postal/app/lib/signer.rb

# frozen_string_literal: true

require "base64"

class Signer

  # Create a new Signer
  #
  # @param [OpenSSL::PKey::RSA] private_key The private key to use for signing
  # @return [Signer]
  def initialize(private_key)
    @private_key = private_key
  end

  # Return the private key
  #
  # @return [OpenSSL::PKey::RSA]
  attr_reader :private_key

  # Return the public key for the private key
  #
  # @return [OpenSSL::PKey::RSA]
  def public_key
    @private_key.public_key
  end

  # Sign the given data
  #
  # @param [String] data The data to sign
  # @return [String] The signature
  def sign(data)
    private_key.sign(OpenSSL::Digest.new("SHA256"), data)
  end

  # Sign the given data and return a Base64-encoded signature
  #
  # @param [String] data The data to sign
  # @return [String] The Base64-encoded signature
  def sign64(data)
    Base64.strict_encode64(sign(data))
  end

  # Return a JWK for the private key
  #
  # @return [JWT::JWK] The JWK
  def jwk
    @jwk ||= JWT::JWK.new(private_key, { use: "sig", alg: "RS256" })
  end

  # Sign the given data using SHA1 (for legacy use)
  #
  # @param [String] data The data to sign
  # @return [String] The signature
  def sha1_sign(data)
    private_key.sign(OpenSSL::Digest.new("SHA1"), data)
  end

  # Sign the given data using SHA1 (for legacy use) and return a Base64-encoded string
  #
  # @param [String] data The data to sign
  # @return [String] The signature
  def sha1_sign64(data)
    Base64.strict_encode64(sha1_sign(data))
  end

end