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plugins: urandom: improve entropy gathering in fallback path

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Enhance fallback entropy generation by mixing in multiple sources:
runtime statistics, PID, and high-resolution timestamps.

This provides better initialization for the PRNG when neither saved
entropy nor hardware RNG are available during early boot.

Signed-off-by: Joachim Wiberg <troglobit@gmail.com>
This commit is contained in:
Joachim Wiberg
2025-02-23 04:51:04 +01:00
parent 1f2c1d2109
commit b75b107d6d
1 changed files with 16 additions and 1 deletions
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plugins/urandom.c
+16 -1
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@@ -26,6 +26,7 @@
#include <sys/stat.h>
#include <sys/time.h> /* gettimeofday() */
#include <sys/types.h>
#include <sys/resource.h> /* getrusage() */
#ifdef _LIBITE_LITE
# include <libite/lite.h>
#else
@@ -43,13 +44,27 @@
#endif
#ifdef RANDOMSEED
/*
* This is the fallback seed function, please make sure you have drivers
* enabling /dev/hwrng instead.
*/
static void fallback(FILE *fp)
{
unsigned long seed;
struct timeval tv;
struct rusage ru;
int iter = 128;
gettimeofday(&tv, NULL);
srandom(tv.tv_sec % 3600);
getrusage(RUSAGE_SELF, &ru);
/* Mix multiple sources of "randomness" */
seed = tv.tv_sec ^ (tv.tv_usec << 16);
seed ^= ru.ru_utime.tv_sec ^ (ru.ru_utime.tv_usec << 16);
seed ^= ru.ru_stime.tv_sec ^ (ru.ru_stime.tv_usec << 16);
seed ^= getpid() << 8;
srandom(seed);
while (iter--) {
uint32_t i, prng = random();