11
/*
 Derived from source code of TrueCrypt 7.1a, which is
 Copyright (c) 2008-2012 TrueCrypt Developers Association and which is governed
 by the TrueCrypt License 3.0.

 Modifications and additions to the original source code (contained in this file)
 and all other portions of this file are Copyright (c) 2013-2016 IDRIX
 and are governed by the Apache License 2.0 the full text of which is
 contained in the file License.txt included in VeraCrypt binary and source
 code distribution packages.
*/

#ifndef TC_HEADER_Main_UserPreferences
#define TC_HEADER_Main_UserPreferences

#include "System.h"
#include "Main.h"
#include "Hotkey.h"

namespace VeraCrypt
{
	struct UserPreferences
	{
		UserPreferences ()
			:
			BackgroundTaskEnabled (true),
			BackgroundTaskMenuDismountItemsEnabled (true),
			BackgroundTaskMenuMountItemsEnabled (true),
			BackgroundTaskMenuOpenItemsEnabled (true),
			BeepAfterHotkeyMountDismount (false),
			CloseBackgroundTaskOnNoVolumes (true),
			CloseExplorerWindowsOnDismount (true),
			CloseSecurityTokenSessionsAfterMount (false),
			DisableKernelEncryptionModeWarning (false),
			DismountOnInactivity (false),
			DismountOnLogOff (true),
			DismountOnPowerSaving (false),
			DismountOnScreenSaver (false),
			DisplayMessageAfterHotkeyDismount (false),
			ForceAutoDismount (true),
			LastSelectedSlotNumber (0),
			MaxVolumeIdleTime (60),
			MountDevicesOnLogon (false),
			MountFavoritesOnLogon (false),
			NonInteractive (false),
			UseStandardInput (false),
			OpenExplorerWindowAfterMount (false),
			SaveHistory (false),
			StartOnLogon (false),
			UseKeyfiles (false),
			Verbose (false),
			WipeCacheOnAutoDismount (true),
			WipeCacheOnClose (false)
		{
		}

		virtual ~UserPreferences ()
		{
		}
		void Load();
		void Save() const;

		HotkeyList Hotkeys;
		KeyfileList DefaultKeyfiles;
		MountOptions DefaultMountOptions;

		bool BackgroundTaskEnabled;
		bool BackgroundTaskMenuDismountItemsEnabled;
		bool BackgroundTaskMenuMountItemsEnabled;
		bool BackgroundTaskMenuOpenItemsEnabled;
		bool BeepAfterHotkeyMountDismount;
		bool CloseBackgroundTaskOnNoVolumes;
		bool CloseExplorerWindowsOnDismount;
		bool CloseSecurityTokenSessionsAfterMount;
		bool DisableKernelEncryptionModeWarning;
		bool DismountOnInactivity;
		bool DismountOnLogOff;
		bool DismountOnPowerSaving;
		bool DismountOnScreenSaver;
		bool DisplayMessageAfterHotkeyDismount;
		bool ForceAutoDismount;
		uint64 LastSelectedSlotNumber;
		int32 MaxVolumeIdleTime;
		bool MountDevicesOnLogon;
		bool MountFavoritesOnLogon;
		bool NonInteractive;
		bool UseStandardInput;
		bool OpenExplorerWindowAfterMount;
		bool SaveHistory;
		FilePath SecurityTokenModule;
		bool StartOnLogon;
		bool UseKeyfiles;
		bool Verbose;
		bool WipeCacheOnAutoDismount;
		bool WipeCacheOnClose;

	protected:
		wxString GetDefaultKeyfilesFileName () const { return L"Default Keyfiles.xml"; }
#ifdef TC_PROTOTYPE
		wxString GetPreferencesFileName () const { return L"Configuration_Debug.xml"; }
#else
		wxString GetPreferencesFileName () const { return L"Configuration.xml"; }
#endif
		void SetValue (const wxString &cfgText, bool &cfgVar);
		void SetValue (const wxString &cfgText, int &cfgVar);
		void SetValue (const wxString &cfgText, uint64 &cfgVar);
		void SetValue (const wxString &cfgText, wstring &cfgVar);
		void SetValue (const wxString &cfgText, wxString &cfgVar);
		void SetValue (const wxString &cfgText, FilesystemPath &cfgVar);
	};
}

#endif // TC_HEADER_Main_UserPreferences

/*
 * Non-physical true random number generator based on timing jitter.
 *
 * Copyright Stephan Mueller <smueller@chronox.de>, 2014 - 2019
 *
 * Design
 * ======
 *
 * See documentation in doc/ folder.
 *
 * Interface
 * =========
 *
 * See documentation in jitterentropy(3) man page.
 *
 * License
 * =======
 *
 * 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 General Public License, in which case the provisions of the GPL2 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, ALL OF
 * WHICH ARE HEREBY 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 NOT ADVISED OF THE POSSIBILITY OF SUCH
 * DAMAGE.
 */

/* Adapted for VeraCrypt */


#ifdef TC_WINDOWS_DRIVER
#define UINT64_MAX	0xffffffffffffffffU
#else
#include <stdint.h>
#endif

#undef _FORTIFY_SOURCE

#ifdef _MSC_VER
#pragma optimize( "", off )
#pragma warning(disable:4242 4244 4334) /* disable warnings on the original code */
#else
#if defined(__clang__)
	#pragma clang optimize off
#elif defined (__GNUC__)
	#pragma GCC optimize ("O0")
#endif
#endif

#include "jitterentropy.h"

#ifdef __OPTIMIZE__
 #error "The CPU Jitter random number generator must not be compiled with optimizations. See documentation. Use the compiler switch -O0 for compiling jitterentropy-base.c."
#endif

#define MAJVERSION 2 /* API / ABI incompatible changes, functional changes that
		      * require consumer to be updated (as long as this number
		      * is zero, the API is not considered stable and can
		      * change without a bump of the major version) */
#define MINVERSION 2 /* API compatible, ABI may change, functional
		      * enhancements only, consumer can be left unchanged if
		      * enhancements are not considered */
#define PATCHLEVEL 0 /* API / ABI compatible, no functional changes, no
		      * enhancements, bug fixes only */

#define ARRAY_SIZE(x) (sizeof(x) / sizeof((x)[0]))

/**
 * jent_version() - Return machine-usable version number of jent library
 *
 * The function returns a version number that is monotonic increasing
 * for newer versions. The version numbers are multiples of 100. For example,
 * version 1.2.3 is converted to 1020300 -- the last two digits are reserved
 * for future use.
 *
 * The result of this function can be used in comparing the version number
 * in a calling program if version-specific calls need to be make.
 *
 * @return Version number of jitterentropy library
 */
JENT_PRIVATE_STATIC
unsigned int jent_version(void)
{
	unsigned int version = 0;

	version =  MAJVERSION * 1000000;
	version += MINVERSION * 10000;
	version += PATCHLEVEL * 100;

	return version;
}

/***************************************************************************
 * Adaptive Proportion Test
 *
 * This test complies with SP800-90B section 4.4.2.
 ***************************************************************************/

/**
 * Reset the APT counter
 *
 * @ec [in] Reference to entropy collector
 */
static void jent_apt_reset(struct rand_data *ec, unsigned int delta_masked)
{
	/* Reset APT counter */
	ec->apt_count = 0;
	ec->apt_base = delta_masked;
	ec->apt_observations = 0;
}

/**
 * Insert a new entropy event into APT
 *
 * @ec [in] Reference to entropy collector
 * @delta_masked [in] Masked time delta to process
 */
static void jent_apt_insert(struct rand_data *ec, unsigned int delta_masked)
{
	/* Initialize the base reference */
	if (!ec->apt_base_set) {
		ec->apt_base = delta_masked;
		ec->apt_base_set = 1;
		return;
	}

	if (delta_masked == ec->apt_base) {
		ec->apt_count++;

		if (ec->apt_count >= JENT_APT_CUTOFF)
			ec->health_failure = 1;
	}

	ec->apt_observations++;

	if (ec->apt_observations >= JENT_APT_WINDOW_SIZE)
		jent_apt_reset(ec, delta_masked);
}

/***************************************************************************
 * Stuck Test and its use as Repetition Count Test
 *
 * The Jitter RNG uses an enhanced version of the Repetition Count Test
 * (RCT) specified in SP800-90B section 4.4.1. Instead of counting identical
 * back-to-back values, the input to the RCT is the counting of the stuck
 * values during the generation of one Jitter RNG output block.
 *
 * The RCT is applied with an alpha of 2^{-30} compliant to FIPS 140-2 IG 9.8.
 *
 * During the counting operation, the Jitter RNG always calculates the RCT
 * cut-off value of C. If that value exceeds the allowed cut-off value,
 * the Jitter RNG output block will be calculated completely but discarded at
 * the end. The caller of the Jitter RNG is informed with an error code.
 ***************************************************************************/

/**
 * Repetition Count Test as defined in SP800-90B section 4.4.1
 *
 * @ec [in] Reference to entropy collector
 * @stuck [in] Indicator whether the value is stuck
 */
static void jent_rct_insert(struct rand_data *ec, int stuck)
{
	/*
	 * If we have a count less than zero, a previous RCT round identified
	 * a failure. We will not overwrite it.
	 */
	if (ec->rct_count < 0)
		return;

	if (stuck) {
		ec->rct_count++;

		/*
		 * The cutoff value is based on the following consideration:
		 * alpha = 2^-30 as recommended in FIPS 140-2 IG 9.8.
		 * In addition, we require an entropy value H of 1/OSR as this
		 * is the minimum entropy required to provide full entropy.
		 * Note, we collect 64 * OSR deltas for inserting them into
		 * the entropy pool which should then have (close to) 64 bits
		 * of entropy.
		 *
		 * Note, ec->rct_count (which equals to value B in the pseudo
		 * code of SP800-90B section 4.4.1) starts with zero. Hence
		 * we need to subtract one from the cutoff value as calculated
		 * following SP800-90B.
		 */
		if ((unsigned int)ec->rct_count >= (30 * ec->osr)) {
			ec->rct_count = -1;
			ec->health_failure = 1;
		}
	} else {
		ec->rct_count = 0;
	}
}

/**
 * Is there an RCT health test failure?
 *
 * @ec [in] Reference to entropy collector
 *
 * @return
 * 	0 No health test failure
 * 	1 Permanent health test failure
 */
static int jent_rct_failure(struct rand_data *ec)
{
	if (ec->rct_count < 0)
		return 1;
	return 0;
}

#ifdef _MSC_VER
static
#endif
VC_INLINE uint64_t jent_delta(uint64_t prev, uint64_t next)
{
	return (prev < next) ? (next - prev) : (UINT64_MAX - prev + 1 + next);
}

/**
 * Stuck test by checking the:
 * 	1st derivative of the jitter measurement (time delta)
 * 	2nd derivative of the jitter measurement (delta of time deltas)
 * 	3rd derivative of the jitter measurement (delta of delta of time deltas)
 *
 * All values must always be non-zero.
 *
 * @ec [in] Reference to entropy collector
 * @current_delta [in] Jitter time delta
 *
 * @return
 * 	0 jitter measurement not stuck (good bit)
 * 	1 jitter measurement stuck (reject bit)
 */
static int jent_stuck(struct rand_data *ec, uint64_t current_delta)
{
	uint64_t delta2 = jent_delta(ec->last_delta, current_delta);
	uint64_t delta3 = jent_delta(ec->last_delta2, delta2);
	unsigned int delta_masked = current_delta & JENT_APT_WORD_MASK;

	ec->last_delta = current_delta;
	ec->last_delta2 = delta2;

	/*
	 * Insert the result of the comparison of two back-to-back time
	 * deltas.
	 */
	jent_apt_insert(ec, delta_masked);

	if (!current_delta || !delta2 || !delta3) {
		/* RCT with a stuck bit */
		jent_rct_insert(ec, 1);
		return 1;
	}

	/* RCT with a non-stuck bit */
	jent_rct_insert(ec, 0);

	return 0;
}

/**
 * Report any health test failures
 *
 * @ec [in] Reference to entropy collector
 *
 * @return
 * 	0 No health test failure
 * 	1 Permanent health test failure
 */
static int jent_health_failure(struct rand_data *ec)
{
	/* Test is only enabled in FIPS mode */
	if (!ec->fips_enabled)
		return 0;

	return ec->health_failure;
}

/***************************************************************************
 * Noise sources
 ***************************************************************************/

/**
 * Update of the loop count used for the next round of
 * an entropy collection.
 *
 * @ec [in] entropy collector struct -- may be NULL
 * @bits [in] is the number of low bits of the timer to consider
 * @min [in] is the number of bits we shift the timer value to the right at
 *	     the end to make sure we have a guaranteed minimum value
 *
 * @return Newly calculated loop counter
 */
static uint64_t jent_loop_shuffle(struct rand_data *ec,
				  unsigned int bits, unsigned int min)
{
	uint64_t time = 0;
	uint64_t shuffle = 0;
	unsigned int i = 0;
	unsigned int mask = (1<<bits) - 1;

	jent_get_nstime(&time);
	/*
	 * Mix the current state of the random number into the shuffle
	 * calculation to balance that shuffle a bit more.
	 */
	if (ec)
		time ^= ec->data;
	/*
	 * We fold the time value as much as possible to ensure that as many
	 * bits of the time stamp are included as possible.
	 */
	for (i = 0; ((DATA_SIZE_BITS + bits - 1) / bits) > i; i++) {
		shuffle ^= time & mask;
		time = time >> bits;
	}

	/*
	 * We add a lower boundary value to ensure we have a minimum
	 * RNG loop count.
	 */
	return (shuffle + (1<<min));
}

/**
 * CPU Jitter noise source -- this is the noise source based on the CPU
 * 			      execution time jitter
 *
 * This function injects the individual bits of the time value into the
 * entropy pool using an LFSR.
 *
 * The code is deliberately inefficient with respect to the bit shifting
 * and shall stay that way. This function is the root cause why the code
 * shall be compiled without optimization. This function not only acts as
 * LFSR operation, but this function's execution is used to measure
 * the CPU execution time jitter. Any change to the loop in this function
 * implies that careful retesting must be done.
 *
 * @ec [in] entropy collector struct -- may be NULL
 * @time [in] time stamp to be injected
 * @loop_cnt [in] if a value not equal to 0 is set, use the given value as
 *		  number of loops to perform the LFSR
 *
 * Output:
 * updated ec->data
 */
static void jent_lfsr_time(struct rand_data *ec, uint64_t time,
			   uint64_t loop_cnt, int stuck)
{
	unsigned int i;
	uint64_t j = 0;
	uint64_t new = 0;
#define MAX_FOLD_LOOP_BIT 4
#define MIN_FOLD_LOOP_BIT 0
	uint64_t lfsr_loop_cnt =
		jent_loop_shuffle(ec, MAX_FOLD_LOOP_BIT, MIN_FOLD_LOOP_BIT);

	/*
	 * testing purposes -- allow test app to set the counter, not
	 * needed during runtime
	 */
	if (loop_cnt)
		lfsr_loop_cnt = loop_cnt;
	for (j = 0; j < lfsr_loop_cnt; j++) {
		new = ec->data;
		for (i = 1; (DATA_SIZE_BITS) >= i; i++) {
			uint64_t tmp = time << (DATA_SIZE_BITS - i);

			tmp = tmp >> (DATA_SIZE_BITS - 1);

			/*
			* Fibonacci LSFR with polynomial of
			*  x^64 + x^61 + x^56 + x^31 + x^28 + x^23 + 1 which is
			*  primitive according to
			*   http://poincare.matf.bg.ac.rs/~ezivkovm/publications/primpol1.pdf
			* (the shift values are the polynomial values minus one
			* due to counting bits from 0 to 63). As the current
			* position is always the LSB, the polynomial only needs
			* to shift data in from the left without wrap.
			*/
			tmp ^= ((new >> 63) & 1);
			tmp ^= ((new >> 60) & 1);
			tmp ^= ((new >> 55) & 1);
			tmp ^= ((new >> 30) & 1);
			tmp ^= ((new >> 27) & 1);
			tmp ^= ((new >> 22) & 1);
			new <<= 1;
			new ^= tmp;
		}
	}

	/*
	 * If the time stamp is stuck, do not finally insert the value into
	 * the entropy pool. Although this operation should not do any harm
	 * even when the time stamp has no entropy, SP800-90B requires that
	 * any conditioning operation (SP800-90B considers the LFSR to be a
	 * conditioning operation) to have an identical amount of input
	 * data according to section 3.1.5.
	 */
	if (!stuck)
		ec->data = new;
}

/**
 * Memory Access noise source -- this is a noise source based on variations in
 * 				 memory access times
 *
 * This function performs memory accesses which will add to the timing
 * variations due to an unknown amount of CPU wait states that need to be
 * added when accessing memory. The memory size should be larger than the L1
 * caches as outlined in the documentation and the associated testing.
 *
 * The L1 cache has a very high bandwidth, albeit its access rate is  usually
 * slower than accessing CPU registers. Therefore, L1 accesses only add minimal
 * variations as the CPU has hardly to wait. Starting with L2, significant
 * variations are added because L2 typically does not belong to the CPU any more
 * and therefore a wider range of CPU wait states is necessary for accesses.
 * L3 and real memory accesses have even a wider range of wait states. However,
 * to reliably access either L3 or memory, the ec->mem memory must be quite
 * large which is usually not desirable.
 *
 * @ec [in] Reference to the entropy collector with the memory access data -- if
 *	    the reference to the memory block to be accessed is NULL, this noise
 *	    source is disabled
 * @loop_cnt [in] if a value not equal to 0 is set, use the given value as
 *		  number of loops to perform the folding
 */
static void jent_memaccess(struct rand_data *ec, uint64_t loop_cnt)
{
	unsigned int wrap = 0;
	uint64_t i = 0;
#define MAX_ACC_LOOP_BIT 7
#define MIN_ACC_LOOP_BIT 0
	uint64_t acc_loop_cnt =
		jent_loop_shuffle(ec, MAX_ACC_LOOP_BIT, MIN_ACC_LOOP_BIT);

	if (NULL == ec || NULL == ec->mem)
		return;
	wrap = ec->memblocksize * ec->memblocks;

	/*
	 * testing purposes -- allow test app to set the counter, not
	 * needed during runtime
	 */
	if (loop_cnt)
		acc_loop_cnt = loop_cnt;

	for (i = 0; i < (ec->memaccessloops + acc_loop_cnt); i++) {
		unsigned char *tmpval = ec->mem + ec->memlocation;
		/*
		 * memory access: just add 1 to one byte,
		 * wrap at 255 -- memory access implies read
		 * from and write to memory location
		 */
		*tmpval = (*tmpval + 1) & 0xff;
		/*
		 * Addition of memblocksize - 1 to pointer
		 * with wrap around logic to ensure that every
		 * memory location is hit evenly
		 */
		ec->memlocation = ec->memlocation + ec->memblocksize - 1;
		ec->memlocation = ec->memlocation % wrap;
	}
}

/***************************************************************************
 * Start of entropy processing logic
 ***************************************************************************/
/**
 * This is the heart of the entropy generation: calculate time deltas and
 * use the CPU jitter in the time deltas. The jitter is injected into the
 * entropy pool.
 *
 * WARNING: ensure that ->prev_time is primed before using the output
 * 	    of this function! This can be done by calling this function
 * 	    and not using its result.
 *
 * @ec [in] Reference to entropy collector
 *
 * @return: result of stuck test
 */
static int jent_measure_jitter(struct rand_data *ec)
{
	uint64_t time = 0;
	uint64_t current_delta = 0;
	int stuck;

	/* Invoke one noise source before time measurement to add variations */
	jent_memaccess(ec, 0);

	/*
	 * Get time stamp and calculate time delta to previous
	 * invocation to measure the timing variations
	 */
	jent_get_nstime(&time);
	current_delta = jent_delta(ec->prev_time, time);
	ec->prev_time = time;

	/* Check whether we have a stuck measurement. */
	stuck = jent_stuck(ec, current_delta);

	/* Now call the next noise sources which also injects the data */
	jent_lfsr_time(ec, current_delta, 0, stuck);

	return stuck;
}

/**
 * Generator of one 64 bit random number
 * Function fills rand_data->data
 *
 * @ec [in] Reference to entropy collector
 */
static void jent_gen_entropy(struct rand_data *ec)
{
	unsigned int k = 0;

	/* priming of the ->prev_time value */
	jent_measure_jitter(ec);

	while (1) {
		/* If a stuck measurement is received, repeat measurement */
		if (jent_measure_jitter(ec))
			continue;

		/*
		 * We multiply the loop value with ->osr to obtain the
		 * oversampling rate requested by the caller
		 */
		if (++k >= (DATA_SIZE_BITS * ec->osr))
			break;
	}
}

/**
 * Entry function: Obtain entropy for the caller.
 *
 * This function invokes the entropy gathering logic as often to generate
 * as many bytes as requested by the caller. The entropy gathering logic
 * creates 64 bit per invocation.
 *
 * This function truncates the last 64 bit entropy value output to the exact
 * size specified by the caller.
 *
 * @ec [in] Reference to entropy collector
 * @data [out] pointer to buffer for storing random data -- buffer must
 *	       already exist
 * @len [in] size of the buffer, specifying also the requested number of random
 *	     in bytes
 *
 * @return number of bytes returned when request is fulfilled or an error
 *
 * The following error codes can occur:
 *	-1	entropy_collector is NULL
 *	-2	RCT failed
 *	-3	Chi-Squared test failed
 */
JENT_PRIVATE_STATIC
ssize_t jent_read_entropy(struct rand_data *ec, char *data, size_t len)
{
	char *p = data;
	size_t orig_len = len;

	if (NULL == ec)
		return -1;

	while (0 < len) {
		size_t tocopy;

		jent_gen_entropy(ec);

		if (jent_health_failure(ec)) {
			if (jent_rct_failure(ec))
				return -2;
			else
				return -3;
		}

		if ((DATA_SIZE_BITS / 8) < len)
			tocopy = (DATA_SIZE_BITS / 8);
		else
			tocopy = len;
		memcpy(p, &ec->data, tocopy);

		len -= tocopy;
		p += tocopy;
	}

	/*
	 * To be on the safe side, we generate one more round of entropy
	 * which we do not give out to the caller. That round shall ensure
	 * that in case the calling application crashes, memory dumps, pages
	 * out, or due to the CPU Jitter RNG lingering in memory for long
	 * time without being moved and an attacker cracks the application,
	 * all he reads in the entropy pool is a value that is NEVER EVER
	 * being used for anything. Thus, he does NOT see the previous value
	 * that was returned to the caller for cryptographic purposes.
	 */
	/*
	 * If we use secured memory, do not use that precaution as the secure
	 * memory protects the entropy pool. Moreover, note that using this
	 * call reduces the speed of the RNG by up to half
	 */
#ifndef CONFIG_CRYPTO_CPU_JITTERENTROPY_SECURE_MEMORY
	jent_gen_entropy(ec);
#endif
	return orig_len;
}

/***************************************************************************
 * Initialization logic
 ***************************************************************************/

JENT_PRIVATE_STATIC
struct rand_data *jent_entropy_collector_alloc(unsigned int osr,
					       unsigned int flags)
{
	struct rand_data *entropy_collector;

	entropy_collector = jent_zalloc(sizeof(struct rand_data));
	if (NULL == entropy_collector)
		return NULL;

	if (!(flags & JENT_DISABLE_MEMORY_ACCESS)) {
		/* Allocate memory for adding variations based on memory
		 * access
		 */
		entropy_collector->mem = 
			(unsigned char *)jent_zalloc(JENT_MEMORY_SIZE);
		if (NULL == entropy_collector->mem) {
			jent_zfree(entropy_collector, sizeof(struct rand_data));
			return NULL;
		}
		entropy_collector->memblocksize = JENT_MEMORY_BLOCKSIZE;
		entropy_collector->memblocks = JENT_MEMORY_BLOCKS;
		entropy_collector->memaccessloops = JENT_MEMORY_ACCESSLOOPS;
	}

	/* verify and set the oversampling rate */
	if (0 == osr)
		osr = 1; /* minimum sampling rate is 1 */
	entropy_collector->osr = osr;

	if (jent_fips_enabled())
		entropy_collector->fips_enabled = 1;

	/* fill the data pad with non-zero values */
	jent_gen_entropy(entropy_collector);

	return entropy_collector;
}

JENT_PRIVATE_STATIC
void jent_entropy_collector_free(struct rand_data *entropy_collector)
{
	if (NULL != entropy_collector) {
		if (NULL != entropy_collector->mem) {
			jent_zfree(entropy_collector->mem, JENT_MEMORY_SIZE);
			entropy_collector->mem = NULL;
		}
		jent_zfree(entropy_collector, sizeof(struct rand_data));
	}
}

JENT_PRIVATE_STATIC
int jent_entropy_init(void)
{
	int i;
	uint64_t delta_sum = 0;
	uint64_t old_delta = 0;
	unsigned int nonstuck = 0;
	int time_backwards = 0;
	int count_mod = 0;
	int count_stuck = 0;
	struct rand_data ec;

	memset(&ec, 0, sizeof(ec));

	/* Required for RCT */
	ec.osr = 1;
	if (jent_fips_enabled())
		ec.fips_enabled = 1;

	/* We could perform statistical tests here, but the problem is
	 * that we only have a few loop counts to do testing. These
	 * loop counts may show some slight skew and we produce
	 * false positives.
	 *
	 * Moreover, only old systems show potentially problematic
	 * jitter entropy that could potentially be caught here. But
	 * the RNG is intended for hardware that is available or widely
	 * used, but not old systems that are long out of favor. Thus,
	 * no statistical tests.
	 */

	/*
	 * We could add a check for system capabilities such as clock_getres or
	 * check for CONFIG_X86_TSC, but it does not make much sense as the
	 * following sanity checks verify that we have a high-resolution
	 * timer.
	 */
	/*
	 * TESTLOOPCOUNT needs some loops to identify edge systems. 100 is
	 * definitely too little.
	 *
	 * SP800-90B requires at least 1024 initial test cycles.
	 */
#define TESTLOOPCOUNT 1024
#define CLEARCACHE 100
	for (i = 0; (TESTLOOPCOUNT + CLEARCACHE) > i; i++) {
		uint64_t time = 0;
		uint64_t time2 = 0;
		uint64_t delta = 0;
		unsigned int lowdelta = 0;
		int stuck;

		/* Invoke core entropy collection logic */
		jent_get_nstime(&time);
		ec.prev_time = time;
		jent_memaccess(&ec, 0);
		jent_lfsr_time(&ec, time, 0, 0);
		jent_get_nstime(&time2);

		/* test whether timer works */
		if (!time || !time2)
			return ENOTIME;
		delta = jent_delta(time, time2);
		/*
		 * test whether timer is fine grained enough to provide
		 * delta even when called shortly after each other -- this
		 * implies that we also have a high resolution timer
		 */
		if (!delta)
			return ECOARSETIME;

		stuck = jent_stuck(&ec, delta);

		/*
		 * up to here we did not modify any variable that will be
		 * evaluated later, but we already performed some work. Thus we
		 * already have had an impact on the caches, branch prediction,
		 * etc. with the goal to clear it to get the worst case
		 * measurements.
		 */
		if (CLEARCACHE > i)
			continue;

		if (stuck)
			count_stuck++;
		else {
			nonstuck++;

			/*
			 * Ensure that the APT succeeded.
			 *
			 * With the check below that count_stuck must be less
			 * than 10% of the overall generated raw entropy values
			 * it is guaranteed that the APT is invoked at
			 * floor((TESTLOOPCOUNT * 0.9) / 64) == 14 times.
			 */
			if ((nonstuck % JENT_APT_WINDOW_SIZE) == 0) {
				jent_apt_reset(&ec,
					       delta & JENT_APT_WORD_MASK);
				if (jent_health_failure(&ec))
					return EHEALTH;
			}
		}

		/* Validate RCT */
		if (jent_rct_failure(&ec))
			return ERCT;

		/* test whether we have an increasing timer */
		if (!(time2 > time))
			time_backwards++;

		/* use 32 bit value to ensure compilation on 32 bit arches */
		lowdelta = (uint64_t)time2 - (uint64_t)time;
		if (!(lowdelta % 100))
			count_mod++;

		/*
		 * ensure that we have a varying delta timer which is necessary
		 * for the calculation of entropy -- perform this check
		 * only after the first loop is executed as we need to prime
		 * the old_data value
		 */
		if (delta > old_delta)
			delta_sum += (delta - old_delta);
		else
			delta_sum += (old_delta - delta);
		old_delta = delta;
	}

	/*
	 * we allow up to three times the time running backwards.
	 * CLOCK_REALTIME is affected by adjtime and NTP operations. Thus,
	 * if such an operation just happens to interfere with our test, it
	 * should not fail. The value of 3 should cover the NTP case being
	 * performed during our test run.
	 */
	if (3 < time_backwards)
		return ENOMONOTONIC;

	/*
	 * Variations of deltas of time must on average be larger
	 * than 1 to ensure the entropy estimation
	 * implied with 1 is preserved
	 */
	if ((delta_sum) <= 1)
		return EMINVARVAR;

	/*
	 * Ensure that we have variations in the time stamp below 10 for at least
	 * 10% of all checks -- on some platforms, the counter increments in
	 * multiples of 100, but not always
	 */
	if ((TESTLOOPCOUNT/10 * 9) < count_mod)
		return ECOARSETIME;

	/*
	 * If we have more than 90% stuck results, then this Jitter RNG is
	 * likely to not work well.
	 */
	if ((TESTLOOPCOUNT/10 * 9) < count_stuck)
		return ESTUCK;

	return 0;
}