discourse/lib/freedom_patches/cose_rsapkcs1.rb

# frozen_string_literal: true

require "cose"
require "openssl/signature_algorithm/rsapkcs1"

# 'cose' gem does not implement all algorithms from the Web Authentication
# (WebAuthn) standard specification. This patch implements one of the missing
# ones, RSASSA-PKCS1-v1_5.
module COSE
  module Algorithm
    def self.registered_algorithm_ids
      @registered_by_id.keys
    end

    class RSAPKCS1 < SignatureAlgorithm
      attr_reader :hash_function

      def initialize(*args, hash_function:)
        super(*args)

        @hash_function = hash_function
      end

      private

      def valid_key?(key)
        to_cose_key(key).is_a?(COSE::Key::RSA)
      end

      def signature_algorithm_class
        OpenSSL::SignatureAlgorithm::RSAPKCS1
      end

      def to_pkey(key)
        case key
        when COSE::Key::RSA
          key.to_pkey
        when OpenSSL::PKey::RSA
          key
        else
          raise(COSE::Error, "Incompatible key for algorithm")
        end
      end
    end

    register(RSAPKCS1.new(-257, "RS256", hash_function: "SHA256"))
  end
end