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// This writes entropy to the Linux /dev/random pool using ioctl, so that entropy increases.
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>
#include <poll.h>
#include <sys/ioctl.h>
#include <fcntl.h>
#include <linux/random.h>
#include "libinfnoise.h"
#define SIZE_PROC_FILENAME "/proc/sys/kernel/random/poolsize"
#define FILL_PROC_FILENAME "/proc/sys/kernel/random/write_wakeup_threshold"
static struct pollfd pfd;
static uint32_t inmFillWatermark;
static struct rand_pool_info *inmPoolInfo;
// Find the entropy pool size.
static uint32_t readNumberFromFile(char *fileName) {
FILE *file = fopen(fileName, "r");
if(file == NULL) {
fprintf(stderr, "Unable to open %s\n", fileName);
exit(1);
}
uint32_t value = 0u;
int32_t c;
while( (c = getc(file)) != EOF
&& '0' <= c && c <= '9' ) {
value *= 10;
value += c - '0';
}
fclose(file);
return value;
}
// Open /dev/random
void inmWriteEntropyStart(uint32_t bufLen, bool debug) {
pfd.events = POLLOUT;
//pfd.fd = open("/dev/random", O_WRONLY);
pfd.fd = open("/dev/random", O_RDWR);
if(pfd.fd < 0) {
fprintf(stderr, "Unable to open /dev/random\n");
exit(1);
}
inmPoolInfo = calloc(1, sizeof(struct rand_pool_info) + bufLen);
if(inmPoolInfo == NULL) {
fprintf(stderr, "Unable to allocate memory\n");
exit(1);
}
inmFillWatermark = readNumberFromFile(FILL_PROC_FILENAME);
if(debug) {
printf("Entropy pool size:%u, fill watermark:%u\n", readNumberFromFile(SIZE_PROC_FILENAME), inmFillWatermark);
}
}
void inmWriteEntropyEnd() {
free( inmPoolInfo );
}
// Block until either the entropy pool has room, or 1 minute has passed.
void inmWaitForPoolToHaveRoom(uint32_t feed_frequency) {
int ent_count;
if (ioctl(pfd.fd, RNDGETENTCNT, &ent_count) == 0 && (uint32_t)ent_count < inmFillWatermark) {
return;
}
poll(&pfd, 1, 1000u * feed_frequency); // waits until /dev/random is in usage
}
// Add the bytes to the entropy pool. This can be unwhitenened, but the estimated bits of
// entropy needs to be accurate or pessimistic. Return false if the Linux entropy pool is
// full after writing.
void inmWriteEntropyToPool(uint8_t *bytes, uint32_t length, uint32_t entropy) {
inmPoolInfo->entropy_count = entropy;
inmPoolInfo->buf_size = length;
memcpy(inmPoolInfo->buf, bytes, length);
//printf("Writing %u bytes with %u bits of entropy to /dev/random\n", length, entropy);
ioctl(pfd.fd, RNDADDENTROPY, inmPoolInfo);
}
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