chanbackup: add rpc to verify emergency.recover file's data.

plugins/chanbackup.c

@@ -762,6 +762,92 @@ static struct command_result *json_restorefrompeer(struct command *cmd,
 				     	    NULL);
 }
 
+/* Returns True if the backup data is correct and
+ * returns false with the reason in `fail` if it's incorrect.
+ * Instead of using `decrypt_scb()` we're using this because
+ * it shuts down the node in case of any discrepancy and that
+ * is not what we want to happen when someone runs `verifybackup`. */
+static bool verify_bkp(struct command *cmd,
+			u8 *filedata,
+			char **fail) {
+
+	bk_crypto_state crypto_state;
+	u64 version;
+	u32 timestamp;
+	struct scb_chan **scb;
+
+	if (tal_bytelen(filedata) <
+		ABYTES + HEADER_LEN) {
+		*fail = "data is corrupted!";
+		return false;
+	}
+
+	u8 *decrypt_scb = tal_arr(tmpctx, u8, tal_bytelen(filedata) -
+				  ABYTES -
+				  HEADER_LEN);
+
+	/* The header part */
+	if (crypto_secretstream_xchacha20poly1305_init_pull(&crypto_state,
+							    filedata,
+							    (&secret)->data) != 0) {
+		*fail = "data is corrupted!";
+		return false;
+	}
+
+	if (crypto_secretstream_xchacha20poly1305_pull(&crypto_state, decrypt_scb,
+						       NULL, 0,
+						       filedata +
+						       HEADER_LEN,
+						       tal_bytelen(filedata)-
+						       HEADER_LEN,
+						       NULL, 0) != 0) {
+		*fail =  "data is corrupted!";
+		return false;
+	}
+
+	if (!fromwire_static_chan_backup(cmd,
+					 decrypt_scb,
+					 &version,
+					 &timestamp,
+					 &scb)) {
+		*fail = "data is corrupted";
+		return false;
+	}
+
+	if (version != VERSION) {
+		*fail = "Incompatible emergency.recover file version on disk,"
+				"contact the admin or update the file asap!";
+		return false;
+	}
+	return true;
+}
+
+
+static struct command_result *json_verifybackup(struct command *cmd,
+						const char *buf,
+						const jsmntok_t *params)
+{
+	struct json_stream *response;
+	char *fail;
+
+	if (!param(cmd, buf, params, NULL))
+		return command_param_failed();
+
+	u8 *filedata = get_file_data(tmpctx, cmd->plugin);
+
+	response = jsonrpc_stream_success(cmd);
+
+	if (!verify_bkp(cmd, filedata, &fail)) {
+		json_add_str_fmt(response, "emergency.recover", "%s, Kindly remove the file and restart the node.", fail);
+	}
+	else {
+		json_add_bool(response, "emergency.recover", true);
+	}
+
+	return command_finished(cmd, response);
+
+}
+
 static const char *init(struct plugin *p,
 			const char *buf UNUSED,
 			const jsmntok_t *config UNUSED)
@@ -834,6 +920,14 @@ static const struct plugin_command commands[] = {
 		"return channel-id's on completion",
 		json_restorefrompeer,
 	},
+	{
+		"verifybackup",
+		"recovery",
+		"Verifies your emergency.recover file and peer storage backup (if exists)."
+		"Also, gives out the channel IDs of the channels contained in the backup.",
+		"returns if the file is valid and the channel ID's contained in it",
+		json_verifybackup,
+	}
 };
 
 int main(int argc, char *argv[])