7ed7014e14
The return type of `getc(3)` is a signed integer, with negative values indicating an error. The changed line stored the return value in an *unsigned* integer, then tested it against a negative error constant, so the error condition would never be detected. This also results in a warning on GCC 10. Further information: - [`getc(3)`](https://man7.org/linux/man-pages/man3/fgetc.3.html) - [C FAQ question 12.1](http://c-faq.com/stdio/getcharc.html)
81 lines
2.5 KiB
C
81 lines
2.5 KiB
C
// This writes entropy to the Linux /dev/random pool using ioctl, so that entropy increases.
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#include <stdio.h>
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#include <stdlib.h>
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#include <string.h>
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#include <unistd.h>
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#include <poll.h>
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#include <sys/ioctl.h>
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#include <fcntl.h>
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#include <linux/random.h>
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#include "libinfnoise.h"
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#define SIZE_PROC_FILENAME "/proc/sys/kernel/random/poolsize"
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#define FILL_PROC_FILENAME "/proc/sys/kernel/random/write_wakeup_threshold"
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static struct pollfd pfd;
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static uint32_t inmFillWatermark;
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static struct rand_pool_info *inmPoolInfo;
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// Find the entropy pool size.
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static uint32_t readNumberFromFile(char *fileName) {
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FILE *file = fopen(fileName, "r");
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if(file == NULL) {
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fprintf(stderr, "Unable to open %s\n", fileName);
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exit(1);
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}
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uint32_t value = 0u;
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int32_t c;
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while( (c = getc(file)) != EOF
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&& '0' <= c && c <= '9' ) {
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value *= 10;
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value += c - '0';
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}
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fclose(file);
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return value;
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}
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// Open /dev/random
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void inmWriteEntropyStart(uint32_t bufLen, bool debug) {
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pfd.events = POLLOUT;
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//pfd.fd = open("/dev/random", O_WRONLY);
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pfd.fd = open("/dev/random", O_RDWR);
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if(pfd.fd < 0) {
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fprintf(stderr, "Unable to open /dev/random\n");
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exit(1);
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}
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inmPoolInfo = calloc(1, sizeof(struct rand_pool_info) + bufLen);
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if(inmPoolInfo == NULL) {
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fprintf(stderr, "Unable to allocate memory\n");
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exit(1);
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}
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inmFillWatermark = readNumberFromFile(FILL_PROC_FILENAME);
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if(debug) {
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printf("Entropy pool size:%u, fill watermark:%u\n", readNumberFromFile(SIZE_PROC_FILENAME), inmFillWatermark);
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}
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}
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void inmWriteEntropyEnd() {
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free( inmPoolInfo );
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}
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// Block until either the entropy pool has room, or 1 minute has passed.
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void inmWaitForPoolToHaveRoom() {
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int ent_count;
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if (ioctl(pfd.fd, RNDGETENTCNT, &ent_count) == 0 && (uint32_t)ent_count < inmFillWatermark) {
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return;
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}
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poll(&pfd, 1, -1); // waits until /dev/random is in usage
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}
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// Add the bytes to the entropy pool. This can be unwhitenened, but the estimated bits of
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// entropy needs to be accurate or pessimistic. Return false if the Linux entropy pool is
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// full after writing.
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void inmWriteEntropyToPool(uint8_t *bytes, uint32_t length, uint32_t entropy) {
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inmPoolInfo->entropy_count = entropy;
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inmPoolInfo->buf_size = length;
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memcpy(inmPoolInfo->buf, bytes, length);
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//printf("Writing %u bytes with %u bits of entropy to /dev/random\n", length, entropy);
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ioctl(pfd.fd, RNDADDENTROPY, inmPoolInfo);
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}
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