class Rack::Session::Encryptor::V1

# File lib/rack/session/encryptor.rb, line 89
def initialize(secret, opts = {})
  raise ArgumentError, 'secret must be a String' unless secret.is_a?(String)
  raise ArgumentError, "invalid secret: #{secret.bytesize}, must be >=64" unless secret.bytesize >= 64

  case opts[:pad_size]
  when nil
  # padding is disabled
  when Integer
    raise ArgumentError, "invalid pad_size: #{opts[:pad_size]}" unless (2..4096).include? opts[:pad_size]
  else
    raise ArgumentError, "invalid pad_size: #{opts[:pad_size]}; must be Integer or nil"
  end

  @options = {
    serialize_json: false, pad_size: 32, purpose: nil
  }.update(opts)

  @hmac_secret = secret.dup.force_encoding(Encoding::BINARY)
  @cipher_secret = @hmac_secret.slice!(0, 32)

  @hmac_secret.freeze
  @cipher_secret.freeze
end

# File lib/rack/session/encryptor.rb, line 113
def decrypt(base64_data)
  data = Base64.urlsafe_decode64(base64_data)

  signature = data.slice!(-32..-1)
  verify_authenticity!(data, signature)

  version = data.slice!(0, 1)
  raise InvalidMessage, 'wrong version' unless version == "\1"

  message_secret = data.slice!(0, 32)
  cipher_iv = data.slice!(0, 16)

  cipher = new_cipher
  cipher.decrypt

  set_cipher_key(cipher, cipher_secret_from_message_secret(message_secret))

  cipher.iv = cipher_iv
  data = cipher.update(data) << cipher.final

  deserialized_message data
rescue ArgumentError
  raise InvalidSignature, 'Message invalid'
end

# File lib/rack/session/encryptor.rb, line 138
def encrypt(message)
  version = "\1"

  serialized_payload = serialize_payload(message)
  message_secret, cipher_secret = new_message_and_cipher_secret

  cipher = new_cipher
  cipher.encrypt

  set_cipher_key(cipher, cipher_secret)

  cipher_iv = cipher.random_iv

  encrypted_data = cipher.update(serialized_payload) << cipher.final

  data = String.new
  data << version
  data << message_secret
  data << cipher_iv
  data << encrypted_data
  data << compute_signature(data)

  Base64.urlsafe_encode64(data)
end

# File lib/rack/session/encryptor.rb, line 175
def cipher_secret_from_message_secret(message_secret)
  OpenSSL::HMAC.digest(OpenSSL::Digest.new('SHA256'), @cipher_secret, message_secret)
end

# File lib/rack/session/encryptor.rb, line 183
def compute_signature(data)
  signing_data = data
  signing_data += @options[:purpose] if @options[:purpose]

  OpenSSL::HMAC.digest(OpenSSL::Digest.new('SHA256'), @hmac_secret, signing_data)
end

# File lib/rack/session/encryptor.rb, line 165
def new_cipher
  OpenSSL::Cipher.new('aes-256-ctr')
end

# File lib/rack/session/encryptor.rb, line 169
def new_message_and_cipher_secret
  message_secret = SecureRandom.random_bytes(32)

  [message_secret, cipher_secret_from_message_secret(message_secret)]
end

# File lib/rack/session/encryptor.rb, line 179
def set_cipher_key(cipher, key)
  cipher.key = key
end

# File lib/rack/session/encryptor.rb, line 190
def verify_authenticity!(data, signature)
  raise InvalidMessage, 'Message is invalid' if data.nil? || signature.nil?

  unless Rack::Utils.secure_compare(signature, compute_signature(data))
    raise InvalidSignature, 'HMAC is invalid'
  end
end