Check the permissions on the history dir on start

Fixes https://github.com/lovasoa/whitebophir/issues/164

package-lock.json

@@ -1,6 +1,6 @@
 {
    "name": "whitebophir",
-   "version": "1.6.5",
+   "version": "1.7.1",
    "lockfileVersion": 1,
    "requires": true,
    "dependencies": {

package.json

@@ -1,7 +1,7 @@
 {
   "name": "whitebophir",
   "description": "Online collaborative whiteboard",
-  "version": "1.7.0",
+  "version": "1.7.1",
   "keywords": [
     "collaborative",
     "whiteboard"

server/check_output_directory.js

@@ -0,0 +1,68 @@
+const fs = require("./fs_promises");
+const path = require('path');
+let os = require('os');
+
+const { R_OK, W_OK } = fs.constants;
+
+/**
+ * Checks that the output directory is writeable
+ * @param {string} directory
+ * @returns {string?}
+ */
+async function get_error(directory) {
+    if (!fs.existsSync(directory)) {
+        return "does not exist";
+    }
+    if (!fs.statSync(directory).isDirectory()) {
+        error = "exists, but is not a directory";
+    }
+    const { uid, gid } = os.userInfo();
+    const tmpfile = path.join(directory, Math.random() + ".json");
+    try {
+        fs.writeFileSync(tmpfile, "{}");
+        fs.unlinkSync(tmpfile);
+    } catch (e) {
+        return "does not allow file creation and deletion. " +
+            "Check the permissions of the directory, and if needed change them so that " +
+            `user with UID ${uid} has access to them. This can be achieved by running the command: chown ${uid}:${gid} on the directory`;
+    }
+    const fileChecks = [];
+    const dir = fs.opendirSync(directory);
+    while (true) {
+        const elem = await dir.read();
+        if (!elem) break;
+        if (/^board-(.*)\.json$/.test(elem.name)) {
+            const elemPath = path.join(directory, elem.name);
+            if (!elem.isFile()) return `contains a board file named "${elemPath}" which is not a normal file`
+            fileChecks.push(fs.promises.access(elemPath, R_OK | W_OK)
+                .catch(function () { return elemPath }))
+        }
+    }
+    dir.closeSync();
+    const errs = (await Promise.all(fileChecks)).filter(function (x) { return x });
+    if (errs.length > 0) {
+        return `contains the following board files that are not readable and writable by the current user: "` +
+            errs.join('", "') +
+            `". Please make all board files accessible with chown 1000:1000.`
+    }
+}
+
+/**
+ * Checks that the output directory is writeable, 
+ * ans exits the current process with an error otherwise.
+ * @param {string} directory
+ */
+function check_output_directory(directory) {
+    get_error(directory).then(function (error) {
+        if (error) {
+            console.error(
+                `The configured history directory in which boards are stored ${error}.` +
+                `\nThe history directory can be configured with the environment variable HISTORY_DIR. ` +
+                `It is currently set to "${directory}".`
+            );
+            process.exit(1);
+        }
+    })
+}
+
+module.exports = check_output_directory

server/server.js

@@ -9,7 +9,8 @@ var app = require('http').createServer(handler)
 	, createSVG = require("./createSVG.js")
 	, templating = require("./templating.js")
 	, config = require("./configuration.js")
-	, polyfillLibrary = require('polyfill-library');
+	, polyfillLibrary = require('polyfill-library')
+	, check_output_directory = require("./check_output_directory.js");
 
 
 var MIN_NODE_VERSION = 8.0;
@@ -20,7 +21,9 @@ if (parseFloat(process.versions.node) < MIN_NODE_VERSION) {
 		", wbo requires at least " + MIN_NODE_VERSION + " !!!");
 }
 
-var io = sockets.start(app);
+check_output_directory(config.HISTORY_DIR);
+
+sockets.start(app);
 
 app.listen(config.PORT, config.HOST);
 log("server started", { port: config.PORT });