/*
 * Routines to get randomness.
 */
#include <syslog.h>
#include <unistd.h>
#include <stdlib.h>
#include <sys/types.h>
#include <limits.h>
#include "arch.h"
#include "pids.h"
#include "random.h"
#include "sanitise.h"	// interesting_numbers
#include "types.h"
#include "utils.h"

void generate_rand_bytes(unsigned char *ptr, unsigned int len)
{
	unsigned int i;
	unsigned char choice = rand() % 3;

	for (i = 0; i < len; i++) {
		switch (choice) {
		case 0:
			/* Complete garbage. */
			ptr[i] = rand();
			break;
		case 1:
			/* printable text strings. */
			ptr[i] = 32 + rand() % (0x7f - 32);
			break;
		case 2:
			/* numbers */
			ptr[i] = '0' + rand() % 10;
			break;
		}
	}
}

unsigned int rand_range(unsigned int min, unsigned int max)
{
	if (min > max)
		swap(min, max);

	return min + rand() / (RAND_MAX / (max - min + 1) + 1);
}

/*
 * OR a random number of bits into a mask.
 * Used by ARG_LIST generation, and get_o_flags()
 */
unsigned long set_rand_bitmask(unsigned int num, const unsigned long *values)
{
	unsigned long i;
	unsigned long mask = 0;
	unsigned int bits;

	bits = rand_range(0, num);      /* num of bits to OR */
	if (bits == 0)
		return mask;

	for (i = 0; i < bits; i++)
		mask |= values[rand() % num];

	return mask;
}

unsigned int rand_bool(void)
{
	return rand() % 2;
}

static unsigned int rand_single_bit(unsigned char size)
{
	return (1UL << (rand() % size));
}

/*
 * set N bits, where N= rand(0 - WORDSIZE/2)
 */
static unsigned long randbits(int limit)
{
	unsigned int num = rand() % (limit / 2);
	unsigned int i;
	unsigned long r = 0;

	for (i = 0; i < num; i++)
		r |= (1UL << (rand() % (limit - 1)));

	return r;
}

/*
 * Based on very similar routine stolen from iknowthis. Thanks Tavis.
 */
static unsigned long taviso(void)
{
	unsigned long r = 0;
	unsigned long temp;

	switch (rand() % 4) {
	case 0:	r = rand() & rand();
#if __WORDSIZE == 64
		r <<= 32;
		r |= rand() & rand();
#endif
		break;

	case 1:	temp = rand();
		r = rand();
		if (temp) r %= temp;
#if __WORDSIZE == 64
		r <<= 32;

		temp = rand();
		if (temp) r |= rand() % temp;
#endif
		break;

	case 2:	r = rand() | rand();
#if __WORDSIZE == 64
		r <<= 32;
		r |= rand() | rand();
#endif
		break;

	case 3:	r = rand();
#if __WORDSIZE == 64
		r <<= 32;
		r |= rand();
#endif
		break;
	}

	return r;
}

/*
 * Pick 8 random bytes, and concatenate them into a long.
 */
static unsigned long rand8x8(void)
{
	unsigned long r = 0UL;
	unsigned int i;

	for (i = rand_range(1, 7); i > 0; --i)
		r = (r << 8) | rand() % 256;

	return r;
}

/*
 * Pick 1 random byte, and repeat it through a long.
 */
static unsigned long rept8(unsigned int num)
{
	unsigned long r = 0UL;
	unsigned int i;
	unsigned char c;

	c = rand() % 256;
	for (i = rand() % (num - 1) ; i > 0; --i)
		r = (r << 8) | c;

	return r;
}

/*
 * "selector" function for 32bit random.
 * only called from rand32()
 */
static unsigned int __rand32(void)
{
	unsigned long r = 0;

	switch (rand() % 7) {
	case 0: r = rand_single_bit(32);
		break;
	case 1:	r = randbits(32);
		break;
	case 2: r = rand();
		break;
	case 3:	r = taviso();
		break;
	case 4:	r = rand8x8();
		break;
	case 5:	r = rept8(4);
		break;
	case 6:	return get_interesting_32bit_value();
	}

	return r;
}

/*
 * Generate, and munge a 32bit number.
 */
unsigned int rand32(void)
{
	unsigned long r = 0;

	r = __rand32();

	if (rand_bool()) {
		unsigned int i;
		unsigned int rounds;

		/* mangle it. */
		rounds = rand() % 3;
		for (i = 0; i < rounds; i++) {
			if (rand_bool())
				r |= __rand32();
			else
				r ^= __rand32();
		}
	}

	/* Sometimes deduct it from INT_MAX */
	if (rand_bool())
		r = INT_MAX - r;

	/* Sometimes flip sign */
	if (rand_bool())
		r |= (1L << 31);

	/* we might get lucky if something is counting ints/longs etc. */
	if (rand() % 100 < 25) {
		int _div = 1 << rand_range(1, 4);	/* 2,4,8 or 16 */
		r /= _div;
	}

	/* limit the size */
	switch (rand() % 5) {
	case 0: r &= 0xff;
		break;
	case 1: r &= 0xffff;
		break;
	case 2: r &= PAGE_MASK;
		break;
	case 3: r &= 0xffffff;
		break;
	case 4:	// do nothing
		break;
	}

	return r;
}

/*
 * Generate and munge a 64bit number.
 */
u64 rand64(void)
{
	unsigned long r = 0;

	if (rand_bool()) {
		/* 32-bit ranges. */
		r = rand32();

	} else {
		/* 33:64-bit ranges. */
		switch (rand() % 7) {
		case 0:	r = rand_single_bit(64);
			break;
		case 1:	r = randbits(64);
			break;
		case 2:	r = rand32() | rand32() << 31;
			break;
		case 3:	r = taviso();
			break;
		case 4:	r = rand8x8();
			break;
		case 5:	r = rept8(8);
			break;
		/* Sometimes pick a not-so-random number. */
		case 6:	return get_interesting_value();
		}

		/* limit the size */
		switch (rand() % 4) {
		case 0: r &= 0x000000ffffffffffULL;
			break;
		case 1: r &= 0x0000ffffffffffffULL;
			break;
		case 2: r &= 0x00ffffffffffffffULL;
			break;
		}
	}

	/* Sometimes invert the generated number. */
	if (rand_bool())
		r = ~r;

	/* increase distribution in MSB */
	if ((rand() % 10)) {
		unsigned int i;
		unsigned int rounds;

		rounds = rand() % 4;
		for (i = 0; i < rounds; i++)
			r |= (1UL << ((__WORDSIZE - 1) - (rand() % 8)));
	}

	/* randomly flip sign bit. */
	if (rand_bool())
		r |= (1UL << (__WORDSIZE - 1));

	return r;
}

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