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+/*
+ * random.c -- A strong random number generator
+ *
+ * Version 1.89, last modified 19-Sep-99
+ *
+ * Copyright Theodore Ts'o, 1994, 1995, 1996, 1997, 1998, 1999. All
+ * rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+ * are met:
+ * 1. Redistributions of source code must retain the above copyright
+ * notice, and the entire permission notice in its entirety,
+ * including the disclaimer of warranties.
+ * 2. Redistributions in binary form must reproduce the above copyright
+ * notice, this list of conditions and the following disclaimer in the
+ * documentation and/or other materials provided with the distribution.
+ * 3. The name of the author may not be used to endorse or promote
+ * products derived from this software without specific prior
+ * written permission.
+ *
+ * ALTERNATIVELY, this product may be distributed under the terms of
+ * the GNU 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_input_randomness(unsigned int type, unsigned int code,
+ * unsigned int value);
+ * void add_interrupt_randomness(int irq);
+ *
+ * add_input_randomness() uses the input layer interrupt timing, as well as
+ * the event type information from the hardware.
+ *
+ * add_interrupt_randomness() uses the inter-interrupt timing as random
+ * inputs to the entropy pool. Note that not all interrupts are good
+ * sources of randomness! For example, the timer interrupts is not a
+ * good choice, because the periodicity of the interrupts is too
+ * regular, and hence predictable to an attacker. Disk interrupts are
+ * a better measure, since the timing of the disk interrupts are more
+ * unpredictable.
+ *
+ * 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/config.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/spinlock.h>
+#include <linux/percpu.h>
+#include <linux/cryptohash.h>
+
+#include <asm/processor.h>
+#include <asm/uaccess.h>
+#include <asm/irq.h>
+#include <asm/io.h>
+
+/*
+ * Configuration information
+ */
+#define INPUT_POOL_WORDS 128
+#define OUTPUT_POOL_WORDS 32
+#define SEC_XFER_SIZE 512
+
+/*
+ * 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 = INPUT_POOL_WORDS * 28;
+
+static DEFINE_PER_CPU(int, trickle_count) = 0;
+
+/*
+ * 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);
+
+#if 0
+static int debug = 0;
+module_param(debug, bool, 0644);
+#define DEBUG_ENT(fmt, arg...) do { if (debug) \
+ printk(KERN_DEBUG "random %04d %04d %04d: " \
+ fmt,\
+ input_pool.entropy_count,\
+ blocking_pool.entropy_count,\
+ nonblocking_pool.entropy_count,\
+ ## arg); } while (0)
+#else
+#define DEBUG_ENT(fmt, arg...) do {} while (0)
+#endif
+
+/**********************************************************************
+ *
+ * OS independent entropy store. Here are the functions which handle
+ * storing entropy in an entropy pool.
+ *
+ **********************************************************************/
+
+struct entropy_store;
+struct entropy_store {
+ /* mostly-read data: */
+ struct poolinfo *poolinfo;
+ __u32 *pool;
+ const char *name;
+ int limit;
+ struct entropy_store *pull;
+
+ /* read-write data: */
+ spinlock_t lock ____cacheline_aligned_in_smp;
+ unsigned add_ptr;
+ int entropy_count;
+ int input_rotate;
+};
+
+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,
+ .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,
+ .pool = blocking_pool_data
+};
+
+static struct entropy_store nonblocking_pool = {
+ .poolinfo = &poolinfo_table[1],
+ .name = "nonblocking",
+ .pull = &input_pool,
+ .lock = SPIN_LOCK_UNLOCKED,
+ .pool = nonblocking_pool_data
+};
+
+/*
+ * This function adds a byte into the entropy "pool". It does not
+ * update the entropy estimate. The caller should call
+ * credit_entropy_store 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 __add_entropy_words(struct entropy_store *r, const __u32 *in,
+ int nwords, __u32 out[16])
+{
+ static __u32 const twist_table[8] = {
+ 0x00000000, 0x3b6e20c8, 0x76dc4190, 0x4db26158,
+ 0xedb88320, 0xd6d6a3e8, 0x9b64c2b0, 0xa00ae278 };
+ unsigned long i, add_ptr, tap1, tap2, tap3, tap4, tap5;
+ int new_rotate, input_rotate;
+ int wordmask = r->poolinfo->poolwords - 1;
+ __u32 w, next_w;
+ unsigned long flags;
+
+ /* Taps are constant, so we can load them without holding r->lock. */
+ tap1 = r->poolinfo->tap1;
+ tap2 = r->poolinfo->tap2;
+ tap3 = r->poolinfo->tap3;
+ tap4 = r->poolinfo->tap4;
+ tap5 = r->poolinfo->tap5;
+ next_w = *in++;
+
+ spin_lock_irqsave(&r->lock, flags);
+ prefetch_range(r->pool, wordmask);
+ input_rotate = r->input_rotate;
+ add_ptr = r->add_ptr;
+
+ while (nwords--) {
+ w = rol32(next_w, input_rotate);
+ if (nwords > 0)
+ next_w = *in++;
+ i = add_ptr = (add_ptr - 1) & wordmask;
+ /*
+ * Normally, we add 7 bits of rotation to the pool.
+ * At the beginning of the pool, add an extra 7 bits
+ * rotation, so that successive passes spread the
+ * input bits across the pool evenly.
+ */
+ new_rotate = input_rotate + 14;
+ if (i)
+ new_rotate = input_rotate + 7;
+ input_rotate = new_rotate & 31;
+
+ /* XOR in the various taps */
+ 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];
+ w ^= r->pool[i];
+ r->pool[i] = (w >> 3) ^ twist_table[w & 7];
+ }
+
+ r->input_rotate = input_rotate;
+ r->add_ptr = add_ptr;
+
+ if (out) {
+ for (i = 0; i < 16; i++) {
+ out[i] = r->pool[add_ptr];
+ add_ptr = (add_ptr - 1) & wordmask;
+ }
+ }
+
+ spin_unlock_irqrestore(&r->lock, flags);
+}
+
+static inline void add_entropy_words(struct entropy_store *r, const __u32 *in,
+ int nwords)
+{
+ __add_entropy_words(r, in, nwords, NULL);
+}
+
+/*
+ * Credit (or debit) the entropy store with n bits of entropy
+ */
+static void credit_entropy_store(struct entropy_store *r, int nbits)
+{
+ unsigned long flags;
+
+ spin_lock_irqsave(&r->lock, flags);
+
+ if (r->entropy_count + nbits < 0) {
+ DEBUG_ENT("negative entropy/overflow (%d+%d)\n",
+ r->entropy_count, nbits);
+ r->entropy_count = 0;
+ } else if (r->entropy_count + nbits > r->poolinfo->POOLBITS) {
+ r->entropy_count = r->poolinfo->POOLBITS;
+ } else {
+ r->entropy_count += nbits;
+ if (nbits)
+ DEBUG_ENT("added %d entropy credits to %s\n",
+ nbits, r->name);
+ }
+
+ spin_unlock_irqrestore(&r->lock, flags);
+}
+
+/*********************************************************************
+ *
+ * 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;
+};
+
+static struct timer_rand_state input_timer_state;
+static struct timer_rand_state *irq_timer_state[NR_IRQS];
+
+/*
+ * 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 {
+ cycles_t cycles;
+ long jiffies;
+ 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 &&
+ (__get_cpu_var(trickle_count)++ & 0xfff))
+ goto out;
+
+ sample.jiffies = jiffies;
+ sample.cycles = get_cycles();
+ sample.num = num;
+ add_entropy_words(&input_pool, (u32 *)&sample, sizeof(sample)/4);
+
+ /*
+ * 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_store(&input_pool,
+ min_t(int, fls(delta>>1), 11));
+ }
+
+ if(input_pool.entropy_count >= random_read_wakeup_thresh)
+ wake_up_interruptible(&random_read_wait);
+
+out:
+ preempt_enable();
+}
+
+extern 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);
+}
+
+void add_interrupt_randomness(int irq)
+{
+ if (irq >= NR_IRQS || irq_timer_state[irq] == 0)
+ return;
+
+ DEBUG_ENT("irq event %d\n", irq);
+ add_timer_randomness(irq_timer_state[irq], 0x100 + irq);
+}
+
+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", disk->major, disk->first_minor);
+
+ add_timer_randomness(disk->random,
+ 0x100 + MKDEV(disk->major, disk->first_minor));
+}
+
+EXPORT_SYMBOL(add_disk_randomness);
+
+#define EXTRACT_SIZE 10
+
+/*********************************************************************
+ *
+ * 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 transfering 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) {
+ int bytes = max_t(int, random_read_wakeup_thresh / 8,
+ min_t(int, nbytes, sizeof(tmp)));
+ int rsvd = r->limit ? 0 : random_read_wakeup_thresh/4;
+
+ DEBUG_ENT("going to reseed %s with %d bits "
+ "(%d 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);
+ add_entropy_words(r, tmp, (bytes + 3) / 4);
+ credit_entropy_store(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;
+
+ BUG_ON(r->entropy_count > r->poolinfo->POOLBITS);
+
+ /* Hold lock while accounting */
+ spin_lock_irqsave(&r->lock, flags);
+
+ DEBUG_ENT("trying to extract %d bits from %s\n",
+ nbytes * 8, r->name);
+
+ /* Can we pull enough? */
+ if (r->entropy_count / 8 < min + reserved) {
+ nbytes = 0;
+ } else {
+ /* If limited, never pull more than available */
+ if (r->limit && nbytes + reserved >= r->entropy_count / 8)
+ nbytes = r->entropy_count/8 - reserved;
+
+ if(r->entropy_count / 8 >= nbytes + reserved)
+ r->entropy_count -= nbytes*8;
+ else
+ r->entropy_count = reserved;
+
+ if (r->entropy_count < random_write_wakeup_thresh)
+ wake_up_interruptible(&random_write_wait);
+ }
+
+ DEBUG_ENT("debiting %d entropy credits from %s%s\n",
+ nbytes * 8, r->name, r->limit ? "" : " (unlimited)");
+
+ spin_unlock_irqrestore(&r->lock, flags);
+
+ return nbytes;
+}
+
+static void extract_buf(struct entropy_store *r, __u8 *out)
+{
+ int i, x;
+ __u32 data[16], buf[5 + SHA_WORKSPACE_WORDS];
+
+ sha_init(buf);
+ /*
+ * As we hash the pool, we mix intermediate values of
+ * the hash back into the pool. This eliminates
+ * 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.
+ */
+ for (i = 0, x = 0; i < r->poolinfo->poolwords; i += 16, x+=2) {
+ sha_transform(buf, (__u8 *)r->pool+i, buf + 5);
+ add_entropy_words(r, &buf[x % 5], 1);
+ }
+
+ /*
+ * To avoid duplicates, we atomically extract a
+ * portion of the pool while mixing, and hash one
+ * final time.
+ */
+ __add_entropy_words(r, &buf[x % 5], 1, data);
+ sha_transform(buf, (__u8 *)data, buf + 5);
+
+ /*
+ * In case the hash function has some recognizable
+ * output pattern, we fold it in half.
+ */
+
+ buf[0] ^= buf[3];
+ buf[1] ^= buf[4];
+ buf[0] ^= rol32(buf[3], 16);
+ memcpy(out, buf, EXTRACT_SIZE);
+ memset(buf, 0, sizeof(buf));
+}
+
+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];
+
+ xfer_secondary_pool(r, nbytes);
+ nbytes = account(r, nbytes, min, reserved);
+
+ while (nbytes) {
+ extract_buf(r, tmp);
+ 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];
+
+ 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 seeding TCP sequence
+ * numbers, etc.
+ */
+void get_random_bytes(void *buf, int nbytes)
+{
+ extract_entropy(&nonblocking_pool, buf, nbytes, 0, 0);
+}
+
+EXPORT_SYMBOL(get_random_bytes);
+
+/*
+ * 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)
+{
+ struct timeval tv;
+ unsigned long flags;
+
+ spin_lock_irqsave(&r->lock, flags);
+ r->entropy_count = 0;
+ spin_unlock_irqrestore(&r->lock, flags);
+
+ do_gettimeofday(&tv);
+ add_entropy_words(r, (__u32 *)&tv, sizeof(tv)/4);
+ add_entropy_words(r, (__u32 *)&system_utsname,
+ sizeof(system_utsname)/4);
+}
+
+static int __init rand_initialize(void)
+{
+ init_std_data(&input_pool);
+ init_std_data(&blocking_pool);
+ init_std_data(&nonblocking_pool);
+ return 0;
+}
+module_init(rand_initialize);
+
+void rand_initialize_irq(int irq)
+{
+ struct timer_rand_state *state;
+
+ if (irq >= NR_IRQS || irq_timer_state[irq])
+ return;
+
+ /*
+ * If kmalloc returns null, we just won't use that entropy
+ * source.
+ */
+ state = kmalloc(sizeof(struct timer_rand_state), GFP_KERNEL);
+ if (state) {
+ memset(state, 0, sizeof(struct timer_rand_state));
+ irq_timer_state[irq] = state;
+ }
+}
+
+void rand_initialize_disk(struct gendisk *disk)
+{
+ struct timer_rand_state *state;
+
+ /*
+ * If kmalloc returns null, we just won't use that entropy
+ * source.
+ */
+ state = kmalloc(sizeof(struct timer_rand_state), GFP_KERNEL);
+ if (state) {
+ memset(state, 0, sizeof(struct timer_rand_state));
+ disk->random = state;
+ }
+}
+
+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 %d bits\n", n*8);
+
+ n = extract_entropy_user(&blocking_pool, buf, n);
+
+ DEBUG_ENT("read got %d bits (%d 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;
+ }
+
+ if (n < 0) {
+ retval = n;
+ break;
+ }
+ count += n;
+ buf += n;
+ nbytes -= n;
+ break; /* This break makes the device work */
+ /* like a named pipe */
+ }
+
+ /*
+ * If we gave the user some bytes, update the access time.
+ */
+ if (count)
+ file_accessed(file);
+
+ 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 ssize_t
+random_write(struct file * file, const char __user * buffer,
+ size_t count, loff_t *ppos)
+{
+ int ret = 0;
+ size_t bytes;
+ __u32 buf[16];
+ const char __user *p = buffer;
+ size_t c = count;
+
+ while (c > 0) {
+ bytes = min(c, sizeof(buf));
+
+ bytes -= copy_from_user(&buf, p, bytes);
+ if (!bytes) {
+ ret = -EFAULT;
+ break;
+ }
+ c -= bytes;
+ p += bytes;
+
+ add_entropy_words(&input_pool, buf, (bytes + 3) / 4);
+ }
+ if (p == buffer) {
+ return (ssize_t)ret;
+ } else {
+ struct inode *inode = file->f_dentry->d_inode;
+ inode->i_mtime = current_fs_time(inode->i_sb);
+ mark_inode_dirty(inode);
+ return (ssize_t)(p - buffer);
+ }
+}
+
+static int
+random_ioctl(struct inode * inode, struct file * file,
+ unsigned int cmd, unsigned long arg)
+{
+ int size, ent_count;
+ int __user *p = (int __user *)arg;
+ int retval;
+
+ switch (cmd) {
+ case RNDGETENTCNT:
+ ent_count = input_pool.entropy_count;
+ 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_store(&input_pool, ent_count);
+ /*
+ * Wake up waiting processes if we have enough
+ * entropy.
+ */
+ if (input_pool.entropy_count >= random_read_wakeup_thresh)
+ wake_up_interruptible(&random_read_wait);
+ 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 = random_write(file, (const char __user *) p,
+ size, &file->f_pos);
+ if (retval < 0)
+ return retval;
+ credit_entropy_store(&input_pool, ent_count);
+ /*
+ * Wake up waiting processes if we have enough
+ * entropy.
+ */
+ if (input_pool.entropy_count >= random_read_wakeup_thresh)
+ wake_up_interruptible(&random_read_wait);
+ return 0;
+ case RNDZAPENTCNT:
+ case RNDCLEARPOOL:
+ /* Clear the entropy pool counters. */
+ if (!capable(CAP_SYS_ADMIN))
+ return -EPERM;
+ init_std_data(&input_pool);
+ init_std_data(&blocking_pool);
+ init_std_data(&nonblocking_pool);
+ return 0;
+ default:
+ return -EINVAL;
+ }
+}
+
+struct file_operations random_fops = {
+ .read = random_read,
+ .write = random_write,
+ .poll = random_poll,
+ .ioctl = random_ioctl,
+};
+
+struct file_operations urandom_fops = {
+ .read = urandom_read,
+ .write = random_write,
+ .ioctl = random_ioctl,
+};
+
+/***************************************************************
+ * 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 --- truely 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(ctl_table *table, int write, struct file *filp,
+ void __user *buffer, size_t *lenp, loff_t *ppos)
+{
+ ctl_table fake_table;
+ unsigned char buf[64], tmp_uuid[16], *uuid;
+
+ uuid = table->data;
+ if (!uuid) {
+ uuid = tmp_uuid;
+ uuid[8] = 0;
+ }
+ if (uuid[8] == 0)
+ generate_random_uuid(uuid);
+
+ sprintf(buf, "%02x%02x%02x%02x-%02x%02x-%02x%02x-%02x%02x-"
+ "%02x%02x%02x%02x%02x%02x",
+ uuid[0], uuid[1], uuid[2], uuid[3],
+ uuid[4], uuid[5], uuid[6], uuid[7],
+ uuid[8], uuid[9], uuid[10], uuid[11],
+ uuid[12], uuid[13], uuid[14], uuid[15]);
+ fake_table.data = buf;
+ fake_table.maxlen = sizeof(buf);
+
+ return proc_dostring(&fake_table, write, filp, buffer, lenp, ppos);
+}
+
+static int uuid_strategy(ctl_table *table, int __user *name, int nlen,
+ void __user *oldval, size_t __user *oldlenp,
+ void __user *newval, size_t newlen, void **context)
+{
+ unsigned char tmp_uuid[16], *uuid;
+ unsigned int len;
+
+ if (!oldval || !oldlenp)
+ return 1;
+
+ uuid = table->data;
+ if (!uuid) {
+ uuid = tmp_uuid;
+ uuid[8] = 0;
+ }
+ if (uuid[8] == 0)
+ generate_random_uuid(uuid);
+
+ if (get_user(len, oldlenp))
+ return -EFAULT;
+ if (len) {
+ if (len > 16)
+ len = 16;
+ if (copy_to_user(oldval, uuid, len) ||
+ put_user(len, oldlenp))
+ return -EFAULT;
+ }
+ return 1;
+}
+
+static int sysctl_poolsize = INPUT_POOL_WORDS * 32;
+ctl_table random_table[] = {
+ {
+ .ctl_name = RANDOM_POOLSIZE,
+ .procname = "poolsize",
+ .data = &sysctl_poolsize,
+ .maxlen = sizeof(int),
+ .mode = 0444,
+ .proc_handler = &proc_dointvec,
+ },
+ {
+ .ctl_name = RANDOM_ENTROPY_COUNT,
+ .procname = "entropy_avail",
+ .maxlen = sizeof(int),
+ .mode = 0444,
+ .proc_handler = &proc_dointvec,
+ .data = &input_pool.entropy_count,
+ },
+ {
+ .ctl_name = RANDOM_READ_THRESH,
+ .procname = "read_wakeup_threshold",
+ .data = &random_read_wakeup_thresh,
+ .maxlen = sizeof(int),
+ .mode = 0644,
+ .proc_handler = &proc_dointvec_minmax,
+ .strategy = &sysctl_intvec,
+ .extra1 = &min_read_thresh,
+ .extra2 = &max_read_thresh,
+ },
+ {
+ .ctl_name = RANDOM_WRITE_THRESH,
+ .procname = "write_wakeup_threshold",
+ .data = &random_write_wakeup_thresh,
+ .maxlen = sizeof(int),
+ .mode = 0644,
+ .proc_handler = &proc_dointvec_minmax,
+ .strategy = &sysctl_intvec,
+ .extra1 = &min_write_thresh,
+ .extra2 = &max_write_thresh,
+ },
+ {
+ .ctl_name = RANDOM_BOOT_ID,
+ .procname = "boot_id",
+ .data = &sysctl_bootid,
+ .maxlen = 16,
+ .mode = 0444,
+ .proc_handler = &proc_do_uuid,
+ .strategy = &uuid_strategy,
+ },
+ {
+ .ctl_name = RANDOM_UUID,
+ .procname = "uuid",
+ .maxlen = 16,
+ .mode = 0444,
+ .proc_handler = &proc_do_uuid,
+ .strategy = &uuid_strategy,
+ },
+ { .ctl_name = 0 }
+};
+#endif /* CONFIG_SYSCTL */
+
+/********************************************************************
+ *
+ * Random funtions for networking
+ *
+ ********************************************************************/
+
+/*
+ * TCP initial sequence number picking. This uses the random number
+ * generator to pick an initial secret value. This value is hashed
+ * along with the TCP endpoint information to provide a unique
+ * starting point for each pair of TCP endpoints. This defeats
+ * attacks which rely on guessing the initial TCP sequence number.
+ * This algorithm was suggested by Steve Bellovin.
+ *
+ * Using a very strong hash was taking an appreciable amount of the total
+ * TCP connection establishment time, so this is a weaker hash,
+ * compensated for by changing the secret periodically.
+ */
+
+/* F, G and H are basic MD4 functions: selection, majority, parity */
+#define F(x, y, z) ((z) ^ ((x) & ((y) ^ (z))))
+#define G(x, y, z) (((x) & (y)) + (((x) ^ (y)) & (z)))
+#define H(x, y, z) ((x) ^ (y) ^ (z))
+
+/*
+ * The generic round function. The application is so specific that
+ * we don't bother protecting all the arguments with parens, as is generally
+ * good macro practice, in favor of extra legibility.
+ * Rotation is separate from addition to prevent recomputation
+ */
+#define ROUND(f, a, b, c, d, x, s) \
+ (a += f(b, c, d) + x, a = (a << s) | (a >> (32 - s)))
+#define K1 0
+#define K2 013240474631UL
+#define K3 015666365641UL
+
+#if defined(CONFIG_IPV6) || defined(CONFIG_IPV6_MODULE)
+
+static __u32 twothirdsMD4Transform (__u32 const buf[4], __u32 const in[12])
+{
+ __u32 a = buf[0], b = buf[1], c = buf[2], d = buf[3];
+
+ /* Round 1 */
+ ROUND(F, a, b, c, d, in[ 0] + K1, 3);
+ ROUND(F, d, a, b, c, in[ 1] + K1, 7);
+ ROUND(F, c, d, a, b, in[ 2] + K1, 11);
+ ROUND(F, b, c, d, a, in[ 3] + K1, 19);
+ ROUND(F, a, b, c, d, in[ 4] + K1, 3);
+ ROUND(F, d, a, b, c, in[ 5] + K1, 7);
+ ROUND(F, c, d, a, b, in[ 6] + K1, 11);
+ ROUND(F, b, c, d, a, in[ 7] + K1, 19);
+ ROUND(F, a, b, c, d, in[ 8] + K1, 3);
+ ROUND(F, d, a, b, c, in[ 9] + K1, 7);
+ ROUND(F, c, d, a, b, in[10] + K1, 11);
+ ROUND(F, b, c, d, a, in[11] + K1, 19);
+
+ /* Round 2 */
+ ROUND(G, a, b, c, d, in[ 1] + K2, 3);
+ ROUND(G, d, a, b, c, in[ 3] + K2, 5);
+ ROUND(G, c, d, a, b, in[ 5] + K2, 9);
+ ROUND(G, b, c, d, a, in[ 7] + K2, 13);
+ ROUND(G, a, b, c, d, in[ 9] + K2, 3);
+ ROUND(G, d, a, b, c, in[11] + K2, 5);
+ ROUND(G, c, d, a, b, in[ 0] + K2, 9);
+ ROUND(G, b, c, d, a, in[ 2] + K2, 13);
+ ROUND(G, a, b, c, d, in[ 4] + K2, 3);
+ ROUND(G, d, a, b, c, in[ 6] + K2, 5);
+ ROUND(G, c, d, a, b, in[ 8] + K2, 9);
+ ROUND(G, b, c, d, a, in[10] + K2, 13);
+
+ /* Round 3 */
+ ROUND(H, a, b, c, d, in[ 3] + K3, 3);
+ ROUND(H, d, a, b, c, in[ 7] + K3, 9);
+ ROUND(H, c, d, a, b, in[11] + K3, 11);
+ ROUND(H, b, c, d, a, in[ 2] + K3, 15);
+ ROUND(H, a, b, c, d, in[ 6] + K3, 3);
+ ROUND(H, d, a, b, c, in[10] + K3, 9);
+ ROUND(H, c, d, a, b, in[ 1] + K3, 11);
+ ROUND(H, b, c, d, a, in[ 5] + K3, 15);
+ ROUND(H, a, b, c, d, in[ 9] + K3, 3);
+ ROUND(H, d, a, b, c, in[ 0] + K3, 9);
+ ROUND(H, c, d, a, b, in[ 4] + K3, 11);
+ ROUND(H, b, c, d, a, in[ 8] + K3, 15);
+
+ return buf[1] + b; /* "most hashed" word */
+ /* Alternative: return sum of all words? */
+}
+#endif
+
+#undef ROUND
+#undef F
+#undef G
+#undef H
+#undef K1
+#undef K2
+#undef K3
+
+/* This should not be decreased so low that ISNs wrap too fast. */
+#define REKEY_INTERVAL (300 * HZ)
+/*
+ * Bit layout of the tcp sequence numbers (before adding current time):
+ * bit 24-31: increased after every key exchange
+ * bit 0-23: hash(source,dest)
+ *
+ * The implementation is similar to the algorithm described
+ * in the Appendix of RFC 1185, except that
+ * - it uses a 1 MHz clock instead of a 250 kHz clock
+ * - it performs a rekey every 5 minutes, which is equivalent
+ * to a (source,dest) tulple dependent forward jump of the
+ * clock by 0..2^(HASH_BITS+1)
+ *
+ * Thus the average ISN wraparound time is 68 minutes instead of
+ * 4.55 hours.
+ *
+ * SMP cleanup and lock avoidance with poor man's RCU.
+ * Manfred Spraul <manfred@colorfullife.com>
+ *
+ */
+#define COUNT_BITS 8
+#define COUNT_MASK ((1 << COUNT_BITS) - 1)
+#define HASH_BITS 24
+#define HASH_MASK ((1 << HASH_BITS) - 1)
+
+static struct keydata {
+ __u32 count; /* already shifted to the final position */
+ __u32 secret[12];
+} ____cacheline_aligned ip_keydata[2];
+
+static unsigned int ip_cnt;
+
+static void rekey_seq_generator(void *private_);
+
+static DECLARE_WORK(rekey_work, rekey_seq_generator, NULL);
+
+/*
+ * Lock avoidance:
+ * The ISN generation runs lockless - it's just a hash over random data.
+ * State changes happen every 5 minutes when the random key is replaced.
+ * Synchronization is performed by having two copies of the hash function
+ * state and rekey_seq_generator always updates the inactive copy.
+ * The copy is then activated by updating ip_cnt.
+ * The implementation breaks down if someone blocks the thread
+ * that processes SYN requests for more than 5 minutes. Should never
+ * happen, and even if that happens only a not perfectly compliant
+ * ISN is generated, nothing fatal.
+ */
+static void rekey_seq_generator(void *private_)
+{
+ struct keydata *keyptr = &ip_keydata[1 ^ (ip_cnt & 1)];
+
+ get_random_bytes(keyptr->secret, sizeof(keyptr->secret));
+ keyptr->count = (ip_cnt & COUNT_MASK) << HASH_BITS;
+ smp_wmb();
+ ip_cnt++;
+ schedule_delayed_work(&rekey_work, REKEY_INTERVAL);
+}
+
+static inline struct keydata *get_keyptr(void)
+{
+ struct keydata *keyptr = &ip_keydata[ip_cnt & 1];
+
+ smp_rmb();
+
+ return keyptr;
+}
+
+static __init int seqgen_init(void)
+{
+ rekey_seq_generator(NULL);
+ return 0;
+}
+late_initcall(seqgen_init);
+
+#if defined(CONFIG_IPV6) || defined(CONFIG_IPV6_MODULE)
+__u32 secure_tcpv6_sequence_number(__u32 *saddr, __u32 *daddr,
+ __u16 sport, __u16 dport)
+{
+ struct timeval tv;
+ __u32 seq;
+ __u32 hash[12];
+ struct keydata *keyptr = get_keyptr();
+
+ /* The procedure is the same as for IPv4, but addresses are longer.
+ * Thus we must use twothirdsMD4Transform.
+ */
+
+ memcpy(hash, saddr, 16);
+ hash[4]=(sport << 16) + dport;
+ memcpy(&hash[5],keyptr->secret,sizeof(__u32) * 7);
+
+ seq = twothirdsMD4Transform(daddr, hash) & HASH_MASK;
+ seq += keyptr->count;
+
+ do_gettimeofday(&tv);
+ seq += tv.tv_usec + tv.tv_sec * 1000000;
+
+ return seq;
+}
+EXPORT_SYMBOL(secure_tcpv6_sequence_number);
+#endif
+
+/* The code below is shamelessly stolen from secure_tcp_sequence_number().
+ * All blames to Andrey V. Savochkin <saw@msu.ru>.
+ */
+__u32 secure_ip_id(__u32 daddr)
+{
+ struct keydata *keyptr;
+ __u32 hash[4];
+
+ keyptr = get_keyptr();
+
+ /*
+ * Pick a unique starting offset for each IP destination.
+ * The dest ip address is placed in the starting vector,
+ * which is then hashed with random data.
+ */
+ hash[0] = daddr;
+ hash[1] = keyptr->secret[9];
+ hash[2] = keyptr->secret[10];
+ hash[3] = keyptr->secret[11];
+
+ return half_md4_transform(hash, keyptr->secret);
+}
+
+#ifdef CONFIG_INET
+
+__u32 secure_tcp_sequence_number(__u32 saddr, __u32 daddr,
+ __u16 sport, __u16 dport)
+{
+ struct timeval tv;
+ __u32 seq;
+ __u32 hash[4];
+ struct keydata *keyptr = get_keyptr();
+
+ /*
+ * Pick a unique starting offset for each TCP connection endpoints
+ * (saddr, daddr, sport, dport).
+ * Note that the words are placed into the starting vector, which is
+ * then mixed with a partial MD4 over random data.
+ */
+ hash[0]=saddr;
+ hash[1]=daddr;
+ hash[2]=(sport << 16) + dport;
+ hash[3]=keyptr->secret[11];
+
+ seq = half_md4_transform(hash, keyptr->secret) & HASH_MASK;
+ seq += keyptr->count;
+ /*
+ * As close as possible to RFC 793, which
+ * suggests using a 250 kHz clock.
+ * Further reading shows this assumes 2 Mb/s networks.
+ * For 10 Mb/s Ethernet, a 1 MHz clock is appropriate.
+ * That's funny, Linux has one built in! Use it!
+ * (Networks are faster now - should this be increased?)
+ */
+ do_gettimeofday(&tv);
+ seq += tv.tv_usec + tv.tv_sec * 1000000;
+#if 0
+ printk("init_seq(%lx, %lx, %d, %d) = %d\n",
+ saddr, daddr, sport, dport, seq);
+#endif
+ return seq;
+}
+
+EXPORT_SYMBOL(secure_tcp_sequence_number);
+
+
+
+/* Generate secure starting point for ephemeral TCP port search */
+u32 secure_tcp_port_ephemeral(__u32 saddr, __u32 daddr, __u16 dport)
+{
+ struct keydata *keyptr = get_keyptr();
+ u32 hash[4];
+
+ /*
+ * Pick a unique starting offset for each ephemeral port search
+ * (saddr, daddr, dport) and 48bits of random data.
+ */
+ hash[0] = saddr;
+ hash[1] = daddr;
+ hash[2] = dport ^ keyptr->secret[10];
+ hash[3] = keyptr->secret[11];
+
+ return half_md4_transform(hash, keyptr->secret);
+}
+
+#if defined(CONFIG_IPV6) || defined(CONFIG_IPV6_MODULE)
+u32 secure_tcpv6_port_ephemeral(const __u32 *saddr, const __u32 *daddr, __u16 dport)
+{
+ struct keydata *keyptr = get_keyptr();
+ u32 hash[12];
+
+ memcpy(hash, saddr, 16);
+ hash[4] = dport;
+ memcpy(&hash[5],keyptr->secret,sizeof(__u32) * 7);
+
+ return twothirdsMD4Transform(daddr, hash);
+}
+EXPORT_SYMBOL(secure_tcpv6_port_ephemeral);
+#endif
+
+#endif /* CONFIG_INET */
+
+
+/*
+ * 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
+ */
+unsigned int get_random_int(void)
+{
+ /*
+ * Use IP's RNG. It suits our purpose perfectly: it re-keys itself
+ * every second, from the entropy pool (and thus creates a limited
+ * drain on it), and uses halfMD4Transform within the second. We
+ * also mix it with jiffies and the PID:
+ */
+ return secure_ip_id(current->pid + jiffies);
+}
+
+/*
+ * 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);
+}