Linux Cross Reference
Linux/drivers/char/random.c

   /*
    * 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 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 512 bytes, which is the size of the entropy pool
  *      if [ -f $random_seed ]; then
  *              cat $random_seed >/dev/urandom
  *      fi
  *      dd if=/dev/urandom of=$random_seed count=1
  *      chmod 600 $random_seed
  *
  * and the following lines in an appropriate script which is run as
  * the system is shutdown:
  * 
  *      # Carry a random seed from shut-down to start-up
  *      # Save 512 bytes, which is the size of the entropy pool
  *      echo "Saving random seed..."
  *      random_seed=/var/run/random-seed
  *      dd if=/dev/urandom of=$random_seed count=1
  *      chmod 600 $random_seed
  * 
  * 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 <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/malloc.h>
 #include <linux/random.h>
 #include <linux/poll.h>
 #include <linux/init.h>
 
 #include <asm/processor.h>
 #include <asm/uaccess.h>
 #include <asm/irq.h>
 #include <asm/io.h>
 
 /*
  * 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 },
 };              
         
 /*
  * 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
  * 
  *****************************************************************/
 
 #ifndef MIN
 #define MIN(a,b) (((a) < (b)) ? (a) : (b))
 #endif
 
 /*
  * 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)
                 :"" (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
 
 /**********************************************************************
  *
  * 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(poolwords*4, GFP_KERNEL);
         if (!r->pool) {
                 kfree(r);
                 return -ENOMEM;
         }
         memset(r->pool, 0, poolwords*4);
         *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.poolwords*4);
 }
 
 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 num)
 {
         static __u32 const twist_table[8] = {
                          0, 0x3b6e20c8, 0x76dc4190, 0x4db26158,
                 0xedb88320, 0xd6d6a3e8, 0x9b64c2b0, 0xa00ae278 };
         unsigned i;
         int new_rotate;
         __u32 w;
 
         while (num--) {
                 w = rotate_left(r->input_rotate, *in);
                 i = r->add_ptr = (r->add_ptr - 1) & (r->poolinfo.poolwords-1);
                 /*
                  * 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)&(r->poolinfo.poolwords-1)];
                 w ^= r->pool[(i+r->poolinfo.tap2)&(r->poolinfo.poolwords-1)];
                 w ^= r->pool[(i+r->poolinfo.tap3)&(r->poolinfo.poolwords-1)];
                 w ^= r->pool[(i+r->poolinfo.tap4)&(r->poolinfo.poolwords-1)];
                 w ^= r->pool[(i+r->poolinfo.tap5)&(r->poolinfo.poolwords-1)];
                 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 num)
 {
         int     max_entropy = r->poolinfo.poolwords*32;
 
         if (r->entropy_count + num < 0)
                 r->entropy_count = 0;
         else if (r->entropy_count + num > max_entropy)
                 r->entropy_count = max_entropy;
         else
                 r->entropy_count = r->entropy_count + num;
 }
 
 /**********************************************************************
  *
  * 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 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;
 }
 
 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 {
 #if 0
                 printk(KERN_NOTICE "random: batch entropy buffer full\n");
 #endif
         }
 }
 
 static void batch_entropy_process(void *private_)
 {
         int     num = 0;
         int     max_entropy;
         struct entropy_store *r = (struct entropy_store *) private_, *p;
         
         if (!batch_max)
                 return;
 
         max_entropy = r->poolinfo.poolwords*32;
         while (batch_head != batch_tail) {
                 add_entropy_words(r, batch_entropy_pool + 2*batch_tail, 2);
                 p = r;
                 if (r->entropy_count > max_entropy && (num & 1))
                         r = sec_random_state;
                 credit_entropy_store(r, batch_entropy_credit[batch_tail]);
                 batch_tail = (batch_tail+1) & (batch_max-1);
                 num++;
         }
         if (r->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;
                 __asm__(".byte 0x0f,0x31"
                         :"=a" (time), "=d" (high));
                 num ^= high;
         } else {
                 time = jiffies;
         }
 #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<<s | 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 extract 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) {
                 extract_entropy(random_state, tmp, sizeof(tmp), 0);
                 add_entropy_words(r, tmp, TMP_BUF_SIZE);
                 credit_entropy_store(r, TMP_BUF_SIZE*8);
         }
         if (r->extract_count > 1024) {
                 extract_entropy(random_state, tmp, sizeof(tmp), 0);
                 add_entropy_words(r, tmp, TMP_BUF_SIZE);
                 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 this function will 
  *
  * 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.poolwords) 
                 r->entropy_count = r->poolinfo.poolwords;
 
         if (flags & EXTRACT_ENTROPY_SECONDARY)
                 xfer_secondary_pool(r, nbytes);
 
         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;
 
                 /* Convert bytes to words */
                 bytes = (bytes + 3) / sizeof(__u32);
                 add_entropy_words(random_state, buf, bytes);
         }
         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++))
                         return -EFAULT;
                         
                 if (get_user(size, p))
                         return -EFAULT;
                 if (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*sizeof(__u32)))
                         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 <linux/sysctl.h>
 
 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.poolwords * 4;
 
         ret = proc_dointvec(table, write, filp, buffer, lenp);
         if (ret || !write ||
             (sysctl_poolsize == random_state->poolinfo.poolwords * 4))
                 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.poolwords * 4;
 
         /*
          * 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.poolwords * 4)
                 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;
         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);
 
         get_user(len, oldlenp);
         if (len) {
                 if (len > 16)
                         len = 16;
                 if (copy_to_user(oldval, table->data, len))
                         return -EFAULT;
                 if (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.poolwords * 32;
         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<<HASH_BITS)-1)) + count;
 
         seq += tv.tv_usec + tv.tv_sec*1000000;
         return seq;
 }
 
 __u32 secure_ipv6_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, 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<<HASH_BITS)-1)) + 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?)
          */
         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;
 }
 
 /*  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)
 {
         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);