Improve support for Unsecured JWT

Allows for symmetric support of Unsecured JWT. It now works as any other algorithm for both encoding and decoding.

Fixes jwt#323.

lib/jwt/algos/none.rb

@@ -0,0 +1,21 @@
+module JWT
+  module Algos
+    module None
+      # Unsecured JWT
+      module_function
+
+      SUPPORTED = %w[none].freeze
+
+      def sign(to_sign)
+        raise EncodeError, 'Signing key not supported for Unsecured JWT' if to_sign.key
+        ''
+      end
+
+      def verify(to_verify)
+        raise VerificationError, 'Signing key not supported for Unsecured JWT' if to_verify.public_key
+        raise VerificationError, 'Signature should be empty for Unsecured JWT' unless to_verify.signature == ''
+        true
+      end
+    end
+  end
+end

lib/jwt/decode.rb

@@ -13,7 +13,7 @@ def initialize(jwt, key, verify, options, &keyfinder)
       @jwt = jwt
       @key = key
       @options = options
-      @segments = jwt.split('.')
+      @segments = jwt.split('.', -1)
       @verify = verify
       @signature = ''
       @keyfinder = keyfinder
@@ -66,7 +66,6 @@ def verify_claims
 
     def validate_segment_count!
       return if segment_length == 3
-      return if !@verify && segment_length == 2 # If no verifying required, the signature is not needed
 
       raise(JWT::DecodeError, 'Not enough or too many segments')
     end

lib/jwt/encode.rb

@@ -52,8 +52,6 @@ def encode_payload
     end
 
     def encode_signature
-      return '' if @algorithm == ALG_NONE
-
       JWT::Base64.url_encode(JWT::Signature.sign(@algorithm, encoded_header_and_payload, @key))
     end
 

lib/jwt/signature.rb

@@ -7,6 +7,7 @@
 require 'jwt/algos/ecdsa'
 require 'jwt/algos/rsa'
 require 'jwt/algos/ps'
+require 'jwt/algos/none'
 require 'jwt/algos/unsupported'
 begin
   require 'rbnacl'
@@ -25,6 +26,7 @@ module Signature
       Algos::Rsa,
       Algos::Eddsa,
       Algos::Ps,
+      Algos::None,
       Algos::Unsupported
     ].freeze
     ToSign = Struct.new(:algorithm, :msg, :key)

spec/jwt_spec.rb

@@ -44,19 +44,45 @@
 
   context 'alg: NONE' do
     let(:alg) { 'none' }
+    let(:sig) { 'kWOVtIOpWcG7JnyJG0qOkTDbOy636XrrQhMm_8JrRQ8' }
 
     it 'should generate a valid token' do
       token = JWT.encode payload, nil, alg
 
       expect(token).to eq data['NONE']
     end
 
+    it 'with key should raise JWT::EncodeError' do
+      expect do
+        JWT.encode payload, data[:secret], alg
+      end.to raise_error JWT::EncodeError, 'Signing key not supported for Unsecured JWT'
+    end
+
     it 'should decode a valid token' do
       jwt_payload, header = JWT.decode data['NONE'], nil, false
 
       expect(header['alg']).to eq alg
       expect(jwt_payload).to eq payload
     end
+
+    it 'should decode and verify a valid token' do
+      jwt_payload, header = JWT.decode data['NONE'], nil, true, algorithm: alg
+
+      expect(header['alg']).to eq alg
+      expect(jwt_payload).to eq payload
+    end
+
+    it 'with signature should raise JWT::VerificationError' do
+      expect do
+        JWT.decode data['NONE'] + sig, nil, true, algorithm: alg
+      end.to raise_error JWT::VerificationError, 'Signature should be empty for Unsecured JWT'
+    end
+
+    it 'with key should raise JWT::VerificationError' do
+      expect do
+        JWT.decode data['NONE'], data[:secret], true, algorithm: alg
+      end.to raise_error JWT::VerificationError, 'Signing key not supported for Unsecured JWT'
+    end
   end
 
   context 'payload validation' do