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apt.c
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apt.c
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/* This file is part of the Theseus distribution.
* Copyright 2023-2024 Joshua E. Hill <[email protected]>
*
* Licensed under the 3-clause BSD license. For details, see the LICENSE file.
*
* Author(s)
* Joshua E. Hill, KeyPair Consulting, Inc. <[email protected]>
*/
#include <assert.h>
#include <errno.h>
#include <getopt.h>
#include <limits.h>
#include <math.h>
#include <stdbool.h>
#include <stddef.h>
#include <stdint.h>
#include <stdio.h>
#include <stdlib.h>
#include <stdnoreturn.h>
#include <string.h>
#include <sysexits.h>
#include "binio.h"
#include "entlib.h"
#include "globals-inst.h"
#include "precision.h"
#include "health-tests.h"
/*
* This program is a demonstration of the APT health test.
* This program is both a proof-of-concept for this health test,
* and a tool that can be used to help establish reasonable cutoffs
* for the APT.
*/
noreturn static void useageExit(void) {
fprintf(stderr, "Usage:\n");
fprintf(stderr, "apt [-v] [-c <value>] [-w <value>] [-t <value>] [-d <value>] <infile>\n");
fprintf(stderr, "Runs the SP 800-90B APT health test on provided values.\n");
fprintf(stderr, "-v Increase verbosity. Can be used multiple times.\n");
fprintf(stderr, "-c <value>\tThe APT cutoff value is <value>.\n");
fprintf(stderr, "-w <value>\tThe APT window value is <value>. (Default is 512 symbols.)\n");
fprintf(stderr, "-t <value>\tTry to find suggested cutoff values, if the desired (per-window) false positive rate is 2^-<value>.\n");
fprintf(stderr, "-d <value>\tData is presumed to be <value>-bit wide symbols. (supported values are 8, 32, and 64-bits).\n");
fprintf(stderr, "-b <value>\tData is bitwise ANDed with <value>.\n");
exit(EX_USAGE);
}
int main(int argc, char *argv[]) {
FILE *infp;
size_t datalen;
statData_t *u8Data = NULL;
uint32_t *u32Data = NULL;
uint64_t *u64Data = NULL;
size_t configAPTC;
size_t configAPTW;
int opt;
unsigned long long inint;
double indouble;
struct APTstate healthTest;
bool configSuggestCutoffs = false;
double configAlphaExp = 0;
uint32_t configBitWidth = 0;
uint64_t configAND = 0xffffffffffffffffULL;
char *endptr=NULL;
configVerbose = 0;
configAPTC = 0;
configAPTW = 512;
while ((opt = getopt(argc, argv, "vc:w:t:d:b:")) != -1) {
switch (opt) {
case 'v':
// Output more debug information.
configVerbose++;
break;
case 'b':
// AND with the provided 64-bit value
endptr=NULL;
inint = strtoull(optarg, &endptr, 0);
if (((inint == ULLONG_MAX) && (errno == ERANGE)) || ((inint == 0) && (endptr == optarg))) {
fprintf(stderr, "Can't interpret bitmask value\n");
useageExit();
}
configAND = (size_t)inint;
break;
case 'c':
// Set the APT bound.
endptr=NULL;
inint = strtoull(optarg, &endptr, 0);
if (((inint == 0) && (endptr == optarg)) || ((inint == ULLONG_MAX) && (errno == EINVAL)) || (inint > SIZE_MAX)) {
fprintf(stderr, "Can't interpret cutoff value\n");
useageExit();
}
configAPTC = (size_t)inint;
break;
case 'w':
// Set the APT window.
endptr=NULL;
inint = strtoull(optarg, &endptr, 0);
if (((inint == 0) && (endptr == optarg)) || ((inint == ULLONG_MAX) && (errno == ERANGE)) || (inint > SIZE_MAX)) {
fprintf(stderr, "Can't interpret window value\n");
useageExit();
}
configAPTW = (size_t)inint;
break;
case 'd':
endptr=NULL;
inint = strtoull(optarg, &endptr, 0);
if (((inint == 0) && (endptr == optarg)) || ((inint == ULLONG_MAX) && (errno == ERANGE)) || ((inint != 8) && (inint != 32) &&(inint != 64))) {
fprintf(stderr, "Unsupported symbol size\n");
useageExit();
}
configBitWidth = (uint32_t)inint;
break;
case 't':
// Estimate the appropriate cutoffs.
configSuggestCutoffs = true;
endptr=NULL;
indouble = strtod(optarg, &endptr);
#pragma GCC diagnostic push
#pragma GCC diagnostic ignored "-Wfloat-equal"
//These double values are flags set by "strtod", so exact comparison is correct.
if (((indouble == 0.0) && (endptr == optarg)) || (((indouble == HUGE_VAL) || (indouble == -HUGE_VAL)) && errno == ERANGE)) {
fprintf(stderr, "Can't interpret target alphaExp value\n");
useageExit();
}
#pragma GCC diagnostic pop
configAlphaExp = indouble;
if ((configAlphaExp < 20.0) || (configAlphaExp > 40.0)) fprintf(stderr, "Desired alphaExp of %g is outside of the recommended interval [20, 40].\n", configAlphaExp);
break;
default: /* ? */
useageExit();
}
}
argc -= optind;
argv += optind;
if (argc != 1) {
useageExit();
}
if(configBitWidth == 0) {
char *suffix;
size_t fileNameLen = strlen(argv[0]);
for(suffix = argv[0] + (fileNameLen - 1); (suffix > argv[0]) && (*suffix != '-'); suffix--);
if(suffix != argv[0]) {
if(strcmp(suffix, "-u64.bin")==0) {
configBitWidth = 64;
} else if(strcmp(suffix, "-u32.bin")==0) {
configBitWidth = 32;
} else if(strcmp(suffix, "-u8.bin")==0) {
configBitWidth = 8;
} else if(strcmp(suffix, "-sd.bin")==0) {
configBitWidth = STATDATA_BITS;
}
}
}
if(configBitWidth == 0) {
fprintf(stderr, "No sample bit width was specified, and it can't be guessed.\n");
useageExit();
}
if(configVerbose > 0) fprintf(stderr, "Using %u bit symbols.\n", configBitWidth);
// Read in the data
if ((infp = fopen(argv[0], "rb")) == NULL) {
perror("Can't open file");
exit(EX_NOINPUT);
}
if(configBitWidth == 8) {
datalen = readuintfile(infp, &u8Data);
assert(u8Data != NULL);
} else if(configBitWidth == 32) {
datalen = readuint32file(infp, &u32Data);
assert(u32Data != NULL);
} else if(configBitWidth == 64) {
datalen = readuint64file(infp, &u64Data);
assert(u64Data != NULL);
} else {
useageExit();
}
assert(datalen > 0);
if (configVerbose > 0) {
fprintf(stderr, "Read in %zu integers\n", datalen);
}
if (fclose(infp) != 0) {
perror("Couldn't close input data file");
exit(EX_OSERR);
}
if((configVerbose > 0) && (configAPTC > 0)) {
printf("APT cutoff: %zu\n", configAPTC);
}
if((configVerbose > 0) && (configAPTW > 0)) {
printf("APT Window Size: %zu\n", configAPTW);
}
initAPT(configAPTC, configAPTW, &healthTest);
// If configVerbose > 1, then we'll keep track of the window statistics.
// This functionality is mainly useful to establish appropriate cutoff settings,
// and would not generally be present in a deployed entropy source.
if (configSuggestCutoffs || (configVerbose > 1)) {
healthTest.APTcounts = calloc(configAPTW+1, sizeof(size_t));
assert(healthTest.APTcounts != NULL);
}
// Feed in all the data to the APT test.
for (size_t i = 0; i < datalen; i++) {
uint64_t curData;
if(configBitWidth==8) curData = (uint64_t)u8Data[i];
else if(configBitWidth==32) curData = (uint64_t)u32Data[i];
else curData = u64Data[i];
APT((curData & configAND), &healthTest);
}
// Report on the results of the test.
if (healthTest.APT_C > 0) {
// We were asked to report on this APT and the failure rates might mean something.
assert(healthTest.APT_Window_Count >= 1);
printf("APT: Per Window Failure Rate: %zu / %zu = %g", healthTest.APT_Failures, healthTest.APT_Window_Count, ((double)(healthTest.APT_Failures)) / ((double)healthTest.APT_Window_Count));
if (healthTest.APT_Failures > 0) {
printf(" ≈ 2^%g\n", log2(((double)(healthTest.APT_Failures)) / ((double)healthTest.APT_Window_Count)));
} else {
printf("\n");
}
}
// If we've been keeping count of the run lengths, print it out.
if (healthTest.APTcounts != NULL) {
char startChar = '{';
for (size_t i = 0; i <= configAPTW; i++) {
if ((configVerbose > 1) && ((healthTest.APTcounts)[i] != 0)) {
printf("%c {%zu, %zu}", startChar, i, healthTest.APTcounts[i]);
startChar = ',';
}
}
if (configVerbose > 1) printf("};\n");
}
if (configSuggestCutoffs) {
long double alpha = powl(2.0L, -(long double)configAlphaExp);
size_t allowedFailures = (size_t)floorl(((long double)healthTest.APT_Window_Count) * alpha);
size_t accumulatedFailures;
assert(healthTest.APTcounts != NULL);
if (configVerbose > 0) fprintf(stderr, "Allowed failures: %zu\n", allowedFailures);
if (allowedFailures < 10) fprintf(stderr, "The bound for the desired number of failures (%zu < 10) may not yield statistically meaningful results.\n", allowedFailures);
accumulatedFailures = 0;
for (size_t j = configAPTW; j > 0; j--) {
accumulatedFailures += healthTest.APTcounts[j];
if (accumulatedFailures > allowedFailures) {
printf("Empirical APT cutoff: %zu\n", j + 1);
break;
}
}
}
// Free all the allocated memory.
if (healthTest.APTcounts != NULL) {
free(healthTest.APTcounts);
healthTest.APTcounts = NULL;
}
if(u64Data!=NULL) free(u64Data);
if(u32Data!=NULL) free(u32Data);
if(u8Data!=NULL) free(u8Data);
return EX_OK;
}