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86 lines
2.4 KiB
Ruby
86 lines
2.4 KiB
Ruby
require 'openssl'
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require 'active_support/base64'
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module ActiveSupport
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# MessageEncryptor is a simple way to encrypt values which get stored somewhere
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# you don't trust.
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#
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# The cipher text and initialization vector are base64 encoded and returned to you.
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#
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# This can be used in situations similar to the <tt>MessageVerifier</tt>, but where you don't
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# want users to be able to determine the value of the payload.
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class MessageEncryptor
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module NullSerializer #:nodoc:
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def self.load(value)
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value
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end
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def self.dump(value)
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value
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end
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end
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class InvalidMessage < StandardError; end
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OpenSSLCipherError = OpenSSL::Cipher.const_defined?(:CipherError) ? OpenSSL::Cipher::CipherError : OpenSSL::CipherError
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def initialize(secret, options = {})
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@secret = secret
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@cipher = options[:cipher] || 'aes-256-cbc'
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@verifier = MessageVerifier.new(@secret, :serializer => NullSerializer)
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@serializer = options[:serializer] || Marshal
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end
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# Encrypt and sign a message. We need to sign the message in order to avoid padding attacks.
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# Reference: http://www.limited-entropy.com/padding-oracle-attacks
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def encrypt_and_sign(value)
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verifier.generate(_encrypt(value))
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end
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# Decrypt and verify a message. We need to verify the message in order to avoid padding attacks.
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# Reference: http://www.limited-entropy.com/padding-oracle-attacks
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def decrypt_and_verify(value)
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_decrypt(verifier.verify(value))
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end
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private
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def _encrypt(value)
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cipher = new_cipher
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# Rely on OpenSSL for the initialization vector
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iv = cipher.random_iv
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cipher.encrypt
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cipher.key = @secret
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cipher.iv = iv
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encrypted_data = cipher.update(@serializer.dump(value))
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encrypted_data << cipher.final
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[encrypted_data, iv].map {|v| ActiveSupport::Base64.encode64s(v)}.join("--")
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end
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def _decrypt(encrypted_message)
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cipher = new_cipher
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encrypted_data, iv = encrypted_message.split("--").map {|v| ActiveSupport::Base64.decode64(v)}
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cipher.decrypt
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cipher.key = @secret
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cipher.iv = iv
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decrypted_data = cipher.update(encrypted_data)
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decrypted_data << cipher.final
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@serializer.load(decrypted_data)
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rescue OpenSSLCipherError, TypeError
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raise InvalidMessage
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end
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def new_cipher
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OpenSSL::Cipher::Cipher.new(@cipher)
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end
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def verifier
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@verifier
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end
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end
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end
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