strip_pkg_signatures is a tool that removes the signature from Apple installer .pkg files. This is only useful to install expired packages. For a detailed description of this issue, see here:

• http://managingosx.wordpress.com/2012/03/24/fixing-packages-with-expired-signatures/
• http://managingosx.wordpress.com/2012/03/24/package-apocalypse/

Apple installer .pkg files are XAR files that have an optional <signature> element in the TOC XML. For each specified file, this tool reads the header and TOC. If the TOC does not have a <signature> then nothing is done. If it does, then it will (atomically) replace the file with a new one that has no <signature> in the TOC.

usage: ./strip_pkg_signature.py [-h] [--dry-run] [--keep-old]
                                XARFILE [XARFILE ...]

positional arguments:
  XARFILE     the xar files to remove signatures from

optional arguments:
  -h, --help  show this help message and exit
  --dry-run   do not write new xar files
  --keep-old  keep the originals as XARFILE.old