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/*
* Non-physical true random number generator based on timing jitter --
* Jitter RNG standalone code.
*
* Copyright Stephan Mueller <smueller@chronox.de>, 2015
*
* 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
*/
#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
typedef unsigned long long __u64;
typedef long long __s64;
typedef unsigned int __u32;
#define NULL ((void *) 0)
/* 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 */
/* -- 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
***************************************************************************/
void jent_get_nstime(__u64 *out);
__u64 jent_rol64(__u64 word, unsigned int shift);
void *jent_zalloc(unsigned int len);
void jent_zfree(void *ptr);
int jent_fips_enabled(void);
void jent_panic(char *s);
void jent_memcpy(void *dest, const void *src, unsigned int n);
/**
* 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
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