
+void add_interrupt_randomness(int irq, int irq_flags, __u64 ip)
+{
+ struct entropy_store *r;
+ struct fast_pool *fast_pool = this_cpu_ptr(&irq_randomness);
+ unsigned long now = jiffies;
+ cycles_t cycles = random_get_entropy();
+ __u32 c_high, j_high;
+ unsigned long seed;
+ int credit = 0;
+
+ if (cycles == 0)
+ cycles = get_reg(fast_pool, NULL);
+ c_high = (sizeof(cycles) > 4) ? cycles >> 32 : 0;
+ j_high = (sizeof(now) > 4) ? now >> 32 : 0;
+ fast_pool->pool[0] ^= cycles ^ j_high ^ irq;
+ fast_pool->pool[1] ^= now ^ c_high;
+ if (!ip)
+ ip = _RET_IP_;
+ fast_pool->pool[2] ^= ip;
+ fast_pool->pool[3] ^= (sizeof(ip) > 4) ? ip >> 32 :
+ get_reg(fast_pool, NULL);
+
+ fast_mix(fast_pool);
+ add_interrupt_bench(cycles);
+
+ if ((fast_pool->count < 64) &&
+ !time_after(now, fast_pool->last + HZ))
+ return;
+
+ r = nonblocking_pool.initialized ? &input_pool : &nonblocking_pool;
+ if (!spin_trylock(&r->lock))
+ return;
+
+ fast_pool->last = now;
+ __mix_pool_bytes(r, &fast_pool->pool, sizeof(fast_pool->pool));
+
+ /*
+ * If we have architectural seed generator, produce a seed and
+ * add it to the pool. For the sake of paranoia don't let the
+ * architectural seed generator dominate the input from the
+ * interrupt noise.
+ */
+ if (arch_get_random_seed_long(&seed)) {
+ __mix_pool_bytes(r, &seed, sizeof(seed));
+ credit = 1;
+ }
+ spin_unlock(&r->lock);
+
+ fast_pool->count = 0;
+
+ /* award one bit for the contents of the fast pool */
+ credit_entropy_bits(r, credit + 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 */
+ add_timer_randomness(disk->random, 0x100 + disk_devt(disk));
+ trace_add_disk_randomness(disk_devt(disk), ENTROPY_BITS(&input_pool));
+}
+EXPORT_SYMBOL_GPL(add_disk_randomness);
+#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);
+static void xfer_secondary_pool(struct entropy_store *r, size_t nbytes)
+{
+ if (!r->pull ||
+ r->entropy_count >= (nbytes << (ENTROPY_SHIFT + 3)) ||
+ r->entropy_count > r->poolinfo->poolfracbits)
+ return;
+
+ if (r->limit == 0 && random_min_urandom_seed) {
+ unsigned long now = jiffies;
+
+ if (time_before(now,
+ r->last_pulled + random_min_urandom_seed * HZ))
+ return;
+ r->last_pulled = now;
+ }
+
+ _xfer_secondary_pool(r, nbytes);
+}
+
+static void _xfer_secondary_pool(struct entropy_store *r, size_t nbytes)
+{
+ __u32 tmp[OUTPUT_POOL_WORDS];
+
+ /* For /dev/random's pool, always leave two wakeups' worth */
+ int rsvd_bytes = r->limit ? 0 : random_read_wakeup_bits / 4;
+ int bytes = nbytes;
+
+ /* pull at least as much as a wakeup */
+ bytes = max_t(int, bytes, random_read_wakeup_bits / 8);
+ /* but never more than the buffer size */
+ bytes = min_t(int, bytes, sizeof(tmp));
+
+ trace_xfer_secondary_pool(r->name, bytes * 8, nbytes * 8,
+ ENTROPY_BITS(r), ENTROPY_BITS(r->pull));
+ bytes = extract_entropy(r->pull, tmp, bytes,
+ random_read_wakeup_bits / 8, rsvd_bytes);
+ mix_pool_bytes(r, tmp, bytes);
+ credit_entropy_bits(r, bytes*8);
+}
+
+/*
+ * Used as a workqueue function so that when the input pool is getting
+ * full, we can "spill over" some entropy to the output pools. That
+ * way the output pools can store some of the excess entropy instead
+ * of letting it go to waste.
+ */
+static void push_to_pool(struct work_struct *work)
+{
+ struct entropy_store *r = container_of(work, struct entropy_store,
+ push_work);
+ BUG_ON(!r);
+ _xfer_secondary_pool(r, random_read_wakeup_bits/8);
+ trace_push_to_pool(r->name, r->entropy_count >> ENTROPY_SHIFT,
+ r->pull->entropy_count >> ENTROPY_SHIFT);
+}
+
+/*
+ * This function decides how many bytes to actually take from the
+ * given pool, and also debits the entropy count accordingly.
+ */
+static size_t account(struct entropy_store *r, size_t nbytes, int min,
+ int reserved)
+{
+ int entropy_count, orig;
+ size_t ibytes, nfrac;
+
+ BUG_ON(r->entropy_count > r->poolinfo->poolfracbits);
+
+ /* Can we pull enough? */
+retry:
+ entropy_count = orig = ACCESS_ONCE(r->entropy_count);
+ ibytes = nbytes;
+ /* If limited, never pull more than available */
+ if (r->limit) {
+ int have_bytes = entropy_count >> (ENTROPY_SHIFT + 3);
+
+ if ((have_bytes -= reserved) < 0)
+ have_bytes = 0;
+ ibytes = min_t(size_t, ibytes, have_bytes);
+ }
+ if (ibytes < min)
+ ibytes = 0;
+
+ if (unlikely(entropy_count < 0)) {
+ pr_warn("random: negative entropy count: pool %s count %d\n",
+ r->name, entropy_count);
+ WARN_ON(1);
+ entropy_count = 0;
+ }
+ nfrac = ibytes << (ENTROPY_SHIFT + 3);
+ if ((size_t) entropy_count > nfrac)
+ entropy_count -= nfrac;
+ else
+ entropy_count = 0;
+
+ if (cmpxchg(&r->entropy_count, orig, entropy_count) != orig)
+ goto retry;
+
+ trace_debit_entropy(r->name, 8 * ibytes);
+ if (ibytes &&
+ (r->entropy_count >> ENTROPY_SHIFT) < random_write_wakeup_bits) {
+ wake_up_interruptible(&random_write_wait);
+ kill_fasync(&fasync, SIGIO, POLL_OUT);
+ }
+
+ return ibytes;
+}
+
+/*
+ * This function does the actual extraction for extract_entropy and
+ * extract_entropy_user.
+ *
+ * Note: we assume that .poolwords is a multiple of 16 words.
+ */
+static void extract_buf(struct entropy_store *r, __u8 *out)
+{
+ int i;
+ union {
+ __u32 w[5];
+ unsigned long l[LONGS(20)];
+ } hash;
+ __u32 workspace[SHA_WORKSPACE_WORDS];
+ unsigned long flags;
+
+ /*
+ * If we have an architectural hardware random number
+ * generator, use it for SHA's initial vector
+ */
+ sha_init(hash.w);
+ for (i = 0; i < LONGS(20); i++) {
+ unsigned long v;
+ if (!arch_get_random_long(&v))
+ break;
+ hash.l[i] = v;
+ }
+
+ /* Generate a hash across the pool, 16 words (512 bits) at a time */
+ 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));
+ spin_unlock_irqrestore(&r->lock, flags);
+
+ memzero_explicit(workspace, 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);
+
+ memcpy(out, &hash, EXTRACT_SIZE);
+ memzero_explicit(&hash, sizeof(hash));
+}
+
+/*
+ * This function 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.
+ */
+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 = 1;
+ spin_unlock_irqrestore(&r->lock, flags);
+ trace_extract_entropy(r->name, EXTRACT_SIZE,
+ ENTROPY_BITS(r), _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, ENTROPY_BITS(r), _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 */
+ memzero_explicit(tmp, sizeof(tmp));
+
+ return ret;
+}
+
+/*
+ * This function extracts randomness from the "entropy pool", and
+ * returns it in a userspace buffer.
+ */
+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];
+ int large_request = (nbytes > 256);
+
+ trace_extract_entropy_user(r->name, nbytes, ENTROPY_BITS(r), _RET_IP_);
+ xfer_secondary_pool(r, nbytes);
+ nbytes = account(r, nbytes, 0, 0);
+
+ while (nbytes) {
+ if (large_request && 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 */
+ memzero_explicit(tmp, 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 rely on the hardware random
+ * number generator. For random bytes direct from the hardware RNG
+ * (when available), use get_random_bytes_arch().
+ */
+void get_random_bytes(void *buf, int nbytes)
+{
+#if DEBUG_RANDOM_BOOT > 0
+ if (unlikely(nonblocking_pool.initialized == 0))
+ printk(KERN_NOTICE "random: %pF get_random_bytes called "
+ "with %d bits of entropy available\n",
+ (void *) _RET_IP_,
+ nonblocking_pool.entropy_total);
+#endif
+ trace_get_random_bytes(nbytes, _RET_IP_);
+ 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_arch(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->last_pulled = jiffies;
+ mix_pool_bytes(r, &now, sizeof(now));
+ for (i = r->poolinfo->poolbytes; i > 0; i -= sizeof(rv)) {
+ if (!arch_get_random_seed_long(&rv) &&
+ !arch_get_random_long(&rv))
+ rv = random_get_entropy();
+ mix_pool_bytes(r, &rv, sizeof(rv));
+ }
+ mix_pool_bytes(r, utsname(), sizeof(*(utsname())));
+}
+
+/*
+ * 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;
+}
+early_initcall(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) {
+ state->last_time = INITIAL_JIFFIES;
+ disk->random = state;
+ }
+}
+#endif
+
+static ssize_t
+_random_read(int nonblock, char __user *buf, size_t nbytes)
+{
+ ssize_t n;
+
+ if (nbytes == 0)
+ return 0;
+
+ nbytes = min_t(size_t, nbytes, SEC_XFER_SIZE);
+ while (1) {
+ n = extract_entropy_user(&blocking_pool, buf, nbytes);
+ if (n < 0)
+ return n;
+ trace_random_read(n*8, (nbytes-n)*8,
+ ENTROPY_BITS(&blocking_pool),
+ ENTROPY_BITS(&input_pool));
+ if (n > 0)
+ return n;
+
+ /* Pool is (near) empty. Maybe wait and retry. */
+ if (nonblock)
+ return -EAGAIN;
+
+ wait_event_interruptible(random_read_wait,
+ ENTROPY_BITS(&input_pool) >=
+ random_read_wakeup_bits);
+ if (signal_pending(current))
+ return -ERESTARTSYS;
+ }
+}
+
+static ssize_t
+random_read(struct file *file, char __user *buf, size_t nbytes, loff_t *ppos)
+{
+ return _random_read(file->f_flags & O_NONBLOCK, buf, nbytes);
+}
+
+static ssize_t
+urandom_read(struct file *file, char __user *buf, size_t nbytes, loff_t *ppos)
+{
+ int ret;
+
+ if (unlikely(nonblocking_pool.initialized == 0))
+ printk_once(KERN_NOTICE "random: %s urandom read "
+ "with %d bits of entropy available\n",
+ current->comm, nonblocking_pool.entropy_total);
+
+ nbytes = min_t(size_t, nbytes, INT_MAX >> (ENTROPY_SHIFT + 3));
+ ret = extract_entropy_user(&nonblocking_pool, buf, nbytes);
+
+ trace_urandom_read(8 * nbytes, ENTROPY_BITS(&nonblocking_pool),
+ ENTROPY_BITS(&input_pool));
+ return ret;
+}
+
+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 (ENTROPY_BITS(&input_pool) >= random_read_wakeup_bits)
+ mask |= POLLIN | POLLRDNORM;
+ if (ENTROPY_BITS(&input_pool) < random_write_wakeup_bits)
+ 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);
+ 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 */
+ ent_count = ENTROPY_BITS(&input_pool);
+ if (put_user(ent_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_safe(&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_safe(&input_pool, ent_count);
+ return 0;
+ case RNDZAPENTCNT:
+ case RNDCLEARPOOL:
+ /*
+ * Clear the entropy pool counters. We no longer clear
+ * the entropy pool, as that's silly.
+ */
+ if (!capable(CAP_SYS_ADMIN))
+ return -EPERM;
+ input_pool.entropy_count = 0;
+ nonblocking_pool.entropy_count = 0;
+ blocking_pool.entropy_count = 0;
+ 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,
+};
+
+SYSCALL_DEFINE3(getrandom, char __user *, buf, size_t, count,
+ unsigned int, flags)
+{
+ if (flags & ~(GRND_NONBLOCK|GRND_RANDOM))
+ return -EINVAL;
+
+ if (count > INT_MAX)
+ count = INT_MAX;
+
+ if (flags & GRND_RANDOM)
+ return _random_read(flags & GRND_NONBLOCK, buf, count);
+
+ if (unlikely(nonblocking_pool.initialized == 0)) {
+ if (flags & GRND_NONBLOCK)
+ return -EAGAIN;
+ wait_event_interruptible(urandom_init_wait,
+ nonblocking_pool.initialized);
+ if (signal_pending(current))
+ return -ERESTARTSYS;
+ }
+ return urandom_read(NULL, buf, count, NULL);
+}
+
+/***************************************************************
+ * 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 = OUTPUT_POOL_WORDS * 32;
+static int max_write_thresh = INPUT_POOL_WORDS * 32;
+static char sysctl_bootid[16];
+
+/*
+ * This function 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, the UUID will be
+ * returned as an ASCII string in the standard UUID format; if via the
+ * sysctl system call, 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);
+}
+
+/*
+ * Return entropy available scaled to integral bits
+ */
+static int proc_do_entropy(struct ctl_table *table, int write,
+ void __user *buffer, size_t *lenp, loff_t *ppos)
+{
+ struct ctl_table fake_table;
+ int entropy_count;
+
+ entropy_count = *(int *)table->data >> ENTROPY_SHIFT;
+
+ fake_table.data = &entropy_count;
+ fake_table.maxlen = sizeof(entropy_count);
+
+ return proc_dointvec(&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_do_entropy,
+ .data = &input_pool.entropy_count,
+ },
+ {
+ .procname = "read_wakeup_threshold",
+ .data = &random_read_wakeup_bits,
+ .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_bits,
+ .maxlen = sizeof(int),
+ .mode = 0644,
+ .proc_handler = proc_dointvec_minmax,
+ .extra1 = &min_write_thresh,
+ .extra2 = &max_write_thresh,
+ },
+ {
+ .procname = "urandom_min_reseed_secs",
+ .data = &random_min_urandom_seed,
+ .maxlen = sizeof(int),
+ .mode = 0644,
+ .proc_handler = proc_dointvec,
+ },
+ {
+ .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,
+ },
+#ifdef ADD_INTERRUPT_BENCH
+ {
+ .procname = "add_interrupt_avg_cycles",
+ .data = &avg_cycles,
+ .maxlen = sizeof(avg_cycles),
+ .mode = 0444,
+ .proc_handler = proc_doulongvec_minmax,
+ },
+ {
+ .procname = "add_interrupt_avg_deviation",
+ .data = &avg_deviation,
+ .maxlen = sizeof(avg_deviation),
+ .mode = 0444,
+ .proc_handler = proc_doulongvec_minmax,
+ },
+#endif
+ { }
+};
+#endif /* CONFIG_SYSCTL */
+
+static u32 random_int_secret[MD5_MESSAGE_BYTES / 4] ____cacheline_aligned;
+
+int random_int_secret_init(void)
+{
+ get_random_bytes(random_int_secret, sizeof(random_int_secret));
+ return 0;
+}
+
+/*
+ * 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 + random_get_entropy();
+ 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);
+}
+
+/* Interface for in-kernel drivers of true hardware RNGs.
+ * Those devices may produce endless random bits and will be throttled
+ * when our pool is full.
+ */
+void add_hwgenerator_randomness(const char *buffer, size_t count,
+ size_t entropy)
+{
+ struct entropy_store *poolp = &input_pool;
+
+ /* Suspend writing if we're above the trickle threshold.
+ * We'll be woken up again once below random_write_wakeup_thresh,
+ * or when the calling thread is about to terminate.
+ */
+ wait_event_interruptible(random_write_wait, kthread_should_stop() ||
+ ENTROPY_BITS(&input_pool) <= random_write_wakeup_bits);
+ mix_pool_bytes(poolp, buffer, count);
+ credit_entropy_bits(poolp, entropy);
+}
+EXPORT_SYMBOL_GPL(add_hwgenerator_randomness);
Code Review / kvmfornfv.git / blobdiff