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Tidus is a Ruby Gem which works in conjunction with ActiveRecord to automatically generate database views for every model which is a direct descendent from ActiveRecord::Base. The purpose of the views is to anonymize the contents of select columns to ensure that no confidential information leave the database while still providing access to the data in general.

Getting started

  1. add the Gem to the Gemfile

     gem 'tidus'
  2. Require the Gem at any point after ActiveRecord but before loading the models. Rails requires all Gems in the Gemfile by default.

  3. Add your anonymization rules

  4. Execute rake db:migrate. The db:clear_views and db:generate_views tasks are hooked to automatically run every time before and after execution of db:migrate or db:rollback.

Anonymization rules

The rules to ensure anonymization can be defined as follows

    anonymizes :column_name, strategy: <strategy_name>, <additional_options>
  • strategy_name: any of the strategies below
  • additional_options: additional settings in key: valuenotation


  • :cond
    • Replaces values by other values of a specific type in case a condition is met. If no condition is met, the current value or a default is used if specified.
    • Options:
      • :default The default value to be used in case no condition is met. If not set the current column value will be used.
      • :default_strategy The default strategy to be used in case no condition is met (alternative to :default). Strategy options are not supported at the moment.
      • :result_type The type to which the resulting value should be cast. Default is text.
      • :conditions Array or hash of one or more condition settings
        • :column Name of the column for the condition
        • :value Value which should be compared to the :column value
        • :type The type to which the column value and the condition value should be cast for comparision. Default is text.
        • :comparator Infix function with which to compare the values. Default is =
        • :result Value which should be used as a replacement in case the condition is met.
  • :ean
    • Replaces all or part of an ean code with a mapping of the digits to scramble the real value.
    • Options:
      • :start Defines the starting point in the value string. Defaults to the beginning if nothing is given.
      • :length Defines the length of the translation. Defaults to the whole remaining length if nothing is given.
      • :cache_key Allows to cache the generated mapping to re-use on another model. Will generate a new mapping if no caching is enabled.
  • :email
    • Replaces the part before the @ by an MD5 Hash of the value with the given length. A hash function is used to have anonymization while allowing to find out whether two addresses are the same.
    • Options:
      • :length Specifies the length of the part which should be kept before the @. Default is 15. Maximum with MD5 is 32.
  • :null
    • Replaces any value with NULL
  • :overlay
    • Adds an overlay to part of the string.
    • Options:
      • :start Defines the starting point in the value string. (required)
      • :length Defines the length of the overlay. (required)
      • :char Defines the character which should be used as an overlay. Default is 'X'.
  • :static
    • Similar to the :null strategy, this strategy allows defining a specific value with which to replace the column value.
    • Options:
      • :value The value used as a replacement in the view. (required)
      • :type The type to which the returned value should be cast. Default is text
  • :text
    • It replaces any string by a randomized string of equal length minding capital letters. The replacement function is the same for every value in the view but it is randomly generated each time the view is created.
  • :regex_replace
    • This strategy allows replacing string matching a pattern with another string.
    • Options:
      • :pattern The regular expression pattern which will be replaced. (required)
      • :replacement The replacement to the pattern. Uses an empty string if none given.
  • :remove_json_keys
    • This strategy allows removing top-level keys from JSON objects.
    • Options:
      • :keys An array of keys on the top level which should be removed. (required)

Note: to provide your own anonymization strategy you can also provide a class name for the strategy, e.g. strategy: Tidus::OverlayAnonymizer. It is expected though that the class is in a submodule. It is recommended to use Tidus as module name for better association of the purpose of the class.

Other options

  • skip_anonymization - Don't create an anonymized view for the model (by default tidus creates an anonymized view even if no fields are anonymized). Add this to the model instead of using anonymizes strategies.

Database support

PostgreSQL SQLite3 MySQL
cond x x
ean x x
email x x
null x
overlay x x
static x x
text x x
replace x x
remove_json_keys x x

Currently the Gem only contains strategy implementations for PostgreSQL.

Backup and Restore

You can use the bash example script located in examples to backup and restore databases prepared with tidus easily. can be called with any parameter other than -d|-r|--dump|--restore to get help for it's usage. The tidus_seq_rst.sql file is necessary for restores since it's will reset all sequences after restore for you - it's not necessary for backups only. You also need the tidus_credentials.conf with the IP/DNS, User and Password of the Dump and Restore users. If you use on separate machines for backup and restore, you can split up the credentials file and only provide the information necessary to backup and restore.

Basic usage

Before dumping or restoring you have to provide the tidus_credentials.conf file with all the informations needed for dumping and restoring. Those parameters are not exposed into the commandline due to security considerations. Also manually edit the and check the dump_it and restore_it functions and add the databases you want to dump or restore as well as the database names in your staging environment and the staging user which will get the permissions after restore.

  • ./ /path/to/tidus_credentials.conf -d /path/to/the/dumps/folder
    • Add all databases you want to dump from in the dump_it function!
  • ./ /path/to/tidus_credentials.conf -r /path/to/the/dumps/folder <Backup-Set-No>
    • Add all databases you want to restore - as well as the destination database names and users - in the restore_it function!
    • Be sure to have the tidus_seq_rst.sqlin the same folder as the script which is required for a successful restore!

Bugs and Contribution

For bugs and feature requests open an issue on Github. For code contributions fork the repo, make your changes and create a pull request.

Extending functionality

The number of strategies implemented so far is limited. You can however very easily define your own anonymization strategy. There is actually only one requirement: The class containing the strategy has to have an anonymize method. By passing the class name as a strategy value to the :strategy key, you are telling the anonymization extension on which class to execute said method.




ActiveRecord database anonymization using views




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