From 81ddf7dcb69efafb37fcf08c5b0eccdb54fa8ed3 Mon Sep 17 00:00:00 2001
From: Dominic Tarr <dominic.tarr@gmail.com>
Date: Mon, 24 Mar 2014 19:57:01 +1300
Subject: [PATCH] emit error on invalid header

---
 extract.js |  9 +++++++--
 headers.js | 43 +++++++++++++++++++++++++------------------
 2 files changed, 32 insertions(+), 20 deletions(-)

diff --git a/extract.js b/extract.js
index 6f3d3c6..280ef55 100644
--- a/extract.js
+++ b/extract.js
@@ -75,7 +75,12 @@ var Extract = function(opts) {
 	};
 
 	var onheader = function() {
-		var header = self._header = headers.decode(b.slice(0, 512));
+		var header
+		try {
+			header = self._header = headers.decode(b.slice(0, 512));
+		} catch (err) {
+			self.emit('error', err)
+		}
 		b.consume(512);
 
 		if (!header) {
@@ -172,4 +177,4 @@ Extract.prototype._write = function(data, enc, cb) {
 	this._onparse();
 };
 
-module.exports = Extract;
\ No newline at end of file
+module.exports = Extract;
diff --git a/headers.js b/headers.js
index e831a0f..cbc8697 100644
--- a/headers.js
+++ b/headers.js
@@ -176,8 +176,6 @@ exports.decode = function(buf) {
 	var typeflag = buf[156] === 0 ? 0 : buf[156] - ZERO_OFFSET;
 	var type = toType(typeflag);
 
-	if (!type) return null;
-
 	var name = decodeStr(buf, 0, 100);
 	var mode = decodeOct(buf, 100);
 	var uid = decodeOct(buf, 108);
@@ -192,20 +190,29 @@ exports.decode = function(buf) {
 
 	if (buf[345]) name = decodeStr(buf, 345, 155)+'/'+name;
 
-	if (cksum(buf) !== decodeOct(buf, 148)) return null;
+	var c = cksum(buf)
+
+	//checksum is still initial value if header was null.
+	if (c === 8*32) return null;
+
+	//valid checksum
+	if (c === decodeOct(buf, 148))
+		return {
+			name: name,
+			mode: mode,
+			uid: uid,
+			gid: gid,
+			size: size,
+			mtime: new Date(1000 * mtime),
+			type: toType(typeflag),
+			linkname: linkname,
+			uname: uname,
+			gname: gname,
+			devmajor: devmajor,
+			devminor: devminor
+		};
+
+	//invalid checksum
+	throw new Error('invalid header');
+};
 
-	return {
-		name: name,
-		mode: mode,
-		uid: uid,
-		gid: gid,
-		size: size,
-		mtime: new Date(1000 * mtime),
-		type: toType(typeflag),
-		linkname: linkname,
-		uname: uname,
-		gname: gname,
-		devmajor: devmajor,
-		devminor: devminor
-	};
-};
\ No newline at end of file