Add basic authentication middleware

src/middleware/basicAuthMiddleware.js

@@ -0,0 +1,39 @@
+/**
+ * When applied, this middleware will ensure the request contains the required header for basic authentication and only
+ * allow access to the endpoint after successful authentication.
+ */
+
+const {dirname} = require('path');
+const appDir = dirname(require.main.filename);
+const config = require(appDir + '/config.conf');
+
+const unauthorizedResponse = (res) => {
+    res.set('WWW-Authenticate', 'Basic realm="SillyTavern", charset="UTF-8"');
+    return res.status(401).send('Authentication required');
+};
+
+const basicAuthMiddleware = function (request, response, callback) {
+    const authHeader = request.headers.authorization;
+
+    if (!authHeader) {
+        return unauthorizedResponse(response);
+    }
+
+    const [scheme, credentials] = authHeader.split(' ');
+
+    if (scheme !== 'Basic' || !credentials) {
+        return unauthorizedResponse(response);
+    }
+
+    const [username, password] = Buffer.from(credentials, 'base64')
+        .toString('utf8')
+        .split(':');
+
+    if (username === config.basicAuthUser.username && password === config.basicAuthUser.password) {
+        return callback();
+    } else {
+        return unauthorizedResponse(response);
+    }
+}
+
+module.exports = basicAuthMiddleware;