2 * random.c -- A strong random number generator
4 * Copyright Matt Mackall <mpm@selenic.com>, 2003, 2004, 2005
6 * Copyright Theodore Ts'o, 1994, 1995, 1996, 1997, 1998, 1999. All
9 * Redistribution and use in source and binary forms, with or without
10 * modification, are permitted provided that the following conditions
12 * 1. Redistributions of source code must retain the above copyright
13 * notice, and the entire permission notice in its entirety,
14 * including the disclaimer of warranties.
15 * 2. Redistributions in binary form must reproduce the above copyright
16 * notice, this list of conditions and the following disclaimer in the
17 * documentation and/or other materials provided with the distribution.
18 * 3. The name of the author may not be used to endorse or promote
19 * products derived from this software without specific prior
22 * ALTERNATIVELY, this product may be distributed under the terms of
23 * the GNU General Public License, in which case the provisions of the GPL are
24 * required INSTEAD OF the above restrictions. (This clause is
25 * necessary due to a potential bad interaction between the GPL and
26 * the restrictions contained in a BSD-style copyright.)
28 * THIS SOFTWARE IS PROVIDED ``AS IS'' AND ANY EXPRESS OR IMPLIED
29 * WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
30 * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE, ALL OF
31 * WHICH ARE HEREBY DISCLAIMED. IN NO EVENT SHALL THE AUTHOR BE
32 * LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
33 * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT
34 * OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR
35 * BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF
36 * LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
37 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE
38 * USE OF THIS SOFTWARE, EVEN IF NOT ADVISED OF THE POSSIBILITY OF SUCH
43 * (now, with legal B.S. out of the way.....)
45 * This routine gathers environmental noise from device drivers, etc.,
46 * and returns good random numbers, suitable for cryptographic use.
47 * Besides the obvious cryptographic uses, these numbers are also good
48 * for seeding TCP sequence numbers, and other places where it is
49 * desirable to have numbers which are not only random, but hard to
50 * predict by an attacker.
55 * Computers are very predictable devices. Hence it is extremely hard
56 * to produce truly random numbers on a computer --- as opposed to
57 * pseudo-random numbers, which can easily generated by using a
58 * algorithm. Unfortunately, it is very easy for attackers to guess
59 * the sequence of pseudo-random number generators, and for some
60 * applications this is not acceptable. So instead, we must try to
61 * gather "environmental noise" from the computer's environment, which
62 * must be hard for outside attackers to observe, and use that to
63 * generate random numbers. In a Unix environment, this is best done
64 * from inside the kernel.
66 * Sources of randomness from the environment include inter-keyboard
67 * timings, inter-interrupt timings from some interrupts, and other
68 * events which are both (a) non-deterministic and (b) hard for an
69 * outside observer to measure. Randomness from these sources are
70 * added to an "entropy pool", which is mixed using a CRC-like function.
71 * This is not cryptographically strong, but it is adequate assuming
72 * the randomness is not chosen maliciously, and it is fast enough that
73 * the overhead of doing it on every interrupt is very reasonable.
74 * As random bytes are mixed into the entropy pool, the routines keep
75 * an *estimate* of how many bits of randomness have been stored into
76 * the random number generator's internal state.
78 * When random bytes are desired, they are obtained by taking the SHA
79 * hash of the contents of the "entropy pool". The SHA hash avoids
80 * exposing the internal state of the entropy pool. It is believed to
81 * be computationally infeasible to derive any useful information
82 * about the input of SHA from its output. Even if it is possible to
83 * analyze SHA in some clever way, as long as the amount of data
84 * returned from the generator is less than the inherent entropy in
85 * the pool, the output data is totally unpredictable. For this
86 * reason, the routine decreases its internal estimate of how many
87 * bits of "true randomness" are contained in the entropy pool as it
88 * outputs random numbers.
90 * If this estimate goes to zero, the routine can still generate
91 * random numbers; however, an attacker may (at least in theory) be
92 * able to infer the future output of the generator from prior
93 * outputs. This requires successful cryptanalysis of SHA, which is
94 * not believed to be feasible, but there is a remote possibility.
95 * Nonetheless, these numbers should be useful for the vast majority
98 * Exported interfaces ---- output
99 * ===============================
101 * There are three exported interfaces; the first is one designed to
102 * be used from within the kernel:
104 * void get_random_bytes(void *buf, int nbytes);
106 * This interface will return the requested number of random bytes,
107 * and place it in the requested buffer.
109 * The two other interfaces are two character devices /dev/random and
110 * /dev/urandom. /dev/random is suitable for use when very high
111 * quality randomness is desired (for example, for key generation or
112 * one-time pads), as it will only return a maximum of the number of
113 * bits of randomness (as estimated by the random number generator)
114 * contained in the entropy pool.
116 * The /dev/urandom device does not have this limit, and will return
117 * as many bytes as are requested. As more and more random bytes are
118 * requested without giving time for the entropy pool to recharge,
119 * this will result in random numbers that are merely cryptographically
120 * strong. For many applications, however, this is acceptable.
122 * Exported interfaces ---- input
123 * ==============================
125 * The current exported interfaces for gathering environmental noise
126 * from the devices are:
128 * void add_input_randomness(unsigned int type, unsigned int code,
129 * unsigned int value);
130 * void add_interrupt_randomness(int irq);
132 * add_input_randomness() uses the input layer interrupt timing, as well as
133 * the event type information from the hardware.
135 * add_interrupt_randomness() uses the inter-interrupt timing as random
136 * inputs to the entropy pool. Note that not all interrupts are good
137 * sources of randomness! For example, the timer interrupts is not a
138 * good choice, because the periodicity of the interrupts is too
139 * regular, and hence predictable to an attacker. Disk interrupts are
140 * a better measure, since the timing of the disk interrupts are more
143 * All of these routines try to estimate how many bits of randomness a
144 * particular randomness source. They do this by keeping track of the
145 * first and second order deltas of the event timings.
147 * Ensuring unpredictability at system startup
148 * ============================================
150 * When any operating system starts up, it will go through a sequence
151 * of actions that are fairly predictable by an adversary, especially
152 * if the start-up does not involve interaction with a human operator.
153 * This reduces the actual number of bits of unpredictability in the
154 * entropy pool below the value in entropy_count. In order to
155 * counteract this effect, it helps to carry information in the
156 * entropy pool across shut-downs and start-ups. To do this, put the
157 * following lines an appropriate script which is run during the boot
160 * echo "Initializing random number generator..."
161 * random_seed=/var/run/random-seed
162 * # Carry a random seed from start-up to start-up
163 * # Load and then save the whole entropy pool
164 * if [ -f $random_seed ]; then
165 * cat $random_seed >/dev/urandom
169 * chmod 600 $random_seed
170 * dd if=/dev/urandom of=$random_seed count=1 bs=512
172 * and the following lines in an appropriate script which is run as
173 * the system is shutdown:
175 * # Carry a random seed from shut-down to start-up
176 * # Save the whole entropy pool
177 * echo "Saving random seed..."
178 * random_seed=/var/run/random-seed
180 * chmod 600 $random_seed
181 * dd if=/dev/urandom of=$random_seed count=1 bs=512
183 * For example, on most modern systems using the System V init
184 * scripts, such code fragments would be found in
185 * /etc/rc.d/init.d/random. On older Linux systems, the correct script
186 * location might be in /etc/rcb.d/rc.local or /etc/rc.d/rc.0.
188 * Effectively, these commands cause the contents of the entropy pool
189 * to be saved at shut-down time and reloaded into the entropy pool at
190 * start-up. (The 'dd' in the addition to the bootup script is to
191 * make sure that /etc/random-seed is different for every start-up,
192 * even if the system crashes without executing rc.0.) Even with
193 * complete knowledge of the start-up activities, predicting the state
194 * of the entropy pool requires knowledge of the previous history of
197 * Configuring the /dev/random driver under Linux
198 * ==============================================
200 * The /dev/random driver under Linux uses minor numbers 8 and 9 of
201 * the /dev/mem major number (#1). So if your system does not have
202 * /dev/random and /dev/urandom created already, they can be created
203 * by using the commands:
205 * mknod /dev/random c 1 8
206 * mknod /dev/urandom c 1 9
211 * Ideas for constructing this random number generator were derived
212 * from Pretty Good Privacy's random number generator, and from private
213 * discussions with Phil Karn. Colin Plumb provided a faster random
214 * number generator, which speed up the mixing function of the entropy
215 * pool, taken from PGPfone. Dale Worley has also contributed many
216 * useful ideas and suggestions to improve this driver.
218 * Any flaws in the design are solely my responsibility, and should
219 * not be attributed to the Phil, Colin, or any of authors of PGP.
221 * Further background information on this topic may be obtained from
222 * RFC 1750, "Randomness Recommendations for Security", by Donald
223 * Eastlake, Steve Crocker, and Jeff Schiller.
226 #include <linux/utsname.h>
227 #include <linux/module.h>
228 #include <linux/kernel.h>
229 #include <linux/major.h>
230 #include <linux/string.h>
231 #include <linux/fcntl.h>
232 #include <linux/slab.h>
233 #include <linux/random.h>
234 #include <linux/poll.h>
235 #include <linux/init.h>
236 #include <linux/fs.h>
237 #include <linux/genhd.h>
238 #include <linux/interrupt.h>
239 #include <linux/spinlock.h>
240 #include <linux/percpu.h>
241 #include <linux/cryptohash.h>
243 #include <asm/processor.h>
244 #include <asm/uaccess.h>
249 * Configuration information
251 #define INPUT_POOL_WORDS 128
252 #define OUTPUT_POOL_WORDS 32
253 #define SEC_XFER_SIZE 512
256 * The minimum number of bits of entropy before we wake up a read on
257 * /dev/random. Should be enough to do a significant reseed.
259 static int random_read_wakeup_thresh
= 64;
262 * If the entropy count falls under this number of bits, then we
263 * should wake up processes which are selecting or polling on write
264 * access to /dev/random.
266 static int random_write_wakeup_thresh
= 128;
269 * When the input pool goes over trickle_thresh, start dropping most
270 * samples to avoid wasting CPU time and reduce lock contention.
273 static int trickle_thresh __read_mostly
= INPUT_POOL_WORDS
* 28;
275 static DEFINE_PER_CPU(int, trickle_count
) = 0;
278 * A pool of size .poolwords is stirred with a primitive polynomial
279 * of degree .poolwords over GF(2). The taps for various sizes are
280 * defined below. They are chosen to be evenly spaced (minimum RMS
281 * distance from evenly spaced; the numbers in the comments are a
282 * scaled squared error sum) except for the last tap, which is 1 to
283 * get the twisting happening as fast as possible.
285 static struct poolinfo
{
287 int tap1
, tap2
, tap3
, tap4
, tap5
;
288 } poolinfo_table
[] = {
289 /* x^128 + x^103 + x^76 + x^51 +x^25 + x + 1 -- 105 */
290 { 128, 103, 76, 51, 25, 1 },
291 /* x^32 + x^26 + x^20 + x^14 + x^7 + x + 1 -- 15 */
292 { 32, 26, 20, 14, 7, 1 },
294 /* x^2048 + x^1638 + x^1231 + x^819 + x^411 + x + 1 -- 115 */
295 { 2048, 1638, 1231, 819, 411, 1 },
297 /* x^1024 + x^817 + x^615 + x^412 + x^204 + x + 1 -- 290 */
298 { 1024, 817, 615, 412, 204, 1 },
300 /* x^1024 + x^819 + x^616 + x^410 + x^207 + x^2 + 1 -- 115 */
301 { 1024, 819, 616, 410, 207, 2 },
303 /* x^512 + x^411 + x^308 + x^208 + x^104 + x + 1 -- 225 */
304 { 512, 411, 308, 208, 104, 1 },
306 /* x^512 + x^409 + x^307 + x^206 + x^102 + x^2 + 1 -- 95 */
307 { 512, 409, 307, 206, 102, 2 },
308 /* x^512 + x^409 + x^309 + x^205 + x^103 + x^2 + 1 -- 95 */
309 { 512, 409, 309, 205, 103, 2 },
311 /* x^256 + x^205 + x^155 + x^101 + x^52 + x + 1 -- 125 */
312 { 256, 205, 155, 101, 52, 1 },
314 /* x^128 + x^103 + x^78 + x^51 + x^27 + x^2 + 1 -- 70 */
315 { 128, 103, 78, 51, 27, 2 },
317 /* x^64 + x^52 + x^39 + x^26 + x^14 + x + 1 -- 15 */
318 { 64, 52, 39, 26, 14, 1 },
322 #define POOLBITS poolwords*32
323 #define POOLBYTES poolwords*4
326 * For the purposes of better mixing, we use the CRC-32 polynomial as
327 * well to make a twisted Generalized Feedback Shift Reigster
329 * (See M. Matsumoto & Y. Kurita, 1992. Twisted GFSR generators. ACM
330 * Transactions on Modeling and Computer Simulation 2(3):179-194.
331 * Also see M. Matsumoto & Y. Kurita, 1994. Twisted GFSR generators
332 * II. ACM Transactions on Mdeling and Computer Simulation 4:254-266)
334 * Thanks to Colin Plumb for suggesting this.
336 * We have not analyzed the resultant polynomial to prove it primitive;
337 * in fact it almost certainly isn't. Nonetheless, the irreducible factors
338 * of a random large-degree polynomial over GF(2) are more than large enough
339 * that periodicity is not a concern.
341 * The input hash is much less sensitive than the output hash. All
342 * that we want of it is that it be a good non-cryptographic hash;
343 * i.e. it not produce collisions when fed "random" data of the sort
344 * we expect to see. As long as the pool state differs for different
345 * inputs, we have preserved the input entropy and done a good job.
346 * The fact that an intelligent attacker can construct inputs that
347 * will produce controlled alterations to the pool's state is not
348 * important because we don't consider such inputs to contribute any
349 * randomness. The only property we need with respect to them is that
350 * the attacker can't increase his/her knowledge of the pool's state.
351 * Since all additions are reversible (knowing the final state and the
352 * input, you can reconstruct the initial state), if an attacker has
353 * any uncertainty about the initial state, he/she can only shuffle
354 * that uncertainty about, but never cause any collisions (which would
355 * decrease the uncertainty).
357 * The chosen system lets the state of the pool be (essentially) the input
358 * modulo the generator polymnomial. Now, for random primitive polynomials,
359 * this is a universal class of hash functions, meaning that the chance
360 * of a collision is limited by the attacker's knowledge of the generator
361 * polynomail, so if it is chosen at random, an attacker can never force
362 * a collision. Here, we use a fixed polynomial, but we *can* assume that
363 * ###--> it is unknown to the processes generating the input entropy. <-###
364 * Because of this important property, this is a good, collision-resistant
365 * hash; hash collisions will occur no more often than chance.
369 * Static global variables
371 static DECLARE_WAIT_QUEUE_HEAD(random_read_wait
);
372 static DECLARE_WAIT_QUEUE_HEAD(random_write_wait
);
375 static int debug
= 0;
376 module_param(debug
, bool, 0644);
377 #define DEBUG_ENT(fmt, arg...) do { if (debug) \
378 printk(KERN_DEBUG "random %04d %04d %04d: " \
380 input_pool.entropy_count,\
381 blocking_pool.entropy_count,\
382 nonblocking_pool.entropy_count,\
385 #define DEBUG_ENT(fmt, arg...) do {} while (0)
388 /**********************************************************************
390 * OS independent entropy store. Here are the functions which handle
391 * storing entropy in an entropy pool.
393 **********************************************************************/
395 struct entropy_store
;
396 struct entropy_store
{
397 /* mostly-read data: */
398 struct poolinfo
*poolinfo
;
402 struct entropy_store
*pull
;
404 /* read-write data: */
405 spinlock_t lock ____cacheline_aligned_in_smp
;
411 static __u32 input_pool_data
[INPUT_POOL_WORDS
];
412 static __u32 blocking_pool_data
[OUTPUT_POOL_WORDS
];
413 static __u32 nonblocking_pool_data
[OUTPUT_POOL_WORDS
];
415 static struct entropy_store input_pool
= {
416 .poolinfo
= &poolinfo_table
[0],
419 .lock
= __SPIN_LOCK_UNLOCKED(&input_pool
.lock
),
420 .pool
= input_pool_data
423 static struct entropy_store blocking_pool
= {
424 .poolinfo
= &poolinfo_table
[1],
428 .lock
= __SPIN_LOCK_UNLOCKED(&blocking_pool
.lock
),
429 .pool
= blocking_pool_data
432 static struct entropy_store nonblocking_pool
= {
433 .poolinfo
= &poolinfo_table
[1],
434 .name
= "nonblocking",
436 .lock
= __SPIN_LOCK_UNLOCKED(&nonblocking_pool
.lock
),
437 .pool
= nonblocking_pool_data
441 * This function adds a byte into the entropy "pool". It does not
442 * update the entropy estimate. The caller should call
443 * credit_entropy_store if this is appropriate.
445 * The pool is stirred with a primitive polynomial of the appropriate
446 * degree, and then twisted. We twist by three bits at a time because
447 * it's cheap to do so and helps slightly in the expected case where
448 * the entropy is concentrated in the low-order bits.
450 static void __add_entropy_words(struct entropy_store
*r
, const __u32
*in
,
451 int nwords
, __u32 out
[16])
453 static __u32
const twist_table
[8] = {
454 0x00000000, 0x3b6e20c8, 0x76dc4190, 0x4db26158,
455 0xedb88320, 0xd6d6a3e8, 0x9b64c2b0, 0xa00ae278 };
456 unsigned long i
, add_ptr
, tap1
, tap2
, tap3
, tap4
, tap5
;
457 int new_rotate
, input_rotate
;
458 int wordmask
= r
->poolinfo
->poolwords
- 1;
462 /* Taps are constant, so we can load them without holding r->lock. */
463 tap1
= r
->poolinfo
->tap1
;
464 tap2
= r
->poolinfo
->tap2
;
465 tap3
= r
->poolinfo
->tap3
;
466 tap4
= r
->poolinfo
->tap4
;
467 tap5
= r
->poolinfo
->tap5
;
470 spin_lock_irqsave(&r
->lock
, flags
);
471 prefetch_range(r
->pool
, wordmask
);
472 input_rotate
= r
->input_rotate
;
473 add_ptr
= r
->add_ptr
;
476 w
= rol32(next_w
, input_rotate
);
479 i
= add_ptr
= (add_ptr
- 1) & wordmask
;
481 * Normally, we add 7 bits of rotation to the pool.
482 * At the beginning of the pool, add an extra 7 bits
483 * rotation, so that successive passes spread the
484 * input bits across the pool evenly.
486 new_rotate
= input_rotate
+ 14;
488 new_rotate
= input_rotate
+ 7;
489 input_rotate
= new_rotate
& 31;
491 /* XOR in the various taps */
492 w
^= r
->pool
[(i
+ tap1
) & wordmask
];
493 w
^= r
->pool
[(i
+ tap2
) & wordmask
];
494 w
^= r
->pool
[(i
+ tap3
) & wordmask
];
495 w
^= r
->pool
[(i
+ tap4
) & wordmask
];
496 w
^= r
->pool
[(i
+ tap5
) & wordmask
];
498 r
->pool
[i
] = (w
>> 3) ^ twist_table
[w
& 7];
501 r
->input_rotate
= input_rotate
;
502 r
->add_ptr
= add_ptr
;
505 for (i
= 0; i
< 16; i
++) {
506 out
[i
] = r
->pool
[add_ptr
];
507 add_ptr
= (add_ptr
- 1) & wordmask
;
511 spin_unlock_irqrestore(&r
->lock
, flags
);
514 static inline void add_entropy_words(struct entropy_store
*r
, const __u32
*in
,
517 __add_entropy_words(r
, in
, nwords
, NULL
);
521 * Credit (or debit) the entropy store with n bits of entropy
523 static void credit_entropy_store(struct entropy_store
*r
, int nbits
)
527 spin_lock_irqsave(&r
->lock
, flags
);
529 if (r
->entropy_count
+ nbits
< 0) {
530 DEBUG_ENT("negative entropy/overflow (%d+%d)\n",
531 r
->entropy_count
, nbits
);
532 r
->entropy_count
= 0;
533 } else if (r
->entropy_count
+ nbits
> r
->poolinfo
->POOLBITS
) {
534 r
->entropy_count
= r
->poolinfo
->POOLBITS
;
536 r
->entropy_count
+= nbits
;
538 DEBUG_ENT("added %d entropy credits to %s\n",
542 spin_unlock_irqrestore(&r
->lock
, flags
);
545 /*********************************************************************
547 * Entropy input management
549 *********************************************************************/
551 /* There is one of these per entropy source */
552 struct timer_rand_state
{
554 long last_delta
,last_delta2
;
555 unsigned dont_count_entropy
:1;
558 static struct timer_rand_state input_timer_state
;
559 static struct timer_rand_state
*irq_timer_state
[NR_IRQS
];
562 * This function adds entropy to the entropy "pool" by using timing
563 * delays. It uses the timer_rand_state structure to make an estimate
564 * of how many bits of entropy this call has added to the pool.
566 * The number "num" is also added to the pool - it should somehow describe
567 * the type of event which just happened. This is currently 0-255 for
568 * keyboard scan codes, and 256 upwards for interrupts.
571 static void add_timer_randomness(struct timer_rand_state
*state
, unsigned num
)
578 long delta
, delta2
, delta3
;
581 /* if over the trickle threshold, use only 1 in 4096 samples */
582 if (input_pool
.entropy_count
> trickle_thresh
&&
583 (__get_cpu_var(trickle_count
)++ & 0xfff))
586 sample
.jiffies
= jiffies
;
587 sample
.cycles
= get_cycles();
589 add_entropy_words(&input_pool
, (u32
*)&sample
, sizeof(sample
)/4);
592 * Calculate number of bits of randomness we probably added.
593 * We take into account the first, second and third-order deltas
594 * in order to make our estimate.
597 if (!state
->dont_count_entropy
) {
598 delta
= sample
.jiffies
- state
->last_time
;
599 state
->last_time
= sample
.jiffies
;
601 delta2
= delta
- state
->last_delta
;
602 state
->last_delta
= delta
;
604 delta3
= delta2
- state
->last_delta2
;
605 state
->last_delta2
= delta2
;
619 * delta is now minimum absolute delta.
620 * Round down by 1 bit on general principles,
621 * and limit entropy entimate to 12 bits.
623 credit_entropy_store(&input_pool
,
624 min_t(int, fls(delta
>>1), 11));
627 if(input_pool
.entropy_count
>= random_read_wakeup_thresh
)
628 wake_up_interruptible(&random_read_wait
);
634 void add_input_randomness(unsigned int type
, unsigned int code
,
637 static unsigned char last_value
;
639 /* ignore autorepeat and the like */
640 if (value
== last_value
)
643 DEBUG_ENT("input event\n");
645 add_timer_randomness(&input_timer_state
,
646 (type
<< 4) ^ code
^ (code
>> 4) ^ value
);
648 EXPORT_SYMBOL_GPL(add_input_randomness
);
650 void add_interrupt_randomness(int irq
)
652 if (irq
>= NR_IRQS
|| irq_timer_state
[irq
] == 0)
655 DEBUG_ENT("irq event %d\n", irq
);
656 add_timer_randomness(irq_timer_state
[irq
], 0x100 + irq
);
660 void add_disk_randomness(struct gendisk
*disk
)
662 if (!disk
|| !disk
->random
)
664 /* first major is 1, so we get >= 0x200 here */
665 DEBUG_ENT("disk event %d:%d\n", disk
->major
, disk
->first_minor
);
667 add_timer_randomness(disk
->random
,
668 0x100 + MKDEV(disk
->major
, disk
->first_minor
));
671 EXPORT_SYMBOL(add_disk_randomness
);
674 #define EXTRACT_SIZE 10
676 /*********************************************************************
678 * Entropy extraction routines
680 *********************************************************************/
682 static ssize_t
extract_entropy(struct entropy_store
*r
, void * buf
,
683 size_t nbytes
, int min
, int rsvd
);
686 * This utility inline function is responsible for transfering entropy
687 * from the primary pool to the secondary extraction pool. We make
688 * sure we pull enough for a 'catastrophic reseed'.
690 static void xfer_secondary_pool(struct entropy_store
*r
, size_t nbytes
)
692 __u32 tmp
[OUTPUT_POOL_WORDS
];
694 if (r
->pull
&& r
->entropy_count
< nbytes
* 8 &&
695 r
->entropy_count
< r
->poolinfo
->POOLBITS
) {
696 int bytes
= max_t(int, random_read_wakeup_thresh
/ 8,
697 min_t(int, nbytes
, sizeof(tmp
)));
698 int rsvd
= r
->limit
? 0 : random_read_wakeup_thresh
/4;
700 DEBUG_ENT("going to reseed %s with %d bits "
701 "(%d of %d requested)\n",
702 r
->name
, bytes
* 8, nbytes
* 8, r
->entropy_count
);
704 bytes
=extract_entropy(r
->pull
, tmp
, bytes
,
705 random_read_wakeup_thresh
/ 8, rsvd
);
706 add_entropy_words(r
, tmp
, (bytes
+ 3) / 4);
707 credit_entropy_store(r
, bytes
*8);
712 * These functions extracts randomness from the "entropy pool", and
713 * returns it in a buffer.
715 * The min parameter specifies the minimum amount we can pull before
716 * failing to avoid races that defeat catastrophic reseeding while the
717 * reserved parameter indicates how much entropy we must leave in the
718 * pool after each pull to avoid starving other readers.
720 * Note: extract_entropy() assumes that .poolwords is a multiple of 16 words.
723 static size_t account(struct entropy_store
*r
, size_t nbytes
, int min
,
728 BUG_ON(r
->entropy_count
> r
->poolinfo
->POOLBITS
);
730 /* Hold lock while accounting */
731 spin_lock_irqsave(&r
->lock
, flags
);
733 DEBUG_ENT("trying to extract %d bits from %s\n",
734 nbytes
* 8, r
->name
);
736 /* Can we pull enough? */
737 if (r
->entropy_count
/ 8 < min
+ reserved
) {
740 /* If limited, never pull more than available */
741 if (r
->limit
&& nbytes
+ reserved
>= r
->entropy_count
/ 8)
742 nbytes
= r
->entropy_count
/8 - reserved
;
744 if(r
->entropy_count
/ 8 >= nbytes
+ reserved
)
745 r
->entropy_count
-= nbytes
*8;
747 r
->entropy_count
= reserved
;
749 if (r
->entropy_count
< random_write_wakeup_thresh
)
750 wake_up_interruptible(&random_write_wait
);
753 DEBUG_ENT("debiting %d entropy credits from %s%s\n",
754 nbytes
* 8, r
->name
, r
->limit
? "" : " (unlimited)");
756 spin_unlock_irqrestore(&r
->lock
, flags
);
761 static void extract_buf(struct entropy_store
*r
, __u8
*out
)
764 __u32 data
[16], buf
[5 + SHA_WORKSPACE_WORDS
];
768 * As we hash the pool, we mix intermediate values of
769 * the hash back into the pool. This eliminates
770 * backtracking attacks (where the attacker knows
771 * the state of the pool plus the current outputs, and
772 * attempts to find previous ouputs), unless the hash
773 * function can be inverted.
775 for (i
= 0; i
< r
->poolinfo
->poolwords
; i
+= 16) {
776 /* hash blocks of 16 words = 512 bits */
777 sha_transform(buf
, (__u8
*)(r
->pool
+ i
), buf
+ 5);
778 /* feed back portion of the resulting hash */
779 add_entropy_words(r
, &buf
[i
% 5], 1);
783 * To avoid duplicates, we atomically extract a
784 * portion of the pool while mixing, and hash one
787 __add_entropy_words(r
, &buf
[i
% 5], 1, data
);
788 sha_transform(buf
, (__u8
*)data
, buf
+ 5);
791 * In case the hash function has some recognizable
792 * output pattern, we fold it in half.
797 buf
[2] ^= rol32(buf
[2], 16);
798 memcpy(out
, buf
, EXTRACT_SIZE
);
799 memset(buf
, 0, sizeof(buf
));
802 static ssize_t
extract_entropy(struct entropy_store
*r
, void * buf
,
803 size_t nbytes
, int min
, int reserved
)
806 __u8 tmp
[EXTRACT_SIZE
];
808 xfer_secondary_pool(r
, nbytes
);
809 nbytes
= account(r
, nbytes
, min
, reserved
);
813 i
= min_t(int, nbytes
, EXTRACT_SIZE
);
820 /* Wipe data just returned from memory */
821 memset(tmp
, 0, sizeof(tmp
));
826 static ssize_t
extract_entropy_user(struct entropy_store
*r
, void __user
*buf
,
830 __u8 tmp
[EXTRACT_SIZE
];
832 xfer_secondary_pool(r
, nbytes
);
833 nbytes
= account(r
, nbytes
, 0, 0);
836 if (need_resched()) {
837 if (signal_pending(current
)) {
846 i
= min_t(int, nbytes
, EXTRACT_SIZE
);
847 if (copy_to_user(buf
, tmp
, i
)) {
857 /* Wipe data just returned from memory */
858 memset(tmp
, 0, sizeof(tmp
));
864 * This function is the exported kernel interface. It returns some
865 * number of good random numbers, suitable for seeding TCP sequence
868 void get_random_bytes(void *buf
, int nbytes
)
870 extract_entropy(&nonblocking_pool
, buf
, nbytes
, 0, 0);
873 EXPORT_SYMBOL(get_random_bytes
);
876 * init_std_data - initialize pool with system data
878 * @r: pool to initialize
880 * This function clears the pool's entropy count and mixes some system
881 * data into the pool to prepare it for use. The pool is not cleared
882 * as that can only decrease the entropy in the pool.
884 static void init_std_data(struct entropy_store
*r
)
889 spin_lock_irqsave(&r
->lock
, flags
);
890 r
->entropy_count
= 0;
891 spin_unlock_irqrestore(&r
->lock
, flags
);
893 now
= ktime_get_real();
894 add_entropy_words(r
, (__u32
*)&now
, sizeof(now
)/4);
895 add_entropy_words(r
, (__u32
*)utsname(),
896 sizeof(*(utsname()))/4);
899 static int __init
rand_initialize(void)
901 init_std_data(&input_pool
);
902 init_std_data(&blocking_pool
);
903 init_std_data(&nonblocking_pool
);
906 module_init(rand_initialize
);
908 void rand_initialize_irq(int irq
)
910 struct timer_rand_state
*state
;
912 if (irq
>= NR_IRQS
|| irq_timer_state
[irq
])
916 * If kzalloc returns null, we just won't use that entropy
919 state
= kzalloc(sizeof(struct timer_rand_state
), GFP_KERNEL
);
921 irq_timer_state
[irq
] = state
;
925 void rand_initialize_disk(struct gendisk
*disk
)
927 struct timer_rand_state
*state
;
930 * If kzalloc returns null, we just won't use that entropy
933 state
= kzalloc(sizeof(struct timer_rand_state
), GFP_KERNEL
);
935 disk
->random
= state
;
940 random_read(struct file
* file
, char __user
* buf
, size_t nbytes
, loff_t
*ppos
)
942 ssize_t n
, retval
= 0, count
= 0;
949 if (n
> SEC_XFER_SIZE
)
952 DEBUG_ENT("reading %d bits\n", n
*8);
954 n
= extract_entropy_user(&blocking_pool
, buf
, n
);
956 DEBUG_ENT("read got %d bits (%d still needed)\n",
960 if (file
->f_flags
& O_NONBLOCK
) {
965 DEBUG_ENT("sleeping?\n");
967 wait_event_interruptible(random_read_wait
,
968 input_pool
.entropy_count
>=
969 random_read_wakeup_thresh
);
971 DEBUG_ENT("awake\n");
973 if (signal_pending(current
)) {
974 retval
= -ERESTARTSYS
;
988 break; /* This break makes the device work */
989 /* like a named pipe */
993 * If we gave the user some bytes, update the access time.
998 return (count
? count
: retval
);
1002 urandom_read(struct file
* file
, char __user
* buf
,
1003 size_t nbytes
, loff_t
*ppos
)
1005 return extract_entropy_user(&nonblocking_pool
, buf
, nbytes
);
1009 random_poll(struct file
*file
, poll_table
* wait
)
1013 poll_wait(file
, &random_read_wait
, wait
);
1014 poll_wait(file
, &random_write_wait
, wait
);
1016 if (input_pool
.entropy_count
>= random_read_wakeup_thresh
)
1017 mask
|= POLLIN
| POLLRDNORM
;
1018 if (input_pool
.entropy_count
< random_write_wakeup_thresh
)
1019 mask
|= POLLOUT
| POLLWRNORM
;
1024 write_pool(struct entropy_store
*r
, const char __user
*buffer
, size_t count
)
1028 const char __user
*p
= buffer
;
1031 bytes
= min(count
, sizeof(buf
));
1032 if (copy_from_user(&buf
, p
, bytes
))
1038 add_entropy_words(r
, buf
, (bytes
+ 3) / 4);
1045 random_write(struct file
* file
, const char __user
* buffer
,
1046 size_t count
, loff_t
*ppos
)
1049 struct inode
*inode
= file
->f_path
.dentry
->d_inode
;
1051 ret
= write_pool(&blocking_pool
, buffer
, count
);
1054 ret
= write_pool(&nonblocking_pool
, buffer
, count
);
1058 inode
->i_mtime
= current_fs_time(inode
->i_sb
);
1059 mark_inode_dirty(inode
);
1060 return (ssize_t
)count
;
1064 random_ioctl(struct inode
* inode
, struct file
* file
,
1065 unsigned int cmd
, unsigned long arg
)
1067 int size
, ent_count
;
1068 int __user
*p
= (int __user
*)arg
;
1073 ent_count
= input_pool
.entropy_count
;
1074 if (put_user(ent_count
, p
))
1077 case RNDADDTOENTCNT
:
1078 if (!capable(CAP_SYS_ADMIN
))
1080 if (get_user(ent_count
, p
))
1082 credit_entropy_store(&input_pool
, ent_count
);
1084 * Wake up waiting processes if we have enough
1087 if (input_pool
.entropy_count
>= random_read_wakeup_thresh
)
1088 wake_up_interruptible(&random_read_wait
);
1091 if (!capable(CAP_SYS_ADMIN
))
1093 if (get_user(ent_count
, p
++))
1097 if (get_user(size
, p
++))
1099 retval
= write_pool(&input_pool
, (const char __user
*)p
,
1103 credit_entropy_store(&input_pool
, ent_count
);
1105 * Wake up waiting processes if we have enough
1108 if (input_pool
.entropy_count
>= random_read_wakeup_thresh
)
1109 wake_up_interruptible(&random_read_wait
);
1113 /* Clear the entropy pool counters. */
1114 if (!capable(CAP_SYS_ADMIN
))
1116 init_std_data(&input_pool
);
1117 init_std_data(&blocking_pool
);
1118 init_std_data(&nonblocking_pool
);
1125 const struct file_operations random_fops
= {
1126 .read
= random_read
,
1127 .write
= random_write
,
1128 .poll
= random_poll
,
1129 .ioctl
= random_ioctl
,
1132 const struct file_operations urandom_fops
= {
1133 .read
= urandom_read
,
1134 .write
= random_write
,
1135 .ioctl
= random_ioctl
,
1138 /***************************************************************
1139 * Random UUID interface
1141 * Used here for a Boot ID, but can be useful for other kernel
1143 ***************************************************************/
1146 * Generate random UUID
1148 void generate_random_uuid(unsigned char uuid_out
[16])
1150 get_random_bytes(uuid_out
, 16);
1151 /* Set UUID version to 4 --- truely random generation */
1152 uuid_out
[6] = (uuid_out
[6] & 0x0F) | 0x40;
1153 /* Set the UUID variant to DCE */
1154 uuid_out
[8] = (uuid_out
[8] & 0x3F) | 0x80;
1157 EXPORT_SYMBOL(generate_random_uuid
);
1159 /********************************************************************
1163 ********************************************************************/
1165 #ifdef CONFIG_SYSCTL
1167 #include <linux/sysctl.h>
1169 static int min_read_thresh
= 8, min_write_thresh
;
1170 static int max_read_thresh
= INPUT_POOL_WORDS
* 32;
1171 static int max_write_thresh
= INPUT_POOL_WORDS
* 32;
1172 static char sysctl_bootid
[16];
1175 * These functions is used to return both the bootid UUID, and random
1176 * UUID. The difference is in whether table->data is NULL; if it is,
1177 * then a new UUID is generated and returned to the user.
1179 * If the user accesses this via the proc interface, it will be returned
1180 * as an ASCII string in the standard UUID format. If accesses via the
1181 * sysctl system call, it is returned as 16 bytes of binary data.
1183 static int proc_do_uuid(ctl_table
*table
, int write
, struct file
*filp
,
1184 void __user
*buffer
, size_t *lenp
, loff_t
*ppos
)
1186 ctl_table fake_table
;
1187 unsigned char buf
[64], tmp_uuid
[16], *uuid
;
1195 generate_random_uuid(uuid
);
1197 sprintf(buf
, "%02x%02x%02x%02x-%02x%02x-%02x%02x-%02x%02x-"
1198 "%02x%02x%02x%02x%02x%02x",
1199 uuid
[0], uuid
[1], uuid
[2], uuid
[3],
1200 uuid
[4], uuid
[5], uuid
[6], uuid
[7],
1201 uuid
[8], uuid
[9], uuid
[10], uuid
[11],
1202 uuid
[12], uuid
[13], uuid
[14], uuid
[15]);
1203 fake_table
.data
= buf
;
1204 fake_table
.maxlen
= sizeof(buf
);
1206 return proc_dostring(&fake_table
, write
, filp
, buffer
, lenp
, ppos
);
1209 static int uuid_strategy(ctl_table
*table
, int __user
*name
, int nlen
,
1210 void __user
*oldval
, size_t __user
*oldlenp
,
1211 void __user
*newval
, size_t newlen
)
1213 unsigned char tmp_uuid
[16], *uuid
;
1216 if (!oldval
|| !oldlenp
)
1225 generate_random_uuid(uuid
);
1227 if (get_user(len
, oldlenp
))
1232 if (copy_to_user(oldval
, uuid
, len
) ||
1233 put_user(len
, oldlenp
))
1239 static int sysctl_poolsize
= INPUT_POOL_WORDS
* 32;
1240 ctl_table random_table
[] = {
1242 .ctl_name
= RANDOM_POOLSIZE
,
1243 .procname
= "poolsize",
1244 .data
= &sysctl_poolsize
,
1245 .maxlen
= sizeof(int),
1247 .proc_handler
= &proc_dointvec
,
1250 .ctl_name
= RANDOM_ENTROPY_COUNT
,
1251 .procname
= "entropy_avail",
1252 .maxlen
= sizeof(int),
1254 .proc_handler
= &proc_dointvec
,
1255 .data
= &input_pool
.entropy_count
,
1258 .ctl_name
= RANDOM_READ_THRESH
,
1259 .procname
= "read_wakeup_threshold",
1260 .data
= &random_read_wakeup_thresh
,
1261 .maxlen
= sizeof(int),
1263 .proc_handler
= &proc_dointvec_minmax
,
1264 .strategy
= &sysctl_intvec
,
1265 .extra1
= &min_read_thresh
,
1266 .extra2
= &max_read_thresh
,
1269 .ctl_name
= RANDOM_WRITE_THRESH
,
1270 .procname
= "write_wakeup_threshold",
1271 .data
= &random_write_wakeup_thresh
,
1272 .maxlen
= sizeof(int),
1274 .proc_handler
= &proc_dointvec_minmax
,
1275 .strategy
= &sysctl_intvec
,
1276 .extra1
= &min_write_thresh
,
1277 .extra2
= &max_write_thresh
,
1280 .ctl_name
= RANDOM_BOOT_ID
,
1281 .procname
= "boot_id",
1282 .data
= &sysctl_bootid
,
1285 .proc_handler
= &proc_do_uuid
,
1286 .strategy
= &uuid_strategy
,
1289 .ctl_name
= RANDOM_UUID
,
1293 .proc_handler
= &proc_do_uuid
,
1294 .strategy
= &uuid_strategy
,
1298 #endif /* CONFIG_SYSCTL */
1300 /********************************************************************
1302 * Random funtions for networking
1304 ********************************************************************/
1307 * TCP initial sequence number picking. This uses the random number
1308 * generator to pick an initial secret value. This value is hashed
1309 * along with the TCP endpoint information to provide a unique
1310 * starting point for each pair of TCP endpoints. This defeats
1311 * attacks which rely on guessing the initial TCP sequence number.
1312 * This algorithm was suggested by Steve Bellovin.
1314 * Using a very strong hash was taking an appreciable amount of the total
1315 * TCP connection establishment time, so this is a weaker hash,
1316 * compensated for by changing the secret periodically.
1319 /* F, G and H are basic MD4 functions: selection, majority, parity */
1320 #define F(x, y, z) ((z) ^ ((x) & ((y) ^ (z))))
1321 #define G(x, y, z) (((x) & (y)) + (((x) ^ (y)) & (z)))
1322 #define H(x, y, z) ((x) ^ (y) ^ (z))
1325 * The generic round function. The application is so specific that
1326 * we don't bother protecting all the arguments with parens, as is generally
1327 * good macro practice, in favor of extra legibility.
1328 * Rotation is separate from addition to prevent recomputation
1330 #define ROUND(f, a, b, c, d, x, s) \
1331 (a += f(b, c, d) + x, a = (a << s) | (a >> (32 - s)))
1333 #define K2 013240474631UL
1334 #define K3 015666365641UL
1336 #if defined(CONFIG_IPV6) || defined(CONFIG_IPV6_MODULE)
1338 static __u32
twothirdsMD4Transform (__u32
const buf
[4], __u32
const in
[12])
1340 __u32 a
= buf
[0], b
= buf
[1], c
= buf
[2], d
= buf
[3];
1343 ROUND(F
, a
, b
, c
, d
, in
[ 0] + K1
, 3);
1344 ROUND(F
, d
, a
, b
, c
, in
[ 1] + K1
, 7);
1345 ROUND(F
, c
, d
, a
, b
, in
[ 2] + K1
, 11);
1346 ROUND(F
, b
, c
, d
, a
, in
[ 3] + K1
, 19);
1347 ROUND(F
, a
, b
, c
, d
, in
[ 4] + K1
, 3);
1348 ROUND(F
, d
, a
, b
, c
, in
[ 5] + K1
, 7);
1349 ROUND(F
, c
, d
, a
, b
, in
[ 6] + K1
, 11);
1350 ROUND(F
, b
, c
, d
, a
, in
[ 7] + K1
, 19);
1351 ROUND(F
, a
, b
, c
, d
, in
[ 8] + K1
, 3);
1352 ROUND(F
, d
, a
, b
, c
, in
[ 9] + K1
, 7);
1353 ROUND(F
, c
, d
, a
, b
, in
[10] + K1
, 11);
1354 ROUND(F
, b
, c
, d
, a
, in
[11] + K1
, 19);
1357 ROUND(G
, a
, b
, c
, d
, in
[ 1] + K2
, 3);
1358 ROUND(G
, d
, a
, b
, c
, in
[ 3] + K2
, 5);
1359 ROUND(G
, c
, d
, a
, b
, in
[ 5] + K2
, 9);
1360 ROUND(G
, b
, c
, d
, a
, in
[ 7] + K2
, 13);
1361 ROUND(G
, a
, b
, c
, d
, in
[ 9] + K2
, 3);
1362 ROUND(G
, d
, a
, b
, c
, in
[11] + K2
, 5);
1363 ROUND(G
, c
, d
, a
, b
, in
[ 0] + K2
, 9);
1364 ROUND(G
, b
, c
, d
, a
, in
[ 2] + K2
, 13);
1365 ROUND(G
, a
, b
, c
, d
, in
[ 4] + K2
, 3);
1366 ROUND(G
, d
, a
, b
, c
, in
[ 6] + K2
, 5);
1367 ROUND(G
, c
, d
, a
, b
, in
[ 8] + K2
, 9);
1368 ROUND(G
, b
, c
, d
, a
, in
[10] + K2
, 13);
1371 ROUND(H
, a
, b
, c
, d
, in
[ 3] + K3
, 3);
1372 ROUND(H
, d
, a
, b
, c
, in
[ 7] + K3
, 9);
1373 ROUND(H
, c
, d
, a
, b
, in
[11] + K3
, 11);
1374 ROUND(H
, b
, c
, d
, a
, in
[ 2] + K3
, 15);
1375 ROUND(H
, a
, b
, c
, d
, in
[ 6] + K3
, 3);
1376 ROUND(H
, d
, a
, b
, c
, in
[10] + K3
, 9);
1377 ROUND(H
, c
, d
, a
, b
, in
[ 1] + K3
, 11);
1378 ROUND(H
, b
, c
, d
, a
, in
[ 5] + K3
, 15);
1379 ROUND(H
, a
, b
, c
, d
, in
[ 9] + K3
, 3);
1380 ROUND(H
, d
, a
, b
, c
, in
[ 0] + K3
, 9);
1381 ROUND(H
, c
, d
, a
, b
, in
[ 4] + K3
, 11);
1382 ROUND(H
, b
, c
, d
, a
, in
[ 8] + K3
, 15);
1384 return buf
[1] + b
; /* "most hashed" word */
1385 /* Alternative: return sum of all words? */
1397 /* This should not be decreased so low that ISNs wrap too fast. */
1398 #define REKEY_INTERVAL (300 * HZ)
1400 * Bit layout of the tcp sequence numbers (before adding current time):
1401 * bit 24-31: increased after every key exchange
1402 * bit 0-23: hash(source,dest)
1404 * The implementation is similar to the algorithm described
1405 * in the Appendix of RFC 1185, except that
1406 * - it uses a 1 MHz clock instead of a 250 kHz clock
1407 * - it performs a rekey every 5 minutes, which is equivalent
1408 * to a (source,dest) tulple dependent forward jump of the
1409 * clock by 0..2^(HASH_BITS+1)
1411 * Thus the average ISN wraparound time is 68 minutes instead of
1414 * SMP cleanup and lock avoidance with poor man's RCU.
1415 * Manfred Spraul <manfred@colorfullife.com>
1418 #define COUNT_BITS 8
1419 #define COUNT_MASK ((1 << COUNT_BITS) - 1)
1420 #define HASH_BITS 24
1421 #define HASH_MASK ((1 << HASH_BITS) - 1)
1423 static struct keydata
{
1424 __u32 count
; /* already shifted to the final position */
1426 } ____cacheline_aligned ip_keydata
[2];
1428 static unsigned int ip_cnt
;
1430 static void rekey_seq_generator(struct work_struct
*work
);
1432 static DECLARE_DELAYED_WORK(rekey_work
, rekey_seq_generator
);
1436 * The ISN generation runs lockless - it's just a hash over random data.
1437 * State changes happen every 5 minutes when the random key is replaced.
1438 * Synchronization is performed by having two copies of the hash function
1439 * state and rekey_seq_generator always updates the inactive copy.
1440 * The copy is then activated by updating ip_cnt.
1441 * The implementation breaks down if someone blocks the thread
1442 * that processes SYN requests for more than 5 minutes. Should never
1443 * happen, and even if that happens only a not perfectly compliant
1444 * ISN is generated, nothing fatal.
1446 static void rekey_seq_generator(struct work_struct
*work
)
1448 struct keydata
*keyptr
= &ip_keydata
[1 ^ (ip_cnt
& 1)];
1450 get_random_bytes(keyptr
->secret
, sizeof(keyptr
->secret
));
1451 keyptr
->count
= (ip_cnt
& COUNT_MASK
) << HASH_BITS
;
1454 schedule_delayed_work(&rekey_work
, REKEY_INTERVAL
);
1457 static inline struct keydata
*get_keyptr(void)
1459 struct keydata
*keyptr
= &ip_keydata
[ip_cnt
& 1];
1466 static __init
int seqgen_init(void)
1468 rekey_seq_generator(NULL
);
1471 late_initcall(seqgen_init
);
1473 #if defined(CONFIG_IPV6) || defined(CONFIG_IPV6_MODULE)
1474 __u32
secure_tcpv6_sequence_number(__be32
*saddr
, __be32
*daddr
,
1475 __be16 sport
, __be16 dport
)
1479 struct keydata
*keyptr
= get_keyptr();
1481 /* The procedure is the same as for IPv4, but addresses are longer.
1482 * Thus we must use twothirdsMD4Transform.
1485 memcpy(hash
, saddr
, 16);
1486 hash
[4]=((__force u16
)sport
<< 16) + (__force u16
)dport
;
1487 memcpy(&hash
[5],keyptr
->secret
,sizeof(__u32
) * 7);
1489 seq
= twothirdsMD4Transform((const __u32
*)daddr
, hash
) & HASH_MASK
;
1490 seq
+= keyptr
->count
;
1492 seq
+= ktime_get_real().tv64
;
1496 EXPORT_SYMBOL(secure_tcpv6_sequence_number
);
1499 /* The code below is shamelessly stolen from secure_tcp_sequence_number().
1500 * All blames to Andrey V. Savochkin <saw@msu.ru>.
1502 __u32
secure_ip_id(__be32 daddr
)
1504 struct keydata
*keyptr
;
1507 keyptr
= get_keyptr();
1510 * Pick a unique starting offset for each IP destination.
1511 * The dest ip address is placed in the starting vector,
1512 * which is then hashed with random data.
1514 hash
[0] = (__force __u32
)daddr
;
1515 hash
[1] = keyptr
->secret
[9];
1516 hash
[2] = keyptr
->secret
[10];
1517 hash
[3] = keyptr
->secret
[11];
1519 return half_md4_transform(hash
, keyptr
->secret
);
1524 __u32
secure_tcp_sequence_number(__be32 saddr
, __be32 daddr
,
1525 __be16 sport
, __be16 dport
)
1529 struct keydata
*keyptr
= get_keyptr();
1532 * Pick a unique starting offset for each TCP connection endpoints
1533 * (saddr, daddr, sport, dport).
1534 * Note that the words are placed into the starting vector, which is
1535 * then mixed with a partial MD4 over random data.
1537 hash
[0]=(__force u32
)saddr
;
1538 hash
[1]=(__force u32
)daddr
;
1539 hash
[2]=((__force u16
)sport
<< 16) + (__force u16
)dport
;
1540 hash
[3]=keyptr
->secret
[11];
1542 seq
= half_md4_transform(hash
, keyptr
->secret
) & HASH_MASK
;
1543 seq
+= keyptr
->count
;
1545 * As close as possible to RFC 793, which
1546 * suggests using a 250 kHz clock.
1547 * Further reading shows this assumes 2 Mb/s networks.
1548 * For 10 Gb/s Ethernet, a 1 GHz clock is appropriate.
1549 * That's funny, Linux has one built in! Use it!
1550 * (Networks are faster now - should this be increased?)
1552 seq
+= ktime_get_real().tv64
;
1554 printk("init_seq(%lx, %lx, %d, %d) = %d\n",
1555 saddr
, daddr
, sport
, dport
, seq
);
1560 /* Generate secure starting point for ephemeral IPV4 transport port search */
1561 u32
secure_ipv4_port_ephemeral(__be32 saddr
, __be32 daddr
, __be16 dport
)
1563 struct keydata
*keyptr
= get_keyptr();
1567 * Pick a unique starting offset for each ephemeral port search
1568 * (saddr, daddr, dport) and 48bits of random data.
1570 hash
[0] = (__force u32
)saddr
;
1571 hash
[1] = (__force u32
)daddr
;
1572 hash
[2] = (__force u32
)dport
^ keyptr
->secret
[10];
1573 hash
[3] = keyptr
->secret
[11];
1575 return half_md4_transform(hash
, keyptr
->secret
);
1578 #if defined(CONFIG_IPV6) || defined(CONFIG_IPV6_MODULE)
1579 u32
secure_ipv6_port_ephemeral(const __be32
*saddr
, const __be32
*daddr
, __be16 dport
)
1581 struct keydata
*keyptr
= get_keyptr();
1584 memcpy(hash
, saddr
, 16);
1585 hash
[4] = (__force u32
)dport
;
1586 memcpy(&hash
[5],keyptr
->secret
,sizeof(__u32
) * 7);
1588 return twothirdsMD4Transform((const __u32
*)daddr
, hash
);
1592 #if defined(CONFIG_IP_DCCP) || defined(CONFIG_IP_DCCP_MODULE)
1593 /* Similar to secure_tcp_sequence_number but generate a 48 bit value
1594 * bit's 32-47 increase every key exchange
1595 * 0-31 hash(source, dest)
1597 u64
secure_dccp_sequence_number(__be32 saddr
, __be32 daddr
,
1598 __be16 sport
, __be16 dport
)
1602 struct keydata
*keyptr
= get_keyptr();
1604 hash
[0] = (__force u32
)saddr
;
1605 hash
[1] = (__force u32
)daddr
;
1606 hash
[2] = ((__force u16
)sport
<< 16) + (__force u16
)dport
;
1607 hash
[3] = keyptr
->secret
[11];
1609 seq
= half_md4_transform(hash
, keyptr
->secret
);
1610 seq
|= ((u64
)keyptr
->count
) << (32 - HASH_BITS
);
1612 seq
+= ktime_get_real().tv64
;
1613 seq
&= (1ull << 48) - 1;
1615 printk("dccp init_seq(%lx, %lx, %d, %d) = %d\n",
1616 saddr
, daddr
, sport
, dport
, seq
);
1621 EXPORT_SYMBOL(secure_dccp_sequence_number
);
1624 #endif /* CONFIG_INET */
1628 * Get a random word for internal kernel use only. Similar to urandom but
1629 * with the goal of minimal entropy pool depletion. As a result, the random
1630 * value is not cryptographically secure but for several uses the cost of
1631 * depleting entropy is too high
1633 unsigned int get_random_int(void)
1636 * Use IP's RNG. It suits our purpose perfectly: it re-keys itself
1637 * every second, from the entropy pool (and thus creates a limited
1638 * drain on it), and uses halfMD4Transform within the second. We
1639 * also mix it with jiffies and the PID:
1641 return secure_ip_id((__force __be32
)(current
->pid
+ jiffies
));
1645 * randomize_range() returns a start address such that
1647 * [...... <range> .....]
1650 * a <range> with size "len" starting at the return value is inside in the
1651 * area defined by [start, end], but is otherwise randomized.
1654 randomize_range(unsigned long start
, unsigned long end
, unsigned long len
)
1656 unsigned long range
= end
- len
- start
;
1658 if (end
<= start
+ len
)
1660 return PAGE_ALIGN(get_random_int() % range
+ start
);