This gem requires that ruby be built against OpenSSL 1.0.1 or higher! Earlier versions don't support PSS signature verification.

require 'openssl_rsa_pss_verify'
pubkey = OpenSSL::PKey::RSA.new File.read("my_pubkey.pem")
raw_data = File.read("my_raw_data")
signature = File.read("my_signature")
salt_lenth = 0

pubkey.verify_pss_sha1(signature, raw_data, salt_length)
#=> true or false

This the above is identical to

openssl sha1 -binary my_raw_data > my_hashed_data
openssl pkeyutl -verify -in my_hashed_data -pubin -inkey my_pubkey.pem \
  -sigfile my_signature -pkeyopt digest:sha1 -pkeyopt rsa_padding_mode:pss \
  -pkeyopt rsa_pss_saltlen:0

See the man page for more information.

• Only supports SHA1
• OpenSSL 1.0.1 is not available on Heroku! I'm working on a custom buildpack, but it's very ad hoc.