qemu: simplify RNG seeding
We don't actualy need to write anything in the pool. Instead, we just force the total over 128, and we should be good to go for all old kernels. We also only need this on getrandom() kernels, which simplifies things too. Signed-off-by: Jason A. Donenfeld <Jason@zx2c4.com>
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1 changed files with 8 additions and 18 deletions
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@ -57,27 +57,17 @@ static void print_banner(void)
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static void seed_rng(void)
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{
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int fd;
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struct {
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int entropy_count;
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int buffer_size;
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unsigned char buffer[256];
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} entropy = {
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.entropy_count = sizeof(entropy.buffer) * 8,
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.buffer_size = sizeof(entropy.buffer),
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.buffer = "Adding real entropy is not actually important for these tests. Don't try this at home, kids!"
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};
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int bits = 4096, fd;
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if (mknod("/dev/urandom", S_IFCHR | 0644, makedev(1, 9)))
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panic("mknod(/dev/urandom)");
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fd = open("/dev/urandom", O_WRONLY);
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pretty_message("[+] Fake seeding RNG...");
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fd = open("/dev/random", O_WRONLY);
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if (fd < 0)
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panic("open(urandom)");
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panic("open(random)");
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for (;;) {
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if (getrandom(entropy.buffer, sizeof(entropy.buffer), GRND_NONBLOCK) != -1 || errno != EAGAIN)
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if (!getrandom(NULL, 0, GRND_NONBLOCK) || errno == ENOSYS)
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break;
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if (ioctl(fd, RNDADDENTROPY, &entropy) < 0)
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panic("ioctl(urandom)");
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if (ioctl(fd, RNDADDTOENTCNT, &bits) < 0)
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panic("ioctl(RNDADDTOENTCNT)");
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}
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close(fd);
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}
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@ -273,10 +263,10 @@ static void check_leaks(void)
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int main(int argc, char *argv[])
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{
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seed_rng();
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ensure_console();
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print_banner();
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mount_filesystems();
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seed_rng();
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kmod_selftests();
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enable_logging();
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clear_leaks();
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