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106 lines
3.6 KiB
Ruby
106 lines
3.6 KiB
Ruby
require 'openssl'
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require 'base64'
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require 'active_support/core_ext/array/extract_options'
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module ActiveSupport
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# MessageEncryptor is a simple way to encrypt values which get stored
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# somewhere you don't trust.
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#
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# The cipher text and initialization vector are base64 encoded and returned
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# to you.
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#
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# This can be used in situations similar to the <tt>MessageVerifier</tt>, but
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# where you don't want users to be able to determine the value of the payload.
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#
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# key = OpenSSL::Digest::SHA256.new('password').digest # => "\x89\xE0\x156\xAC..."
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# crypt = ActiveSupport::MessageEncryptor.new(key) # => #<ActiveSupport::MessageEncryptor ...>
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# encrypted_data = crypt.encrypt_and_sign('my secret data') # => "NlFBTTMwOUV5UlA1QlNEN2xkY2d6eThYWWh..."
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# crypt.decrypt_and_verify(encrypted_data) # => "my secret data"
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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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# Initialize a new MessageEncryptor. +secret+ must be at least as long as
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# the cipher key size. For the default 'aes-256-cbc' cipher, this is 256
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# bits. If you are using a user-entered secret, you can generate a suitable
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# key with <tt>OpenSSL::Digest::SHA256.new(user_secret).digest</tt> or
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# similar.
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#
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# Options:
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# * <tt>:cipher</tt> - Cipher to use. Can be any cipher returned by
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# <tt>OpenSSL::Cipher.ciphers</tt>. Default is 'aes-256-cbc'.
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# * <tt>:serializer</tt> - Object serializer to use. Default is +Marshal+.
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def initialize(secret, *signature_key_or_options)
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options = signature_key_or_options.extract_options!
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sign_secret = signature_key_or_options.first
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@secret = secret
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@sign_secret = sign_secret
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@cipher = options[:cipher] || 'aes-256-cbc'
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@verifier = MessageVerifier.new(@sign_secret || @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
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# padding attacks. 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
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# avoid padding attacks. 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| ::Base64.strict_encode64(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| ::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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