/* * 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_keyboard_randomness(unsigned char scancode); * void add_mouse_randomness(__u32 mouse_data); * void add_interrupt_randomness(int irq); * void add_blkdev_randomness(int irq); * * add_keyboard_randomness() uses the inter-keypress timing, as well as the * scancode as random inputs into the "entropy pool". * * add_mouse_randomness() uses the mouse interrupt timing, as well as * the reported position of the mouse 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. * * add_blkdev_randomness() times the finishing time of block requests. * * 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 * poolfile=/proc/sys/kernel/random/poolsize * [ -r $poolfile ] && bytes=`cat $poolfile` || bytes=512 * dd if=/dev/urandom of=$random_seed count=1 bs=bytes * * 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 * poolfile=/proc/sys/kernel/random/poolsize * [ -r $poolfile ] && bytes=`cat $poolfile` || bytes=512 * dd if=/dev/urandom of=$random_seed count=1 bs=bytes * * 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. * * The code for SHA transform was taken from Peter Gutmann's * implementation, which has been placed in the public domain. * The code for MD5 transform was taken from Colin Plumb's * implementation, which has been placed in the public domain. * The MD5 cryptographic checksum was devised by Ronald Rivest, and is * documented in RFC 1321, "The MD5 Message Digest Algorithm". * * 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 #include #include #include #include #include #include #include #include #include #include #include #include #include #include /* * Configuration information */ #define DEFAULT_POOL_SIZE 512 #define SECONDARY_POOL_SIZE 128 #define BATCH_ENTROPY_SIZE 256 #define USE_SHA /* * The minimum number of bits of entropy before we wake up a read on * /dev/random. Should always be at least 8, or at least 1 byte. */ static int random_read_wakeup_thresh = 8; /* * 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; /* * 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^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 }, #if 0 /* Alternate polynomial */ /* x^1024 + x^819 + x^616 + x^410 + x^207 + x^2 + 1 -- 115 */ { 1024, 819, 616, 410, 207, 2 }, #endif /* x^512 + x^411 + x^308 + x^208 + x^104 + x + 1 -- 225 */ { 512, 411, 308, 208, 104, 1 }, #if 0 /* Alternates */ /* 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 }, #endif /* x^256 + x^205 + x^155 + x^101 + x^52 + x + 1 -- 125 */ { 256, 205, 155, 101, 52, 1 }, /* x^128 + x^103 + x^76 + x^51 +x^25 + x + 1 -- 105 */ { 128, 103, 76, 51, 25, 1 }, #if 0 /* Alternate polynomial */ /* x^128 + x^103 + x^78 + x^51 + x^27 + x^2 + 1 -- 70 */ { 128, 103, 78, 51, 27, 2 }, #endif /* x^64 + x^52 + x^39 + x^26 + x^14 + x + 1 -- 15 */ { 64, 52, 39, 26, 14, 1 }, /* x^32 + x^26 + x^20 + x^14 + x^7 + x + 1 -- 15 */ { 32, 26, 20, 14, 7, 1 }, { 0, 0, 0, 0, 0, 0 }, }; #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. */ /* * Linux 2.2 compatibility */ #ifndef DECLARE_WAITQUEUE #define DECLARE_WAITQUEUE(WAIT, PTR) struct wait_queue WAIT = { PTR, NULL } #endif #ifndef DECLARE_WAIT_QUEUE_HEAD #define DECLARE_WAIT_QUEUE_HEAD(WAIT) struct wait_queue *WAIT #endif /* * Static global variables */ static struct entropy_store *random_state; /* The default global store */ static struct entropy_store *sec_random_state; /* secondary store */ static DECLARE_WAIT_QUEUE_HEAD(random_read_wait); static DECLARE_WAIT_QUEUE_HEAD(random_write_wait); /* * Forward procedure declarations */ #ifdef CONFIG_SYSCTL static void sysctl_init_random(struct entropy_store *random_state); #endif /***************************************************************** * * Utility functions, with some ASM defined functions for speed * purposes * *****************************************************************/ /* * Unfortunately, while the GCC optimizer for the i386 understands how * to optimize a static rotate left of x bits, it doesn't know how to * deal with a variable rotate of x bits. So we use a bit of asm magic. */ #if (!defined (__i386__)) extern inline __u32 rotate_left(int i, __u32 word) { return (word << i) | (word >> (32 - i)); } #else extern inline __u32 rotate_left(int i, __u32 word) { __asm__("roll %%cl,%0" :"=r" (word) :"0" (word),"c" (i)); return word; } #endif /* * More asm magic.... * * For entropy estimation, we need to do an integral base 2 * logarithm. * * Note the "12bits" suffix - this is used for numbers between * 0 and 4095 only. This allows a few shortcuts. */ #if 0 /* Slow but clear version */ static inline __u32 int_ln_12bits(__u32 word) { __u32 nbits = 0; while (word >>= 1) nbits++; return nbits; } #else /* Faster (more clever) version, courtesy Colin Plumb */ static inline __u32 int_ln_12bits(__u32 word) { /* Smear msbit right to make an n-bit mask */ word |= word >> 8; word |= word >> 4; word |= word >> 2; word |= word >> 1; /* Remove one bit to make this a logarithm */ word >>= 1; /* Count the bits set in the word */ word -= (word >> 1) & 0x555; word = (word & 0x333) + ((word >> 2) & 0x333); word += (word >> 4); word += (word >> 8); return word & 15; } #endif #if 0 #define DEBUG_ENT(fmt, arg...) printk(KERN_DEBUG "random: " fmt, ## arg) #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 { unsigned add_ptr; int entropy_count; int input_rotate; int extract_count; struct poolinfo poolinfo; __u32 *pool; }; /* * Initialize the entropy store. The input argument is the size of * the random pool. * * Returns an negative error if there is a problem. */ static int create_entropy_store(int size, struct entropy_store **ret_bucket) { struct entropy_store *r; struct poolinfo *p; int poolwords; poolwords = (size + 3) / 4; /* Convert bytes->words */ /* The pool size must be a multiple of 16 32-bit words */ poolwords = ((poolwords + 15) / 16) * 16; for (p = poolinfo_table; p->poolwords; p++) { if (poolwords == p->poolwords) break; } if (p->poolwords == 0) return -EINVAL; r = kmalloc(sizeof(struct entropy_store), GFP_KERNEL); if (!r) return -ENOMEM; memset (r, 0, sizeof(struct entropy_store)); r->poolinfo = *p; r->pool = kmalloc(POOLBYTES, GFP_KERNEL); if (!r->pool) { kfree(r); return -ENOMEM; } memset(r->pool, 0, POOLBYTES); *ret_bucket = r; return 0; } /* Clear the entropy pool and associated counters. */ static void clear_entropy_store(struct entropy_store *r) { r->add_ptr = 0; r->entropy_count = 0; r->input_rotate = 0; r->extract_count = 0; memset(r->pool, 0, r->poolinfo.POOLBYTES); } static void free_entropy_store(struct entropy_store *r) { if (r->pool) kfree(r->pool); kfree(r); } /* * 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) { static __u32 const twist_table[8] = { 0, 0x3b6e20c8, 0x76dc4190, 0x4db26158, 0xedb88320, 0xd6d6a3e8, 0x9b64c2b0, 0xa00ae278 }; unsigned i; int new_rotate; int wordmask = r->poolinfo.poolwords - 1; __u32 w; while (nwords--) { w = rotate_left(r->input_rotate, *in++); i = r->add_ptr = (r->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 = r->input_rotate + 14; if (i) new_rotate = r->input_rotate + 7; r->input_rotate = new_rotate & 31; /* XOR in the various taps */ w ^= r->pool[(i + r->poolinfo.tap1) & wordmask]; w ^= r->pool[(i + r->poolinfo.tap2) & wordmask]; w ^= r->pool[(i + r->poolinfo.tap3) & wordmask]; w ^= r->pool[(i + r->poolinfo.tap4) & wordmask]; w ^= r->pool[(i + r->poolinfo.tap5) & wordmask]; w ^= r->pool[i]; r->pool[i] = (w >> 3) ^ twist_table[w & 7]; } } /* * Credit (or debit) the entropy store with n bits of entropy */ static void credit_entropy_store(struct entropy_store *r, int nbits) { 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("%s added %d bits, now %d\n", r == sec_random_state ? "secondary" : r == random_state ? "primary" : "unknown", nbits, r->entropy_count); } } /********************************************************************** * * Entropy batch input management * * We batch entropy to be added to avoid increasing interrupt latency * **********************************************************************/ static __u32 *batch_entropy_pool; static int *batch_entropy_credit; static int batch_max; static int batch_head, batch_tail; static struct tq_struct batch_tqueue; static void batch_entropy_process(void *private_); /* note: the size must be a power of 2 */ static int __init batch_entropy_init(int size, struct entropy_store *r) { batch_entropy_pool = kmalloc(2*size*sizeof(__u32), GFP_KERNEL); if (!batch_entropy_pool) return -1; batch_entropy_credit =kmalloc(size*sizeof(int), GFP_KERNEL); if (!batch_entropy_credit) { kfree(batch_entropy_pool); return -1; } batch_head = batch_tail = 0; batch_max = size; batch_tqueue.routine = batch_entropy_process; batch_tqueue.data = r; return 0; } /* * Changes to the entropy data is put into a queue rather than being added to * the entropy counts directly. This is presumably to avoid doing heavy * hashing calculations during an interrupt in add_timer_randomness(). * Instead, the entropy is only added to the pool once per timer tick. */ void batch_entropy_store(u32 a, u32 b, int num) { int new; if (!batch_max) return; batch_entropy_pool[2*batch_head] = a; batch_entropy_pool[(2*batch_head) + 1] = b; batch_entropy_credit[batch_head] = num; new = (batch_head+1) & (batch_max-1); if (new != batch_tail) { queue_task(&batch_tqueue, &tq_timer); batch_head = new; } else { DEBUG_ENT("batch entropy buffer full\n"); } } /* * Flush out the accumulated entropy operations, adding entropy to the passed * store (normally random_state). If that store has enough entropy, alternate * between randomizing the data of the primary and secondary stores. */ static void batch_entropy_process(void *private_) { struct entropy_store *r = (struct entropy_store *) private_, *p; int max_entropy = r->poolinfo.POOLBITS; if (!batch_max) return; p = r; while (batch_head != batch_tail) { if (r->entropy_count >= max_entropy) { r = (r == sec_random_state) ? random_state : sec_random_state; max_entropy = r->poolinfo.POOLBITS; } add_entropy_words(r, batch_entropy_pool + 2*batch_tail, 2); credit_entropy_store(r, batch_entropy_credit[batch_tail]); batch_tail = (batch_tail+1) & (batch_max-1); } if (p->entropy_count >= random_read_wakeup_thresh) wake_up_interruptible(&random_read_wait); } /********************************************************************* * * Entropy input management * *********************************************************************/ /* There is one of these per entropy source */ struct timer_rand_state { __u32 last_time; __s32 last_delta,last_delta2; int dont_count_entropy:1; }; static struct timer_rand_state keyboard_timer_state; static struct timer_rand_state mouse_timer_state; static struct timer_rand_state extract_timer_state; static struct timer_rand_state *irq_timer_state[NR_IRQS]; static struct timer_rand_state *blkdev_timer_state[MAX_BLKDEV]; /* * 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. * On the i386, this is assumed to be at most 16 bits, and the high bits * are used for a high-resolution timer. * */ static void add_timer_randomness(struct timer_rand_state *state, unsigned num) { __u32 time; __s32 delta, delta2, delta3; int entropy = 0; #if defined (__i386__) if ( test_bit(X86_FEATURE_TSC, &boot_cpu_data.x86_capability) ) { __u32 high; rdtsc(time, high); num ^= high; } else { time = jiffies; } #elif defined (__x86_64__) __u32 high; rdtsc(time, high); num ^= high; #else time = jiffies; #endif /* * 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 = time - state->last_time; state->last_time = time; 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. */ delta >>= 1; delta &= (1 << 12) - 1; entropy = int_ln_12bits(delta); } batch_entropy_store(num, time, entropy); } void add_keyboard_randomness(unsigned char scancode) { static unsigned char last_scancode; /* ignore autorepeat (multiple key down w/o key up) */ if (scancode != last_scancode) { last_scancode = scancode; add_timer_randomness(&keyboard_timer_state, scancode); } } void add_mouse_randomness(__u32 mouse_data) { add_timer_randomness(&mouse_timer_state, mouse_data); } void add_interrupt_randomness(int irq) { if (irq >= NR_IRQS || irq_timer_state[irq] == 0) return; add_timer_randomness(irq_timer_state[irq], 0x100+irq); } void add_blkdev_randomness(int major) { if (major >= MAX_BLKDEV) return; if (blkdev_timer_state[major] == 0) { rand_initialize_blkdev(major, GFP_ATOMIC); if (blkdev_timer_state[major] == 0) return; } add_timer_randomness(blkdev_timer_state[major], 0x200+major); } /****************************************************************** * * Hash function definition * *******************************************************************/ /* * This chunk of code defines a function * void HASH_TRANSFORM(__u32 digest[HASH_BUFFER_SIZE + HASH_EXTRA_SIZE], * __u32 const data[16]) * * The function hashes the input data to produce a digest in the first * HASH_BUFFER_SIZE words of the digest[] array, and uses HASH_EXTRA_SIZE * more words for internal purposes. (This buffer is exported so the * caller can wipe it once rather than this code doing it each call, * and tacking it onto the end of the digest[] array is the quick and * dirty way of doing it.) * * It so happens that MD5 and SHA share most of the initial vector * used to initialize the digest[] array before the first call: * 1) 0x67452301 * 2) 0xefcdab89 * 3) 0x98badcfe * 4) 0x10325476 * 5) 0xc3d2e1f0 (SHA only) * * For /dev/random purposes, the length of the data being hashed is * fixed in length, so appending a bit count in the usual way is not * cryptographically necessary. */ #ifdef USE_SHA #define HASH_BUFFER_SIZE 5 #define HASH_EXTRA_SIZE 80 #define HASH_TRANSFORM SHATransform /* Various size/speed tradeoffs are available. Choose 0..3. */ #define SHA_CODE_SIZE 0 /* * SHA transform algorithm, taken from code written by Peter Gutmann, * and placed in the public domain. */ /* The SHA f()-functions. */ #define f1(x,y,z) ( z ^ (x & (y^z)) ) /* Rounds 0-19: x ? y : z */ #define f2(x,y,z) (x ^ y ^ z) /* Rounds 20-39: XOR */ #define f3(x,y,z) ( (x & y) + (z & (x ^ y)) ) /* Rounds 40-59: majority */ #define f4(x,y,z) (x ^ y ^ z) /* Rounds 60-79: XOR */ /* The SHA Mysterious Constants */ #define K1 0x5A827999L /* Rounds 0-19: sqrt(2) * 2^30 */ #define K2 0x6ED9EBA1L /* Rounds 20-39: sqrt(3) * 2^30 */ #define K3 0x8F1BBCDCL /* Rounds 40-59: sqrt(5) * 2^30 */ #define K4 0xCA62C1D6L /* Rounds 60-79: sqrt(10) * 2^30 */ #define ROTL(n,X) ( ( ( X ) << n ) | ( ( X ) >> ( 32 - n ) ) ) #define subRound(a, b, c, d, e, f, k, data) \ ( e += ROTL( 5, a ) + f( b, c, d ) + k + data, b = ROTL( 30, b ) ) static void SHATransform(__u32 digest[85], __u32 const data[16]) { __u32 A, B, C, D, E; /* Local vars */ __u32 TEMP; int i; #define W (digest + HASH_BUFFER_SIZE) /* Expanded data array */ /* * Do the preliminary expansion of 16 to 80 words. Doing it * out-of-line line this is faster than doing it in-line on * register-starved machines like the x86, and not really any * slower on real processors. */ memcpy(W, data, 16*sizeof(__u32)); for (i = 0; i < 64; i++) { TEMP = W[i] ^ W[i+2] ^ W[i+8] ^ W[i+13]; W[i+16] = ROTL(1, TEMP); } /* Set up first buffer and local data buffer */ A = digest[ 0 ]; B = digest[ 1 ]; C = digest[ 2 ]; D = digest[ 3 ]; E = digest[ 4 ]; /* Heavy mangling, in 4 sub-rounds of 20 iterations each. */ #if SHA_CODE_SIZE == 0 /* * Approximately 50% of the speed of the largest version, but * takes up 1/16 the space. Saves about 6k on an i386 kernel. */ for (i = 0; i < 80; i++) { if (i < 40) { if (i < 20) TEMP = f1(B, C, D) + K1; else TEMP = f2(B, C, D) + K2; } else { if (i < 60) TEMP = f3(B, C, D) + K3; else TEMP = f4(B, C, D) + K4; } TEMP += ROTL(5, A) + E + W[i]; E = D; D = C; C = ROTL(30, B); B = A; A = TEMP; } #elif SHA_CODE_SIZE == 1 for (i = 0; i < 20; i++) { TEMP = f1(B, C, D) + K1 + ROTL(5, A) + E + W[i]; E = D; D = C; C = ROTL(30, B); B = A; A = TEMP; } for (; i < 40; i++) { TEMP = f2(B, C, D) + K2 + ROTL(5, A) + E + W[i]; E = D; D = C; C = ROTL(30, B); B = A; A = TEMP; } for (; i < 60; i++) { TEMP = f3(B, C, D) + K3 + ROTL(5, A) + E + W[i]; E = D; D = C; C = ROTL(30, B); B = A; A = TEMP; } for (; i < 80; i++) { TEMP = f4(B, C, D) + K4 + ROTL(5, A) + E + W[i]; E = D; D = C; C = ROTL(30, B); B = A; A = TEMP; } #elif SHA_CODE_SIZE == 2 for (i = 0; i < 20; i += 5) { subRound( A, B, C, D, E, f1, K1, W[ i ] ); subRound( E, A, B, C, D, f1, K1, W[ i+1 ] ); subRound( D, E, A, B, C, f1, K1, W[ i+2 ] ); subRound( C, D, E, A, B, f1, K1, W[ i+3 ] ); subRound( B, C, D, E, A, f1, K1, W[ i+4 ] ); } for (; i < 40; i += 5) { subRound( A, B, C, D, E, f2, K2, W[ i ] ); subRound( E, A, B, C, D, f2, K2, W[ i+1 ] ); subRound( D, E, A, B, C, f2, K2, W[ i+2 ] ); subRound( C, D, E, A, B, f2, K2, W[ i+3 ] ); subRound( B, C, D, E, A, f2, K2, W[ i+4 ] ); } for (; i < 60; i += 5) { subRound( A, B, C, D, E, f3, K3, W[ i ] ); subRound( E, A, B, C, D, f3, K3, W[ i+1 ] ); subRound( D, E, A, B, C, f3, K3, W[ i+2 ] ); subRound( C, D, E, A, B, f3, K3, W[ i+3 ] ); subRound( B, C, D, E, A, f3, K3, W[ i+4 ] ); } for (; i < 80; i += 5) { subRound( A, B, C, D, E, f4, K4, W[ i ] ); subRound( E, A, B, C, D, f4, K4, W[ i+1 ] ); subRound( D, E, A, B, C, f4, K4, W[ i+2 ] ); subRound( C, D, E, A, B, f4, K4, W[ i+3 ] ); subRound( B, C, D, E, A, f4, K4, W[ i+4 ] ); } #elif SHA_CODE_SIZE == 3 /* Really large version */ subRound( A, B, C, D, E, f1, K1, W[ 0 ] ); subRound( E, A, B, C, D, f1, K1, W[ 1 ] ); subRound( D, E, A, B, C, f1, K1, W[ 2 ] ); subRound( C, D, E, A, B, f1, K1, W[ 3 ] ); subRound( B, C, D, E, A, f1, K1, W[ 4 ] ); subRound( A, B, C, D, E, f1, K1, W[ 5 ] ); subRound( E, A, B, C, D, f1, K1, W[ 6 ] ); subRound( D, E, A, B, C, f1, K1, W[ 7 ] ); subRound( C, D, E, A, B, f1, K1, W[ 8 ] ); subRound( B, C, D, E, A, f1, K1, W[ 9 ] ); subRound( A, B, C, D, E, f1, K1, W[ 10 ] ); subRound( E, A, B, C, D, f1, K1, W[ 11 ] ); subRound( D, E, A, B, C, f1, K1, W[ 12 ] ); subRound( C, D, E, A, B, f1, K1, W[ 13 ] ); subRound( B, C, D, E, A, f1, K1, W[ 14 ] ); subRound( A, B, C, D, E, f1, K1, W[ 15 ] ); subRound( E, A, B, C, D, f1, K1, W[ 16 ] ); subRound( D, E, A, B, C, f1, K1, W[ 17 ] ); subRound( C, D, E, A, B, f1, K1, W[ 18 ] ); subRound( B, C, D, E, A, f1, K1, W[ 19 ] ); subRound( A, B, C, D, E, f2, K2, W[ 20 ] ); subRound( E, A, B, C, D, f2, K2, W[ 21 ] ); subRound( D, E, A, B, C, f2, K2, W[ 22 ] ); subRound( C, D, E, A, B, f2, K2, W[ 23 ] ); subRound( B, C, D, E, A, f2, K2, W[ 24 ] ); subRound( A, B, C, D, E, f2, K2, W[ 25 ] ); subRound( E, A, B, C, D, f2, K2, W[ 26 ] ); subRound( D, E, A, B, C, f2, K2, W[ 27 ] ); subRound( C, D, E, A, B, f2, K2, W[ 28 ] ); subRound( B, C, D, E, A, f2, K2, W[ 29 ] ); subRound( A, B, C, D, E, f2, K2, W[ 30 ] ); subRound( E, A, B, C, D, f2, K2, W[ 31 ] ); subRound( D, E, A, B, C, f2, K2, W[ 32 ] ); subRound( C, D, E, A, B, f2, K2, W[ 33 ] ); subRound( B, C, D, E, A, f2, K2, W[ 34 ] ); subRound( A, B, C, D, E, f2, K2, W[ 35 ] ); subRound( E, A, B, C, D, f2, K2, W[ 36 ] ); subRound( D, E, A, B, C, f2, K2, W[ 37 ] ); subRound( C, D, E, A, B, f2, K2, W[ 38 ] ); subRound( B, C, D, E, A, f2, K2, W[ 39 ] ); subRound( A, B, C, D, E, f3, K3, W[ 40 ] ); subRound( E, A, B, C, D, f3, K3, W[ 41 ] ); subRound( D, E, A, B, C, f3, K3, W[ 42 ] ); subRound( C, D, E, A, B, f3, K3, W[ 43 ] ); subRound( B, C, D, E, A, f3, K3, W[ 44 ] ); subRound( A, B, C, D, E, f3, K3, W[ 45 ] ); subRound( E, A, B, C, D, f3, K3, W[ 46 ] ); subRound( D, E, A, B, C, f3, K3, W[ 47 ] ); subRound( C, D, E, A, B, f3, K3, W[ 48 ] ); subRound( B, C, D, E, A, f3, K3, W[ 49 ] ); subRound( A, B, C, D, E, f3, K3, W[ 50 ] ); subRound( E, A, B, C, D, f3, K3, W[ 51 ] ); subRound( D, E, A, B, C, f3, K3, W[ 52 ] ); subRound( C, D, E, A, B, f3, K3, W[ 53 ] ); subRound( B, C, D, E, A, f3, K3, W[ 54 ] ); subRound( A, B, C, D, E, f3, K3, W[ 55 ] ); subRound( E, A, B, C, D, f3, K3, W[ 56 ] ); subRound( D, E, A, B, C, f3, K3, W[ 57 ] ); subRound( C, D, E, A, B, f3, K3, W[ 58 ] ); subRound( B, C, D, E, A, f3, K3, W[ 59 ] ); subRound( A, B, C, D, E, f4, K4, W[ 60 ] ); subRound( E, A, B, C, D, f4, K4, W[ 61 ] ); subRound( D, E, A, B, C, f4, K4, W[ 62 ] ); subRound( C, D, E, A, B, f4, K4, W[ 63 ] ); subRound( B, C, D, E, A, f4, K4, W[ 64 ] ); subRound( A, B, C, D, E, f4, K4, W[ 65 ] ); subRound( E, A, B, C, D, f4, K4, W[ 66 ] ); subRound( D, E, A, B, C, f4, K4, W[ 67 ] ); subRound( C, D, E, A, B, f4, K4, W[ 68 ] ); subRound( B, C, D, E, A, f4, K4, W[ 69 ] ); subRound( A, B, C, D, E, f4, K4, W[ 70 ] ); subRound( E, A, B, C, D, f4, K4, W[ 71 ] ); subRound( D, E, A, B, C, f4, K4, W[ 72 ] ); subRound( C, D, E, A, B, f4, K4, W[ 73 ] ); subRound( B, C, D, E, A, f4, K4, W[ 74 ] ); subRound( A, B, C, D, E, f4, K4, W[ 75 ] ); subRound( E, A, B, C, D, f4, K4, W[ 76 ] ); subRound( D, E, A, B, C, f4, K4, W[ 77 ] ); subRound( C, D, E, A, B, f4, K4, W[ 78 ] ); subRound( B, C, D, E, A, f4, K4, W[ 79 ] ); #else #error Illegal SHA_CODE_SIZE #endif /* Build message digest */ digest[ 0 ] += A; digest[ 1 ] += B; digest[ 2 ] += C; digest[ 3 ] += D; digest[ 4 ] += E; /* W is wiped by the caller */ #undef W } #undef ROTL #undef f1 #undef f2 #undef f3 #undef f4 #undef K1 #undef K2 #undef K3 #undef K4 #undef subRound #else /* !USE_SHA - Use MD5 */ #define HASH_BUFFER_SIZE 4 #define HASH_EXTRA_SIZE 0 #define HASH_TRANSFORM MD5Transform /* * MD5 transform algorithm, taken from code written by Colin Plumb, * and put into the public domain */ /* The four core functions - F1 is optimized somewhat */ /* #define F1(x, y, z) (x & y | ~x & z) */ #define F1(x, y, z) (z ^ (x & (y ^ z))) #define F2(x, y, z) F1(z, x, y) #define F3(x, y, z) (x ^ y ^ z) #define F4(x, y, z) (y ^ (x | ~z)) /* This is the central step in the MD5 algorithm. */ #define MD5STEP(f, w, x, y, z, data, s) \ ( w += f(x, y, z) + data, w = w<>(32-s), w += x ) /* * The core of the MD5 algorithm, this alters an existing MD5 hash to * reflect the addition of 16 longwords of new data. MD5Update blocks * the data and converts bytes into longwords for this routine. */ static void MD5Transform(__u32 buf[HASH_BUFFER_SIZE], __u32 const in[16]) { __u32 a, b, c, d; a = buf[0]; b = buf[1]; c = buf[2]; d = buf[3]; MD5STEP(F1, a, b, c, d, in[ 0]+0xd76aa478, 7); MD5STEP(F1, d, a, b, c, in[ 1]+0xe8c7b756, 12); MD5STEP(F1, c, d, a, b, in[ 2]+0x242070db, 17); MD5STEP(F1, b, c, d, a, in[ 3]+0xc1bdceee, 22); MD5STEP(F1, a, b, c, d, in[ 4]+0xf57c0faf, 7); MD5STEP(F1, d, a, b, c, in[ 5]+0x4787c62a, 12); MD5STEP(F1, c, d, a, b, in[ 6]+0xa8304613, 17); MD5STEP(F1, b, c, d, a, in[ 7]+0xfd469501, 22); MD5STEP(F1, a, b, c, d, in[ 8]+0x698098d8, 7); MD5STEP(F1, d, a, b, c, in[ 9]+0x8b44f7af, 12); MD5STEP(F1, c, d, a, b, in[10]+0xffff5bb1, 17); MD5STEP(F1, b, c, d, a, in[11]+0x895cd7be, 22); MD5STEP(F1, a, b, c, d, in[12]+0x6b901122, 7); MD5STEP(F1, d, a, b, c, in[13]+0xfd987193, 12); MD5STEP(F1, c, d, a, b, in[14]+0xa679438e, 17); MD5STEP(F1, b, c, d, a, in[15]+0x49b40821, 22); MD5STEP(F2, a, b, c, d, in[ 1]+0xf61e2562, 5); MD5STEP(F2, d, a, b, c, in[ 6]+0xc040b340, 9); MD5STEP(F2, c, d, a, b, in[11]+0x265e5a51, 14); MD5STEP(F2, b, c, d, a, in[ 0]+0xe9b6c7aa, 20); MD5STEP(F2, a, b, c, d, in[ 5]+0xd62f105d, 5); MD5STEP(F2, d, a, b, c, in[10]+0x02441453, 9); MD5STEP(F2, c, d, a, b, in[15]+0xd8a1e681, 14); MD5STEP(F2, b, c, d, a, in[ 4]+0xe7d3fbc8, 20); MD5STEP(F2, a, b, c, d, in[ 9]+0x21e1cde6, 5); MD5STEP(F2, d, a, b, c, in[14]+0xc33707d6, 9); MD5STEP(F2, c, d, a, b, in[ 3]+0xf4d50d87, 14); MD5STEP(F2, b, c, d, a, in[ 8]+0x455a14ed, 20); MD5STEP(F2, a, b, c, d, in[13]+0xa9e3e905, 5); MD5STEP(F2, d, a, b, c, in[ 2]+0xfcefa3f8, 9); MD5STEP(F2, c, d, a, b, in[ 7]+0x676f02d9, 14); MD5STEP(F2, b, c, d, a, in[12]+0x8d2a4c8a, 20); MD5STEP(F3, a, b, c, d, in[ 5]+0xfffa3942, 4); MD5STEP(F3, d, a, b, c, in[ 8]+0x8771f681, 11); MD5STEP(F3, c, d, a, b, in[11]+0x6d9d6122, 16); MD5STEP(F3, b, c, d, a, in[14]+0xfde5380c, 23); MD5STEP(F3, a, b, c, d, in[ 1]+0xa4beea44, 4); MD5STEP(F3, d, a, b, c, in[ 4]+0x4bdecfa9, 11); MD5STEP(F3, c, d, a, b, in[ 7]+0xf6bb4b60, 16); MD5STEP(F3, b, c, d, a, in[10]+0xbebfbc70, 23); MD5STEP(F3, a, b, c, d, in[13]+0x289b7ec6, 4); MD5STEP(F3, d, a, b, c, in[ 0]+0xeaa127fa, 11); MD5STEP(F3, c, d, a, b, in[ 3]+0xd4ef3085, 16); MD5STEP(F3, b, c, d, a, in[ 6]+0x04881d05, 23); MD5STEP(F3, a, b, c, d, in[ 9]+0xd9d4d039, 4); MD5STEP(F3, d, a, b, c, in[12]+0xe6db99e5, 11); MD5STEP(F3, c, d, a, b, in[15]+0x1fa27cf8, 16); MD5STEP(F3, b, c, d, a, in[ 2]+0xc4ac5665, 23); MD5STEP(F4, a, b, c, d, in[ 0]+0xf4292244, 6); MD5STEP(F4, d, a, b, c, in[ 7]+0x432aff97, 10); MD5STEP(F4, c, d, a, b, in[14]+0xab9423a7, 15); MD5STEP(F4, b, c, d, a, in[ 5]+0xfc93a039, 21); MD5STEP(F4, a, b, c, d, in[12]+0x655b59c3, 6); MD5STEP(F4, d, a, b, c, in[ 3]+0x8f0ccc92, 10); MD5STEP(F4, c, d, a, b, in[10]+0xffeff47d, 15); MD5STEP(F4, b, c, d, a, in[ 1]+0x85845dd1, 21); MD5STEP(F4, a, b, c, d, in[ 8]+0x6fa87e4f, 6); MD5STEP(F4, d, a, b, c, in[15]+0xfe2ce6e0, 10); MD5STEP(F4, c, d, a, b, in[ 6]+0xa3014314, 15); MD5STEP(F4, b, c, d, a, in[13]+0x4e0811a1, 21); MD5STEP(F4, a, b, c, d, in[ 4]+0xf7537e82, 6); MD5STEP(F4, d, a, b, c, in[11]+0xbd3af235, 10); MD5STEP(F4, c, d, a, b, in[ 2]+0x2ad7d2bb, 15); MD5STEP(F4, b, c, d, a, in[ 9]+0xeb86d391, 21); buf[0] += a; buf[1] += b; buf[2] += c; buf[3] += d; } #undef F1 #undef F2 #undef F3 #undef F4 #undef MD5STEP #endif /* !USE_SHA */ /********************************************************************* * * Entropy extraction routines * *********************************************************************/ #define EXTRACT_ENTROPY_USER 1 #define EXTRACT_ENTROPY_SECONDARY 2 #define TMP_BUF_SIZE (HASH_BUFFER_SIZE + HASH_EXTRA_SIZE) #define SEC_XFER_SIZE (TMP_BUF_SIZE*4) static ssize_t extract_entropy(struct entropy_store *r, void * buf, size_t nbytes, int flags); /* * This utility inline function is responsible for transfering entropy * from the primary pool to the secondary extraction pool. We pull * randomness under two conditions; one is if there isn't enough entropy * in the secondary pool. The other is after we have extracted 1024 bytes, * at which point we do a "catastrophic reseeding". */ static inline void xfer_secondary_pool(struct entropy_store *r, size_t nbytes) { __u32 tmp[TMP_BUF_SIZE]; if (r->entropy_count < nbytes * 8 && r->entropy_count < r->poolinfo.POOLBITS) { int nwords = min_t(int, r->poolinfo.poolwords - r->entropy_count/32, sizeof(tmp) / 4); DEBUG_ENT("xfer %d from primary to %s (have %d, need %d)\n", nwords * 32, r == sec_random_state ? "secondary" : "unknown", r->entropy_count, nbytes * 8); extract_entropy(random_state, tmp, nwords * 4, 0); add_entropy_words(r, tmp, nwords); credit_entropy_store(r, nwords * 32); } if (r->extract_count > 1024) { DEBUG_ENT("reseeding %s with %d from primary\n", r == sec_random_state ? "secondary" : "unknown", sizeof(tmp) * 8); extract_entropy(random_state, tmp, sizeof(tmp), 0); add_entropy_words(r, tmp, sizeof(tmp) / 4); r->extract_count = 0; } } /* * This function extracts randomness from the "entropy pool", and * returns it in a buffer. This function computes how many remaining * bits of entropy are left in the pool, but it does not restrict the * number of bytes that are actually obtained. If the EXTRACT_ENTROPY_USER * flag is given, then the buf pointer is assumed to be in user space. * * If the EXTRACT_ENTROPY_SECONDARY flag is given, then we are actually * extracting entropy from the secondary pool, and can refill from the * primary pool if needed. * * Note: extract_entropy() assumes that .poolwords is a multiple of 16 words. */ static ssize_t extract_entropy(struct entropy_store *r, void * buf, size_t nbytes, int flags) { ssize_t ret, i; __u32 tmp[TMP_BUF_SIZE]; __u32 x; add_timer_randomness(&extract_timer_state, nbytes); /* Redundant, but just in case... */ if (r->entropy_count > r->poolinfo.POOLBITS) r->entropy_count = r->poolinfo.POOLBITS; if (flags & EXTRACT_ENTROPY_SECONDARY) xfer_secondary_pool(r, nbytes); DEBUG_ENT("%s has %d bits, want %d bits\n", r == sec_random_state ? "secondary" : r == random_state ? "primary" : "unknown", r->entropy_count, nbytes * 8); if (r->entropy_count / 8 >= nbytes) r->entropy_count -= nbytes*8; else r->entropy_count = 0; if (r->entropy_count < random_write_wakeup_thresh) wake_up_interruptible(&random_write_wait); r->extract_count += nbytes; ret = 0; while (nbytes) { /* * Check if we need to break out or reschedule.... */ if ((flags & EXTRACT_ENTROPY_USER) && current->need_resched) { if (signal_pending(current)) { if (ret == 0) ret = -ERESTARTSYS; break; } schedule(); } /* Hash the pool to get the output */ tmp[0] = 0x67452301; tmp[1] = 0xefcdab89; tmp[2] = 0x98badcfe; tmp[3] = 0x10325476; #ifdef USE_SHA tmp[4] = 0xc3d2e1f0; #endif /* * 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) { HASH_TRANSFORM(tmp, r->pool+i); add_entropy_words(r, &tmp[x%HASH_BUFFER_SIZE], 1); } /* * In case the hash function has some recognizable * output pattern, we fold it in half. */ for (i = 0; i < HASH_BUFFER_SIZE/2; i++) tmp[i] ^= tmp[i + (HASH_BUFFER_SIZE+1)/2]; #if HASH_BUFFER_SIZE & 1 /* There's a middle word to deal with */ x = tmp[HASH_BUFFER_SIZE/2]; x ^= (x >> 16); /* Fold it in half */ ((__u16 *)tmp)[HASH_BUFFER_SIZE-1] = (__u16)x; #endif /* Copy data to destination buffer */ i = min(nbytes, HASH_BUFFER_SIZE*sizeof(__u32)/2); if (flags & EXTRACT_ENTROPY_USER) { i -= copy_to_user(buf, (__u8 const *)tmp, i); if (!i) { ret = -EFAULT; break; } } else memcpy(buf, (__u8 const *)tmp, i); nbytes -= i; buf += i; ret += i; add_timer_randomness(&extract_timer_state, nbytes); } /* 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) { if (sec_random_state) extract_entropy(sec_random_state, (char *) buf, nbytes, EXTRACT_ENTROPY_SECONDARY); else if (random_state) extract_entropy(random_state, (char *) buf, nbytes, 0); else printk(KERN_NOTICE "get_random_bytes called before " "random driver initialization\n"); } /********************************************************************* * * Functions to interface with Linux * *********************************************************************/ /* * Initialize the random pool with standard stuff. * * NOTE: This is an OS-dependent function. */ static void init_std_data(struct entropy_store *r) { struct timeval tv; __u32 words[2]; char *p; int i; do_gettimeofday(&tv); words[0] = tv.tv_sec; words[1] = tv.tv_usec; add_entropy_words(r, words, 2); /* * This doesn't lock system.utsname. However, we are generating * entropy so a race with a name set here is fine. */ p = (char *) &system_utsname; for (i = sizeof(system_utsname) / sizeof(words); i; i--) { memcpy(words, p, sizeof(words)); add_entropy_words(r, words, sizeof(words)/4); p += sizeof(words); } } void __init rand_initialize(void) { int i; if (create_entropy_store(DEFAULT_POOL_SIZE, &random_state)) return; /* Error, return */ if (batch_entropy_init(BATCH_ENTROPY_SIZE, random_state)) return; /* Error, return */ if (create_entropy_store(SECONDARY_POOL_SIZE, &sec_random_state)) return; /* Error, return */ clear_entropy_store(random_state); clear_entropy_store(sec_random_state); init_std_data(random_state); #ifdef CONFIG_SYSCTL sysctl_init_random(random_state); #endif for (i = 0; i < NR_IRQS; i++) irq_timer_state[i] = NULL; for (i = 0; i < MAX_BLKDEV; i++) blkdev_timer_state[i] = NULL; memset(&keyboard_timer_state, 0, sizeof(struct timer_rand_state)); memset(&mouse_timer_state, 0, sizeof(struct timer_rand_state)); memset(&extract_timer_state, 0, sizeof(struct timer_rand_state)); extract_timer_state.dont_count_entropy = 1; } 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_blkdev(int major, int mode) { struct timer_rand_state *state; if (major >= MAX_BLKDEV || blkdev_timer_state[major]) return; /* * If kmalloc returns null, we just won't use that entropy * source. */ state = kmalloc(sizeof(struct timer_rand_state), mode); if (state) { memset(state, 0, sizeof(struct timer_rand_state)); blkdev_timer_state[major] = state; } } static ssize_t random_read(struct file * file, char * buf, size_t nbytes, loff_t *ppos) { DECLARE_WAITQUEUE(wait, current); ssize_t n, retval = 0, count = 0; if (nbytes == 0) return 0; add_wait_queue(&random_read_wait, &wait); while (nbytes > 0) { set_current_state(TASK_INTERRUPTIBLE); n = nbytes; if (n > SEC_XFER_SIZE) n = SEC_XFER_SIZE; if (n > random_state->entropy_count / 8) n = random_state->entropy_count / 8; if (n == 0) { if (file->f_flags & O_NONBLOCK) { retval = -EAGAIN; break; } if (signal_pending(current)) { retval = -ERESTARTSYS; break; } schedule(); continue; } n = extract_entropy(sec_random_state, buf, n, EXTRACT_ENTROPY_USER | EXTRACT_ENTROPY_SECONDARY); if (n < 0) { retval = n; break; } count += n; buf += n; nbytes -= n; break; /* This break makes the device work */ /* like a named pipe */ } current->state = TASK_RUNNING; remove_wait_queue(&random_read_wait, &wait); /* * If we gave the user some bytes, update the access time. */ if (count != 0) { UPDATE_ATIME(file->f_dentry->d_inode); } return (count ? count : retval); } static ssize_t urandom_read(struct file * file, char * buf, size_t nbytes, loff_t *ppos) { return extract_entropy(sec_random_state, buf, nbytes, EXTRACT_ENTROPY_USER | EXTRACT_ENTROPY_SECONDARY); } 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 (random_state->entropy_count >= random_read_wakeup_thresh) mask |= POLLIN | POLLRDNORM; if (random_state->entropy_count < random_write_wakeup_thresh) mask |= POLLOUT | POLLWRNORM; return mask; } static ssize_t random_write(struct file * file, const char * buffer, size_t count, loff_t *ppos) { int ret = 0; size_t bytes; __u32 buf[16]; const char *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(random_state, buf, (bytes + 3) / 4); } if (p == buffer) { return (ssize_t)ret; } else { file->f_dentry->d_inode->i_mtime = CURRENT_TIME; mark_inode_dirty(file->f_dentry->d_inode); return (ssize_t)(p - buffer); } } static int random_ioctl(struct inode * inode, struct file * file, unsigned int cmd, unsigned long arg) { int *p, size, ent_count; int retval; switch (cmd) { case RNDGETENTCNT: ent_count = random_state->entropy_count; if (put_user(ent_count, (int *) arg)) return -EFAULT; return 0; case RNDADDTOENTCNT: if (!capable(CAP_SYS_ADMIN)) return -EPERM; if (get_user(ent_count, (int *) arg)) return -EFAULT; credit_entropy_store(random_state, ent_count); /* * Wake up waiting processes if we have enough * entropy. */ if (random_state->entropy_count >= random_read_wakeup_thresh) wake_up_interruptible(&random_read_wait); return 0; case RNDGETPOOL: if (!capable(CAP_SYS_ADMIN)) return -EPERM; p = (int *) arg; ent_count = random_state->entropy_count; if (put_user(ent_count, p++) || get_user(size, p) || put_user(random_state->poolinfo.poolwords, p++)) return -EFAULT; if (size < 0) return -EINVAL; if (size > random_state->poolinfo.poolwords) size = random_state->poolinfo.poolwords; if (copy_to_user(p, random_state->pool, size * 4)) return -EFAULT; return 0; case RNDADDENTROPY: if (!capable(CAP_SYS_ADMIN)) return -EPERM; p = (int *) arg; 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 *) p, size, &file->f_pos); if (retval < 0) return retval; credit_entropy_store(random_state, ent_count); /* * Wake up waiting processes if we have enough * entropy. */ if (random_state->entropy_count >= random_read_wakeup_thresh) wake_up_interruptible(&random_read_wait); return 0; case RNDZAPENTCNT: if (!capable(CAP_SYS_ADMIN)) return -EPERM; random_state->entropy_count = 0; return 0; case RNDCLEARPOOL: /* Clear the entropy pool and associated counters. */ if (!capable(CAP_SYS_ADMIN)) return -EPERM; clear_entropy_store(random_state); init_std_data(random_state); 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; } /******************************************************************** * * Sysctl interface * ********************************************************************/ #ifdef CONFIG_SYSCTL #include static int sysctl_poolsize; static int min_read_thresh, max_read_thresh; static int min_write_thresh, max_write_thresh; static char sysctl_bootid[16]; /* * This function handles a request from the user to change the pool size * of the primary entropy store. */ static int change_poolsize(int poolsize) { struct entropy_store *new_store, *old_store; int ret; if ((ret = create_entropy_store(poolsize, &new_store))) return ret; add_entropy_words(new_store, random_state->pool, random_state->poolinfo.poolwords); credit_entropy_store(new_store, random_state->entropy_count); sysctl_init_random(new_store); old_store = random_state; random_state = batch_tqueue.data = new_store; free_entropy_store(old_store); return 0; } static int proc_do_poolsize(ctl_table *table, int write, struct file *filp, void *buffer, size_t *lenp) { int ret; sysctl_poolsize = random_state->poolinfo.POOLBYTES; ret = proc_dointvec(table, write, filp, buffer, lenp); if (ret || !write || (sysctl_poolsize == random_state->poolinfo.POOLBYTES)) return ret; return change_poolsize(sysctl_poolsize); } static int poolsize_strategy(ctl_table *table, int *name, int nlen, void *oldval, size_t *oldlenp, void *newval, size_t newlen, void **context) { int len; sysctl_poolsize = random_state->poolinfo.POOLBYTES; /* * We only handle the write case, since the read case gets * handled by the default handler (and we don't care if the * write case happens twice; it's harmless). */ if (newval && newlen) { len = newlen; if (len > table->maxlen) len = table->maxlen; if (copy_from_user(table->data, newval, len)) return -EFAULT; } if (sysctl_poolsize != random_state->poolinfo.POOLBYTES) return change_poolsize(sysctl_poolsize); return 0; } /* * 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 *buffer, size_t *lenp) { 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); } static int uuid_strategy(ctl_table *table, int *name, int nlen, void *oldval, size_t *oldlenp, void *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; } ctl_table random_table[] = { {RANDOM_POOLSIZE, "poolsize", &sysctl_poolsize, sizeof(int), 0644, NULL, &proc_do_poolsize, &poolsize_strategy}, {RANDOM_ENTROPY_COUNT, "entropy_avail", NULL, sizeof(int), 0444, NULL, &proc_dointvec}, {RANDOM_READ_THRESH, "read_wakeup_threshold", &random_read_wakeup_thresh, sizeof(int), 0644, NULL, &proc_dointvec_minmax, &sysctl_intvec, 0, &min_read_thresh, &max_read_thresh}, {RANDOM_WRITE_THRESH, "write_wakeup_threshold", &random_write_wakeup_thresh, sizeof(int), 0644, NULL, &proc_dointvec_minmax, &sysctl_intvec, 0, &min_write_thresh, &max_write_thresh}, {RANDOM_BOOT_ID, "boot_id", &sysctl_bootid, 16, 0444, NULL, &proc_do_uuid, &uuid_strategy}, {RANDOM_UUID, "uuid", NULL, 16, 0444, NULL, &proc_do_uuid, &uuid_strategy}, {0} }; static void sysctl_init_random(struct entropy_store *random_state) { min_read_thresh = 8; min_write_thresh = 0; max_read_thresh = max_write_thresh = random_state->poolinfo.POOLBITS; random_table[1].data = &random_state->entropy_count; } #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 /* * Basic cut-down MD4 transform. Returns only 32 bits of result. */ static __u32 halfMD4Transform (__u32 const buf[4], __u32 const in[8]) { __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 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[0] + K2, 3); ROUND(G, d, a, b, c, in[2] + K2, 5); ROUND(G, c, d, a, b, in[4] + K2, 9); ROUND(G, b, c, d, a, in[6] + 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[2] + K3, 11); ROUND(H, b, c, d, a, in[6] + K3, 15); ROUND(H, a, b, c, d, in[1] + K3, 3); ROUND(H, d, a, b, c, in[5] + K3, 9); ROUND(H, c, d, a, b, in[0] + K3, 11); ROUND(H, b, c, d, a, in[4] + K3, 15); return buf[1] + b; /* "most hashed" word */ /* Alternative: return sum of all words? */ } #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 #define HASH_BITS 24 #if defined(CONFIG_IPV6) || defined(CONFIG_IPV6_MODULE) __u32 secure_tcpv6_sequence_number(__u32 *saddr, __u32 *daddr, __u16 sport, __u16 dport) { static __u32 rekey_time; static __u32 count; static __u32 secret[12]; struct timeval tv; __u32 seq; /* The procedure is the same as for IPv4, but addresses are longer. */ do_gettimeofday(&tv); /* We need the usecs below... */ if (!rekey_time || (tv.tv_sec - rekey_time) > REKEY_INTERVAL) { rekey_time = tv.tv_sec; /* First five words are overwritten below. */ get_random_bytes(&secret[5], sizeof(secret)-5*4); count = (tv.tv_sec/REKEY_INTERVAL) << HASH_BITS; } memcpy(secret, saddr, 16); secret[4]=(sport << 16) + dport; seq = (twothirdsMD4Transform(daddr, secret) & ((1< REKEY_INTERVAL) { rekey_time = t; /* First word is overwritten below. */ get_random_bytes(secret, sizeof(secret)); } return twothirdsMD4Transform(daddr, secret); } #endif __u32 secure_tcp_sequence_number(__u32 saddr, __u32 daddr, __u16 sport, __u16 dport) { static __u32 rekey_time; static __u32 count; static __u32 secret[12]; struct timeval tv; __u32 seq; /* * Pick a random secret every REKEY_INTERVAL seconds. */ do_gettimeofday(&tv); /* We need the usecs below... */ if (!rekey_time || (tv.tv_sec - rekey_time) > REKEY_INTERVAL) { rekey_time = tv.tv_sec; /* First three words are overwritten below. */ get_random_bytes(&secret[3], sizeof(secret)-12); count = (tv.tv_sec/REKEY_INTERVAL) << HASH_BITS; } /* * Pick a unique starting offset for each TCP connection endpoints * (saddr, daddr, sport, dport). * Note that the words are placed into the first words to be * mixed in with the halfMD4. This is because the starting * vector is also a random secret (at secret+8), and further * hashing fixed data into it isn't going to improve anything, * so we should get started with the variable data. */ secret[0]=saddr; secret[1]=daddr; secret[2]=(sport << 16) + dport; seq = (halfMD4Transform(secret+8, secret) & ((1<. */ __u32 secure_ip_id(__u32 daddr) { static time_t rekey_time; static __u32 secret[12]; time_t t; /* * Pick a random secret every REKEY_INTERVAL seconds. */ t = CURRENT_TIME; if (!rekey_time || (t - rekey_time) > REKEY_INTERVAL) { rekey_time = t; /* First word is overwritten below. */ get_random_bytes(secret+1, sizeof(secret)-4); } /* * Pick a unique starting offset for each IP destination. * Note that the words are placed into the first words to be * mixed in with the halfMD4. This is because the starting * vector is also a random secret (at secret+8), and further * hashing fixed data into it isn't going to improve anything, * so we should get started with the variable data. */ secret[0]=daddr; return halfMD4Transform(secret+8, secret); } #ifdef CONFIG_SYN_COOKIES /* * Secure SYN cookie computation. This is the algorithm worked out by * Dan Bernstein and Eric Schenk. * * For linux I implement the 1 minute counter by looking at the jiffies clock. * The count is passed in as a parameter, so this code doesn't much care. */ #define COOKIEBITS 24 /* Upper bits store count */ #define COOKIEMASK (((__u32)1 << COOKIEBITS) - 1) static int syncookie_init; static __u32 syncookie_secret[2][16-3+HASH_BUFFER_SIZE]; __u32 secure_tcp_syn_cookie(__u32 saddr, __u32 daddr, __u16 sport, __u16 dport, __u32 sseq, __u32 count, __u32 data) { __u32 tmp[16 + HASH_BUFFER_SIZE + HASH_EXTRA_SIZE]; __u32 seq; /* * Pick two random secrets the first time we need a cookie. */ if (syncookie_init == 0) { get_random_bytes(syncookie_secret, sizeof(syncookie_secret)); syncookie_init = 1; } /* * Compute the secure sequence number. * The output should be: * HASH(sec1,saddr,sport,daddr,dport,sec1) + sseq + (count * 2^24) * + (HASH(sec2,saddr,sport,daddr,dport,count,sec2) % 2^24). * Where sseq is their sequence number and count increases every * minute by 1. * As an extra hack, we add a small "data" value that encodes the * MSS into the second hash value. */ memcpy(tmp+3, syncookie_secret[0], sizeof(syncookie_secret[0])); tmp[0]=saddr; tmp[1]=daddr; tmp[2]=(sport << 16) + dport; HASH_TRANSFORM(tmp+16, tmp); seq = tmp[17] + sseq + (count << COOKIEBITS); memcpy(tmp+3, syncookie_secret[1], sizeof(syncookie_secret[1])); tmp[0]=saddr; tmp[1]=daddr; tmp[2]=(sport << 16) + dport; tmp[3] = count; /* minute counter */ HASH_TRANSFORM(tmp+16, tmp); /* Add in the second hash and the data */ return seq + ((tmp[17] + data) & COOKIEMASK); } /* * This retrieves the small "data" value from the syncookie. * If the syncookie is bad, the data returned will be out of * range. This must be checked by the caller. * * The count value used to generate the cookie must be within * "maxdiff" if the current (passed-in) "count". The return value * is (__u32)-1 if this test fails. */ __u32 check_tcp_syn_cookie(__u32 cookie, __u32 saddr, __u32 daddr, __u16 sport, __u16 dport, __u32 sseq, __u32 count, __u32 maxdiff) { __u32 tmp[16 + HASH_BUFFER_SIZE + HASH_EXTRA_SIZE]; __u32 diff; if (syncookie_init == 0) return (__u32)-1; /* Well, duh! */ /* Strip away the layers from the cookie */ memcpy(tmp+3, syncookie_secret[0], sizeof(syncookie_secret[0])); tmp[0]=saddr; tmp[1]=daddr; tmp[2]=(sport << 16) + dport; HASH_TRANSFORM(tmp+16, tmp); cookie -= tmp[17] + sseq; /* Cookie is now reduced to (count * 2^24) ^ (hash % 2^24) */ diff = (count - (cookie >> COOKIEBITS)) & ((__u32)-1 >> COOKIEBITS); if (diff >= maxdiff) return (__u32)-1; memcpy(tmp+3, syncookie_secret[1], sizeof(syncookie_secret[1])); tmp[0] = saddr; tmp[1] = daddr; tmp[2] = (sport << 16) + dport; tmp[3] = count - diff; /* minute counter */ HASH_TRANSFORM(tmp+16, tmp); return (cookie - tmp[17]) & COOKIEMASK; /* Leaving the data behind */ } #endif EXPORT_SYMBOL(add_keyboard_randomness); EXPORT_SYMBOL(add_mouse_randomness); EXPORT_SYMBOL(add_interrupt_randomness); EXPORT_SYMBOL(add_blkdev_randomness); EXPORT_SYMBOL(batch_entropy_store); EXPORT_SYMBOL(generate_random_uuid);