swift-digisign

An OpenStack/Swift middleware for digital signature calculation and verification of stored objects.

This is a "proof-of-concept" implementation for server-side digital signature framework. The current implementation signs stored objects during PUT request handling, using prebuilt (hard-coded) sets of DSA key pairs that are stored on the same server, and performs signature verification during GET request processing. A requested object with a valid signature is returned to the client along with the signature metadata (X-Object-Meta-Sig-User contains the signing user name, X-Object-Meta-DSA-Signature contains a DSA signature tuple), in order to allow the client to verify the signature herself (see example in the demo file in the test directory).

Presentation: http://prezi.com/lr1mji53inxv/extending-swift-with-digital-signature-middleware/

Developed and presented as part of the Tel-Aviv University course "Advanced Topics in Storage Systems" (http://www.eng.tau.ac.il/semcom/), spring 2013.

Installation & Configuration

• Install the module on the proxy server node (using python setup.py install)

• Add "digisign" to the proxy server pipeline (after auth module!)

• Add a configuration section to the bottom of the proxy server configuration file:

    [filter:digisign]
    use = egg:digisign#digisign
    keys_file = /path/to/prebuilt-key-file.dat
  

The prebuilt key-file is a pickled Python dictionary, with an element for every user in the system, where the element key is the username and the element value is a DSA key object generated by PyCrypto (see keygen.py in the test directory for an example of key-file generation).

This module uses PyCrypto and WebOb.

Warnings & Disclaimers

• This is just a POC submitted as an academic project - far from ready for use in production!
• Specifically, all cryptography and key handling happens on the same proxy server node (and not a dedicated HSM or something of this sort), which makes it inadequate in face of malicious administrators...
• There is NO "real" key management - keys are static and configured manually...
• Certificates are not used. A malicious user can resign objects and change the metadata to contain her public key!
• The implementation contains a "backdoor" (disabled by default) for demo purposes.