Allow a proc to be passed for JTI verification

README.md

@@ -267,8 +267,6 @@ From [Oauth JSON Web Token 4.1.7. "jti" (JWT ID) Claim](https://tools.ietf.org/h
 > The `jti` (JWT ID) claim provides a unique identifier for the JWT. The identifier value MUST be assigned in a manner that ensures that there is a negligible probability that the same value will be accidentally assigned to a different data object; if the application uses multiple issuers, collisions MUST be prevented among values produced by different issuers as well. The `jti` claim can be used to prevent the JWT from being replayed. The `jti` value is a case-sensitive string. Use of this claim is OPTIONAL.
 
 ```ruby
-# in order to use JTI you have to add iat
-iat = Time.now.to_i
 # Use the secret and iat to create a unique key per request to prevent replay attacks
 jti_raw = [hmac_secret, iat].join(':').to_s
 jti = Digest::MD5.hexdigest(jti_raw)
@@ -277,9 +275,10 @@ jti_payload = { :data => 'data', :iat => iat, :jti => jti }
 token = JWT.encode jti_payload, hmac_secret, 'HS256'
 
 begin
-  # Add jti and iat to the validation to check if the token has been manipulated
-  decoded_token = JWT.decode token, hmac_secret, true, { 'jti' => jti, :verify_jti => true, :algorithm => 'HS256' }
-  # Check if the JTI has already been used
+  # If :verify_jti is true, validation will pass if a JTI is present
+  #decoded_token = JWT.decode token, hmac_secret, true, { :verify_jti => true, :algorithm => 'HS256' }
+  # Alternatively, pass a proc with your own code to check if the JTI has already been used
+  decoded_token = JWT.decode token, hmac_secret, true, { :verify_jti => proc { |jti| my_validation_method(jti) }, :algorithm => 'HS256' }
 rescue JWT::InvalidJtiError
   # Handle invalid token, e.g. logout user or deny access
   puts 'Error'

lib/jwt/verify.rb

@@ -37,7 +37,11 @@ def self.verify_iat(payload, options)
     end
 
     def self.verify_jti(payload, _options)
-      fail(JWT::InvalidJtiError, 'Missing jti') if payload['jti'].to_s == ''
+      if _options[:verify_jti].class == Proc
+        fail(JWT::InvalidJtiError, 'Invalid jti') unless _options[:verify_jti].call(payload['jti'])
+      else
+        fail(JWT::InvalidJtiError, 'Missing jti') if payload['jti'].to_s == ''
+      end
     end
 
     def self.verify_aud(payload, options)

spec/jwt_spec.rb

@@ -377,6 +377,18 @@
           JWT.decode token, data[:secret], true, verify_jti: true
         end.to_not raise_error
       end
+
+      it 'false proc should raise JWT::InvalidJtiError' do
+        expect do
+          JWT.decode token, data[:secret], true, verify_jti: lambda { |jti| false }
+        end.to raise_error JWT::InvalidJtiError
+      end
+
+      it 'true proc should not raise JWT::InvalidJtiError' do
+        expect do
+          JWT.decode invalid_token, data[:secret], true, verify_jti: lambda { |jti| true }
+        end.to_not raise_error
+      end
     end
   end