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![Thorsten Blum](/assets/img/avatar_default.png)
The PDF is also available via https. Signed-off-by: Thorsten Blum <thorsten.blum@toblux.com> Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>
829 lines
26 KiB
C
829 lines
26 KiB
C
/*
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* Non-physical true random number generator based on timing jitter --
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* Jitter RNG standalone code.
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*
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* Copyright Stephan Mueller <smueller@chronox.de>, 2015 - 2023
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*
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* Design
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* ======
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*
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* See https://www.chronox.de/jent.html
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*
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* License
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* =======
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*
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* Redistribution and use in source and binary forms, with or without
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* modification, are permitted provided that the following conditions
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* are met:
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* 1. Redistributions of source code must retain the above copyright
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* notice, and the entire permission notice in its entirety,
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* including the disclaimer of warranties.
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* 2. Redistributions in binary form must reproduce the above copyright
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* notice, this list of conditions and the following disclaimer in the
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* documentation and/or other materials provided with the distribution.
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* 3. The name of the author may not be used to endorse or promote
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* products derived from this software without specific prior
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* written permission.
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*
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* ALTERNATIVELY, this product may be distributed under the terms of
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* the GNU General Public License, in which case the provisions of the GPL2 are
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* required INSTEAD OF the above restrictions. (This clause is
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* necessary due to a potential bad interaction between the GPL and
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* the restrictions contained in a BSD-style copyright.)
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*
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* THIS SOFTWARE IS PROVIDED ``AS IS'' AND ANY EXPRESS OR IMPLIED
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* WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
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* OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE, ALL OF
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* WHICH ARE HEREBY DISCLAIMED. IN NO EVENT SHALL THE AUTHOR BE
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* LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
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* CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT
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* OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR
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* BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF
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* LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
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* (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE
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* USE OF THIS SOFTWARE, EVEN IF NOT ADVISED OF THE POSSIBILITY OF SUCH
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* DAMAGE.
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*/
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/*
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* This Jitterentropy RNG is based on the jitterentropy library
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* version 3.4.0 provided at https://www.chronox.de/jent.html
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*/
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#ifdef __OPTIMIZE__
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#error "The CPU Jitter random number generator must not be compiled with optimizations. See documentation. Use the compiler switch -O0 for compiling jitterentropy.c."
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#endif
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typedef unsigned long long __u64;
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typedef long long __s64;
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typedef unsigned int __u32;
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typedef unsigned char u8;
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#define NULL ((void *) 0)
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/* The entropy pool */
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struct rand_data {
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/* SHA3-256 is used as conditioner */
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#define DATA_SIZE_BITS 256
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/* all data values that are vital to maintain the security
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* of the RNG are marked as SENSITIVE. A user must not
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* access that information while the RNG executes its loops to
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* calculate the next random value. */
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void *hash_state; /* SENSITIVE hash state entropy pool */
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__u64 prev_time; /* SENSITIVE Previous time stamp */
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__u64 last_delta; /* SENSITIVE stuck test */
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__s64 last_delta2; /* SENSITIVE stuck test */
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unsigned int flags; /* Flags used to initialize */
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unsigned int osr; /* Oversample rate */
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#define JENT_MEMORY_ACCESSLOOPS 128
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#define JENT_MEMORY_SIZE \
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(CONFIG_CRYPTO_JITTERENTROPY_MEMORY_BLOCKS * \
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CONFIG_CRYPTO_JITTERENTROPY_MEMORY_BLOCKSIZE)
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unsigned char *mem; /* Memory access location with size of
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* memblocks * memblocksize */
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unsigned int memlocation; /* Pointer to byte in *mem */
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unsigned int memblocks; /* Number of memory blocks in *mem */
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unsigned int memblocksize; /* Size of one memory block in bytes */
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unsigned int memaccessloops; /* Number of memory accesses per random
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* bit generation */
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/* Repetition Count Test */
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unsigned int rct_count; /* Number of stuck values */
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/* Adaptive Proportion Test cutoff values */
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unsigned int apt_cutoff; /* Intermittent health test failure */
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unsigned int apt_cutoff_permanent; /* Permanent health test failure */
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#define JENT_APT_WINDOW_SIZE 512 /* Data window size */
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/* LSB of time stamp to process */
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#define JENT_APT_LSB 16
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#define JENT_APT_WORD_MASK (JENT_APT_LSB - 1)
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unsigned int apt_observations; /* Number of collected observations */
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unsigned int apt_count; /* APT counter */
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unsigned int apt_base; /* APT base reference */
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unsigned int health_failure; /* Record health failure */
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unsigned int apt_base_set:1; /* APT base reference set? */
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};
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/* Flags that can be used to initialize the RNG */
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#define JENT_DISABLE_MEMORY_ACCESS (1<<2) /* Disable memory access for more
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* entropy, saves MEMORY_SIZE RAM for
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* entropy collector */
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/* -- error codes for init function -- */
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#define JENT_ENOTIME 1 /* Timer service not available */
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#define JENT_ECOARSETIME 2 /* Timer too coarse for RNG */
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#define JENT_ENOMONOTONIC 3 /* Timer is not monotonic increasing */
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#define JENT_EVARVAR 5 /* Timer does not produce variations of
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* variations (2nd derivation of time is
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* zero). */
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#define JENT_ESTUCK 8 /* Too many stuck results during init. */
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#define JENT_EHEALTH 9 /* Health test failed during initialization */
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#define JENT_ERCT 10 /* RCT failed during initialization */
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#define JENT_EHASH 11 /* Hash self test failed */
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#define JENT_EMEM 12 /* Can't allocate memory for initialization */
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#define JENT_RCT_FAILURE 1 /* Failure in RCT health test. */
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#define JENT_APT_FAILURE 2 /* Failure in APT health test. */
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#define JENT_PERMANENT_FAILURE_SHIFT 16
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#define JENT_PERMANENT_FAILURE(x) (x << JENT_PERMANENT_FAILURE_SHIFT)
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#define JENT_RCT_FAILURE_PERMANENT JENT_PERMANENT_FAILURE(JENT_RCT_FAILURE)
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#define JENT_APT_FAILURE_PERMANENT JENT_PERMANENT_FAILURE(JENT_APT_FAILURE)
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/*
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* The output n bits can receive more than n bits of min entropy, of course,
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* but the fixed output of the conditioning function can only asymptotically
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* approach the output size bits of min entropy, not attain that bound. Random
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* maps will tend to have output collisions, which reduces the creditable
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* output entropy (that is what SP 800-90B Section 3.1.5.1.2 attempts to bound).
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*
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* The value "64" is justified in Appendix A.4 of the current 90C draft,
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* and aligns with NIST's in "epsilon" definition in this document, which is
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* that a string can be considered "full entropy" if you can bound the min
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* entropy in each bit of output to at least 1-epsilon, where epsilon is
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* required to be <= 2^(-32).
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*/
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#define JENT_ENTROPY_SAFETY_FACTOR 64
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#include <linux/fips.h>
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#include "jitterentropy.h"
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/***************************************************************************
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* Adaptive Proportion Test
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*
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* This test complies with SP800-90B section 4.4.2.
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***************************************************************************/
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/*
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* See the SP 800-90B comment #10b for the corrected cutoff for the SP 800-90B
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* APT.
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* https://www.untruth.org/~josh/sp80090b/UL%20SP800-90B-final%20comments%20v1.9%2020191212.pdf
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* In the syntax of R, this is C = 2 + qbinom(1 − 2^(−30), 511, 2^(-1/osr)).
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* (The original formula wasn't correct because the first symbol must
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* necessarily have been observed, so there is no chance of observing 0 of these
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* symbols.)
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*
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* For the alpha < 2^-53, R cannot be used as it uses a float data type without
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* arbitrary precision. A SageMath script is used to calculate those cutoff
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* values.
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*
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* For any value above 14, this yields the maximal allowable value of 512
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* (by FIPS 140-2 IG 7.19 Resolution # 16, we cannot choose a cutoff value that
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* renders the test unable to fail).
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*/
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static const unsigned int jent_apt_cutoff_lookup[15] = {
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325, 422, 459, 477, 488, 494, 499, 502,
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505, 507, 508, 509, 510, 511, 512 };
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static const unsigned int jent_apt_cutoff_permanent_lookup[15] = {
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355, 447, 479, 494, 502, 507, 510, 512,
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512, 512, 512, 512, 512, 512, 512 };
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#define ARRAY_SIZE(x) (sizeof(x) / sizeof((x)[0]))
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static void jent_apt_init(struct rand_data *ec, unsigned int osr)
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{
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/*
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* Establish the apt_cutoff based on the presumed entropy rate of
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* 1/osr.
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*/
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if (osr >= ARRAY_SIZE(jent_apt_cutoff_lookup)) {
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ec->apt_cutoff = jent_apt_cutoff_lookup[
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ARRAY_SIZE(jent_apt_cutoff_lookup) - 1];
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ec->apt_cutoff_permanent = jent_apt_cutoff_permanent_lookup[
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ARRAY_SIZE(jent_apt_cutoff_permanent_lookup) - 1];
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} else {
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ec->apt_cutoff = jent_apt_cutoff_lookup[osr - 1];
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ec->apt_cutoff_permanent =
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jent_apt_cutoff_permanent_lookup[osr - 1];
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}
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}
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/*
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* Reset the APT counter
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*
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* @ec [in] Reference to entropy collector
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*/
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static void jent_apt_reset(struct rand_data *ec, unsigned int delta_masked)
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{
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/* Reset APT counter */
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ec->apt_count = 0;
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ec->apt_base = delta_masked;
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ec->apt_observations = 0;
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}
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/*
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* Insert a new entropy event into APT
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*
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* @ec [in] Reference to entropy collector
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* @delta_masked [in] Masked time delta to process
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*/
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static void jent_apt_insert(struct rand_data *ec, unsigned int delta_masked)
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{
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/* Initialize the base reference */
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if (!ec->apt_base_set) {
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ec->apt_base = delta_masked;
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ec->apt_base_set = 1;
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return;
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}
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if (delta_masked == ec->apt_base) {
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ec->apt_count++;
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/* Note, ec->apt_count starts with one. */
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if (ec->apt_count >= ec->apt_cutoff_permanent)
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ec->health_failure |= JENT_APT_FAILURE_PERMANENT;
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else if (ec->apt_count >= ec->apt_cutoff)
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ec->health_failure |= JENT_APT_FAILURE;
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}
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ec->apt_observations++;
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if (ec->apt_observations >= JENT_APT_WINDOW_SIZE)
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jent_apt_reset(ec, delta_masked);
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}
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/***************************************************************************
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* Stuck Test and its use as Repetition Count Test
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*
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* The Jitter RNG uses an enhanced version of the Repetition Count Test
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* (RCT) specified in SP800-90B section 4.4.1. Instead of counting identical
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* back-to-back values, the input to the RCT is the counting of the stuck
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* values during the generation of one Jitter RNG output block.
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*
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* The RCT is applied with an alpha of 2^{-30} compliant to FIPS 140-2 IG 9.8.
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*
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* During the counting operation, the Jitter RNG always calculates the RCT
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* cut-off value of C. If that value exceeds the allowed cut-off value,
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* the Jitter RNG output block will be calculated completely but discarded at
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* the end. The caller of the Jitter RNG is informed with an error code.
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***************************************************************************/
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/*
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* Repetition Count Test as defined in SP800-90B section 4.4.1
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*
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* @ec [in] Reference to entropy collector
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* @stuck [in] Indicator whether the value is stuck
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*/
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static void jent_rct_insert(struct rand_data *ec, int stuck)
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{
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if (stuck) {
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ec->rct_count++;
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/*
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* The cutoff value is based on the following consideration:
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* alpha = 2^-30 or 2^-60 as recommended in SP800-90B.
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* In addition, we require an entropy value H of 1/osr as this
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* is the minimum entropy required to provide full entropy.
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* Note, we collect (DATA_SIZE_BITS + ENTROPY_SAFETY_FACTOR)*osr
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* deltas for inserting them into the entropy pool which should
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* then have (close to) DATA_SIZE_BITS bits of entropy in the
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* conditioned output.
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*
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* Note, ec->rct_count (which equals to value B in the pseudo
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* code of SP800-90B section 4.4.1) starts with zero. Hence
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* we need to subtract one from the cutoff value as calculated
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* following SP800-90B. Thus C = ceil(-log_2(alpha)/H) = 30*osr
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* or 60*osr.
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*/
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if ((unsigned int)ec->rct_count >= (60 * ec->osr)) {
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ec->rct_count = -1;
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ec->health_failure |= JENT_RCT_FAILURE_PERMANENT;
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} else if ((unsigned int)ec->rct_count >= (30 * ec->osr)) {
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ec->rct_count = -1;
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ec->health_failure |= JENT_RCT_FAILURE;
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}
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} else {
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/* Reset RCT */
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ec->rct_count = 0;
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}
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}
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static inline __u64 jent_delta(__u64 prev, __u64 next)
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{
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#define JENT_UINT64_MAX (__u64)(~((__u64) 0))
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return (prev < next) ? (next - prev) :
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(JENT_UINT64_MAX - prev + 1 + next);
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}
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/*
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* Stuck test by checking the:
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* 1st derivative of the jitter measurement (time delta)
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* 2nd derivative of the jitter measurement (delta of time deltas)
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* 3rd derivative of the jitter measurement (delta of delta of time deltas)
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*
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* All values must always be non-zero.
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*
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* @ec [in] Reference to entropy collector
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* @current_delta [in] Jitter time delta
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*
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* @return
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* 0 jitter measurement not stuck (good bit)
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* 1 jitter measurement stuck (reject bit)
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*/
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static int jent_stuck(struct rand_data *ec, __u64 current_delta)
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{
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__u64 delta2 = jent_delta(ec->last_delta, current_delta);
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__u64 delta3 = jent_delta(ec->last_delta2, delta2);
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ec->last_delta = current_delta;
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ec->last_delta2 = delta2;
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/*
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* Insert the result of the comparison of two back-to-back time
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* deltas.
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*/
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jent_apt_insert(ec, current_delta);
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if (!current_delta || !delta2 || !delta3) {
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/* RCT with a stuck bit */
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jent_rct_insert(ec, 1);
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return 1;
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}
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/* RCT with a non-stuck bit */
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jent_rct_insert(ec, 0);
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return 0;
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}
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/*
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* Report any health test failures
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*
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* @ec [in] Reference to entropy collector
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*
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* @return a bitmask indicating which tests failed
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* 0 No health test failure
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* 1 RCT failure
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* 2 APT failure
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* 1<<JENT_PERMANENT_FAILURE_SHIFT RCT permanent failure
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* 2<<JENT_PERMANENT_FAILURE_SHIFT APT permanent failure
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*/
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static unsigned int jent_health_failure(struct rand_data *ec)
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{
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/* Test is only enabled in FIPS mode */
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if (!fips_enabled)
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return 0;
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return ec->health_failure;
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}
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/***************************************************************************
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* Noise sources
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***************************************************************************/
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/*
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* Update of the loop count used for the next round of
|
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* an entropy collection.
|
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*
|
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* Input:
|
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* @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
|
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* the end to make sure we have a guaranteed minimum value
|
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*
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* @return Newly calculated loop counter
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*/
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static __u64 jent_loop_shuffle(unsigned int bits, unsigned int min)
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{
|
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__u64 time = 0;
|
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__u64 shuffle = 0;
|
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unsigned int i = 0;
|
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unsigned int mask = (1<<bits) - 1;
|
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|
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jent_get_nstime(&time);
|
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|
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/*
|
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* We fold the time value as much as possible to ensure that as many
|
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* bits of the time stamp are included as possible.
|
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*/
|
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for (i = 0; ((DATA_SIZE_BITS + bits - 1) / bits) > i; i++) {
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shuffle ^= time & mask;
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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 a hash.
|
||
*
|
||
* ec [in] entropy collector
|
||
* time [in] time stamp to be injected
|
||
* stuck [in] Is the time stamp identified as stuck?
|
||
*
|
||
* Output:
|
||
* updated hash context in the entropy collector or error code
|
||
*/
|
||
static int jent_condition_data(struct rand_data *ec, __u64 time, int stuck)
|
||
{
|
||
#define SHA3_HASH_LOOP (1<<3)
|
||
struct {
|
||
int rct_count;
|
||
unsigned int apt_observations;
|
||
unsigned int apt_count;
|
||
unsigned int apt_base;
|
||
} addtl = {
|
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ec->rct_count,
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ec->apt_observations,
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ec->apt_count,
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ec->apt_base
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||
};
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||
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return jent_hash_time(ec->hash_state, time, (u8 *)&addtl, sizeof(addtl),
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SHA3_HASH_LOOP, stuck);
|
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}
|
||
|
||
/*
|
||
* 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
|
||
* number of loops to perform the LFSR
|
||
*/
|
||
static void jent_memaccess(struct rand_data *ec, __u64 loop_cnt)
|
||
{
|
||
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(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, __u64 *ret_current_delta)
|
||
{
|
||
__u64 time = 0;
|
||
__u64 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 */
|
||
if (jent_condition_data(ec, current_delta, stuck))
|
||
stuck = 1;
|
||
|
||
/* return the raw entropy value */
|
||
if (ret_current_delta)
|
||
*ret_current_delta = current_delta;
|
||
|
||
return stuck;
|
||
}
|
||
|
||
/*
|
||
* Generator of one 64 bit random number
|
||
* Function fills rand_data->hash_state
|
||
*
|
||
* @ec [in] Reference to entropy collector
|
||
*/
|
||
static void jent_gen_entropy(struct rand_data *ec)
|
||
{
|
||
unsigned int k = 0, safety_factor = 0;
|
||
|
||
if (fips_enabled)
|
||
safety_factor = JENT_ENTROPY_SAFETY_FACTOR;
|
||
|
||
/* priming of the ->prev_time value */
|
||
jent_measure_jitter(ec, NULL);
|
||
|
||
while (!jent_health_failure(ec)) {
|
||
/* If a stuck measurement is received, repeat measurement */
|
||
if (jent_measure_jitter(ec, NULL))
|
||
continue;
|
||
|
||
/*
|
||
* We multiply the loop value with ->osr to obtain the
|
||
* oversampling rate requested by the caller
|
||
*/
|
||
if (++k >= ((DATA_SIZE_BITS + safety_factor) * 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 [in] 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 0 when request is fulfilled or an error
|
||
*
|
||
* The following error codes can occur:
|
||
* -1 entropy_collector is NULL or the generation failed
|
||
* -2 Intermittent health failure
|
||
* -3 Permanent health failure
|
||
*/
|
||
int jent_read_entropy(struct rand_data *ec, unsigned char *data,
|
||
unsigned int len)
|
||
{
|
||
unsigned char *p = data;
|
||
|
||
if (!ec)
|
||
return -1;
|
||
|
||
while (len > 0) {
|
||
unsigned int tocopy, health_test_result;
|
||
|
||
jent_gen_entropy(ec);
|
||
|
||
health_test_result = jent_health_failure(ec);
|
||
if (health_test_result > JENT_PERMANENT_FAILURE_SHIFT) {
|
||
/*
|
||
* At this point, the Jitter RNG instance is considered
|
||
* as a failed instance. There is no rerun of the
|
||
* startup test any more, because the caller
|
||
* is assumed to not further use this instance.
|
||
*/
|
||
return -3;
|
||
} else if (health_test_result) {
|
||
/*
|
||
* Perform startup health tests and return permanent
|
||
* error if it fails.
|
||
*/
|
||
if (jent_entropy_init(0, 0, NULL, ec)) {
|
||
/* Mark the permanent error */
|
||
ec->health_failure &=
|
||
JENT_RCT_FAILURE_PERMANENT |
|
||
JENT_APT_FAILURE_PERMANENT;
|
||
return -3;
|
||
}
|
||
|
||
return -2;
|
||
}
|
||
|
||
if ((DATA_SIZE_BITS / 8) < len)
|
||
tocopy = (DATA_SIZE_BITS / 8);
|
||
else
|
||
tocopy = len;
|
||
if (jent_read_random_block(ec->hash_state, p, tocopy))
|
||
return -1;
|
||
|
||
len -= tocopy;
|
||
p += tocopy;
|
||
}
|
||
|
||
return 0;
|
||
}
|
||
|
||
/***************************************************************************
|
||
* Initialization logic
|
||
***************************************************************************/
|
||
|
||
struct rand_data *jent_entropy_collector_alloc(unsigned int osr,
|
||
unsigned int flags,
|
||
void *hash_state)
|
||
{
|
||
struct rand_data *entropy_collector;
|
||
|
||
entropy_collector = jent_zalloc(sizeof(struct rand_data));
|
||
if (!entropy_collector)
|
||
return NULL;
|
||
|
||
if (!(flags & JENT_DISABLE_MEMORY_ACCESS)) {
|
||
/* Allocate memory for adding variations based on memory
|
||
* access
|
||
*/
|
||
entropy_collector->mem = jent_kvzalloc(JENT_MEMORY_SIZE);
|
||
if (!entropy_collector->mem) {
|
||
jent_zfree(entropy_collector);
|
||
return NULL;
|
||
}
|
||
entropy_collector->memblocksize =
|
||
CONFIG_CRYPTO_JITTERENTROPY_MEMORY_BLOCKSIZE;
|
||
entropy_collector->memblocks =
|
||
CONFIG_CRYPTO_JITTERENTROPY_MEMORY_BLOCKS;
|
||
entropy_collector->memaccessloops = JENT_MEMORY_ACCESSLOOPS;
|
||
}
|
||
|
||
/* verify and set the oversampling rate */
|
||
if (osr == 0)
|
||
osr = 1; /* H_submitter = 1 / osr */
|
||
entropy_collector->osr = osr;
|
||
entropy_collector->flags = flags;
|
||
|
||
entropy_collector->hash_state = hash_state;
|
||
|
||
/* Initialize the APT */
|
||
jent_apt_init(entropy_collector, osr);
|
||
|
||
/* fill the data pad with non-zero values */
|
||
jent_gen_entropy(entropy_collector);
|
||
|
||
return entropy_collector;
|
||
}
|
||
|
||
void jent_entropy_collector_free(struct rand_data *entropy_collector)
|
||
{
|
||
jent_kvzfree(entropy_collector->mem, JENT_MEMORY_SIZE);
|
||
entropy_collector->mem = NULL;
|
||
jent_zfree(entropy_collector);
|
||
}
|
||
|
||
int jent_entropy_init(unsigned int osr, unsigned int flags, void *hash_state,
|
||
struct rand_data *p_ec)
|
||
{
|
||
/*
|
||
* If caller provides an allocated ec, reuse it which implies that the
|
||
* health test entropy data is used to further still the available
|
||
* entropy pool.
|
||
*/
|
||
struct rand_data *ec = p_ec;
|
||
int i, time_backwards = 0, ret = 0, ec_free = 0;
|
||
unsigned int health_test_result;
|
||
|
||
if (!ec) {
|
||
ec = jent_entropy_collector_alloc(osr, flags, hash_state);
|
||
if (!ec)
|
||
return JENT_EMEM;
|
||
ec_free = 1;
|
||
} else {
|
||
/* Reset the APT */
|
||
jent_apt_reset(ec, 0);
|
||
/* Ensure that a new APT base is obtained */
|
||
ec->apt_base_set = 0;
|
||
/* Reset the RCT */
|
||
ec->rct_count = 0;
|
||
/* Reset intermittent, leave permanent health test result */
|
||
ec->health_failure &= (~JENT_RCT_FAILURE);
|
||
ec->health_failure &= (~JENT_APT_FAILURE);
|
||
}
|
||
|
||
/* 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++) {
|
||
__u64 start_time = 0, end_time = 0, delta = 0;
|
||
|
||
/* Invoke core entropy collection logic */
|
||
jent_measure_jitter(ec, &delta);
|
||
end_time = ec->prev_time;
|
||
start_time = ec->prev_time - delta;
|
||
|
||
/* test whether timer works */
|
||
if (!start_time || !end_time) {
|
||
ret = JENT_ENOTIME;
|
||
goto out;
|
||
}
|
||
|
||
/*
|
||
* 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 || (end_time == start_time)) {
|
||
ret = JENT_ECOARSETIME;
|
||
goto out;
|
||
}
|
||
|
||
/*
|
||
* 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 (i < CLEARCACHE)
|
||
continue;
|
||
|
||
/* test whether we have an increasing timer */
|
||
if (!(end_time > start_time))
|
||
time_backwards++;
|
||
}
|
||
|
||
/*
|
||
* 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 (time_backwards > 3) {
|
||
ret = JENT_ENOMONOTONIC;
|
||
goto out;
|
||
}
|
||
|
||
/* Did we encounter a health test failure? */
|
||
health_test_result = jent_health_failure(ec);
|
||
if (health_test_result) {
|
||
ret = (health_test_result & JENT_RCT_FAILURE) ? JENT_ERCT :
|
||
JENT_EHEALTH;
|
||
goto out;
|
||
}
|
||
|
||
out:
|
||
if (ec_free)
|
||
jent_entropy_collector_free(ec);
|
||
|
||
return ret;
|
||
}
|