Update some demos

demos/otp/otp-setup.c

@@ -0,0 +1,37 @@
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include <libgen.h>
+#include <openssl/err.h>
+#include <openssl/bio.h>
+#include <openssl/rand.h>
+#include <openssl/is_gmssl.h>
+
+int main(int argc, char **argv)
+{
+	BIO *bio = NULL;
+	unsigned char key[32];
+
+	if (!RAND_bytes(key, sizeof(key))) {
+		ERR_print_errors_fp(stderr);
+		return -1;
+	}
+
+	if (!(bio = BIO_new_file(".otp_secret", "w"))) {
+		ERR_print_errors_fp(stderr);
+		return -1;
+	}
+
+	if (BIO_write(bio, key, sizeof(key)) != sizeof(key)) {
+		ERR_print_errors_fp(stderr);
+		BIO_free(bio);
+		return -1;
+	}
+
+	printf("generate OTP seed in '.otp_secret'\n");
+
+	BIO_free(bio);
+	OPENSSL_cleanse(key, sizeof(key));
+
+	return 0;
+}