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Diffstat (limited to 'drivers/char/random.c')
| -rw-r--r-- | drivers/char/random.c | 1629 |
1 files changed, 1629 insertions, 0 deletions
diff --git a/drivers/char/random.c b/drivers/char/random.c new file mode 100644 index 000000000000..ad9b52c2ae3c --- /dev/null +++ b/drivers/char/random.c @@ -0,0 +1,1629 @@ +/* + * 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); +} |