Do not raise error when verifying bad HMAC signature

Author: hieuk09

CHANGELOG.md

@@ -13,6 +13,7 @@
 **Fixes and enhancements:**
 
 - Handle invalid algorithm when decoding JWT [#559](https://github.com/jwt/ruby-jwt/pull/559) - [@nataliastanko](https://github.com/nataliastanko)
+- Do not raise error when verifying bad HMAC signature [#563](https://github.com/jwt/ruby-jwt/pull/563) - [@hieuk09](https://github.com/hieuk09)
 - Your contribution here
 
 ## [v2.7.0](https://github.com/jwt/ruby-jwt/tree/v2.7.0) (2023-02-01)

lib/jwt/algos/hmac_rbnacl.rb

@@ -28,7 +28,7 @@ def verify(algorithm, key, signing_input, signature)
         else
           Hmac.verify(algorithm, key, signing_input, signature)
         end
-      rescue ::RbNaCl::BadAuthenticatorError
+      rescue ::RbNaCl::BadAuthenticatorError, ::RbNaCl::LengthError
         false
       end
 

lib/jwt/algos/hmac_rbnacl_fixed.rb

@@ -36,7 +36,7 @@ def verify(algorithm, key, signing_input, signature)
         else
           Hmac.verify(algorithm, key, signing_input, signature)
         end
-      rescue ::RbNaCl::BadAuthenticatorError
+      rescue ::RbNaCl::BadAuthenticatorError, ::RbNaCl::LengthError
         false
       end
 

spec/jwt/algos/hmac_rbnacl_fixed_spec.rb

@@ -30,6 +30,17 @@
         expect(OpenSSL::HMAC).to have_received(:digest).once
       end
     end
+
+    context 'when signature is invalid' do
+      let(:key) { 'a' * 100 }
+      let(:signature) { JWT::Base64.url_decode('some_random_signature') }
+
+      it 'can verify without error' do
+        allow(OpenSSL::HMAC).to receive(:digest).and_call_original
+        expect(described_class.verify('HS256', key, data, signature)).to eq(false)
+        expect(OpenSSL::HMAC).not_to have_received(:digest)
+      end
+    end
   end
 
   describe '.sign' do

spec/jwt/algos/hmac_rbnacl_spec.rb

@@ -30,6 +30,17 @@
         expect(OpenSSL::HMAC).not_to have_received(:digest)
       end
     end
+
+    context 'when signature is invalid' do
+      let(:key) { 'a' * 100 }
+      let(:signature) { JWT::Base64.url_decode('some_random_signature') }
+
+      it 'can verify without error' do
+        allow(OpenSSL::HMAC).to receive(:digest).and_call_original
+        expect(described_class.verify('HS256', key, data, signature)).to eq(false)
+        expect(OpenSSL::HMAC).not_to have_received(:digest)
+      end
+    end
   end
 
   describe '.sign' do