View source for RSA-PSS Support in compliance with RFC 7427 and RFC 8247


== Introduction ==

As part of Google summer of Code work in 2017 described in , RFC-7427 Digital Signature Authentication was implemented with support for RSA v1.5.
But RFC-8247, in section 3.2 Digital Signature Recommendations, mandates the support for RSASSA-PSS with SHA-256.
RSASSA-PSS  was developed in an effort to have more mathematically provable security. PKCS #1 v1.5 signatures were developed in an ad hoc manner;
RSASSA-PSS was developed based on mathematical foundations.

== Implementation  ==
 
To make Libreswan RFC 7427 and RFC 8247 compliant, the following items have been implemented :

1. Removing support of RSA v1.5 with SHA1 as Digital Signature Authentication method

2. Support for SHA2 and its variants.
authby =rsa-sha2, rsa-sha2_256, rsa-sha2_384,rsa-sha2_512
authby = rsasig (old style RSA with SHA1 and without Digital Signature Authentication)

3. Signature generation and Verification for RSA-PSS through NSS APIs

4. Test Suite changes

The Test Suite was extended by adding test cases to verify feature functionality and perform interoperability tests with strong swan.

== Future work ==
To make RSA with SHA2 as default and fall back to RSA with SHA1  (if configured)
Example : authby=rsa-sha2,rsasig - RSA with SHA1 and without Digital Signature Authentication

Interoperability test with Elvis Plus

== Source code ==

Code commit : https://github.com/libreswan/libreswan/commit/fd547b0

Testing commit : https://github.com/libreswan/libreswan/commit/83fc58d

The implementation for this project is done by Sahana Prasad (sahana.prasad07@gmail.com) under the tutelage of Paul Wouters.