make reading from file safer and handle unexpected end of file

Author: sokra

lib/serialization/FileMiddleware.js

@@ -229,9 +229,33 @@ const createPointer = (filename, offset, size) => {
 	});
 };
 
+const readFileSectionToBuffer = (fd, buffer, offset, position, callback) => {
+	const remaining = buffer.length - offset;
+	fs.read(fd, buffer, offset, remaining, position, (err, bytesRead) => {
+		if (err) return callback(err);
+		if (bytesRead === 0) {
+			return callback(
+				new Error(
+					`Unexpected end of file (${remaining} bytes missing at pos ${position}`
+				)
+			);
+		}
+		if (bytesRead < remaining) {
+			return readFileSectionToBuffer(
+				fd,
+				buffer,
+				offset + bytesRead,
+				position + bytesRead,
+				callback
+			);
+		}
+		return callback();
+	});
+};
+
 const readSection = (filename, file, offset, size, callback) => {
 	const buffer = Buffer.alloc(size);
-	fs.read(file, buffer, 0, size, offset, err => {
+	readFileSectionToBuffer(file, buffer, 0, offset, err => {
 		if (err) return callback(err);
 
 		const result = [];
@@ -345,7 +369,7 @@ class FileMiddleware extends SerializerMiddleware {
 				false,
 				(file, callback) => {
 					const sizeBuf = Buffer.alloc(4);
-					fs.read(file, sizeBuf, 0, 4, 0, err => {
+					readFileSectionToBuffer(file, sizeBuf, 0, 0, err => {
 						if (err) return callback(err);
 
 						const rootSize = sizeBuf.readUInt32LE(0);