/*
* random.c -- A strong random number generator
*
* Version 1.04, last modified 26-Apr-98
*
* Copyright Theodore Ts'o, 1994, 1995, 1996, 1997, 1998. 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 ARE
* 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 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 to
* 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/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
*/
#undef RANDOM_BENCHMARK
#undef BENCHMARK_NOINT
#define ROTATE_PARANOIA
#define POOLWORDS 128 /* Power of 2 - note that this is 32-bit words */
#define POOLBITS (POOLWORDS*32)
/*
* The pool 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.
*/
#if POOLWORDS == 2048 /* 115 x^2048+x^1638+x^1231+x^819+x^411+x^1+1 */
#define TAP1 1638
#define TAP2 1231
#define TAP3 819
#define TAP4 411
#define TAP5 1
#elif POOLWORDS == 1024 /* 290 x^1024+x^817+x^615+x^412+x^204+x^1+1 */
/* Alt: 115 x^1024+x^819+x^616+x^410+x^207+x^2+1 */
#define TAP1 817
#define TAP2 615
#define TAP3 412
#define TAP4 204
#define TAP5 1
#elif POOLWORDS == 512 /* 225 x^512+x^411+x^308+x^208+x^104+x+1 */
/* Alt: 95 x^512+x^409+x^307+x^206+x^102+x^2+1
* 95 x^512+x^409+x^309+x^205+x^103+x^2+1 */
#define TAP1 411
#define TAP2 308
#define TAP3 208
#define TAP4 104
#define TAP5 1
#elif POOLWORDS == 256 /* 125 x^256+x^205+x^155+x^101+x^52+x+1 */
#define TAP1 205
#define TAP2 155
#define TAP3 101
#define TAP4 52
#define TAP5 1
#elif POOLWORDS == 128 /* 105 x^128+x^103+x^76+x^51+x^25+x+1 */
/* Alt: 70 x^128+x^103+x^78+x^51+x^27+x^2+1 */
#define TAP1 103
#define TAP2 76
#define TAP3 51
#define TAP4 25
#define TAP5 1
#elif POOLWORDS == 64 /* 15 x^64+x^52+x^39+x^26+x^14+x+1 */
#define TAP1 52
#define TAP2 39
#define TAP3 26
#define TAP4 14
#define TAP5 1
#elif POOLWORDS == 32 /* 15 x^32+x^26+x^20+x^14+x^7+x^1+1 */
#define TAP1 26
#define TAP2 20
#define TAP3 14
#define TAP4 7
#define TAP5 1
#elif POOLWORDS & (POOLWORDS-1)
#error POOLWORDS must be a power of 2
#else
#error No primitive polynomial available for chosen POOLWORDS
#endif
/*
* 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.
*/
/*
* The minimum number of bits to release a "wait on input". Should
* probably always be 8, since a /dev/random read can return a single
* byte.
*/
#define WAIT_INPUT_BITS 8
/*
* The limit number of bits under which to release a "wait on
* output". Should probably always be the same as WAIT_INPUT_BITS, so
* that an output wait releases when and only when a wait on input
* would block.
*/
#define WAIT_OUTPUT_BITS WAIT_INPUT_BITS
/* There is actually only one of these, globally. */
struct random_bucket {
unsigned add_ptr;
unsigned entropy_count;
#ifdef ROTATE_PARANOIA
int input_rotate;
#endif
__u32 pool[POOLWORDS];
};
#ifdef RANDOM_BENCHMARK
/* For benchmarking only */
struct random_benchmark {
unsigned long long start_time;
int times; /* # of samples */
unsigned long min;
unsigned long max;
unsigned long accum; /* accumulator for average */
const char *descr;
int unit;
unsigned long flags;
};
#define BENCHMARK_INTERVAL 500
static void initialize_benchmark(struct random_benchmark *bench,
const char *descr, int unit);
static void begin_benchmark(struct random_benchmark *bench);
static void end_benchmark(struct random_benchmark *bench);
struct random_benchmark timer_benchmark;
#endif
/* 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 random_bucket random_state;
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];
static struct wait_queue *random_read_wait;
static struct wait_queue *random_write_wait;
static ssize_t random_read(struct file * file, char * buf,
size_t nbytes, loff_t *ppos);
static ssize_t random_read_unlimited(struct file * file, char * buf,
size_t nbytes, loff_t *ppos);
static unsigned int random_poll(struct file *file, poll_table * wait);
static ssize_t random_write(struct file * file, const char * buffer,
size_t count, loff_t *ppos);
static int random_ioctl(struct inode * inode, struct file * file,
unsigned int cmd, unsigned long arg);
static inline void fast_add_entropy_words(struct random_bucket *r,
__u32 x, __u32 y);
static void add_entropy_words(struct random_bucket *r, __u32 x, __u32 y);
#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)
:"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
/*
* Initialize the random pool with standard stuff.
*
* NOTE: This is an OS-dependent function.
*/
static void init_std_data(struct random_bucket *r)
{
__u32 words[2], *p;
int i;
struct timeval tv;
do_gettimeofday(&tv);
add_entropy_words(r, tv.tv_sec, tv.tv_usec);
/*
* This doesnt lock system.utsname. Howeve we are generating
* entropy so a race with a name set here is fine.
*/
p = (__u32 *)&system_utsname;
for (i = sizeof(system_utsname) / sizeof(words); i; i--) {
memcpy(words, p, sizeof(words));
add_entropy_words(r, words[0], words[1]);
p += sizeof(words)/sizeof(*words);
}
}
/* Clear the entropy pool and associated counters. */
static void rand_clear_pool(void)
{
memset(&random_state, 0, sizeof(random_state));
init_std_data(&random_state);
}
__initfunc(void rand_initialize(void))
{
int i;
rand_clear_pool();
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));
#ifdef RANDOM_BENCHMARK
initialize_benchmark(&timer_benchmark, "timer", 0);
#endif
extract_timer_state.dont_count_entropy = 1;
random_read_wait = NULL;
random_write_wait = NULL;
}
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) {
irq_timer_state[irq] = state;
memset(state, 0, sizeof(struct timer_rand_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) {
blkdev_timer_state[major] = state;
memset(state, 0, sizeof(struct timer_rand_state));
}
}
/*
* This function adds a byte into the entropy "pool". It does not
* update the entropy estimate. The caller must do this if appropriate.
*
* This function is tuned for speed above most other considerations.
*
* 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.
*/
#define MASK(x) ((x) & (POOLWORDS-1)) /* Convenient abreviation */
static inline void fast_add_entropy_words(struct random_bucket *r,
__u32 x, __u32 y)
{
static __u32 const twist_table[8] = {
0, 0x3b6e20c8, 0x76dc4190, 0x4db26158,
0xedb88320, 0xd6d6a3e8, 0x9b64c2b0, 0xa00ae278 };
unsigned i, j;
i = MASK(r->add_ptr - 2); /* i is always even */
r->add_ptr = i;
#ifdef ROTATE_PARANOIA
j = r->input_rotate + 14;
if (i)
j -= 7;
r->input_rotate = j & 31;
x = rotate_left(r->input_rotate, x);
y = rotate_left(r->input_rotate, y);
#endif
/*
* XOR in the various taps. Even though logically, we compute
* x and then compute y, we read in y then x order because most
* caches work slightly better with increasing read addresses.
* If a tap is even then we can use the fact that i is even to
* avoid a masking operation. Every polynomial has at least one
* even tap, so j is always used.
* (Is there a nicer way to arrange this code?)
*/
#if TAP1 & 1
y ^= r->pool[MASK(i+TAP1)]; x ^= r->pool[MASK(i+TAP1+1)];
#else
j = MASK(i+TAP1); y ^= r->pool[j]; x ^= r->pool[j+1];
#endif
#if TAP2 & 1
y ^= r->pool[MASK(i+TAP2)]; x ^= r->pool[MASK(i+TAP2+1)];
#else
j = MASK(i+TAP2); y ^= r->pool[j]; x ^= r->pool[j+1];
#endif
#if TAP3 & 1
y ^= r->pool[MASK(i+TAP3)]; x ^= r->pool[MASK(i+TAP3+1)];
#else
j = MASK(i+TAP3); y ^= r->pool[j]; x ^= r->pool[j+1];
#endif
#if TAP4 & 1
y ^= r->pool[MASK(i+TAP4)]; x ^= r->pool[MASK(i+TAP4+1)];
#else
j = MASK(i+TAP4); y ^= r->pool[j]; x ^= r->pool[j+1];
#endif
#if TAP5 == 1
/* We need to pretend to write pool[i+1] before computing y */
y ^= r->pool[i];
x ^= r->pool[i+1];
x ^= r->pool[MASK(i+TAP5+1)];
y ^= r->pool[i+1] = x = (x >> 3) ^ twist_table[x & 7];
r->pool[i] = (y >> 3) ^ twist_table[y & 7];
#else
# if TAP5 & 1
y ^= r->pool[MASK(i+TAP5)]; x ^= r->pool[MASK(i+TAP5+1)];
# else
j = MASK(i+TAP5); y ^= r->pool[j]; x ^= r->pool[j+1];
# endif
y ^= r->pool[i];
x ^= r->pool[i+1];
r->pool[i] = (y >> 3) ^ twist_table[y & 7];
r->pool[i+1] = (x >> 3) ^ twist_table[x & 7];
#endif
}
/*
* For places where we don't need the inlined version
*/
static void add_entropy_words(struct random_bucket *r, __u32 x, __u32 y)
{
fast_add_entropy_words(r, x, y);
}
/*
* 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 random_bucket *r,
struct timer_rand_state *state, unsigned num)
{
__u32 time;
__s32 delta, delta2, delta3;
#ifdef RANDOM_BENCHMARK
begin_benchmark(&timer_benchmark);
#endif
#if defined (__i386__)
if (boot_cpu_data.x86_capability & X86_FEATURE_TSC) {
__u32 high;
__asm__(".byte 0x0f,0x31"
:"=a" (time), "=d" (high));
num ^= high;
} else {
time = jiffies;
}
#else
time = jiffies;
#endif
fast_add_entropy_words(r, (__u32)num, time);
/*
* 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 ((r->entropy_count < POOLBITS) && !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;
r->entropy_count += int_ln_12bits(delta);
/* Prevent overflow */
if (r->entropy_count > POOLBITS)
r->entropy_count = POOLBITS;
/* Wake up waiting processes, if we have enough entropy. */
if (r->entropy_count >= WAIT_INPUT_BITS)
wake_up_interruptible(&random_read_wait);
}
#ifdef RANDOM_BENCHMARK
end_benchmark(&timer_benchmark);
#endif
}
void add_keyboard_randomness(unsigned char scancode)
{
add_timer_randomness(&random_state, &keyboard_timer_state, scancode);
}
void add_mouse_randomness(__u32 mouse_data)
{
add_timer_randomness(&random_state, &mouse_timer_state, mouse_data);
}
void add_interrupt_randomness(int irq)
{
if (irq >= NR_IRQS || irq_timer_state[irq] == 0)
return;
add_timer_randomness(&random_state, 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(&random_state, blkdev_timer_state[major],
0x200+major);
}
/*
* 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 (at POOLWORDS words), so appending a bit count in
* the usual way is not cryptographically necessary.
*/
#define USE_SHA
#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
*
* QUESTION: Replace this with SHA, which as generally received better
* reviews from the cryptographic community?
*/
/* 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 */
#if POOLWORDS % 16 != 0
#error extract_entropy() assumes that POOLWORDS is a multiple of 16 words.
#endif
/*
* 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.
*/
static ssize_t extract_entropy(struct random_bucket *r, char * buf,
size_t nbytes, int to_user)
{
ssize_t ret, i;
__u32 tmp[HASH_BUFFER_SIZE + HASH_EXTRA_SIZE];
__u32 x;
add_timer_randomness(r, &extract_timer_state, nbytes);
/* Redundant, but just in case... */
if (r->entropy_count > POOLBITS)
r->entropy_count = POOLBITS;
ret = nbytes;
if (r->entropy_count / 8 >= nbytes)
r->entropy_count -= nbytes*8;
else
r->entropy_count = 0;
if (r->entropy_count < WAIT_OUTPUT_BITS)
wake_up_interruptible(&random_write_wait);
while (nbytes) {
/* 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
for (i = 0; i < POOLWORDS; i += 16)
HASH_TRANSFORM(tmp, r->pool+i);
/*
* The following code does two separate things that happen
* to both work two words at a time, so are convenient
* to do together.
*
* First, this feeds the output back into the pool so
* that the next call will return different results.
* Any perturbation of the pool's state would do, even
* changing one bit, but this mixes the pool nicely.
*
* Second, this folds the output in half to hide the data
* fed back into the pool from the user and further mask
* any patterns in the hash output. (The exact folding
* pattern is not important; the one used here is quick.)
*/
for (i = 0; i < HASH_BUFFER_SIZE/2; i++) {
x = tmp[i + (HASH_BUFFER_SIZE+1)/2];
add_entropy_words(r, tmp[i], x);
tmp[i] ^= x;
}
#if HASH_BUFFER_SIZE & 1 /* There's a middle word to deal with */
x = tmp[HASH_BUFFER_SIZE/2];
add_entropy_words(r, x, (__u32)buf);
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 (to_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;
add_timer_randomness(r, &extract_timer_state, nbytes);
if (to_user && current->need_resched)
schedule();
}
/* Wipe data just returned from memory */
memset(tmp, 0, sizeof(tmp));
return ret;
}
/*
* This function is the exported kernel interface. It returns some
* number of good random numbers, suitable for seeding TCP sequence
* numbers, etc.
*/
void get_random_bytes(void *buf, int nbytes)
{
extract_entropy(&random_state, (char *) buf, nbytes, 0);
}
static ssize_t
random_read(struct file * file, char * buf, size_t nbytes, loff_t *ppos)
{
struct wait_queue wait = { current, NULL };
ssize_t n, retval = 0, count = 0;
if (nbytes == 0)
return 0;
add_wait_queue(&random_read_wait, &wait);
while (nbytes > 0) {
current->state = TASK_INTERRUPTIBLE;
n = nbytes;
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(&random_state, buf, n, 1);
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
random_read_unlimited(struct file * file, char * buf,
size_t nbytes, loff_t *ppos)
{
return extract_entropy(&random_state, buf, nbytes, 1);
}
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 >= WAIT_INPUT_BITS)
mask |= POLLIN | POLLRDNORM;
if (random_state.entropy_count < WAIT_OUTPUT_BITS)
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;
unsigned i;
__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;
i = (unsigned)((bytes-1) / (2 * sizeof(__u32)));
do {
add_entropy_words(&random_state, buf[2*i], buf[2*i+1]);
} while (i--);
}
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:
retval = verify_area(VERIFY_WRITE, (void *) arg, sizeof(int));
if (retval)
return(retval);
ent_count = random_state.entropy_count;
put_user(ent_count, (int *) arg);
return 0;
case RNDADDTOENTCNT:
if (!capable(CAP_SYS_ADMIN))
return -EPERM;
retval = verify_area(VERIFY_READ, (void *) arg, sizeof(int));
if (retval)
return(retval);
get_user(ent_count, (int *) arg);
/*
* Add i to entropy_count, limiting the result to be
* between 0 and POOLBITS.
*/
if (ent_count < -random_state.entropy_count)
random_state.entropy_count = 0;
else if (ent_count > POOLBITS)
random_state.entropy_count = POOLBITS;
else {
random_state.entropy_count += ent_count;
if (random_state.entropy_count > POOLBITS)
random_state.entropy_count = POOLBITS;
if (random_state.entropy_count < 0)
random_state.entropy_count = 0;
}
/*
* Wake up waiting processes if we have enough
* entropy.
*/
if (random_state.entropy_count >= WAIT_INPUT_BITS)
wake_up_interruptible(&random_read_wait);
return 0;
case RNDGETPOOL:
if (!capable(CAP_SYS_ADMIN))
return -EPERM;
p = (int *) arg;
retval = verify_area(VERIFY_WRITE, (void *) p, sizeof(int));
if (retval)
return(retval);
ent_count = random_state.entropy_count;
put_user(ent_count, p++);
retval = verify_area(VERIFY_WRITE, (void *) p, sizeof(int));
if (retval)
return(retval);
get_user(size, p);
put_user(POOLWORDS, p++);
if (size < 0)
return -EINVAL;
if (size > POOLWORDS)
size = 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;
retval = verify_area(VERIFY_READ, (void *) p, 2*sizeof(int));
if (retval)
return(retval);
get_user(ent_count, p++);
if (ent_count < 0)
return -EINVAL;
get_user(size, p++);
retval = verify_area(VERIFY_READ, (void *) p, size);
if (retval)
return retval;
retval = random_write(file, (const char *) p,
size, &file->f_pos);
if (retval < 0)
return retval;
/*
* Add ent_count to entropy_count, limiting the result to be
* between 0 and POOLBITS.
*/
if (ent_count > POOLBITS)
random_state.entropy_count = POOLBITS;
else {
random_state.entropy_count += ent_count;
if (random_state.entropy_count > POOLBITS)
random_state.entropy_count = POOLBITS;
if (random_state.entropy_count < 0)
random_state.entropy_count = 0;
}
/*
* Wake up waiting processes if we have enough
* entropy.
*/
if (random_state.entropy_count >= WAIT_INPUT_BITS)
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;
rand_clear_pool();
return 0;
default:
return -EINVAL;
}
}
struct file_operations random_fops = {
NULL, /* random_lseek */
random_read,
random_write,
NULL, /* random_readdir */
random_poll, /* random_poll */
random_ioctl,
NULL, /* random_mmap */
NULL, /* no special open code */
NULL /* no special release code */
};
struct file_operations urandom_fops = {
NULL, /* unrandom_lseek */
random_read_unlimited,
random_write,
NULL, /* urandom_readdir */
NULL, /* urandom_poll */
random_ioctl,
NULL, /* urandom_mmap */
NULL, /* no special open code */
NULL /* no special release code */
};
/*
* 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 0 /* May be needed for IPv6 */
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
__u32 secure_tcp_sequence_number(__u32 saddr, __u32 daddr,
__u16 sport, __u16 dport)
{
static __u32 rekey_time = 0;
static __u32 count = 0;
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;
}
#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 = 0;
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
#ifdef RANDOM_BENCHMARK
/*
* This is so we can do some benchmarking of the random driver, to see
* how much overhead add_timer_randomness really takes. This only
* works on a Pentium, since it depends on the timer clock...
*
* Note: the results of this benchmark as of this writing (5/27/96)
*
* On a Pentium, add_timer_randomness() takes between 150 and 1000
* clock cycles, with an average of around 600 clock cycles. On a 75
* MHz Pentium, this translates to 2 to 13 microseconds, with an
* average time of 8 microseconds. This should be fast enough so we
* can use add_timer_randomness() even with the fastest of interrupts...
*/
static inline unsigned long long get_clock_cnt(void)
{
unsigned long low, high;
__asm__(".byte 0x0f,0x31" :"=a" (low), "=d" (high));
return (((unsigned long long) high << 32) | low);
}
__initfunc(static void
initialize_benchmark(struct random_benchmark *bench,
const char *descr, int unit))
{
bench->times = 0;
bench->accum = 0;
bench->max = 0;
bench->min = 1 << 31;
bench->descr = descr;
bench->unit = unit;
}
static void begin_benchmark(struct random_benchmark *bench)
{
#ifdef BENCHMARK_NOINT
save_flags(bench->flags); cli();
#endif
bench->start_time = get_clock_cnt();
}
static void end_benchmark(struct random_benchmark *bench)
{
unsigned long ticks;
ticks = (unsigned long) (get_clock_cnt() - bench->start_time);
#ifdef BENCHMARK_NOINT
restore_flags(bench->flags);
#endif
if (ticks < bench->min)
bench->min = ticks;
if (ticks > bench->max)
bench->max = ticks;
bench->accum += ticks;
bench->times++;
if (bench->times == BENCHMARK_INTERVAL) {
printk("Random benchmark: %s %d: %lu min, %lu avg, "
"%lu max\n", bench->descr, bench->unit, bench->min,
bench->accum / BENCHMARK_INTERVAL, bench->max);
bench->times = 0;
bench->accum = 0;
bench->max = 0;
bench->min = 1 << 31;
}
}
#endif /* RANDOM_BENCHMARK */