Re: [Buildroot] [PATCH v3] package/urandom-scripts: actually credit seed files via seedrng

[David Laight <David.Laight@ACULAB.COM>]

I used the following small program instead of dd to credit the entropy.

+#include <linux/random.h>
+#include <sys/ioctl.h>
+#include <unistd.h>
+#include <fcntl.h>
+
+/* Just writing to /dev/urandom doesn't credit any entropy
+ * so the crng remains uninitialised.
+ * So use the relevant ioctl instead. */
+
+int main(int argc, char **argv)
+{
+	int fd;
+	int len;
+	struct {
+		struct rand_pool_info info;
+		int buf[4096];
+	} rnd_info;
+
+	if (!argv[1])
+		return 1;
+
+	fd = open(argv[1], O_RDONLY);
+	if (fd < 0)
+		return 1;
+	len = read(fd, rnd_info.buf, sizeof rnd_info.buf);
+	close(fd);
+	if (len <= 0)
+		return 1;
+
+	fd = open("/dev/urandom", O_RDWR);
+	if (fd < 0)
+		return 1;
+	rnd_info.info.entropy_count = len * 8;
+	rnd_info.info.buf_size = len;
+
+	len = ioctl(fd, RNDADDENTROPY, &rnd_info);
+
+	return len ? 1 : 0;
+}

Seems to do the trick.
Something that size is probably a candidate for busybox.
Although it does really need to run before udev is initialised.

	David

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