2 * random.c -- A strong random number generator
4 * Version 0.95, last modified 4-Nov-95
6 * Copyright Theodore Ts'o, 1994, 1995. All rights reserved.
8 * Redistribution and use in source and binary forms, with or without
9 * modification, are permitted provided that the following conditions
11 * 1. Redistributions of source code must retain the above copyright
12 * notice, and the entire permission notice in its entirety,
13 * including the disclaimer of warranties.
14 * 2. Redistributions in binary form must reproduce the above copyright
15 * notice, this list of conditions and the following disclaimer in the
16 * documentation and/or other materials provided with the distribution.
17 * 3. The name of the author may not be used to endorse or promote
18 * products derived from this software without specific prior
21 * ALTERNATIVELY, this product may be distributed under the terms of
22 * the GNU Public License, in which case the provisions of the GPL are
23 * required INSTEAD OF the above restrictions. (This clause is
24 * necessary due to a potential bad interaction between the GPL and
25 * the restrictions contained in a BSD-style copyright.)
27 * THIS SOFTWARE IS PROVIDED ``AS IS'' AND ANY EXPRESS OR IMPLIED
28 * WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
29 * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
30 * DISCLAIMED. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT,
31 * INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
32 * (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
33 * SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
34 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT,
35 * STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
36 * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED
37 * OF THE POSSIBILITY OF SUCH DAMAGE.
41 * (now, with legal B.S. out of the way.....)
43 * This routine gathers environmental noise from device drivers, etc.,
44 * and returns good random numbers, suitable for cryptographic use.
45 * Besides the obvious cryptographic uses, these numbers are also good
46 * for seeding TCP sequence numbers, and other places where it is
47 * desireable to have numbers which are not only random, but hard to
48 * predict by an attacker.
53 * Computers are very predictable devices. Hence it is extremely hard
54 * to produce truely random numbers on a computer --- as opposed to
55 * pseudo-random numbers, which can easily generated by using a
56 * algorithm. Unfortunately, it is very easy for attackers to guess
57 * the sequence of pseudo-random number generators, and for some
58 * applications this is not acceptable. So instead, we must try to
59 * gather "environmental noise" from the computer's environment, which
60 * must be hard for outside attackers to observe, and use that to
61 * generate random numbers. In a Unix environment, this is best done
62 * from inside the kernel.
64 * Sources of randomness from the environment include inter-keyboard
65 * timings, inter-interrupt timings from some interrupts, and other
66 * events which are both (a) non-deterministic and (b) hard for an
67 * outside observer to measure. Randomness from these sources are
68 * added to an "entropy pool", which is mixed using a CRC-like function.
69 * This is not cryptographically strong, but it is adequate assuming
70 * the randomness is not chosen maliciously, and it is fast enough that
71 * the overhead of doing it on every interrupt is very reasonable.
72 * As random bytes are mixed into the entropy pool, the routines keep
73 * an *estimate* of how many bits of randomness have been stored into
74 * the random number generator's internal state.
76 * When random bytes are desired, they are obtained by taking the MD5
77 * hash of the contents of the "entropy pool". The MD5 hash avoids
78 * exposing the internal state of the entropy pool. It is believed to
79 * be computationally infeasible to derive any useful information
80 * about the input of MD5 from its output. Even if it is possible to
81 * analyze MD5 in some clever way, as long as the amount of data
82 * returned from the generator is less than the inherent entropy in
83 * the pool, the output data is totally unpredictable. For this
84 * reason, the routine decreases its internal estimate of how many
85 * bits of "true randomness" are contained in the entropy pool as it
86 * outputs random numbers.
88 * If this estimate goes to zero, the routine can still generate
89 * random numbers; however, an attacker may (at least in theory) be
90 * able to infer the future output of the generator from prior
91 * outputs. This requires successful cryptanalysis of MD5, which is
92 * not believed to be feasible, but there is a remote possiblility.
93 * Nonetheless, these numbers should be useful for the vast majority
96 * Exported interfaces ---- output
97 * ===============================
99 * There are three exported interfaces; the first is one designed to
100 * be used from within the kernel:
102 * void get_random_bytes(void *buf, int nbytes);
104 * This interface will return the requested number of random bytes,
105 * and place it in the requested buffer.
107 * The two other interfaces are two character devices /dev/random and
108 * /dev/urandom. /dev/random is suitable for use when very high
109 * quality randomness is desired (for example, for key generation or
110 * one-time pads), as it will only return a maximum of the number of
111 * bits of randomness (as estimated by the random number generator)
112 * contained in the entropy pool.
114 * The /dev/urandom device does not have this limit, and will return
115 * as many bytes as are requested. As more and more random bytes are
116 * requested without giving time for the entropy pool to recharge,
117 * this will result in random numbers that are merely cryptographically
118 * strong. For many applications, however, this is acceptable.
120 * Exported interfaces ---- input
121 * ==============================
123 * The current exported interfaces for gathering environmental noise
124 * from the devices are:
126 * void add_keyboard_randomness(unsigned char scancode);
127 * void add_mouse_randomness(__u32 mouse_data);
128 * void add_interrupt_randomness(int irq);
129 * void add_blkdev_randomness(int irq);
131 * add_keyboard_randomness() uses the inter-keypress timing, as well as the
132 * scancode as random inputs into the "entropy pool".
134 * add_mouse_randomness() uses the mouse interrupt timing, as well as
135 * the reported position of the mouse from the hardware.
137 * add_interrupt_randomness() uses the inter-interrupt timing as random
138 * inputs to the entropy pool. Note that not all interrupts are good
139 * sources of randomness! For example, the timer interrupts is not a
140 * good choice, because the periodicity of the interrupts is to
141 * regular, and hence predictable to an attacker. Disk interrupts are
142 * a better measure, since the timing of the disk interrupts are more
145 * add_blkdev_randomness() times the finishing time of block requests.
147 * All of these routines try to estimate how many bits of randomness a
148 * particular randomness source. They do this by keeping track of the
149 * first and second order deltas of the event timings.
154 * Ideas for constructing this random number generator were derived
155 * from the Pretty Good Privacy's random number generator, and from
156 * private discussions with Phil Karn. Colin Plumb provided a faster
157 * random number generator, which speed up the mixing function of the
158 * entropy pool, taken from PGP 3.0 (under development). It has since
159 * been modified by myself to provide better mixing in the case where
160 * the input values to add_entropy_word() are mostly small numbers.
162 * Any flaws in the design are solely my responsibility, and should
163 * not be attributed to the Phil, Colin, or any of authors of PGP.
165 * The code for MD5 transform was taken from Colin Plumb's
166 * implementation, which has been placed in the public domain. The
167 * MD5 cryptographic checksum was devised by Ronald Rivest, and is
168 * documented in RFC 1321, "The MD5 Message Digest Algorithm".
170 * Further background information on this topic may be obtained from
171 * RFC 1750, "Randomness Recommendations for Security", by Donald
172 * Eastlake, Steve Crocker, and Jeff Schiller.
175 #include <linux/sched.h>
176 #include <linux/kernel.h>
177 #include <linux/major.h>
178 #include <linux/string.h>
179 #include <linux/fcntl.h>
180 #include <linux/malloc.h>
181 #include <linux/random.h>
183 #include <asm/segment.h>
188 * The pool is stirred with a primitive polynomial of degree 128
189 * over GF(2), namely x^128 + x^99 + x^59 + x^31 + x^9 + x^7 + 1.
190 * For a pool of size 64, try x^64+x^62+x^38+x^10+x^6+x+1.
192 #define POOLWORDS 128 /* Power of 2 - note that this is 32-bit words */
193 #define POOLBITS (POOLWORDS*32)
195 #define TAP1 99 /* The polynomial taps */
200 #elif POOLWORDS == 64
201 #define TAP1 62 /* The polynomial taps */
207 #error No primitive polynomial available for chosen POOLWORDS
210 /* There is actually only one of these, globally. */
211 struct random_bucket
{
213 unsigned entropy_count
;
218 /* There is one of these per entropy source */
219 struct timer_rand_state
{
220 unsigned long last_time
;
222 int dont_count_entropy
:1;
225 static struct random_bucket random_state
;
226 static __u32 random_pool
[POOLWORDS
];
227 static struct timer_rand_state keyboard_timer_state
;
228 static struct timer_rand_state mouse_timer_state
;
229 static struct timer_rand_state extract_timer_state
;
230 static struct timer_rand_state
*irq_timer_state
[NR_IRQS
];
231 static struct timer_rand_state
*blkdev_timer_state
[MAX_BLKDEV
];
232 static struct wait_queue
*random_wait
;
234 static int random_read(struct inode
* inode
, struct file
* file
,
235 char * buf
, int nbytes
);
236 static int random_read_unlimited(struct inode
* inode
, struct file
* file
,
237 char * buf
, int nbytes
);
238 static int random_select(struct inode
*inode
, struct file
*file
,
239 int sel_type
, select_table
* wait
);
240 static int random_write(struct inode
* inode
, struct file
* file
,
241 const char * buffer
, int count
);
242 static int random_ioctl(struct inode
* inode
, struct file
* file
,
243 unsigned int cmd
, unsigned long arg
);
247 #define MIN(a,b) (((a) < (b)) ? (a) : (b))
250 void rand_initialize(void)
252 random_state
.add_ptr
= 0;
253 random_state
.entropy_count
= 0;
254 random_state
.pool
= random_pool
;
255 memset(irq_timer_state
, 0, sizeof(irq_timer_state
));
256 memset(blkdev_timer_state
, 0, sizeof(blkdev_timer_state
));
257 extract_timer_state
.dont_count_entropy
= 1;
261 void rand_initialize_irq(int irq
)
263 struct timer_rand_state
*state
;
265 if (irq
>= NR_IRQS
|| irq_timer_state
[irq
])
269 * If kamlloc returns null, we just won't use that entropy
272 state
= kmalloc(sizeof(struct timer_rand_state
), GFP_KERNEL
);
274 irq_timer_state
[irq
] = state
;
275 memset(state
, 0, sizeof(struct timer_rand_state
));
279 void rand_initialize_blkdev(int major
)
281 struct timer_rand_state
*state
;
283 if (major
>= MAX_BLKDEV
|| blkdev_timer_state
[major
])
287 * If kamlloc returns null, we just won't use that entropy
290 state
= kmalloc(sizeof(struct timer_rand_state
), GFP_KERNEL
);
292 blkdev_timer_state
[major
] = state
;
293 memset(state
, 0, sizeof(struct timer_rand_state
));
298 * This function adds a byte into the entropy "pool". It does not
299 * update the entropy estimate. The caller must do this if appropriate.
301 * The pool is stirred with a primitive polynomial of degree 128
302 * over GF(2), namely x^128 + x^99 + x^59 + x^31 + x^9 + x^7 + 1.
303 * For a pool of size 64, try x^64+x^62+x^38+x^10+x^6+x+1.
305 * We rotate the input word by a changing number of bits, to help
306 * assure that all bits in the entropy get toggled. Otherwise, if we
307 * consistently feed the entropy pool small numbers (like jiffies and
308 * scancodes, for example), the upper bits of the entropy pool don't
309 * get affected. --- TYT, 10/11/95
311 static inline void add_entropy_word(struct random_bucket
*r
,
317 w
= (input
<< r
->input_rotate
) | (input
>> (32 - r
->input_rotate
));
318 i
= r
->add_ptr
= (r
->add_ptr
- 1) & (POOLWORDS
-1);
320 r
->input_rotate
= (r
->input_rotate
+ 7) & 31;
323 * At the beginning of the pool, add an extra 7 bits
324 * rotation, so that successive passes spread the
325 * input bits across the pool evenly.
327 r
->input_rotate
= (r
->input_rotate
+ 14) & 31;
329 /* XOR in the various taps */
330 w
^= r
->pool
[(i
+TAP1
)&(POOLWORDS
-1)];
331 w
^= r
->pool
[(i
+TAP2
)&(POOLWORDS
-1)];
332 w
^= r
->pool
[(i
+TAP3
)&(POOLWORDS
-1)];
333 w
^= r
->pool
[(i
+TAP4
)&(POOLWORDS
-1)];
334 w
^= r
->pool
[(i
+TAP5
)&(POOLWORDS
-1)];
336 /* Rotate w left 1 bit (stolen from SHA) and store */
337 r
->pool
[i
] = (w
<< 1) | (w
>> 31);
341 * This function adds entropy to the entropy "pool" by using timing
342 * delays. It uses the timer_rand_state structure to make an estimate
343 * of how many bits of entropy this call has added to the pool.
345 * The number "num" is also added to the pool - it should somehow describe
346 * the type of event which just happened. This is currently 0-255 for
347 * keyboard scan codes, and 256 upwards for interrupts.
348 * On the i386, this is assumed to be at most 16 bits, and the high bits
349 * are used for a high-resolution timer.
351 * TODO: Read the time stamp register on the Pentium.
353 static void add_timer_randomness(struct random_bucket
*r
,
354 struct timer_rand_state
*state
, unsigned num
)
360 #if defined (__i386__)
361 if (x86_capability
& 16) {
362 unsigned long low
, high
;
363 __asm__(".byte 0x0f,0x31"
364 :"=a" (low
), "=d" (high
));
370 * On a 386, read the high resolution timer. We assume that
371 * this gives us 2 bits of randomness.
373 * This is turned off for now because of the speed hit
376 outb_p(0x00, 0x43); /* latch the count ASAP */
377 num
|= inb_p(0x40) << 16;
378 num
|= inb(0x40) << 24;
379 if (!state
->dont_count_entropy
)
380 r
->entropy_count
+= 2;
389 add_entropy_word(r
, (__u32
) num
);
390 add_entropy_word(r
, time
);
393 * Calculate number of bits of randomness we probably
394 * added. We take into account the first and second order
395 * deltas in order to make our estimate.
397 if (!state
->dont_count_entropy
) {
398 delta
= time
- state
->last_time
;
399 state
->last_time
= time
;
401 delta2
= delta
- state
->last_delta
;
402 state
->last_delta
= delta
;
404 if (delta
< 0) delta
= -delta
;
405 if (delta2
< 0) delta2
= -delta2
;
406 delta
= MIN(delta
, delta2
) >> 1;
407 for (nbits
= 0; delta
; nbits
++)
410 r
->entropy_count
+= nbits
;
412 /* Prevent overflow */
413 if (r
->entropy_count
> POOLBITS
)
414 r
->entropy_count
= POOLBITS
;
417 wake_up_interruptible(&random_wait
);
420 void add_keyboard_randomness(unsigned char scancode
)
422 add_timer_randomness(&random_state
, &keyboard_timer_state
, scancode
);
425 void add_mouse_randomness(__u32 mouse_data
)
427 add_timer_randomness(&random_state
, &mouse_timer_state
, mouse_data
);
430 void add_interrupt_randomness(int irq
)
432 if (irq
>= NR_IRQS
|| irq_timer_state
[irq
] == 0)
435 add_timer_randomness(&random_state
, irq_timer_state
[irq
], 0x100+irq
);
438 void add_blkdev_randomness(int major
)
440 if (major
>= MAX_BLKDEV
|| blkdev_timer_state
[major
] == 0)
443 add_timer_randomness(&random_state
, blkdev_timer_state
[major
],
448 * MD5 transform algorithm, taken from code written by Colin Plumb,
449 * and put into the public domain
451 * QUESTION: Replace this with SHA, which as generally received better
452 * reviews from the cryptographic community?
455 /* The four core functions - F1 is optimized somewhat */
457 /* #define F1(x, y, z) (x & y | ~x & z) */
458 #define F1(x, y, z) (z ^ (x & (y ^ z)))
459 #define F2(x, y, z) F1(z, x, y)
460 #define F3(x, y, z) (x ^ y ^ z)
461 #define F4(x, y, z) (y ^ (x | ~z))
463 /* This is the central step in the MD5 algorithm. */
464 #define MD5STEP(f, w, x, y, z, data, s) \
465 ( w += f(x, y, z) + data, w = w<<s | w>>(32-s), w += x )
468 * The core of the MD5 algorithm, this alters an existing MD5 hash to
469 * reflect the addition of 16 longwords of new data. MD5Update blocks
470 * the data and converts bytes into longwords for this routine.
472 static void MD5Transform(__u32 buf
[4],
482 MD5STEP(F1
, a
, b
, c
, d
, in
[ 0]+0xd76aa478, 7);
483 MD5STEP(F1
, d
, a
, b
, c
, in
[ 1]+0xe8c7b756, 12);
484 MD5STEP(F1
, c
, d
, a
, b
, in
[ 2]+0x242070db, 17);
485 MD5STEP(F1
, b
, c
, d
, a
, in
[ 3]+0xc1bdceee, 22);
486 MD5STEP(F1
, a
, b
, c
, d
, in
[ 4]+0xf57c0faf, 7);
487 MD5STEP(F1
, d
, a
, b
, c
, in
[ 5]+0x4787c62a, 12);
488 MD5STEP(F1
, c
, d
, a
, b
, in
[ 6]+0xa8304613, 17);
489 MD5STEP(F1
, b
, c
, d
, a
, in
[ 7]+0xfd469501, 22);
490 MD5STEP(F1
, a
, b
, c
, d
, in
[ 8]+0x698098d8, 7);
491 MD5STEP(F1
, d
, a
, b
, c
, in
[ 9]+0x8b44f7af, 12);
492 MD5STEP(F1
, c
, d
, a
, b
, in
[10]+0xffff5bb1, 17);
493 MD5STEP(F1
, b
, c
, d
, a
, in
[11]+0x895cd7be, 22);
494 MD5STEP(F1
, a
, b
, c
, d
, in
[12]+0x6b901122, 7);
495 MD5STEP(F1
, d
, a
, b
, c
, in
[13]+0xfd987193, 12);
496 MD5STEP(F1
, c
, d
, a
, b
, in
[14]+0xa679438e, 17);
497 MD5STEP(F1
, b
, c
, d
, a
, in
[15]+0x49b40821, 22);
499 MD5STEP(F2
, a
, b
, c
, d
, in
[ 1]+0xf61e2562, 5);
500 MD5STEP(F2
, d
, a
, b
, c
, in
[ 6]+0xc040b340, 9);
501 MD5STEP(F2
, c
, d
, a
, b
, in
[11]+0x265e5a51, 14);
502 MD5STEP(F2
, b
, c
, d
, a
, in
[ 0]+0xe9b6c7aa, 20);
503 MD5STEP(F2
, a
, b
, c
, d
, in
[ 5]+0xd62f105d, 5);
504 MD5STEP(F2
, d
, a
, b
, c
, in
[10]+0x02441453, 9);
505 MD5STEP(F2
, c
, d
, a
, b
, in
[15]+0xd8a1e681, 14);
506 MD5STEP(F2
, b
, c
, d
, a
, in
[ 4]+0xe7d3fbc8, 20);
507 MD5STEP(F2
, a
, b
, c
, d
, in
[ 9]+0x21e1cde6, 5);
508 MD5STEP(F2
, d
, a
, b
, c
, in
[14]+0xc33707d6, 9);
509 MD5STEP(F2
, c
, d
, a
, b
, in
[ 3]+0xf4d50d87, 14);
510 MD5STEP(F2
, b
, c
, d
, a
, in
[ 8]+0x455a14ed, 20);
511 MD5STEP(F2
, a
, b
, c
, d
, in
[13]+0xa9e3e905, 5);
512 MD5STEP(F2
, d
, a
, b
, c
, in
[ 2]+0xfcefa3f8, 9);
513 MD5STEP(F2
, c
, d
, a
, b
, in
[ 7]+0x676f02d9, 14);
514 MD5STEP(F2
, b
, c
, d
, a
, in
[12]+0x8d2a4c8a, 20);
516 MD5STEP(F3
, a
, b
, c
, d
, in
[ 5]+0xfffa3942, 4);
517 MD5STEP(F3
, d
, a
, b
, c
, in
[ 8]+0x8771f681, 11);
518 MD5STEP(F3
, c
, d
, a
, b
, in
[11]+0x6d9d6122, 16);
519 MD5STEP(F3
, b
, c
, d
, a
, in
[14]+0xfde5380c, 23);
520 MD5STEP(F3
, a
, b
, c
, d
, in
[ 1]+0xa4beea44, 4);
521 MD5STEP(F3
, d
, a
, b
, c
, in
[ 4]+0x4bdecfa9, 11);
522 MD5STEP(F3
, c
, d
, a
, b
, in
[ 7]+0xf6bb4b60, 16);
523 MD5STEP(F3
, b
, c
, d
, a
, in
[10]+0xbebfbc70, 23);
524 MD5STEP(F3
, a
, b
, c
, d
, in
[13]+0x289b7ec6, 4);
525 MD5STEP(F3
, d
, a
, b
, c
, in
[ 0]+0xeaa127fa, 11);
526 MD5STEP(F3
, c
, d
, a
, b
, in
[ 3]+0xd4ef3085, 16);
527 MD5STEP(F3
, b
, c
, d
, a
, in
[ 6]+0x04881d05, 23);
528 MD5STEP(F3
, a
, b
, c
, d
, in
[ 9]+0xd9d4d039, 4);
529 MD5STEP(F3
, d
, a
, b
, c
, in
[12]+0xe6db99e5, 11);
530 MD5STEP(F3
, c
, d
, a
, b
, in
[15]+0x1fa27cf8, 16);
531 MD5STEP(F3
, b
, c
, d
, a
, in
[ 2]+0xc4ac5665, 23);
533 MD5STEP(F4
, a
, b
, c
, d
, in
[ 0]+0xf4292244, 6);
534 MD5STEP(F4
, d
, a
, b
, c
, in
[ 7]+0x432aff97, 10);
535 MD5STEP(F4
, c
, d
, a
, b
, in
[14]+0xab9423a7, 15);
536 MD5STEP(F4
, b
, c
, d
, a
, in
[ 5]+0xfc93a039, 21);
537 MD5STEP(F4
, a
, b
, c
, d
, in
[12]+0x655b59c3, 6);
538 MD5STEP(F4
, d
, a
, b
, c
, in
[ 3]+0x8f0ccc92, 10);
539 MD5STEP(F4
, c
, d
, a
, b
, in
[10]+0xffeff47d, 15);
540 MD5STEP(F4
, b
, c
, d
, a
, in
[ 1]+0x85845dd1, 21);
541 MD5STEP(F4
, a
, b
, c
, d
, in
[ 8]+0x6fa87e4f, 6);
542 MD5STEP(F4
, d
, a
, b
, c
, in
[15]+0xfe2ce6e0, 10);
543 MD5STEP(F4
, c
, d
, a
, b
, in
[ 6]+0xa3014314, 15);
544 MD5STEP(F4
, b
, c
, d
, a
, in
[13]+0x4e0811a1, 21);
545 MD5STEP(F4
, a
, b
, c
, d
, in
[ 4]+0xf7537e82, 6);
546 MD5STEP(F4
, d
, a
, b
, c
, in
[11]+0xbd3af235, 10);
547 MD5STEP(F4
, c
, d
, a
, b
, in
[ 2]+0x2ad7d2bb, 15);
548 MD5STEP(F4
, b
, c
, d
, a
, in
[ 9]+0xeb86d391, 21);
564 #error extract_entropy() assumes that POOLWORDS is a multiple of 16 words.
567 * This function extracts randomness from the "entropy pool", and
568 * returns it in a buffer. This function computes how many remaining
569 * bits of entropy are left in the pool, but it does not restrict the
570 * number of bytes that are actually obtained.
572 static inline int extract_entropy(struct random_bucket
*r
, char * buf
,
573 int nbytes
, int to_user
)
578 add_timer_randomness(r
, &extract_timer_state
, nbytes
);
580 /* Redundant, but just in case... */
581 if (r
->entropy_count
> POOLBITS
)
582 r
->entropy_count
= POOLBITS
;
583 /* Why is this here? Left in from Ted Ts'o. Perhaps to limit time. */
588 if (r
->entropy_count
/ 8 >= nbytes
)
589 r
->entropy_count
-= nbytes
*8;
591 r
->entropy_count
= 0;
594 /* Hash the pool to get the output */
599 for (i
= 0; i
< POOLWORDS
; i
+= 16)
600 MD5Transform(tmp
, r
->pool
+i
);
601 /* Modify pool so next hash will produce different results */
602 add_entropy_word(r
, tmp
[0]);
603 add_entropy_word(r
, tmp
[1]);
604 add_entropy_word(r
, tmp
[2]);
605 add_entropy_word(r
, tmp
[3]);
607 * Run the MD5 Transform one more time, since we want
608 * to add at least minimal obscuring of the inputs to
609 * add_entropy_word(). --- TYT
611 MD5Transform(tmp
, r
->pool
);
613 /* Copy data to destination buffer */
616 memcpy_tofs(buf
, (__u8
const *)tmp
, i
);
618 memcpy(buf
, (__u8
const *)tmp
, i
);
623 /* Wipe data from memory */
624 memset(tmp
, 0, sizeof(tmp
));
630 * This function is the exported kernel interface. It returns some
631 * number of good random numbers, suitable for seeding TCP sequence
634 void get_random_bytes(void *buf
, int nbytes
)
636 extract_entropy(&random_state
, (char *) buf
, nbytes
, 0);
640 random_read(struct inode
* inode
, struct file
* file
, char * buf
, int nbytes
)
642 struct wait_queue wait
= { current
, NULL
};
650 add_wait_queue(&random_wait
, &wait
);
652 current
->state
= TASK_INTERRUPTIBLE
;
655 if (n
> random_state
.entropy_count
/ 8)
656 n
= random_state
.entropy_count
/ 8;
658 if (file
->f_flags
& O_NONBLOCK
) {
662 if (current
->signal
& ~current
->blocked
) {
663 retval
= -ERESTARTSYS
;
669 n
= extract_entropy(&random_state
, buf
, n
, 1);
673 break; /* This break makes the device work */
674 /* like a named pipe */
676 current
->state
= TASK_RUNNING
;
677 remove_wait_queue(&random_wait
, &wait
);
679 return (count
? count
: retval
);
683 random_read_unlimited(struct inode
* inode
, struct file
* file
,
684 char * buf
, int nbytes
)
686 return extract_entropy(&random_state
, buf
, nbytes
, 1);
690 random_select(struct inode
*inode
, struct file
*file
,
691 int sel_type
, select_table
* wait
)
693 if (sel_type
== SEL_IN
) {
694 if (random_state
.entropy_count
>= 8)
696 select_wait(&random_wait
, wait
);
702 random_write(struct inode
* inode
, struct file
* file
,
703 const char * buffer
, int count
)
708 for (i
= count
, p
= (__u32
*)buffer
;
710 i
-= sizeof(__u32
), p
++) {
711 memcpy_fromfs(&word
, p
, sizeof(__u32
));
712 add_entropy_word(&random_state
, word
);
716 memcpy_fromfs(&word
, p
, i
);
717 add_entropy_word(&random_state
, word
);
720 inode
->i_mtime
= CURRENT_TIME
;
725 random_ioctl(struct inode
* inode
, struct file
* file
,
726 unsigned int cmd
, unsigned long arg
)
728 int *p
, size
, ent_count
;
733 retval
= verify_area(VERIFY_WRITE
, (void *) arg
, sizeof(int));
736 put_user(random_state
.entropy_count
, (int *) arg
);
741 retval
= verify_area(VERIFY_READ
, (void *) arg
, sizeof(int));
744 random_state
.entropy_count
+= get_user((int *) arg
);
745 if (random_state
.entropy_count
> POOLBITS
)
746 random_state
.entropy_count
= POOLBITS
;
752 retval
= verify_area(VERIFY_WRITE
, (void *) p
, sizeof(int));
755 put_user(random_state
.entropy_count
, p
++);
756 retval
= verify_area(VERIFY_READ
, (void *) p
, sizeof(int));
760 put_user(POOLWORDS
, p
);
763 if (size
> POOLWORDS
)
765 memcpy_tofs(++p
, random_state
.pool
,
772 retval
= verify_area(VERIFY_READ
, (void *) p
, 2*sizeof(int));
775 ent_count
= get_user(p
++);
776 size
= get_user(p
++);
777 (void) random_write(0, file
, (const char *) p
, size
);
778 random_state
.entropy_count
+= ent_count
;
779 if (random_state
.entropy_count
> POOLBITS
)
780 random_state
.entropy_count
= POOLBITS
;
785 random_state
.entropy_count
= 0;
792 struct file_operations random_fops
= {
793 NULL
, /* random_lseek */
796 NULL
, /* random_readdir */
797 random_select
, /* random_select */
799 NULL
, /* random_mmap */
800 NULL
, /* no special open code */
801 NULL
/* no special release code */
804 struct file_operations urandom_fops
= {
805 NULL
, /* unrandom_lseek */
806 random_read_unlimited
,
808 NULL
, /* urandom_readdir */
809 NULL
, /* urandom_select */
811 NULL
, /* urandom_mmap */
812 NULL
, /* no special open code */
813 NULL
/* no special release code */