class RubyRNCryptor

# File lib/ruby_rncryptor.rb, line 12
def self.decrypt(data, password)

        version =                     data[0,1]
        raise "RubyRNCryptor only decrypts version 2 or 3" unless (version == "\x02" || version == "\x03")
        options =                     data[1,1]
        encryption_salt =     data[2,8]
        hmac_salt =                   data[10,8]
        iv =                          data[18,16]
        cipher_text =         data[34,data.length-66]
        hmac =                                data[data.length-32,32]

        msg = version + options + encryption_salt + hmac_salt + iv + cipher_text

        # Verify password is correct. First try with correct encoding
        hmac_key = PKCS5.pbkdf2_hmac_sha1(password, hmac_salt, 10000, 32)
        verified = eql_time_cmp([HMAC.hexdigest('sha256', hmac_key, msg)].pack('H*'), hmac)

        if !verified && version == "\x02"
                # Version 2 Cocoa version truncated multibyte passwords, so try truncating.
                password = RubyRNCryptor.truncate_multibyte_password(password)
                hmac_key = PKCS5.pbkdf2_hmac_sha1(password, hmac_salt, 10000, 32)
                verified = eql_time_cmp([HMAC.hexdigest('sha256', hmac_key, msg)].pack('H*'), hmac)
        end

        raise "Password may be incorrect, or the data has been corrupted. (HMAC could not be verified)" unless verified

        # HMAC was verified, now decrypt it.
        cipher = Cipher.new('aes-256-cbc')
        cipher.decrypt
        cipher.iv = iv
        cipher.key = PKCS5.pbkdf2_hmac_sha1(password, encryption_salt, 10000, 32)

        cipher.update(cipher_text) + cipher.final
end

# File lib/ruby_rncryptor.rb, line 47
def self.encrypt(data, password, version = 3)

        raise "RubyRNCryptor only encrypts version 2 or 3" unless (version == 2 || version == 3)

        version =                     version.chr.to_s          # Currently version 3
        options =                     1.chr.to_s                                # Uses password
        encryption_salt =     SecureRandom.random_bytes(8)
        hmac_salt =                   SecureRandom.random_bytes(8)
        iv =                          SecureRandom.random_bytes(16)
        cipher_text =         data[34,data.length-66]

        hmac_key = PKCS5.pbkdf2_hmac_sha1(password, hmac_salt, 10000, 32)

        cipher = Cipher.new('aes-256-cbc')
        cipher.encrypt
        cipher.iv = iv
        cipher.key = PKCS5.pbkdf2_hmac_sha1(password, encryption_salt, 10000, 32)
        cipher_text = cipher.update(data) + cipher.final

        msg = version + options + encryption_salt + hmac_salt + iv + cipher_text
        hmac = [HMAC.hexdigest('sha256', hmac_key, msg)].pack('H*')

        msg + hmac
end

# File lib/ruby_rncryptor.rb, line 80
def self.eql_time_cmp(a, b)
        unless a.length == b.length
                return false
        end
        cmp = b.bytes.to_a
        result = 0
        a.bytes.each_with_index {|c,i|
                result |= c ^ cmp[i]
        }
        result == 0
end

# File lib/ruby_rncryptor.rb, line 72
def self.truncate_multibyte_password(str)
        if str.bytes.to_a.count == str.length
                return str
        end
        str.bytes.to_a[0...str.length].map {|c| c.chr}.join
end