Methods

Instance Public methods

find_signed(signed_id, purpose: nil)

Lets you find a record based on a signed id that's safe to put into the world without risk of tampering. This is particularly useful for things like password reset or email verification, where you want the bearer of the signed id to be able to interact with the underlying record, but usually only within a certain time period.

You set the time period that the signed id is valid for during generation, using the instance method signed_id(expires_in: 15.minutes). If the time has elapsed before a signed find is attempted, the signed id will no longer be valid, and nil is returned.

It's possible to further restrict the use of a signed id with a purpose. This helps when you have a general base model, like a User, which might have signed ids for several things, like password reset or email verification. The purpose that was set during generation must match the purpose set when finding. If there's a mismatch, nil is again returned.

Examples

signed_id = User.first.signed_id expires_in: 15.minutes, purpose: :password_reset

User.find_signed signed_id # => nil, since the purpose does not match

travel 16.minutes
User.find_signed signed_id, purpose: :password_reset # => nil, since the signed id has expired

travel_back
User.find_signed signed_id, purpose: :password_reset # => User.first
📝 Source code 
# File activerecord/lib/active_record/signed_id.rb, line 42
      def find_signed(signed_id, purpose: nil)
        raise UnknownPrimaryKey.new(self) if primary_key.nil?

        if id = signed_id_verifier.verified(signed_id, purpose: combine_signed_id_purposes(purpose))
          find_by primary_key => id
        end
      end
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find_signed!(signed_id, purpose: nil)

Works like find_signed, but will raise an ActiveSupport::MessageVerifier::InvalidSignature exception if the signed_id has either expired, has a purpose mismatch, is for another record, or has been tampered with. It will also raise an ActiveRecord::RecordNotFound exception if the valid signed id can't find a record.

Examples

User.find_signed! "bad data" # => ActiveSupport::MessageVerifier::InvalidSignature

signed_id = User.first.signed_id
User.first.destroy
User.find_signed! signed_id # => ActiveRecord::RecordNotFound
📝 Source code 
# File activerecord/lib/active_record/signed_id.rb, line 62
      def find_signed!(signed_id, purpose: nil)
        if id = signed_id_verifier.verify(signed_id, purpose: combine_signed_id_purposes(purpose))
          find(id)
        end
      end
🔎 See on GitHub

signed_id_verifier()

The verifier instance that all signed ids are generated and verified from. By default, it'll be initialized with the class-level signed_id_verifier_secret, which within Rails comes from the Rails.application.key_generator. By default, it's SHA256 for the digest and JSON for the serialization.

📝 Source code 
# File activerecord/lib/active_record/signed_id.rb, line 71
      def signed_id_verifier
        @signed_id_verifier ||= begin
          secret = signed_id_verifier_secret
          secret = secret.call if secret.respond_to?(:call)

          if secret.nil?
            raise ArgumentError, "You must set ActiveRecord::Base.signed_id_verifier_secret to use signed ids"
          else
            ActiveSupport::MessageVerifier.new secret, digest: "SHA256", serializer: JSON
          end
        end
      end
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signed_id_verifier=(verifier)

Allows you to pass in a custom verifier used for the signed ids. This also allows you to use different verifiers for different classes. This is also helpful if you need to rotate keys, as you can prepare your custom verifier for that in advance. See ActiveSupport::MessageVerifier for details.

📝 Source code 
# File activerecord/lib/active_record/signed_id.rb, line 87
      def signed_id_verifier=(verifier)
        @signed_id_verifier = verifier
      end
🔎 See on GitHub