test-cli/get-revocation-secret: new helper.

Give the revocation secret (or hash) for a given index number.

Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>

test-cli/get-revocation-secret.c

@@ -0,0 +1,45 @@
+#include <ccan/crypto/shachain/shachain.h>
+#include <ccan/short_types/short_types.h>
+#include <ccan/tal/tal.h>
+#include <ccan/opt/opt.h>
+#include <ccan/str/hex/hex.h>
+#include <ccan/err/err.h>
+#include <ccan/read_write_all/read_write_all.h>
+#include <unistd.h>
+
+int main(int argc, char *argv[])
+{
+	struct sha256 seed, secret;
+	bool do_hash = false;
+	char hexstr[hex_str_size(sizeof(secret))];
+
+	err_set_progname(argv[0]);
+
+	opt_register_noarg("--help|-h", opt_usage_and_exit,
+			   "<seed> <index>\n"
+			   "A test program to output secret or hash to stdout.",
+			   "Print this message.");
+	opt_register_noarg("--hash", opt_set_bool, &do_hash,
+			   "Output hash instead of secret itself");
+
+ 	opt_parse(&argc, argv, opt_log_stderr_exit);
+
+	if (argc != 3)
+		opt_usage_exit_fail("Expected 2 arguments");
+
+	if (!hex_decode(argv[1], strlen(argv[1]), &seed, sizeof(seed)))
+		errx(1, "Invalid seed '%s' - need 256 hex bits", argv[1]);
+
+	/* Get the given revoction secret. */
+	shachain_from_seed(&seed, atoi(argv[2]), &secret);
+	if (do_hash)
+		sha256(&secret, secret.u.u8, sizeof(secret.u.u8));
+
+	if (!hex_encode(&secret, sizeof(secret), hexstr, sizeof(hexstr)))
+		abort();
+
+	if (!write_all(STDOUT_FILENO, hexstr, strlen(hexstr)))
+		err(1, "Writing out hexstr");
+
+	return 0;
+}