daemon: primitive privkey handling.

Eventually this will be in a separate process, etc.

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

daemon/secrets.c

@@ -0,0 +1,88 @@
+#include "bitcoin/privkey.h"
+#include "bitcoin/shadouble.h"
+#include "bitcoin/signature.h"
+#include "lightningd.h"
+#include "log.h"
+#include "peer.h"
+#include "secrets.h"
+#include <ccan/crypto/sha256/sha256.h>
+#include <ccan/mem/mem.h>
+#include <ccan/noerr/noerr.h>
+#include <ccan/read_write_all/read_write_all.h>
+#include <ccan/short_types/short_types.h>
+#include <errno.h>
+#include <fcntl.h>
+#include <openssl/rand.h>
+#include <secp256k1.h>
+#include <sys/stat.h>
+#include <sys/types.h>
+#include <unistd.h>
+
+struct secret {
+	/* Secret ID of our node; public is state->id. */
+	struct privkey privkey;
+};
+
+void privkey_sign(struct peer *peer, const void *src, size_t len,
+		  struct signature *sig)
+{
+	struct sha256_double h;
+
+	sha256_double(&h, memcheck(src, len), len);
+	sign_hash(peer->state->secpctx,
+		  &peer->state->secret->privkey, &h, sig);
+}
+
+void secrets_init(struct lightningd_state *state)
+{
+	int fd;
+
+	state->secret = tal(state, struct secret);
+
+	fd = open("privkey", O_RDONLY);
+	if (fd < 0) {
+		if (errno != ENOENT)
+			fatal("Failed to open privkey: %s", strerror(errno));
+
+		log_unusual(state->base_log, "Creating privkey file");
+		do {
+			if (RAND_bytes(state->secret->privkey.secret,
+				       sizeof(state->secret->privkey.secret))
+			    != 1)
+				fatal("Could not get random bytes for privkey");
+		} while (!pubkey_from_privkey(state->secpctx,
+					      &state->secret->privkey,
+					      &state->id,
+					      SECP256K1_EC_COMPRESSED));
+
+		fd = open("privkey", O_CREAT|O_EXCL|O_WRONLY, 0400);
+		if (fd < 0)
+		 	fatal("Failed to create privkey file: %s",
+			      strerror(errno));
+		if (!write_all(fd, state->secret->privkey.secret,
+			       sizeof(state->secret->privkey.secret))) {
+			unlink_noerr("privkey");
+		 	fatal("Failed to write to privkey file: %s",
+			      strerror(errno));
+		}
+		if (fsync(fd) != 0)
+		 	fatal("Failed to sync to privkey file: %s",
+			      strerror(errno));
+		close(fd);
+
+		fd = open("privkey", O_RDONLY);
+		if (fd < 0)
+			fatal("Failed to reopen privkey: %s", strerror(errno));
+	}
+	if (!read_all(fd, state->secret->privkey.secret,
+		      sizeof(state->secret->privkey.secret)))
+		fatal("Failed to read privkey: %s", strerror(errno));
+	close(fd);
+	if (!pubkey_from_privkey(state->secpctx,
+				 &state->secret->privkey, &state->id,
+				 SECP256K1_EC_COMPRESSED))
+		fatal("Invalid privkey");
+
+	log_info(state->base_log, "ID: ");
+	log_add_hex(state->base_log, state->id.der, pubkey_derlen(&state->id));
+}