tools: add dump-appimage.py tool.

tools/dump-appimage.py

@@ -0,0 +1,53 @@
+#!/usr/bin/env python
+#
+# Copyright 2018 The 'mumble-releng' Authors. All rights reserved.
+# Use of this source code is governed by a BSD-style license that
+# can be found in the LICENSE file in the source tree or at
+# <http://mumble.info/mumble-releng/LICENSE>.
+
+# Dump a .squashfs file from an .AppImage.
+#
+# Sometimes, unsquashfs gets confused and can't find
+# the superblock. We find it, via 'hsqs' header and
+# major version == 4 and copy the squashfs filesystem
+# to its own file.
+
+from __future__ import (unicode_literals, print_function, division)
+
+import os
+import sys
+
+def usage():
+	print('dump-appimage.py <appimage-fn>')
+	print('')
+	print('Writes resulting .squashfs file to')
+	print('<appimage-fn>.squashfs.')
+	sys.exit(1)
+
+def main():
+	if len(sys.argv) < 2:
+		usage()
+	fn = sys.argv[1]
+	f = open(fn, 'r')
+	all = f.read()
+	f.close()
+
+	squashMagic = bytearray((ord('h'), ord('s'), ord('q'), ord('s')))
+	squashOffset = 0
+	squashMajor = 0
+	for i in range(0, len(all)):
+		if all[i:i+len(squashMagic)] == squashMagic:
+			squashOffset = i
+			squashMajor = (ord(all[i+29]) << 8) | ord(all[i+28])
+			if squashMajor == 4:
+				break
+
+	if squashOffset == 0 or squashMajor != 4:
+		raise Exception('no squashfs image found')
+
+	newf = open(fn + '.squashfs', 'w')
+	newf.write(all[i:])
+	newf.close()
+
+if __name__ == '__main__':
+	main()