--- /dev/null
+/*
+ * Non-physical true random number generator based on timing jitter.
+ *
+ * Copyright Stephan Mueller <smueller@chronox.de>, 2014
+ *
+ * Design
+ * ======
+ *
+ * See http://www.chronox.de/jent.html
+ *
+ * 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.
+ */
+
+/*
+ * This Jitterentropy RNG is based on the jitterentropy library
+ * version 1.1.0 provided at http://www.chronox.de/jent.html
+ */
+
+#include <linux/module.h>
+#include <linux/slab.h>
+#include <linux/module.h>
+#include <linux/fips.h>
+#include <linux/time.h>
+#include <linux/crypto.h>
+#include <crypto/internal/rng.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.c."
+#endif
+
+/* The entropy pool */
+struct rand_data {
+ /* all data values that are vital to maintain the security
+ * of the RNG are marked as SENSITIVE. A user must not
+ * access that information while the RNG executes its loops to
+ * calculate the next random value. */
+ __u64 data; /* SENSITIVE Actual random number */
+ __u64 old_data; /* SENSITIVE Previous random number */
+ __u64 prev_time; /* SENSITIVE Previous time stamp */
+#define DATA_SIZE_BITS ((sizeof(__u64)) * 8)
+ __u64 last_delta; /* SENSITIVE stuck test */
+ __s64 last_delta2; /* SENSITIVE stuck test */
+ unsigned int stuck:1; /* Time measurement stuck */
+ unsigned int osr; /* Oversample rate */
+ unsigned int stir:1; /* Post-processing stirring */
+ unsigned int disable_unbias:1; /* Deactivate Von-Neuman unbias */
+#define JENT_MEMORY_BLOCKS 64
+#define JENT_MEMORY_BLOCKSIZE 32
+#define JENT_MEMORY_ACCESSLOOPS 128
+#define JENT_MEMORY_SIZE (JENT_MEMORY_BLOCKS*JENT_MEMORY_BLOCKSIZE)
+ unsigned char *mem; /* Memory access location with size of
+ * memblocks * memblocksize */
+ unsigned int memlocation; /* Pointer to byte in *mem */
+ unsigned int memblocks; /* Number of memory blocks in *mem */
+ unsigned int memblocksize; /* Size of one memory block in bytes */
+ unsigned int memaccessloops; /* Number of memory accesses per random
+ * bit generation */
+};
+
+/* Flags that can be used to initialize the RNG */
+#define JENT_DISABLE_STIR (1<<0) /* Disable stirring the entropy pool */
+#define JENT_DISABLE_UNBIAS (1<<1) /* Disable the Von-Neuman Unbiaser */
+#define JENT_DISABLE_MEMORY_ACCESS (1<<2) /* Disable memory access for more
+ * entropy, saves MEMORY_SIZE RAM for
+ * entropy collector */
+
+#define DRIVER_NAME "jitterentropy"
+
+/* -- error codes for init function -- */
+#define JENT_ENOTIME 1 /* Timer service not available */
+#define JENT_ECOARSETIME 2 /* Timer too coarse for RNG */
+#define JENT_ENOMONOTONIC 3 /* Timer is not monotonic increasing */
+#define JENT_EMINVARIATION 4 /* Timer variations too small for RNG */
+#define JENT_EVARVAR 5 /* Timer does not produce variations of
+ * variations (2nd derivation of time is
+ * zero). */
+#define JENT_EMINVARVAR 6 /* Timer variations of variations is tooi
+ * small. */
+
+/***************************************************************************
+ * Helper functions
+ ***************************************************************************/
+
+static inline void jent_get_nstime(__u64 *out)
+{
+ struct timespec ts;
+ __u64 tmp = 0;
+
+ tmp = random_get_entropy();
+
+ /*
+ * If random_get_entropy does not return a value (which is possible on,
+ * for example, MIPS), invoke __getnstimeofday
+ * hoping that there are timers we can work with.
+ *
+ * The list of available timers can be obtained from
+ * /sys/devices/system/clocksource/clocksource0/available_clocksource
+ * and are registered with clocksource_register()
+ */
+ if ((0 == tmp) &&
+#ifndef MODULE
+ (0 == timekeeping_valid_for_hres()) &&
+#endif
+ (0 == __getnstimeofday(&ts))) {
+ tmp = ts.tv_sec;
+ tmp = tmp << 32;
+ tmp = tmp | ts.tv_nsec;
+ }
+
+ *out = tmp;
+}
+
+
+/**
+ * Update of the loop count used for the next round of
+ * an entropy collection.
+ *
+ * Input:
+ * @ec entropy collector struct -- may be NULL
+ * @bits is the number of low bits of the timer to consider
+ * @min 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 __u64 jent_loop_shuffle(struct rand_data *ec,
+ unsigned int bits, unsigned int min)
+{
+ __u64 time = 0;
+ __u64 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) > 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));
+}
+
+/***************************************************************************
+ * Noise sources
+ ***************************************************************************/
+
+/**
+ * CPU Jitter noise source -- this is the noise source based on the CPU
+ * execution time jitter
+ *
+ * This function folds the time into one bit units by iterating
+ * through the DATA_SIZE_BITS bit time value as follows: assume our time value
+ * is 0xabcd
+ * 1st loop, 1st shift generates 0xd000
+ * 1st loop, 2nd shift generates 0x000d
+ * 2nd loop, 1st shift generates 0xcd00
+ * 2nd loop, 2nd shift generates 0x000c
+ * 3rd loop, 1st shift generates 0xbcd0
+ * 3rd loop, 2nd shift generates 0x000b
+ * 4th loop, 1st shift generates 0xabcd
+ * 4th loop, 2nd shift generates 0x000a
+ * Now, the values at the end of the 2nd shifts are XORed together.
+ *
+ * The code is deliberately inefficient 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 folding 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.
+ *
+ * Input:
+ * @ec entropy collector struct -- may be NULL
+ * @time time stamp to be folded
+ * @loop_cnt if a value not equal to 0 is set, use the given value as number of
+ * loops to perform the folding
+ *
+ * Output:
+ * @folded result of folding operation
+ *
+ * @return Number of loops the folding operation is performed
+ */
+static __u64 jent_fold_time(struct rand_data *ec, __u64 time,
+ __u64 *folded, __u64 loop_cnt)
+{
+ unsigned int i;
+ __u64 j = 0;
+ __u64 new = 0;
+#define MAX_FOLD_LOOP_BIT 4
+#define MIN_FOLD_LOOP_BIT 0
+ __u64 fold_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)
+ fold_loop_cnt = loop_cnt;
+ for (j = 0; j < fold_loop_cnt; j++) {
+ new = 0;
+ for (i = 1; (DATA_SIZE_BITS) >= i; i++) {
+ __u64 tmp = time << (DATA_SIZE_BITS - i);
+
+ tmp = tmp >> (DATA_SIZE_BITS - 1);
+ new ^= tmp;
+ }
+ }
+ *folded = new;
+ return fold_loop_cnt;
+}
+
+/**
+ * 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.
+ *
+ * Input:
+ * @ec 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 if a value not equal to 0 is set, use the given value as number of
+ * loops to perform the folding
+ *
+ * @return Number of memory access operations
+ */
+static unsigned int jent_memaccess(struct rand_data *ec, __u64 loop_cnt)
+{
+ unsigned char *tmpval = NULL;
+ unsigned int wrap = 0;
+ __u64 i = 0;
+#define MAX_ACC_LOOP_BIT 7
+#define MIN_ACC_LOOP_BIT 0
+ __u64 acc_loop_cnt =
+ jent_loop_shuffle(ec, MAX_ACC_LOOP_BIT, MIN_ACC_LOOP_BIT);
+
+ if (NULL == ec || NULL == ec->mem)
+ return 0;
+ 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++) {
+ 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;
+ }
+ return i;
+}
+
+/***************************************************************************
+ * Start of entropy processing logic
+ ***************************************************************************/
+
+/**
+ * Stuck test by checking the:
+ * 1st derivation of the jitter measurement (time delta)
+ * 2nd derivation of the jitter measurement (delta of time deltas)
+ * 3rd derivation of the jitter measurement (delta of delta of time deltas)
+ *
+ * All values must always be non-zero.
+ *
+ * Input:
+ * @ec Reference to entropy collector
+ * @current_delta Jitter time delta
+ *
+ * @return
+ * 0 jitter measurement not stuck (good bit)
+ * 1 jitter measurement stuck (reject bit)
+ */
+static void jent_stuck(struct rand_data *ec, __u64 current_delta)
+{
+ __s64 delta2 = ec->last_delta - current_delta;
+ __s64 delta3 = delta2 - ec->last_delta2;
+
+ ec->last_delta = current_delta;
+ ec->last_delta2 = delta2;
+
+ if (!current_delta || !delta2 || !delta3)
+ ec->stuck = 1;
+}
+
+/**
+ * This is the heart of the entropy generation: calculate time deltas and
+ * use the CPU jitter in the time deltas. The jitter is folded into one
+ * bit. You can call this function the "random bit generator" as it
+ * produces one random bit per invocation.
+ *
+ * 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.
+ *
+ * Input:
+ * @entropy_collector Reference to entropy collector
+ *
+ * @return One random bit
+ */
+static __u64 jent_measure_jitter(struct rand_data *ec)
+{
+ __u64 time = 0;
+ __u64 data = 0;
+ __u64 current_delta = 0;
+
+ /* 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 = time - ec->prev_time;
+ ec->prev_time = time;
+
+ /* Now call the next noise sources which also folds the data */
+ jent_fold_time(ec, current_delta, &data, 0);
+
+ /*
+ * Check whether we have a stuck measurement. The enforcement
+ * is performed after the stuck value has been mixed into the
+ * entropy pool.
+ */
+ jent_stuck(ec, current_delta);
+
+ return data;
+}
+
+/**
+ * Von Neuman unbias as explained in RFC 4086 section 4.2. As shown in the
+ * documentation of that RNG, the bits from jent_measure_jitter are considered
+ * independent which implies that the Von Neuman unbias operation is applicable.
+ * A proof of the Von-Neumann unbias operation to remove skews is given in the
+ * document "A proposal for: Functionality classes for random number
+ * generators", version 2.0 by Werner Schindler, section 5.4.1.
+ *
+ * Input:
+ * @entropy_collector Reference to entropy collector
+ *
+ * @return One random bit
+ */
+static __u64 jent_unbiased_bit(struct rand_data *entropy_collector)
+{
+ do {
+ __u64 a = jent_measure_jitter(entropy_collector);
+ __u64 b = jent_measure_jitter(entropy_collector);
+
+ if (a == b)
+ continue;
+ if (1 == a)
+ return 1;
+ else
+ return 0;
+ } while (1);
+}
+
+/**
+ * Shuffle the pool a bit by mixing some value with a bijective function (XOR)
+ * into the pool.
+ *
+ * The function generates a mixer value that depends on the bits set and the
+ * location of the set bits in the random number generated by the entropy
+ * source. Therefore, based on the generated random number, this mixer value
+ * can have 2**64 different values. That mixer value is initialized with the
+ * first two SHA-1 constants. After obtaining the mixer value, it is XORed into
+ * the random number.
+ *
+ * The mixer value is not assumed to contain any entropy. But due to the XOR
+ * operation, it can also not destroy any entropy present in the entropy pool.
+ *
+ * Input:
+ * @entropy_collector Reference to entropy collector
+ */
+static void jent_stir_pool(struct rand_data *entropy_collector)
+{
+ /*
+ * to shut up GCC on 32 bit, we have to initialize the 64 variable
+ * with two 32 bit variables
+ */
+ union c {
+ __u64 u64;
+ __u32 u32[2];
+ };
+ /*
+ * This constant is derived from the first two 32 bit initialization
+ * vectors of SHA-1 as defined in FIPS 180-4 section 5.3.1
+ */
+ union c constant;
+ /*
+ * The start value of the mixer variable is derived from the third
+ * and fourth 32 bit initialization vector of SHA-1 as defined in
+ * FIPS 180-4 section 5.3.1
+ */
+ union c mixer;
+ unsigned int i = 0;
+
+ /*
+ * Store the SHA-1 constants in reverse order to make up the 64 bit
+ * value -- this applies to a little endian system, on a big endian
+ * system, it reverses as expected. But this really does not matter
+ * as we do not rely on the specific numbers. We just pick the SHA-1
+ * constants as they have a good mix of bit set and unset.
+ */
+ constant.u32[1] = 0x67452301;
+ constant.u32[0] = 0xefcdab89;
+ mixer.u32[1] = 0x98badcfe;
+ mixer.u32[0] = 0x10325476;
+
+ for (i = 0; i < DATA_SIZE_BITS; i++) {
+ /*
+ * get the i-th bit of the input random number and only XOR
+ * the constant into the mixer value when that bit is set
+ */
+ if ((entropy_collector->data >> i) & 1)
+ mixer.u64 ^= constant.u64;
+ mixer.u64 = rol64(mixer.u64, 1);
+ }
+ entropy_collector->data ^= mixer.u64;
+}
+
+/**
+ * Generator of one 64 bit random number
+ * Function fills rand_data->data
+ *
+ * Input:
+ * @ec 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) {
+ __u64 data = 0;
+
+ if (ec->disable_unbias == 1)
+ data = jent_measure_jitter(ec);
+ else
+ data = jent_unbiased_bit(ec);
+
+ /* enforcement of the jent_stuck test */
+ if (ec->stuck) {
+ /*
+ * We only mix in the bit considered not appropriate
+ * without the LSFR. The reason is that if we apply
+ * the LSFR and we do not rotate, the 2nd bit with LSFR
+ * will cancel out the first LSFR application on the
+ * bad bit.
+ *
+ * And we do not rotate as we apply the next bit to the
+ * current bit location again.
+ */
+ ec->data ^= data;
+ ec->stuck = 0;
+ continue;
+ }
+
+ /*
+ * Fibonacci LSFR with polynom 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 polynom values minus one
+ * due to counting bits from 0 to 63). As the current
+ * position is always the LSB, the polynom only needs
+ * to shift data in from the left without wrap.
+ */
+ ec->data ^= data;
+ ec->data ^= ((ec->data >> 63) & 1);
+ ec->data ^= ((ec->data >> 60) & 1);
+ ec->data ^= ((ec->data >> 55) & 1);
+ ec->data ^= ((ec->data >> 30) & 1);
+ ec->data ^= ((ec->data >> 27) & 1);
+ ec->data ^= ((ec->data >> 22) & 1);
+ ec->data = rol64(ec->data, 1);
+
+ /*
+ * We multiply the loop value with ->osr to obtain the
+ * oversampling rate requested by the caller
+ */
+ if (++k >= (DATA_SIZE_BITS * ec->osr))
+ break;
+ }
+ if (ec->stir)
+ jent_stir_pool(ec);
+}
+
+/**
+ * The continuous test required by FIPS 140-2 -- the function automatically
+ * primes the test if needed.
+ *
+ * Return:
+ * 0 if FIPS test passed
+ * < 0 if FIPS test failed
+ */
+static void jent_fips_test(struct rand_data *ec)
+{
+ if (!fips_enabled)
+ return;
+
+ /* prime the FIPS test */
+ if (!ec->old_data) {
+ ec->old_data = ec->data;
+ jent_gen_entropy(ec);
+ }
+
+ if (ec->data == ec->old_data)
+ panic(DRIVER_NAME ": Duplicate output detected\n");
+
+ ec->old_data = ec->data;
+}
+
+
+/**
+ * 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.
+ *
+ * Input:
+ * @ec Reference to entropy collector
+ * @data pointer to buffer for storing random data -- buffer must already
+ * exist
+ * @len size of the buffer, specifying also the requested number of random
+ * in bytes
+ *
+ * @return 0 when request is fulfilled or an error
+ *
+ * The following error codes can occur:
+ * -1 entropy_collector is NULL
+ */
+static ssize_t jent_read_entropy(struct rand_data *ec, u8 *data, size_t len)
+{
+ u8 *p = data;
+
+ if (!ec)
+ return -EINVAL;
+
+ while (0 < len) {
+ size_t tocopy;
+
+ jent_gen_entropy(ec);
+ jent_fips_test(ec);
+ if ((DATA_SIZE_BITS / 8) < len)
+ tocopy = (DATA_SIZE_BITS / 8);
+ else
+ tocopy = len;
+ memcpy(p, &ec->data, tocopy);
+
+ len -= tocopy;
+ p += tocopy;
+ }
+
+ return 0;
+}
+
+/***************************************************************************
+ * Initialization logic
+ ***************************************************************************/
+
+static struct rand_data *jent_entropy_collector_alloc(unsigned int osr,
+ unsigned int flags)
+{
+ struct rand_data *entropy_collector;
+
+ entropy_collector = kzalloc(sizeof(struct rand_data), GFP_KERNEL);
+ if (!entropy_collector)
+ return NULL;
+
+ if (!(flags & JENT_DISABLE_MEMORY_ACCESS)) {
+ /* Allocate memory for adding variations based on memory
+ * access
+ */
+ entropy_collector->mem = kzalloc(JENT_MEMORY_SIZE, GFP_KERNEL);
+ if (!entropy_collector->mem) {
+ kfree(entropy_collector);
+ 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;
+
+ entropy_collector->stir = 1;
+ if (flags & JENT_DISABLE_STIR)
+ entropy_collector->stir = 0;
+ if (flags & JENT_DISABLE_UNBIAS)
+ entropy_collector->disable_unbias = 1;
+
+ /* fill the data pad with non-zero values */
+ jent_gen_entropy(entropy_collector);
+
+ return entropy_collector;
+}
+
+static void jent_entropy_collector_free(struct rand_data *entropy_collector)
+{
+ if (entropy_collector->mem)
+ kzfree(entropy_collector->mem);
+ entropy_collector->mem = NULL;
+ if (entropy_collector)
+ kzfree(entropy_collector);
+ entropy_collector = NULL;
+}
+
+static int jent_entropy_init(void)
+{
+ int i;
+ __u64 delta_sum = 0;
+ __u64 old_delta = 0;
+ int time_backwards = 0;
+ int count_var = 0;
+ int count_mod = 0;
+
+ /* 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.
+ */
+#define TESTLOOPCOUNT 300
+#define CLEARCACHE 100
+ for (i = 0; (TESTLOOPCOUNT + CLEARCACHE) > i; i++) {
+ __u64 time = 0;
+ __u64 time2 = 0;
+ __u64 folded = 0;
+ __u64 delta = 0;
+ unsigned int lowdelta = 0;
+
+ jent_get_nstime(&time);
+ jent_fold_time(NULL, time, &folded, 1<<MIN_FOLD_LOOP_BIT);
+ jent_get_nstime(&time2);
+
+ /* test whether timer works */
+ if (!time || !time2)
+ return JENT_ENOTIME;
+ delta = time2 - time;
+ /*
+ * 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 JENT_ECOARSETIME;
+
+ /*
+ * 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;
+
+ /* test whether we have an increasing timer */
+ if (!(time2 > time))
+ time_backwards++;
+
+ /*
+ * Avoid modulo of 64 bit integer to allow code to compile
+ * on 32 bit architectures.
+ */
+ lowdelta = time2 - 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 (i) {
+ if (delta != old_delta)
+ count_var++;
+ 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 JENT_ENOMONOTONIC;
+ /* Error if the time variances are always identical */
+ if (!delta_sum)
+ return JENT_EVARVAR;
+
+ /*
+ * 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 JENT_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 JENT_ECOARSETIME;
+
+ return 0;
+}
+
+/***************************************************************************
+ * Kernel crypto API interface
+ ***************************************************************************/
+
+struct jitterentropy {
+ spinlock_t jent_lock;
+ struct rand_data *entropy_collector;
+};
+
+static int jent_kcapi_init(struct crypto_tfm *tfm)
+{
+ struct jitterentropy *rng = crypto_tfm_ctx(tfm);
+ int ret = 0;
+
+ rng->entropy_collector = jent_entropy_collector_alloc(1, 0);
+ if (!rng->entropy_collector)
+ ret = -ENOMEM;
+
+ spin_lock_init(&rng->jent_lock);
+ return ret;
+}
+
+static void jent_kcapi_cleanup(struct crypto_tfm *tfm)
+{
+ struct jitterentropy *rng = crypto_tfm_ctx(tfm);
+
+ spin_lock(&rng->jent_lock);
+ if (rng->entropy_collector)
+ jent_entropy_collector_free(rng->entropy_collector);
+ rng->entropy_collector = NULL;
+ spin_unlock(&rng->jent_lock);
+}
+
+static int jent_kcapi_random(struct crypto_rng *tfm,
+ const u8 *src, unsigned int slen,
+ u8 *rdata, unsigned int dlen)
+{
+ struct jitterentropy *rng = crypto_rng_ctx(tfm);
+ int ret = 0;
+
+ spin_lock(&rng->jent_lock);
+ ret = jent_read_entropy(rng->entropy_collector, rdata, dlen);
+ spin_unlock(&rng->jent_lock);
+
+ return ret;
+}
+
+static int jent_kcapi_reset(struct crypto_rng *tfm,
+ const u8 *seed, unsigned int slen)
+{
+ return 0;
+}
+
+static struct rng_alg jent_alg = {
+ .generate = jent_kcapi_random,
+ .seed = jent_kcapi_reset,
+ .seedsize = 0,
+ .base = {
+ .cra_name = "jitterentropy_rng",
+ .cra_driver_name = "jitterentropy_rng",
+ .cra_priority = 100,
+ .cra_ctxsize = sizeof(struct jitterentropy),
+ .cra_module = THIS_MODULE,
+ .cra_init = jent_kcapi_init,
+ .cra_exit = jent_kcapi_cleanup,
+
+ }
+};
+
+static int __init jent_mod_init(void)
+{
+ int ret = 0;
+
+ ret = jent_entropy_init();
+ if (ret) {
+ pr_info(DRIVER_NAME ": Initialization failed with host not compliant with requirements: %d\n", ret);
+ return -EFAULT;
+ }
+ return crypto_register_rng(&jent_alg);
+}
+
+static void __exit jent_mod_exit(void)
+{
+ crypto_unregister_rng(&jent_alg);
+}
+
+module_init(jent_mod_init);
+module_exit(jent_mod_exit);
+
+MODULE_LICENSE("Dual BSD/GPL");
+MODULE_AUTHOR("Stephan Mueller <smueller@chronox.de>");
+MODULE_DESCRIPTION("Non-physical True Random Number Generator based on CPU Jitter");
+MODULE_ALIAS_CRYPTO("jitterentropy_rng");
projects / GitHub / LineageOS / G12 / android_kernel_amlogic_linux-4.9.git / commitdiff