63 lines
1.2 KiB
C
63 lines
1.2 KiB
C
#ifndef _IPXE_RTC_ENTROPY_H
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#define _IPXE_RTC_ENTROPY_H
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/** @file
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*
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* RTC-based entropy source
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*
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*/
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FILE_LICENCE ( GPL2_OR_LATER_OR_UBDL );
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#include <stdint.h>
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#ifdef ENTROPY_RTC
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#define ENTROPY_PREFIX_rtc
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#else
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#define ENTROPY_PREFIX_rtc __rtc_
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#endif
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/**
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* min-entropy per sample
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*
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* @ret min_entropy min-entropy of each sample
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*/
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static inline __always_inline double
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ENTROPY_INLINE ( rtc, min_entropy_per_sample ) ( void ) {
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/* The min-entropy has been measured on several platforms
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* using the entropy_sample test code. Modelling the samples
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* as independent, and using a confidence level of 99.99%, the
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* measurements were as follows:
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*
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* qemu-kvm : 7.38 bits
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* VMware : 7.46 bits
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* Physical hardware : 2.67 bits
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*
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* We choose the lowest of these (2.67 bits) and apply a 50%
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* safety margin to allow for some potential non-independence
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* of samples.
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*/
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return 1.3;
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}
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extern uint8_t rtc_sample ( void );
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/**
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* Get noise sample
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*
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* @ret noise Noise sample
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* @ret rc Return status code
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*/
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static inline __always_inline int
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ENTROPY_INLINE ( rtc, get_noise ) ( noise_sample_t *noise ) {
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/* Get sample */
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*noise = rtc_sample();
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/* Always successful */
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return 0;
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}
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#endif /* _IPXE_RTC_ENTROPY_H */
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