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require 'openssl'
module ActiveSupport
# MessageEncryptor is a simple way to encrypt values which get stored somewhere
# you don't trust.
#
# The cipher text and initialization vector are base64 encoded and returned to you.
#
# This can be used in situations similar to the MessageVerifier, but where you don't
# want users to be able to determine the value of the payload.
class MessageEncryptor
class InvalidMessage < StandardError; end
def initialize(secret, cipher = 'aes-256-cbc')
@secret = secret
@cipher = cipher
end
def encrypt(value)
cipher = new_cipher
# Rely on OpenSSL for the initialization vector
iv = cipher.random_iv
cipher.encrypt
cipher.key = @secret
cipher.iv = iv
encrypted_data = cipher.update(Marshal.dump(value))
encrypted_data << cipher.final
[encrypted_data, iv].map {|v| ActiveSupport::Base64.encode64s(v)}.join("--")
end
def decrypt(encrypted_message)
cipher = new_cipher
encrypted_data, iv = encrypted_message.split("--").map {|v| ActiveSupport::Base64.decode64(v)}
cipher.decrypt
cipher.key = @secret
cipher.iv = iv
decrypted_data = cipher.update(encrypted_data)
decrypted_data << cipher.final
Marshal.load(decrypted_data)
rescue OpenSSL::CipherError, TypeError
raise InvalidMessage
end
def encrypt_and_sign(value)
verifier.generate(encrypt(value))
end
def decrypt_and_verify(value)
decrypt(verifier.verify(value))
end
private
def new_cipher
OpenSSL::Cipher::Cipher.new(@cipher)
end
def verifier
MessageVerifier.new(@secret)
end
end
end
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