95 lines
3.4 KiB
Ruby
95 lines
3.4 KiB
Ruby
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# frozen_string_literal: true
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module Gitlab
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module BackgroundMigration
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# EncryptColumn migrates data from an unencrypted column - `foo`, say - to
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# an encrypted column - `encrypted_foo`, say.
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#
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# For this background migration to work, the table that is migrated _has_ to
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# have an `id` column as the primary key. Additionally, the encrypted column
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# should be managed by attr_encrypted, and map to an attribute with the same
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# name as the unencrypted column (i.e., the unencrypted column should be
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# shadowed).
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#
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# To avoid depending on a particular version of the model in app/, add a
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# model to `lib/gitlab/background_migration/models/encrypt_columns` and use
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# it in the migration that enqueues the jobs, so code can be shared.
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class EncryptColumns
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def perform(model, attributes, from, to)
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model = model.constantize if model.is_a?(String)
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# If sidekiq hasn't undergone a restart, its idea of what columns are
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# present may be inaccurate, so ensure this is as fresh as possible
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model.reset_column_information
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model.define_attribute_methods
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attributes = expand_attributes(model, Array(attributes).map(&:to_sym))
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model.transaction do
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# Use SELECT ... FOR UPDATE to prevent the value being changed while
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# we are encrypting it
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relation = model.where(id: from..to).lock
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relation.each do |instance|
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encrypt!(instance, attributes)
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end
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end
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end
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private
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# Build a hash of { attribute => encrypted column name }
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def expand_attributes(klass, attributes)
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expanded = attributes.flat_map do |attribute|
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attr_config = klass.encrypted_attributes[attribute]
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crypt_column_name = attr_config&.fetch(:attribute)
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raise "Couldn't determine encrypted column for #{klass}##{attribute}" if
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crypt_column_name.nil?
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raise "#{klass} source column: #{attribute} is missing" unless
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klass.column_names.include?(attribute.to_s)
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# Running the migration without the destination column being present
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# leads to data loss
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raise "#{klass} destination column: #{crypt_column_name} is missing" unless
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klass.column_names.include?(crypt_column_name.to_s)
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[attribute, crypt_column_name]
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end
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Hash[*expanded]
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end
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# Generate ciphertext for each column and update the database
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def encrypt!(instance, attributes)
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to_clear = attributes
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.map { |plain, crypt| apply_attribute!(instance, plain, crypt) }
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.compact
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.flat_map { |plain| [plain, nil] }
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to_clear = Hash[*to_clear]
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if instance.changed?
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instance.save!
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instance.update_columns(to_clear)
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end
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end
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def apply_attribute!(instance, plain_column, crypt_column)
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plaintext = instance[plain_column]
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ciphertext = instance[crypt_column]
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# No need to do anything if the plaintext is nil, or an encrypted
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# value already exists
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return nil unless plaintext.present? && !ciphertext.present?
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# attr_encrypted will calculate and set the expected value for us
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instance.public_send("#{plain_column}=", plaintext) # rubocop:disable GitlabSecurity/PublicSend
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plain_column
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end
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end
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end
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end
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