/*
* random.c -- A strong random number generator
*
* Version 0.95, last modified 4-Nov-95
*
* Copyright Theodore Ts'o, 1994, 1995. 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
* desireable 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 truely 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 MD5
* hash of the contents of the "entropy pool". The MD5 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 MD5 from its output. Even if it is possible to
* analyze MD5 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 MD5, which is
* not believed to be feasible, but there is a remote possiblility.
* 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.
*
* Acknowledgements:
* =================
*
* Ideas for constructing this random number generator were derived
* from the 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 PGP 3.0 (under development). It has since
* been modified by myself to provide better mixing in the case where
* the input values to add_entropy_word() are mostly small numbers.
*
* 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 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
#include
#include
#include
#include
#include
#include
#include
#include
#include
/*
* The pool is stirred with a primitive polynomial of degree 128
* over GF(2), namely x^128 + x^99 + x^59 + x^31 + x^9 + x^7 + 1.
* For a pool of size 64, try x^64+x^62+x^38+x^10+x^6+x+1.
*/
#define POOLWORDS 128 /* Power of 2 - note that this is 32-bit words */
#define POOLBITS (POOLWORDS*32)
#if POOLWORDS == 128
#define TAP1 99 /* The polynomial taps */
#define TAP2 59
#define TAP3 31
#define TAP4 9
#define TAP5 7
#elif POOLWORDS == 64
#define TAP1 62 /* The polynomial taps */
#define TAP2 38
#define TAP3 10
#define TAP4 6
#define TAP5 1
#else
#error No primitive polynomial available for chosen POOLWORDS
#endif
/* There is actually only one of these, globally. */
struct random_bucket {
unsigned add_ptr;
unsigned entropy_count;
int input_rotate;
__u32 *pool;
};
/* There is one of these per entropy source */
struct timer_rand_state {
unsigned long last_time;
int last_delta;
int dont_count_entropy:1;
};
static struct random_bucket random_state;
static __u32 random_pool[POOLWORDS];
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_wait;
static int random_read(struct inode * inode, struct file * file,
char * buf, int nbytes);
static int random_read_unlimited(struct inode * inode, struct file * file,
char * buf, int nbytes);
static int random_select(struct inode *inode, struct file *file,
int sel_type, select_table * wait);
static int random_write(struct inode * inode, struct file * file,
const char * buffer, int count);
static int random_ioctl(struct inode * inode, struct file * file,
unsigned int cmd, unsigned long arg);
#ifndef MIN
#define MIN(a,b) (((a) < (b)) ? (a) : (b))
#endif
void rand_initialize(void)
{
random_state.add_ptr = 0;
random_state.entropy_count = 0;
random_state.pool = random_pool;
memset(irq_timer_state, 0, sizeof(irq_timer_state));
memset(blkdev_timer_state, 0, sizeof(blkdev_timer_state));
extract_timer_state.dont_count_entropy = 1;
random_wait = NULL;
}
void rand_initialize_irq(int irq)
{
struct timer_rand_state *state;
if (irq >= NR_IRQS || irq_timer_state[irq])
return;
/*
* If kamlloc 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)
{
struct timer_rand_state *state;
if (major >= MAX_BLKDEV || blkdev_timer_state[major])
return;
/*
* If kamlloc returns null, we just won't use that entropy
* source.
*/
state = kmalloc(sizeof(struct timer_rand_state), GFP_KERNEL);
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.
*
* The pool is stirred with a primitive polynomial of degree 128
* over GF(2), namely x^128 + x^99 + x^59 + x^31 + x^9 + x^7 + 1.
* For a pool of size 64, try x^64+x^62+x^38+x^10+x^6+x+1.
*
* We rotate the input word by a changing number of bits, to help
* assure that all bits in the entropy get toggled. Otherwise, if we
* consistently feed the entropy pool small numbers (like jiffies and
* scancodes, for example), the upper bits of the entropy pool don't
* get affected. --- TYT, 10/11/95
*/
static inline void add_entropy_word(struct random_bucket *r,
const __u32 input)
{
unsigned i;
__u32 w;
w = (input << r->input_rotate) | (input >> (32 - r->input_rotate));
i = r->add_ptr = (r->add_ptr - 1) & (POOLWORDS-1);
if (i)
r->input_rotate = (r->input_rotate + 7) & 31;
else
/*
* At the beginning of the pool, add an extra 7 bits
* rotation, so that successive passes spread the
* input bits across the pool evenly.
*/
r->input_rotate = (r->input_rotate + 14) & 31;
/* XOR in the various taps */
w ^= r->pool[(i+TAP1)&(POOLWORDS-1)];
w ^= r->pool[(i+TAP2)&(POOLWORDS-1)];
w ^= r->pool[(i+TAP3)&(POOLWORDS-1)];
w ^= r->pool[(i+TAP4)&(POOLWORDS-1)];
w ^= r->pool[(i+TAP5)&(POOLWORDS-1)];
w ^= r->pool[i];
/* Rotate w left 1 bit (stolen from SHA) and store */
r->pool[i] = (w << 1) | (w >> 31);
}
/*
* 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.
*
* TODO: Read the time stamp register on the Pentium.
*/
static void add_timer_randomness(struct random_bucket *r,
struct timer_rand_state *state, unsigned num)
{
int delta, delta2;
unsigned nbits;
__u32 time;
#if defined (__i386__)
if (x86_capability & 16) {
unsigned long low, high;
__asm__(".byte 0x0f,0x31"
:"=a" (low), "=d" (high));
time = (__u32) low;
num ^= (__u32) high;
} else {
#if 0
/*
* On a 386, read the high resolution timer. We assume that
* this gives us 2 bits of randomness.
*
* This is turned off for now because of the speed hit
* it entails.
*/
outb_p(0x00, 0x43); /* latch the count ASAP */
num |= inb_p(0x40) << 16;
num |= inb(0x40) << 24;
if (!state->dont_count_entropy)
r->entropy_count += 2;
#endif
time = jiffies;
}
#else
time = jiffies;
#endif
add_entropy_word(r, (__u32) num);
add_entropy_word(r, time);
/*
* Calculate number of bits of randomness we probably
* added. We take into account the first and second order
* deltas in order to make our estimate.
*/
if (!state->dont_count_entropy) {
delta = time - state->last_time;
state->last_time = time;
delta2 = delta - state->last_delta;
state->last_delta = delta;
if (delta < 0) delta = -delta;
if (delta2 < 0) delta2 = -delta2;
delta = MIN(delta, delta2) >> 1;
for (nbits = 0; delta; nbits++)
delta >>= 1;
r->entropy_count += nbits;
/* Prevent overflow */
if (r->entropy_count > POOLBITS)
r->entropy_count = POOLBITS;
}
wake_up_interruptible(&random_wait);
}
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 || blkdev_timer_state[major] == 0)
return;
add_timer_randomness(&random_state, blkdev_timer_state[major],
0x200+major);
}
/*
* 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<~~>(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[4],
__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
#if POOLWORDS % 16
#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 inline int extract_entropy(struct random_bucket *r, char * buf,
int nbytes, int to_user)
{
int ret, i;
__u32 tmp[4];
add_timer_randomness(r, &extract_timer_state, nbytes);
/* Redundant, but just in case... */
if (r->entropy_count > POOLBITS)
r->entropy_count = POOLBITS;
/* Why is this here? Left in from Ted Ts'o. Perhaps to limit time. */
if (nbytes > 32768)
nbytes = 32768;
ret = nbytes;
if (r->entropy_count / 8 >= nbytes)
r->entropy_count -= nbytes*8;
else
r->entropy_count = 0;
while (nbytes) {
/* Hash the pool to get the output */
tmp[0] = 0x67452301;
tmp[1] = 0xefcdab89;
tmp[2] = 0x98badcfe;
tmp[3] = 0x10325476;
for (i = 0; i < POOLWORDS; i += 16)
MD5Transform(tmp, r->pool+i);
/* Modify pool so next hash will produce different results */
add_entropy_word(r, tmp[0]);
add_entropy_word(r, tmp[1]);
add_entropy_word(r, tmp[2]);
add_entropy_word(r, tmp[3]);
/*
* Run the MD5 Transform one more time, since we want
* to add at least minimal obscuring of the inputs to
* add_entropy_word(). --- TYT
*/
MD5Transform(tmp, r->pool);
/* Copy data to destination buffer */
i = MIN(nbytes, 16);
if (to_user)
memcpy_tofs(buf, (__u8 const *)tmp, i);
else
memcpy(buf, (__u8 const *)tmp, i);
nbytes -= i;
buf += i;
}
/* Wipe data 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 int
random_read(struct inode * inode, struct file * file, char * buf, int nbytes)
{
struct wait_queue wait = { current, NULL };
int n;
int retval = 0;
int count = 0;
if (nbytes == 0)
return 0;
add_wait_queue(&random_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 (current->signal & ~current->blocked) {
retval = -ERESTARTSYS;
break;
}
schedule();
continue;
}
n = extract_entropy(&random_state, buf, n, 1);
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_wait, &wait);
return (count ? count : retval);
}
static int
random_read_unlimited(struct inode * inode, struct file * file,
char * buf, int nbytes)
{
return extract_entropy(&random_state, buf, nbytes, 1);
}
static int
random_select(struct inode *inode, struct file *file,
int sel_type, select_table * wait)
{
if (sel_type == SEL_IN) {
if (random_state.entropy_count >= 8)
return 1;
select_wait(&random_wait, wait);
}
return 0;
}
static int
random_write(struct inode * inode, struct file * file,
const char * buffer, int count)
{
int i;
__u32 word, *p;
for (i = count, p = (__u32 *)buffer;
i >= sizeof(__u32);
i-= sizeof(__u32), p++) {
memcpy_fromfs(&word, p, sizeof(__u32));
add_entropy_word(&random_state, word);
}
if (i) {
word = 0;
memcpy_fromfs(&word, p, i);
add_entropy_word(&random_state, word);
}
if (inode)
inode->i_mtime = CURRENT_TIME;
return count;
}
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);
put_user(random_state.entropy_count, (int *) arg);
return 0;
case RNDADDTOENTCNT:
if (!suser())
return -EPERM;
retval = verify_area(VERIFY_READ, (void *) arg, sizeof(int));
if (retval)
return(retval);
random_state.entropy_count += get_user((int *) arg);
if (random_state.entropy_count > POOLBITS)
random_state.entropy_count = POOLBITS;
return 0;
case RNDGETPOOL:
if (!suser())
return -EPERM;
p = (int *) arg;
retval = verify_area(VERIFY_WRITE, (void *) p, sizeof(int));
if (retval)
return(retval);
put_user(random_state.entropy_count, p++);
retval = verify_area(VERIFY_READ, (void *) p, sizeof(int));
if (retval)
return(retval);
size = get_user(p);
put_user(POOLWORDS, p);
if (size < 0)
return -EINVAL;
if (size > POOLWORDS)
size = POOLWORDS;
memcpy_tofs(++p, random_state.pool,
size*sizeof(__u32));
return 0;
case RNDADDENTROPY:
if (!suser())
return -EPERM;
p = (int *) arg;
retval = verify_area(VERIFY_READ, (void *) p, 2*sizeof(int));
if (retval)
return(retval);
ent_count = get_user(p++);
size = get_user(p++);
(void) random_write(0, file, (const char *) p, size);
random_state.entropy_count += ent_count;
if (random_state.entropy_count > POOLBITS)
random_state.entropy_count = POOLBITS;
return 0;
case RNDZAPENTCNT:
if (!suser())
return -EPERM;
random_state.entropy_count = 0;
return 0;
default:
return -EINVAL;
}
}
struct file_operations random_fops = {
NULL, /* random_lseek */
random_read,
random_write,
NULL, /* random_readdir */
random_select, /* random_select */
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_select */
random_ioctl,
NULL, /* urandom_mmap */
NULL, /* no special open code */
NULL /* no special release code */
};
~~