Fix String length calculation in presence of special characters (#108)

* add the reproducer to the testsuite

* comprhensive tests for special characters

Author: andreaTP

core/pom.xml

@@ -55,6 +55,12 @@
       <version>2.20.0</version>
       <scope>test</scope>
     </dependency>
+    <dependency>
+      <groupId>org.instancio</groupId>
+      <artifactId>instancio-junit</artifactId>
+      <version>5.5.1</version>
+      <scope>test</scope>
+    </dependency>
   </dependencies>
 
   <build>

core/src/main/java/com/styra/opa/wasm/OpaPolicy.java

@@ -13,6 +13,7 @@
 import java.io.FileNotFoundException;
 import java.io.InputStream;
 import java.nio.ByteBuffer;
+import java.nio.charset.StandardCharsets;
 import java.nio.file.Path;
 import java.util.ArrayList;
 import java.util.HashMap;
@@ -60,9 +61,10 @@ public OpaPolicy entrypoint(String entrypoint) {
     }
 
     private int loadJson(String data) {
-        var dataStrAddr = wasm.exports().opaMalloc(data.length());
-        wasm.memory().writeCString(dataStrAddr, data);
-        var dstAddr = wasm.exports().opaJsonParse(dataStrAddr, data.length());
+        var dataBytes = data.getBytes(StandardCharsets.UTF_8);
+        var dataStrAddr = wasm.exports().opaMalloc(dataBytes.length);
+        wasm.memory().write(dataStrAddr, dataBytes);
+        var dstAddr = wasm.exports().opaJsonParse(dataStrAddr, dataBytes.length);
         wasm.exports().opaFree(dataStrAddr);
         return dstAddr;
     }

core/src/test/java/com/styra/opa/wasm/OpaTest.java

@@ -4,20 +4,34 @@
 
 import com.dylibso.chicory.runtime.ByteBufferMemory;
 import com.dylibso.chicory.wasm.types.MemoryLimits;
+import com.fasterxml.jackson.core.JsonProcessingException;
 import java.io.FileInputStream;
 import java.nio.file.Path;
+import org.instancio.Instancio;
+import org.instancio.junit.Given;
+import org.instancio.junit.GivenProvider;
+import org.instancio.junit.InstancioExtension;
+import org.instancio.junit.InstancioSource;
 import org.junit.jupiter.api.Assertions;
 import org.junit.jupiter.api.BeforeAll;
 import org.junit.jupiter.api.Test;
+import org.junit.jupiter.api.extension.ExtendWith;
+import org.junit.jupiter.params.ParameterizedTest;
 
+@ExtendWith(InstancioExtension.class)
 public class OpaTest {
     static Path wasmFile;
     static Path issue69WasmFile;
+    static OpaPolicy issue107Policy;
 
     @BeforeAll
     public static void beforeAll() throws Exception {
         wasmFile = OpaCli.compile("base", "opa/wasm/test/allowed").resolve("policy.wasm");
         issue69WasmFile = OpaCli.compile("issue69", "authz/allow").resolve("policy.wasm");
+        issue107Policy =
+                OpaPolicy.builder()
+                        .withPolicy(OpaCli.compile("issue107", "test").resolve("policy.wasm"))
+                        .build();
     }
 
     @Test
@@ -106,6 +120,51 @@ public void issue69() throws Exception {
         Assertions.assertFalse(Utils.getResult(policy.evaluate()).asBoolean());
     }
 
+    @Test
+    public void issue107() {
+        var policy = issue107Policy;
+
+        policy.input("{\"role\": \"admin\",\"name\": \"Doe\"}");
+        var result = policy.evaluate();
+        Assertions.assertTrue(Utils.getResult(result).get("allow").asBoolean());
+
+        var input = "{\"role\": \"admin\",\"name\": \"Štěpán\"}";
+
+        policy.input(input);
+        result = policy.evaluate();
+        Assertions.assertTrue(Utils.getResult(result).get("allow").asBoolean());
+    }
+
+    static class InputStringProvider implements GivenProvider {
+        @Override
+        public Object provide(ElementContext context) {
+            String randomName = Instancio.gen().string().unicode().mixedCase().get();
+            try {
+                String input = "{\"role\": \"admin\",\"name\": \"" + randomName + "\"}";
+                DefaultMappers.jsonMapper.readTree(input);
+                return randomName;
+            } catch (JsonProcessingException e) {
+                // the generated input name breaks the json escaping
+                return provide(context);
+            }
+        }
+    }
+
+    @InstancioSource(samples = 1000)
+    @ParameterizedTest
+    public void issue107Parametrized(@Given(InputStringProvider.class) String name) {
+        var policy = issue107Policy;
+
+        policy.input("{\"role\": \"admin\",\"name\": \"" + name + "\"}");
+        var result = policy.evaluate();
+        Assertions.assertTrue(Utils.getResult(result).get("allow").asBoolean());
+
+        policy.input("{\"role\": \"notadmin\",\"name\": \"" + name + "\"}");
+
+        result = policy.evaluate();
+        Assertions.assertFalse(Utils.getResult(result).get("allow").asBoolean());
+    }
+
     @Test
     public void issue78Sprintf() throws Exception {
         var policyWasm =

core/src/test/resources/fixtures/issue107/policy.rego

@@ -0,0 +1,9 @@
+package test
+
+import rego.v1
+
+default allow := false
+
+allow if {
+    input.role == "admin"
+}