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828 lines
26 KiB
828 lines
26 KiB
/* |
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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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/* |
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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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|
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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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|
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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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|
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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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|
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/* Repetition Count Test */ |
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unsigned int rct_count; /* Number of stuck values */ |
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|
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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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|
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unsigned int apt_base_set:1; /* APT base reference set? */ |
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}; |
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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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|
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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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|
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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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/* |
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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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/*************************************************************************** |
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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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/* |
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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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* http://www.untruth.org/~josh/sp80090b/UL%20SP800-90B-final%20comments%20v1.9%2020191212.pdf |
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* In 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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/* |
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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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|
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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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/*************************************************************************** |
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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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/* |
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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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/* |
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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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|
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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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/* |
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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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|
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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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|
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/* RCT with a non-stuck bit */ |
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jent_rct_insert(ec, 0); |
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|
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return 0; |
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} |
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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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|
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return ec->health_failure; |
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} |
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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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/* |
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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 |
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* @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; |
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} |
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|
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/* |
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* We add a lower boundary value to ensure we have a minimum |
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* RNG loop count. |
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*/ |
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return (shuffle + (1<<min)); |
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} |
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|
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/* |
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* CPU Jitter noise source -- this is the noise source based on the CPU |
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* execution time jitter |
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* |
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* This function injects the individual bits of the time value into the |
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* entropy pool using a hash. |
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* |
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* ec [in] entropy collector |
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* time [in] time stamp to be injected |
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* stuck [in] Is the time stamp identified as stuck? |
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* |
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* Output: |
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* updated hash context in the entropy collector or error code |
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*/ |
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static int jent_condition_data(struct rand_data *ec, __u64 time, int stuck) |
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{ |
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#define SHA3_HASH_LOOP (1<<3) |
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struct { |
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int rct_count; |
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unsigned int apt_observations; |
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unsigned int apt_count; |
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unsigned int apt_base; |
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} 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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} |
|
|
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/* |
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* Memory Access noise source -- this is a noise source based on variations in |
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* memory access times |
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* |
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* This function performs memory accesses which will add to the timing |
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* 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. |
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* |
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* 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, |
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* to reliably access either L3 or memory, the ec->mem memory must be quite |
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* large which is usually not desirable. |
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* |
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* @ec [in] Reference to the entropy collector with the memory access data -- if |
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* the reference to the memory block to be accessed is NULL, this noise |
|
* source is disabled |
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* @loop_cnt [in] if a value not equal to 0 is set, use the given value |
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* number of loops to perform the LFSR |
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*/ |
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static void jent_memaccess(struct rand_data *ec, __u64 loop_cnt) |
|
{ |
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unsigned int wrap = 0; |
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__u64 i = 0; |
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#define MAX_ACC_LOOP_BIT 7 |
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#define MIN_ACC_LOOP_BIT 0 |
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__u64 acc_loop_cnt = |
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jent_loop_shuffle(MAX_ACC_LOOP_BIT, MIN_ACC_LOOP_BIT); |
|
|
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if (NULL == ec || NULL == ec->mem) |
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return; |
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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; |
|
}
|
|
|