swh:1:snp:49cd9498d6cccc5e78252c27dcb645bcf7bf0c91
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 General Public License, in which case the provisions of the GPL are
* required INSTEAD OF the above restrictions. (This clause is
* necessary due to a potential bad interaction between the GPL and
* the restrictions contained in a BSD-style copyright.)
*
* THIS SOFTWARE IS PROVIDED ``AS IS'' AND ANY EXPRESS OR IMPLIED
* WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
* OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE, ALL OF
* WHICH ARE HEREBY DISCLAIMED. IN NO EVENT SHALL THE AUTHOR BE
* LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
* CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT
* OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR
* BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF
* LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
* (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE
* USE OF THIS SOFTWARE, EVEN IF NOT ADVISED OF THE POSSIBILITY OF SUCH
* DAMAGE.
*/
/*
* (now, with legal B.S. out of the way.....)
*
* This routine gathers environmental noise from device drivers, etc.,
* and returns good random numbers, suitable for cryptographic use.
* Besides the obvious cryptographic uses, these numbers are also good
* for seeding TCP sequence numbers, and other places where it is
* desirable to have numbers which are not only random, but hard to
* predict by an attacker.
*
* Theory of operation
* ===================
*
* Computers are very predictable devices. Hence it is extremely hard
* to produce truly random numbers on a computer --- as opposed to
* pseudo-random numbers, which can easily generated by using a
* algorithm. Unfortunately, it is very easy for attackers to guess
* the sequence of pseudo-random number generators, and for some
* applications this is not acceptable. So instead, we must try to
* gather "environmental noise" from the computer's environment, which
* must be hard for outside attackers to observe, and use that to
* generate random numbers. In a Unix environment, this is best done
* from inside the kernel.
*
* Sources of randomness from the environment include inter-keyboard
* timings, inter-interrupt timings from some interrupts, and other
* events which are both (a) non-deterministic and (b) hard for an
* outside observer to measure. Randomness from these sources are
* added to an "entropy pool", which is mixed using a CRC-like function.
* This is not cryptographically strong, but it is adequate assuming
* the randomness is not chosen maliciously, and it is fast enough that
* the overhead of doing it on every interrupt is very reasonable.
* As random bytes are mixed into the entropy pool, the routines keep
* an *estimate* of how many bits of randomness have been stored into
* the random number generator's internal state.
*
* When random bytes are desired, they are obtained by taking the SHA
* hash of the contents of the "entropy pool". The SHA hash avoids
* exposing the internal state of the entropy pool. It is believed to
* be computationally infeasible to derive any useful information
* about the input of SHA from its output. Even if it is possible to
* analyze SHA in some clever way, as long as the amount of data
* returned from the generator is less than the inherent entropy in
* the pool, the output data is totally unpredictable. For this
* reason, the routine decreases its internal estimate of how many
* bits of "true randomness" are contained in the entropy pool as it
* outputs random numbers.
*
* If this estimate goes to zero, the routine can still generate
* random numbers; however, an attacker may (at least in theory) be
* able to infer the future output of the generator from prior
* outputs. This requires successful cryptanalysis of SHA, which is
* not believed to be feasible, but there is a remote possibility.
* Nonetheless, these numbers should be useful for the vast majority
* of purposes.
*
* Exported interfaces ---- output
* ===============================
*
* There are three exported interfaces; the first is one designed to
* be used from within the kernel:
*
* void get_random_bytes(void *buf, int nbytes);
*
* This interface will return the requested number of random bytes,
* and place it in the requested buffer.
*
* The two other interfaces are two character devices /dev/random and
* /dev/urandom. /dev/random is suitable for use when very high
* quality randomness is desired (for example, for key generation or
* one-time pads), as it will only return a maximum of the number of
* bits of randomness (as estimated by the random number generator)
* contained in the entropy pool.
*
* The /dev/urandom device does not have this limit, and will return
* as many bytes as are requested. As more and more random bytes are
* requested without giving time for the entropy pool to recharge,
* this will result in random numbers that are merely cryptographically
* strong. For many applications, however, this is acceptable.
*
* Exported interfaces ---- input
* ==============================
*
* The current exported interfaces for gathering environmental noise
* from the devices are:
*
* void add_input_randomness(unsigned int type, unsigned int code,
* unsigned int value);
* void add_interrupt_randomness(int irq);
*
* add_input_randomness() uses the input layer interrupt timing, as well as
* the event type information from the hardware.
*
* add_interrupt_randomness() uses the inter-interrupt timing as random
* inputs to the entropy pool. Note that not all interrupts are good
* sources of randomness! For example, the timer interrupts is not a
* good choice, because the periodicity of the interrupts is too
* regular, and hence predictable to an attacker. Disk interrupts are
* a better measure, since the timing of the disk interrupts are more
* unpredictable.
*
* All of these routines try to estimate how many bits of randomness a
* particular randomness source. They do this by keeping track of the
* first and second order deltas of the event timings.
*
* Ensuring unpredictability at system startup
* ============================================
*
* When any operating system starts up, it will go through a sequence
* of actions that are fairly predictable by an adversary, especially
* if the start-up does not involve interaction with a human operator.
* This reduces the actual number of bits of unpredictability in the
* entropy pool below the value in entropy_count. In order to
* counteract this effect, it helps to carry information in the
* entropy pool across shut-downs and start-ups. To do this, put the
* following lines an appropriate script which is run during the boot
* sequence:
*
* echo "Initializing random number generator..."
* random_seed=/var/run/random-seed
* # Carry a random seed from start-up to start-up
* # Load and then save the whole entropy pool
* if [ -f $random_seed ]; then
* cat $random_seed >/dev/urandom
* else
* touch $random_seed
* fi
* chmod 600 $random_seed
* dd if=/dev/urandom of=$random_seed count=1 bs=512
*
* and the following lines in an appropriate script which is run as
* the system is shutdown:
*
* # Carry a random seed from shut-down to start-up
* # Save the whole entropy pool
* echo "Saving random seed..."
* random_seed=/var/run/random-seed
* touch $random_seed
* chmod 600 $random_seed
* dd if=/dev/urandom of=$random_seed count=1 bs=512
*
* For example, on most modern systems using the System V init
* scripts, such code fragments would be found in
* /etc/rc.d/init.d/random. On older Linux systems, the correct script
* location might be in /etc/rcb.d/rc.local or /etc/rc.d/rc.0.
*
* Effectively, these commands cause the contents of the entropy pool
* to be saved at shut-down time and reloaded into the entropy pool at
* start-up. (The 'dd' in the addition to the bootup script is to
* make sure that /etc/random-seed is different for every start-up,
* even if the system crashes without executing rc.0.) Even with
* complete knowledge of the start-up activities, predicting the state
* of the entropy pool requires knowledge of the previous history of
* the system.
*
* Configuring the /dev/random driver under Linux
* ==============================================
*
* The /dev/random driver under Linux uses minor numbers 8 and 9 of
* the /dev/mem major number (#1). So if your system does not have
* /dev/random and /dev/urandom created already, they can be created
* by using the commands:
*
* mknod /dev/random c 1 8
* mknod /dev/urandom c 1 9
*
* Acknowledgements:
* =================
*
* Ideas for constructing this random number generator were derived
* from Pretty Good Privacy's random number generator, and from private
* discussions with Phil Karn. Colin Plumb provided a faster random
* number generator, which speed up the mixing function of the entropy
* pool, taken from PGPfone. Dale Worley has also contributed many
* useful ideas and suggestions to improve this driver.
*
* Any flaws in the design are solely my responsibility, and should
* not be attributed to the Phil, Colin, or any of authors of PGP.
*
* 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/slab.h>
#include <linux/random.h>
#include <linux/poll.h>
#include <linux/init.h>
#include <linux/fs.h>
#include <linux/workqueue.h>
#include <linux/genhd.h>
#include <linux/interrupt.h>
#include <linux/spinlock.h>
#include <linux/percpu.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 be enough to do a significant reseed.
*/
static int random_read_wakeup_thresh = 64;
/*
* If the entropy count falls under this number of bits, then we
* should wake up processes which are selecting or polling on write
* access to /dev/random.
*/
static int random_write_wakeup_thresh = 128;
/*
* When the input pool goes over trickle_thresh, start dropping most
* samples to avoid wasting CPU time and reduce lock contention.
*/
static int trickle_thresh = DEFAULT_POOL_SIZE * 7;
static DEFINE_PER_CPU(int, trickle_count) = 0;
/*
* A pool of size .poolwords is stirred with a primitive polynomial
* of degree .poolwords over GF(2). The taps for various sizes are
* defined below. They are chosen to be evenly spaced (minimum RMS
* distance from evenly spaced; the numbers in the comments are a
* scaled squared error sum) except for the last tap, which is 1 to
* get the twisting happening as fast as possible.
*/
static struct poolinfo {
int poolwords;
int tap1, tap2, tap3, tap4, tap5;
} poolinfo_table[] = {
/* x^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 struct entropy_store *urandom_state; /* For urandom */
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__))
static inline __u32 rotate_left(int i, __u32 word)
{
return (word << i) | (word >> (32 - i));
}
#else
static 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
static int debug = 0;
module_param(debug, bool, 0644);
#define DEBUG_ENT(fmt, arg...) do { if (debug) \
printk(KERN_DEBUG "random %04d %04d %04d: " \
fmt,\
random_state->entropy_count,\
sec_random_state->entropy_count,\
urandom_state->entropy_count,\
## arg); } while (0)
#else
#define DEBUG_ENT(fmt, arg...) do {} while (0)
#endif
/**********************************************************************
*
* OS independent entropy store. Here are the functions which handle
* storing entropy in an entropy pool.
*
**********************************************************************/
struct entropy_store {
/* mostly-read data: */
struct poolinfo poolinfo;
__u32 *pool;
const char *name;
/* read-write data: */
spinlock_t lock ____cacheline_aligned_in_smp;
unsigned add_ptr;
int entropy_count;
int input_rotate;
};
/*
* 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, const char *name,
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);
spin_lock_init(&r->lock);
r->name = name;
*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;
memset(r->pool, 0, r->poolinfo.POOLBYTES);
}
/*
* This function adds a byte into the entropy "pool". It does not
* update the entropy estimate. The caller should call
* credit_entropy_store if this is appropriate.
*
* The pool is stirred with a primitive polynomial of the appropriate
* degree, and then twisted. We twist by three bits at a time because
* it's cheap to do so and helps slightly in the expected case where
* the entropy is concentrated in the low-order bits.
*/
static void __add_entropy_words(struct entropy_store *r, const __u32 *in,
int nwords, __u32 out[16])
{
static __u32 const twist_table[8] = {
0x00000000, 0x3b6e20c8, 0x76dc4190, 0x4db26158,
0xedb88320, 0xd6d6a3e8, 0x9b64c2b0, 0xa00ae278 };
unsigned long i, add_ptr, tap1, tap2, tap3, tap4, tap5;
int new_rotate, input_rotate;
int wordmask = r->poolinfo.poolwords - 1;
__u32 w, next_w;
unsigned long flags;
/* Taps are constant, so we can load them without holding r->lock. */
tap1 = r->poolinfo.tap1;
tap2 = r->poolinfo.tap2;
tap3 = r->poolinfo.tap3;
tap4 = r->poolinfo.tap4;
tap5 = r->poolinfo.tap5;
next_w = *in++;
spin_lock_irqsave(&r->lock, flags);
prefetch_range(r->pool, wordmask);
input_rotate = r->input_rotate;
add_ptr = r->add_ptr;
while (nwords--) {
w = rotate_left(input_rotate, next_w);
if (nwords > 0)
next_w = *in++;
i = add_ptr = (add_ptr - 1) & wordmask;
/*
* Normally, we add 7 bits of rotation to the pool.
* At the beginning of the pool, add an extra 7 bits
* rotation, so that successive passes spread the
* input bits across the pool evenly.
*/
new_rotate = input_rotate + 14;
if (i)
new_rotate = input_rotate + 7;
input_rotate = new_rotate & 31;
/* XOR in the various taps */
w ^= r->pool[(i + tap1) & wordmask];
w ^= r->pool[(i + tap2) & wordmask];
w ^= r->pool[(i + tap3) & wordmask];
w ^= r->pool[(i + tap4) & wordmask];
w ^= r->pool[(i + tap5) & wordmask];
w ^= r->pool[i];
r->pool[i] = (w >> 3) ^ twist_table[w & 7];
}
r->input_rotate = input_rotate;
r->add_ptr = add_ptr;
if (out) {
for (i = 0; i < 16; i++) {
out[i] = r->pool[add_ptr];
add_ptr = (add_ptr - 1) & wordmask;
}
}
spin_unlock_irqrestore(&r->lock, flags);
}
static inline void add_entropy_words(struct entropy_store *r, const __u32 *in,
int nwords)
{
__add_entropy_words(r, in, nwords, NULL);
}
/*
* Credit (or debit) the entropy store with n bits of entropy
*/
static void credit_entropy_store(struct entropy_store *r, int nbits)
{
unsigned long flags;
spin_lock_irqsave(&r->lock, flags);
if (r->entropy_count + nbits < 0) {
DEBUG_ENT("negative entropy/overflow (%d+%d)\n",
r->entropy_count, nbits);
r->entropy_count = 0;
} else if (r->entropy_count + nbits > r->poolinfo.POOLBITS) {
r->entropy_count = r->poolinfo.POOLBITS;
} else {
r->entropy_count += nbits;
if (nbits)
DEBUG_ENT("added %d entropy credits to %s\n",
nbits, r->name);
}
spin_unlock_irqrestore(&r->lock, flags);
}
/**********************************************************************
*
* Entropy batch input management
*
* We batch entropy to be added to avoid increasing interrupt latency
*
**********************************************************************/
struct sample {
__u32 data[2];
int credit;
};
static struct sample *batch_entropy_pool, *batch_entropy_copy;
static int batch_head, batch_tail;
static DEFINE_SPINLOCK(batch_lock);
static int batch_max;
static void batch_entropy_process(void *private_);
static DECLARE_WORK(batch_work, batch_entropy_process, NULL);
/* 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(size*sizeof(struct sample), GFP_KERNEL);
if (!batch_entropy_pool)
return -1;
batch_entropy_copy = kmalloc(size*sizeof(struct sample), GFP_KERNEL);
if (!batch_entropy_copy) {
kfree(batch_entropy_pool);
return -1;
}
batch_head = batch_tail = 0;
batch_work.data = r;
batch_max = size;
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 by keventd.
*/
static void batch_entropy_store(u32 a, u32 b, int num)
{
int new;
unsigned long flags;
if (!batch_max)
return;
spin_lock_irqsave(&batch_lock, flags);
batch_entropy_pool[batch_head].data[0] = a;
batch_entropy_pool[batch_head].data[1] = b;
batch_entropy_pool[batch_head].credit = num;
if (((batch_head - batch_tail) & (batch_max - 1)) >= (batch_max / 2))
schedule_delayed_work(&batch_work, 1);
new = (batch_head + 1) & (batch_max - 1);
if (new == batch_tail)
DEBUG_ENT("batch entropy buffer full\n");
else
batch_head = new;
spin_unlock_irqrestore(&batch_lock, flags);
}
/*
* 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;
unsigned head, tail;
/* Mixing into the pool is expensive, so copy over the batch
* data and release the batch lock. The pool is at least half
* full, so don't worry too much about copying only the used
* part.
*/
spin_lock_irq(&batch_lock);
memcpy(batch_entropy_copy, batch_entropy_pool,
batch_max * sizeof(struct sample));
head = batch_head;
tail = batch_tail;
batch_tail = batch_head;
spin_unlock_irq(&batch_lock);
p = r;
while (head != 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_copy[tail].data, 2);
credit_entropy_store(r, batch_entropy_copy[tail].credit);
tail = (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 {
cycles_t last_time;
long last_delta,last_delta2;
unsigned dont_count_entropy:1;
};
static struct timer_rand_state input_timer_state;
static struct timer_rand_state extract_timer_state;
static struct timer_rand_state *irq_timer_state[NR_IRQS];
/*
* This function adds entropy to the entropy "pool" by using timing
* delays. It uses the timer_rand_state structure to make an estimate
* of how many bits of entropy this call has added to the pool.
*
* The number "num" is also added to the pool - it should somehow describe
* the type of event which just happened. This is currently 0-255 for
* keyboard scan codes, and 256 upwards for interrupts.
*
*/
static void add_timer_randomness(struct timer_rand_state *state, unsigned num)
{
cycles_t data;
long delta, delta2, delta3, time;
int entropy = 0;
preempt_disable();
/* if over the trickle threshold, use only 1 in 4096 samples */
if (random_state->entropy_count > trickle_thresh &&
(__get_cpu_var(trickle_count)++ & 0xfff))
goto out;
/*
* 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.
*/
time = jiffies;
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);
}
/*
* Use get_cycles() if implemented, otherwise fall back to
* jiffies.
*/
data = get_cycles();
if (data)
num ^= (u32)((data >> 31) >> 1);
else
data = time;
batch_entropy_store(num, data, entropy);
out:
preempt_enable();
}
extern void add_input_randomness(unsigned int type, unsigned int code,
unsigned int value)
{
static unsigned char last_value;
/* ignore autorepeat and the like */
if (value == last_value)
return;
DEBUG_ENT("input event\n");
last_value = value;
add_timer_randomness(&input_timer_state,
(type << 4) ^ code ^ (code >> 4) ^ value);
}
void add_interrupt_randomness(int irq)
{
if (irq >= NR_IRQS || irq_timer_state[irq] == 0)
return;
DEBUG_ENT("irq event %d\n", irq);
add_timer_randomness(irq_timer_state[irq], 0x100 + irq);
}
void add_disk_randomness(struct gendisk *disk)
{
if (!disk || !disk->random)
return;
/* first major is 1, so we get >= 0x200 here */
DEBUG_ENT("disk event %d:%d\n", disk->major, disk->first_minor);
add_timer_randomness(disk->random,
0x100 + MKDEV(disk->major, disk->first_minor));
}
EXPORT_SYMBOL(add_disk_randomness);
/******************************************************************
*
* 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 EXTRACT_ENTROPY_LIMIT 4
#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 make
* sure we pull enough for a 'catastrophic reseed'.
*/
static inline void xfer_secondary_pool(struct entropy_store *r,
size_t nbytes, __u32 *tmp)
{
if (r->entropy_count < nbytes * 8 &&
r->entropy_count < r->poolinfo.POOLBITS) {
int bytes = max_t(int, random_read_wakeup_thresh / 8,
min_t(int, nbytes, TMP_BUF_SIZE));
DEBUG_ENT("going to reseed %s with %d bits "
"(%d of %d requested)\n",
r->name, bytes * 8, nbytes * 8, r->entropy_count);
bytes=extract_entropy(random_state, tmp, bytes,
EXTRACT_ENTROPY_LIMIT);
add_entropy_words(r, tmp, (bytes + 3) / 4);
credit_entropy_store(r, bytes*8);
}
}
/*
* 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], data[16];
__u32 x;
unsigned long cpuflags;
/* 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, tmp);
/* Hold lock while accounting */
spin_lock_irqsave(&r->lock, cpuflags);
DEBUG_ENT("trying to extract %d bits from %s\n",
nbytes * 8, r->name);
if (flags & EXTRACT_ENTROPY_LIMIT && nbytes >= r->entropy_count / 8)
nbytes = r->entropy_count / 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);
DEBUG_ENT("debiting %d entropy credits from %s%s\n",
nbytes * 8, r->name,
flags & EXTRACT_ENTROPY_LIMIT ? "" : " (unlimited)");
spin_unlock_irqrestore(&r->lock, cpuflags);
ret = 0;
while (nbytes) {
/*
* Check if we need to break out or reschedule....
*/
if ((flags & EXTRACT_ENTROPY_USER) && 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);
}
/*
* To avoid duplicates, we atomically extract a
* portion of the pool while mixing, and hash one
* final time.
*/
__add_entropy_words(r, &tmp[x%HASH_BUFFER_SIZE], 1, data);
HASH_TRANSFORM(tmp, data);
/*
* 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;
}
/* 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)
{
struct entropy_store *r = urandom_state;
int flags = EXTRACT_ENTROPY_SECONDARY;
if (!r)
r = sec_random_state;
if (!r) {
r = random_state;
flags = 0;
}
if (!r) {
printk(KERN_NOTICE "get_random_bytes called before "
"random driver initialization\n");
return;
}
extract_entropy(r, (char *) buf, nbytes, flags);
}
EXPORT_SYMBOL(get_random_bytes);
/*********************************************************************
*
* 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);
}
}
static int __init rand_initialize(void)
{
int i;
if (create_entropy_store(DEFAULT_POOL_SIZE, "primary", &random_state))
goto err;
if (batch_entropy_init(BATCH_ENTROPY_SIZE, random_state))
goto err;
if (create_entropy_store(SECONDARY_POOL_SIZE, "secondary",
&sec_random_state))
goto err;
if (create_entropy_store(SECONDARY_POOL_SIZE, "urandom",
&urandom_state))
goto err;
clear_entropy_store(random_state);
clear_entropy_store(sec_random_state);
clear_entropy_store(urandom_state);
init_std_data(random_state);
init_std_data(sec_random_state);
init_std_data(urandom_state);
#ifdef CONFIG_SYSCTL
sysctl_init_random(random_state);
#endif
for (i = 0; i < NR_IRQS; i++)
irq_timer_state[i] = NULL;
memset(&input_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;
return 0;
err:
return -1;
}
module_init(rand_initialize);
void rand_initialize_irq(int irq)
{
struct timer_rand_state *state;
if (irq >= NR_IRQS || irq_timer_state[irq])
return;
/*
* If kmalloc returns null, we just won't use that entropy
* source.
*/
state = kmalloc(sizeof(struct timer_rand_state), GFP_KERNEL);
if (state) {
memset(state, 0, sizeof(struct timer_rand_state));
irq_timer_state[irq] = state;
}
}
void rand_initialize_disk(struct gendisk *disk)
{
struct timer_rand_state *state;
/*
* If kmalloc returns null, we just won't use that entropy
* source.
*/
state = kmalloc(sizeof(struct timer_rand_state), GFP_KERNEL);
if (state) {
memset(state, 0, sizeof(struct timer_rand_state));
disk->random = state;
}
}
static ssize_t
random_read(struct file * file, char __user * buf, size_t nbytes, loff_t *ppos)
{
DECLARE_WAITQUEUE(wait, current);
ssize_t n, retval = 0, count = 0;
if (nbytes == 0)
return 0;
while (nbytes > 0) {
n = nbytes;
if (n > SEC_XFER_SIZE)
n = SEC_XFER_SIZE;
DEBUG_ENT("reading %d bits\n", n*8);
n = extract_entropy(sec_random_state, buf, n,
EXTRACT_ENTROPY_USER |
EXTRACT_ENTROPY_LIMIT |
EXTRACT_ENTROPY_SECONDARY);
DEBUG_ENT("read got %d bits (%d still needed)\n",
n*8, (nbytes-n)*8);
if (n == 0) {
if (file->f_flags & O_NONBLOCK) {
retval = -EAGAIN;
break;
}
if (signal_pending(current)) {
retval = -ERESTARTSYS;
break;
}
set_current_state(TASK_INTERRUPTIBLE);
add_wait_queue(&random_read_wait, &wait);
if (sec_random_state->entropy_count / 8 == 0)
schedule();
set_current_state(TASK_RUNNING);
remove_wait_queue(&random_read_wait, &wait);
continue;
}
if (n < 0) {
retval = n;
break;
}
count += n;
buf += n;
nbytes -= n;
break; /* This break makes the device work */
/* like a named pipe */
}
/*
* If we gave the user some bytes, update the access time.
*/
if (count)
file_accessed(file);
return (count ? count : retval);
}
static ssize_t
urandom_read(struct file * file, char __user * buf,
size_t nbytes, loff_t *ppos)
{
int flags = EXTRACT_ENTROPY_USER;
unsigned long cpuflags;
spin_lock_irqsave(&random_state->lock, cpuflags);
if (random_state->entropy_count > random_state->poolinfo.POOLBITS)
flags |= EXTRACT_ENTROPY_SECONDARY;
spin_unlock_irqrestore(&random_state->lock, cpuflags);
return extract_entropy(urandom_state, buf, nbytes, flags);
}
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 __user * buffer,
size_t count, loff_t *ppos)
{
int ret = 0;
size_t bytes;
__u32 buf[16];
const char __user *p = buffer;
size_t c = count;
while (c > 0) {
bytes = min(c, sizeof(buf));
bytes -= copy_from_user(&buf, p, bytes);
if (!bytes) {
ret = -EFAULT;
break;
}
c -= bytes;
p += bytes;
add_entropy_words(random_state, buf, (bytes + 3) / 4);
}
if (p == buffer) {
return (ssize_t)ret;
} else {
struct inode *inode = file->f_dentry->d_inode;
inode->i_mtime = current_fs_time(inode->i_sb);
mark_inode_dirty(inode);
return (ssize_t)(p - buffer);
}
}
static int
random_ioctl(struct inode * inode, struct file * file,
unsigned int cmd, unsigned long arg)
{
int size, ent_count;
int __user *p = (int __user *)arg;
int retval;
switch (cmd) {
case RNDGETENTCNT:
ent_count = random_state->entropy_count;
if (put_user(ent_count, p))
return -EFAULT;
return 0;
case RNDADDTOENTCNT:
if (!capable(CAP_SYS_ADMIN))
return -EPERM;
if (get_user(ent_count, p))
return -EFAULT;
credit_entropy_store(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 RNDADDENTROPY:
if (!capable(CAP_SYS_ADMIN))
return -EPERM;
if (get_user(ent_count, p++))
return -EFAULT;
if (ent_count < 0)
return -EINVAL;
if (get_user(size, p++))
return -EFAULT;
retval = random_write(file, (const char __user *) p,
size, &file->f_pos);
if (retval < 0)
return retval;
credit_entropy_store(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;
}
EXPORT_SYMBOL(generate_random_uuid);
/********************************************************************
*
* Sysctl interface
*
********************************************************************/
#ifdef CONFIG_SYSCTL
#include <linux/sysctl.h>
static int min_read_thresh, max_read_thresh;
static int min_write_thresh, max_write_thresh;
static char sysctl_bootid[16];
/*
* These functions is used to return both the bootid UUID, and random
* UUID. The difference is in whether table->data is NULL; if it is,
* then a new UUID is generated and returned to the user.
*
* If the user accesses this via the proc interface, it will be returned
* as an ASCII string in the standard UUID format. If accesses via the
* sysctl system call, it is returned as 16 bytes of binary data.
*/
static int proc_do_uuid(ctl_table *table, int write, struct file *filp,
void __user *buffer, size_t *lenp, loff_t *ppos)
{
ctl_table fake_table;
unsigned char buf[64], tmp_uuid[16], *uuid;
uuid = table->data;
if (!uuid) {
uuid = tmp_uuid;
uuid[8] = 0;
}
if (uuid[8] == 0)
generate_random_uuid(uuid);
sprintf(buf, "%02x%02x%02x%02x-%02x%02x-%02x%02x-%02x%02x-"
"%02x%02x%02x%02x%02x%02x",
uuid[0], uuid[1], uuid[2], uuid[3],
uuid[4], uuid[5], uuid[6], uuid[7],
uuid[8], uuid[9], uuid[10], uuid[11],
uuid[12], uuid[13], uuid[14], uuid[15]);
fake_table.data = buf;
fake_table.maxlen = sizeof(buf);
return proc_dostring(&fake_table, write, filp, buffer, lenp, ppos);
}
static int uuid_strategy(ctl_table *table, int __user *name, int nlen,
void __user *oldval, size_t __user *oldlenp,
void __user *newval, size_t newlen, void **context)
{
unsigned char tmp_uuid[16], *uuid;
unsigned int len;
if (!oldval || !oldlenp)
return 1;
uuid = table->data;
if (!uuid) {
uuid = tmp_uuid;
uuid[8] = 0;
}
if (uuid[8] == 0)
generate_random_uuid(uuid);
if (get_user(len, oldlenp))
return -EFAULT;
if (len) {
if (len > 16)
len = 16;
if (copy_to_user(oldval, uuid, len) ||
put_user(len, oldlenp))
return -EFAULT;
}
return 1;
}
static int sysctl_poolsize = DEFAULT_POOL_SIZE;
ctl_table random_table[] = {
{
.ctl_name = RANDOM_POOLSIZE,
.procname = "poolsize",
.data = &sysctl_poolsize,
.maxlen = sizeof(int),
.mode = 0444,
.proc_handler = &proc_dointvec,
},
{
.ctl_name = RANDOM_ENTROPY_COUNT,
.procname = "entropy_avail",
.maxlen = sizeof(int),
.mode = 0444,
.proc_handler = &proc_dointvec,
},
{
.ctl_name = RANDOM_READ_THRESH,
.procname = "read_wakeup_threshold",
.data = &random_read_wakeup_thresh,
.maxlen = sizeof(int),
.mode = 0644,
.proc_handler = &proc_dointvec_minmax,
.strategy = &sysctl_intvec,
.extra1 = &min_read_thresh,
.extra2 = &max_read_thresh,
},
{
.ctl_name = RANDOM_WRITE_THRESH,
.procname = "write_wakeup_threshold",
.data = &random_write_wakeup_thresh,
.maxlen = sizeof(int),
.mode = 0644,
.proc_handler = &proc_dointvec_minmax,
.strategy = &sysctl_intvec,
.extra1 = &min_write_thresh,
.extra2 = &max_write_thresh,
},
{
.ctl_name = RANDOM_BOOT_ID,
.procname = "boot_id",
.data = &sysctl_bootid,
.maxlen = 16,
.mode = 0444,
.proc_handler = &proc_do_uuid,
.strategy = &uuid_strategy,
},
{
.ctl_name = RANDOM_UUID,
.procname = "uuid",
.maxlen = 16,
.mode = 0444,
.proc_handler = &proc_do_uuid,
.strategy = &uuid_strategy,
},
{ .ctl_name = 0 }
};
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
*
********************************************************************/
#ifdef CONFIG_INET
/*
* 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 * HZ)
/*
* Bit layout of the tcp sequence numbers (before adding current time):
* bit 24-31: increased after every key exchange
* bit 0-23: hash(source,dest)
*
* The implementation is similar to the algorithm described
* in the Appendix of RFC 1185, except that
* - it uses a 1 MHz clock instead of a 250 kHz clock
* - it performs a rekey every 5 minutes, which is equivalent
* to a (source,dest) tulple dependent forward jump of the
* clock by 0..2^(HASH_BITS+1)
*
* Thus the average ISN wraparound time is 68 minutes instead of
* 4.55 hours.
*
* SMP cleanup and lock avoidance with poor man's RCU.
* Manfred Spraul <manfred@colorfullife.com>
*
*/
#define COUNT_BITS 8
#define COUNT_MASK ((1 << COUNT_BITS) - 1)
#define HASH_BITS 24
#define HASH_MASK ((1 << HASH_BITS) - 1)
static struct keydata {
__u32 count; /* already shifted to the final position */
__u32 secret[12];
} ____cacheline_aligned ip_keydata[2];
static unsigned int ip_cnt;
static void rekey_seq_generator(void *private_);
static DECLARE_WORK(rekey_work, rekey_seq_generator, NULL);
/*
* Lock avoidance:
* The ISN generation runs lockless - it's just a hash over random data.
* State changes happen every 5 minutes when the random key is replaced.
* Synchronization is performed by having two copies of the hash function
* state and rekey_seq_generator always updates the inactive copy.
* The copy is then activated by updating ip_cnt.
* The implementation breaks down if someone blocks the thread
* that processes SYN requests for more than 5 minutes. Should never
* happen, and even if that happens only a not perfectly compliant
* ISN is generated, nothing fatal.
*/
static void rekey_seq_generator(void *private_)
{
struct keydata *keyptr = &ip_keydata[1 ^ (ip_cnt & 1)];
get_random_bytes(keyptr->secret, sizeof(keyptr->secret));
keyptr->count = (ip_cnt & COUNT_MASK) << HASH_BITS;
smp_wmb();
ip_cnt++;
schedule_delayed_work(&rekey_work, REKEY_INTERVAL);
}
static inline struct keydata *get_keyptr(void)
{
struct keydata *keyptr = &ip_keydata[ip_cnt & 1];
smp_rmb();
return keyptr;
}
static __init int seqgen_init(void)
{
rekey_seq_generator(NULL);
return 0;
}
late_initcall(seqgen_init);
#if defined(CONFIG_IPV6) || defined(CONFIG_IPV6_MODULE)
__u32 secure_tcpv6_sequence_number(__u32 *saddr, __u32 *daddr,
__u16 sport, __u16 dport)
{
struct timeval tv;
__u32 seq;
__u32 hash[12];
struct keydata *keyptr = get_keyptr();
/* The procedure is the same as for IPv4, but addresses are longer.
* Thus we must use twothirdsMD4Transform.
*/
memcpy(hash, saddr, 16);
hash[4]=(sport << 16) + dport;
memcpy(&hash[5],keyptr->secret,sizeof(__u32) * 7);
seq = twothirdsMD4Transform(daddr, hash) & HASH_MASK;
seq += keyptr->count;
do_gettimeofday(&tv);
seq += tv.tv_usec + tv.tv_sec * 1000000;
return seq;
}
EXPORT_SYMBOL(secure_tcpv6_sequence_number);
#endif
__u32 secure_tcp_sequence_number(__u32 saddr, __u32 daddr,
__u16 sport, __u16 dport)
{
struct timeval tv;
__u32 seq;
__u32 hash[4];
struct keydata *keyptr = get_keyptr();
/*
* Pick a unique starting offset for each TCP connection endpoints
* (saddr, daddr, sport, dport).
* Note that the words are placed into the starting vector, which is
* then mixed with a partial MD4 over random data.
*/
hash[0]=saddr;
hash[1]=daddr;
hash[2]=(sport << 16) + dport;
hash[3]=keyptr->secret[11];
seq = halfMD4Transform(hash, keyptr->secret) & HASH_MASK;
seq += keyptr->count;
/*
* As close as possible to RFC 793, which
* suggests using a 250 kHz clock.
* Further reading shows this assumes 2 Mb/s networks.
* For 10 Mb/s Ethernet, a 1 MHz clock is appropriate.
* That's funny, Linux has one built in! Use it!
* (Networks are faster now - should this be increased?)
*/
do_gettimeofday(&tv);
seq += tv.tv_usec + tv.tv_sec * 1000000;
#if 0
printk("init_seq(%lx, %lx, %d, %d) = %d\n",
saddr, daddr, sport, dport, seq);
#endif
return seq;
}
EXPORT_SYMBOL(secure_tcp_sequence_number);
/* The code below is shamelessly stolen from secure_tcp_sequence_number().
* All blames to Andrey V. Savochkin <saw@msu.ru>.
*/
__u32 secure_ip_id(__u32 daddr)
{
struct keydata *keyptr;
__u32 hash[4];
keyptr = get_keyptr();
/*
* Pick a unique starting offset for each IP destination.
* The dest ip address is placed in the starting vector,
* which is then hashed with random data.
*/
hash[0] = daddr;
hash[1] = keyptr->secret[9];
hash[2] = keyptr->secret[10];
hash[3] = keyptr->secret[11];
return halfMD4Transform(hash, keyptr->secret);
}
/* Generate secure starting point for ephemeral TCP port search */
u32 secure_tcp_port_ephemeral(__u32 saddr, __u32 daddr, __u16 dport)
{
struct keydata *keyptr = get_keyptr();
u32 hash[4];
/*
* Pick a unique starting offset for each ephemeral port search
* (saddr, daddr, dport) and 48bits of random data.
*/
hash[0] = saddr;
hash[1] = daddr;
hash[2] = dport ^ keyptr->secret[10];
hash[3] = keyptr->secret[11];
return halfMD4Transform(hash, keyptr->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
#endif /* CONFIG_INET */
