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linux: add forced CRNG reseed option for newer kernels #38

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linux: add forced CRNG reseed option for newer kernels #38

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15 changes: 12 additions & 3 deletions software/infnoise.c
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Original file line number Diff line number Diff line change
Expand Up @@ -32,6 +32,7 @@ void term(int signum)
static void initOpts(struct opt_struct *opts) {
opts->outputMultiplier = 0u;
opts->feedFreq = 30u;
opts->forceReseed = false;
opts->daemon = false;
opts->debug = false;
opts->devRandom = false;
Expand All @@ -50,6 +51,7 @@ static struct option longopts[] = {
{"raw", no_argument, NULL, 'r'},
{"debug", no_argument, NULL, 'D'},
{"dev-random", no_argument, NULL, 'R'},
{"reseed-crng", no_argument, NULL, 'C'},
{"no-output", no_argument, NULL, 'n'},
{"feed-frequency", required_argument, NULL, 'f'},
{"multiplier", required_argument, NULL, 'm'},
Expand All @@ -62,7 +64,7 @@ static struct option longopts[] = {
{NULL, 0, NULL, 0}};

// Write the bytes to either stdout, or /dev/random.
bool outputBytes(uint8_t *bytes, uint32_t length, uint32_t entropy, bool writeDevRandom, uint32_t feedFrequency, const char **message) {
bool outputBytes(uint8_t *bytes, uint32_t length, uint32_t entropy, bool writeDevRandom, bool forceKernelReseed, uint32_t feedFrequency, const char **message) {
if (!writeDevRandom) {
if (fwrite(bytes, 1, length, stdout) != length) {
*message = "Unable to write output from Infinite Noise Multiplier";
Expand Down Expand Up @@ -99,6 +101,9 @@ bool outputBytes(uint8_t *bytes, uint32_t length, uint32_t entropy, bool writeDe
#ifdef LINUX
inmWaitForPoolToHaveRoom(feedFrequency);
inmWriteEntropyToPool(bytes, length, entropy);
if(forceKernelReseed) {
inmForceKernelRngReseed();
}
#endif
}
return true;
Expand All @@ -113,7 +118,7 @@ int main(int argc, char **argv) {
initOpts(&opts);

// Process arguments
while ((ch = getopt_long(argc, argv, "rDRnf:m:p:s:dlvh", longopts, NULL)) !=
while ((ch = getopt_long(argc, argv, "rDRCnf:m:p:s:dlvh", longopts, NULL)) !=
-1) {
switch (ch) {
case 'r':
Expand All @@ -125,6 +130,9 @@ int main(int argc, char **argv) {
case 'R':
opts.devRandom = true;
break;
case 'C':
opts.forceReseed = true;
break;
case 'n':
opts.noOutput = true;
break;
Expand Down Expand Up @@ -183,6 +191,7 @@ int main(int argc, char **argv) {
" -D, --debug - turn on some debug output\n"
" -R, --dev-random - write entropy to /dev/random instead of "
"stdout\n"
" -C, --reseed-crng - force reseed of /dev/random on write\n"
" -r, --raw - do not whiten the output\n"
" -m, --multiplier <value> - write 256 bits * value for each 512 bits written to\n"
" the Keccak sponge. Default of 0 means write all the entropy.\n"
Expand Down Expand Up @@ -311,7 +320,7 @@ int main(int argc, char **argv) {
}

if (!opts.noOutput
&& !outputBytes(result, bytesWritten, context.entropyThisTime, opts.devRandom, opts.feedFreq, &context.message)) {
&& !outputBytes(result, bytesWritten, context.entropyThisTime, opts.devRandom, opts.forceReseed, opts.feedFreq, &context.message)) {
fprintf(stderr, "Error: %s\n", context.message);
return 1;
}
Expand Down
2 changes: 2 additions & 0 deletions software/infnoise.h
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Original file line number Diff line number Diff line change
Expand Up @@ -14,6 +14,7 @@ struct opt_struct {
bool daemon; // Run as daemon?
bool debug; // Print debugging info?
bool devRandom; // Feed /dev/random?
bool forceReseed; // Force reseed when feeding /dev/random?
bool noOutput; // Supress output?
bool listDevices; // List possible USB-devices?
bool help; // Show help
Expand All @@ -28,6 +29,7 @@ struct opt_struct {
void inmWriteEntropyStart(uint32_t bufLen, bool debug);
void inmWriteEntropyEnd();
void inmWriteEntropyToPool(uint8_t *bytes, uint32_t length, uint32_t entropy);
void inmForceKernelRngReseed();
void inmWaitForPoolToHaveRoom(uint32_t feedFreq);

void startDaemon(struct opt_struct *opts);
14 changes: 14 additions & 0 deletions software/writeentropy.c
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Original file line number Diff line number Diff line change
@@ -1,5 +1,6 @@
// This writes entropy to the Linux /dev/random pool using ioctl, so that entropy increases.

#include <errno.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
Expand Down Expand Up @@ -59,6 +60,19 @@ void inmWriteEntropyEnd() {
free( inmPoolInfo );
}

// recent Linux kernels seldomly reseed from the input pool (60s),
// this call can be used to force faster reseeds
void inmForceKernelRngReseed() {
#ifdef RNDRESEEDCRNG
// printf("force CRNG reseed\n");
if(ioctl(pfd.fd, RNDRESEEDCRNG) < 0 && errno != EINVAL) {
fprintf(stderr, "RNDRESEEDCRNG on /dev/random failed.\n");
}
#else
fprintf(stderr, "/dev/random does not support RNDRESEEDCRNG\n");
#endif
}

// Block until either the entropy pool has room, or 1 minute has passed.
void inmWaitForPoolToHaveRoom(uint32_t feed_frequency) {
int ent_count;
Expand Down