Added support for key rotation

ankane · May 30, 2024 · feba5a1 · feba5a1
1 parent d1bb229
commit feba5a1
Show file tree

Hide file tree

Showing 3 changed files with 26 additions and 8 deletions.
diff --git a/CHANGELOG.md b/CHANGELOG.md
@@ -1,3 +1,7 @@
+## 2.3.0 (unreleased)
+
+- Added support for key rotation
+
 ## 2.2.0 (2023-07-02)
 
 - Removed support for Ruby < 3 and Rails < 6.1

diff --git a/app/controllers/ahoy/messages_controller.rb b/app/controllers/ahoy/messages_controller.rb
@@ -11,24 +11,23 @@ def open
     end
 
     def click
-      if params[:id]
-        # legacy
+      legacy = params[:id]
+      if legacy
         token = params[:id].to_s
+        campaign = nil
         url = params[:url].to_s
         signature = params[:signature].to_s
-        expected_signature = OpenSSL::HMAC.hexdigest("SHA1", AhoyEmail::Utils.secret_token, url)
       else
         token = params[:t].to_s
         campaign = params[:c].to_s
         url = params[:u].to_s
         signature = params[:s].to_s
-        expected_signature = AhoyEmail::Utils.signature(token: token, campaign: campaign, url: url)
       end
 
       redirect_options = {}
       redirect_options[:allow_other_host] = true if ActionPack::VERSION::MAJOR >= 7
 
-      if ActiveSupport::SecurityUtils.secure_compare(signature, expected_signature)
+      if AhoyEmail::Utils.signature_verified?(legacy: legacy, token: token, campaign: campaign, url: url, signature: signature)
         data = {}
         data[:campaign] = campaign if campaign
         data[:token] = token

diff --git a/lib/ahoy_email/utils.rb b/lib/ahoy_email/utils.rb
@@ -7,13 +7,28 @@ class Utils
     }
 
     class << self
-      def signature(token:, campaign:, url:)
+      def signature(token:, campaign:, url:, secret_token: nil)
+        secret_token ||= self.secret_tokens.first
+
         # encode and join with a character outside encoding
         data = [token, campaign, url].map { |v| Base64.strict_encode64(v.to_s) }.join("|")
 
         Base64.urlsafe_encode64(OpenSSL::HMAC.digest("SHA256", secret_token, data), padding: false)
       end
 
+      def signature_verified?(legacy:, token:, campaign:, url:, signature:)
+        secret_tokens.any? do |secret_token|
+          expected_signature =
+            if legacy
+              OpenSSL::HMAC.hexdigest("SHA1", secret_token, url)
+            else
+              signature(token: token, campaign: campaign, url: url, secret_token: secret_token)
+            end
+
+          ActiveSupport::SecurityUtils.secure_compare(signature, expected_signature)
+        end
+      end
+
       def publish(name, event)
         method_name = "track_#{name}"
         AhoyEmail.subscribers.each do |subscriber|
@@ -27,8 +42,8 @@ def publish(name, event)
         end
       end
 
-      def secret_token
-        AhoyEmail.secret_token || (raise "Secret token is empty")
+      def secret_tokens
+        Array(AhoyEmail.secret_token || (raise "Secret token is empty"))
       end
     end
   end