Tainting the velocity context isn't exploitable

Author: atorralba

java/ql/lib/semmle/code/java/dataflow/ExternalFlow.qll

@@ -117,7 +117,6 @@ private module Frameworks {
   private import semmle.code.java.frameworks.Retrofit
   private import semmle.code.java.frameworks.Stream
   private import semmle.code.java.frameworks.Strings
-  private import semmle.code.java.frameworks.Velocity
   private import semmle.code.java.frameworks.ratpack.Ratpack
   private import semmle.code.java.frameworks.ratpack.RatpackExec
   private import semmle.code.java.frameworks.spring.SpringCache

java/ql/lib/semmle/code/java/frameworks/Velocity.qll

@@ -89,18 +89,14 @@ private class TemplateInjectionSinkModels extends SinkModelCsv {
         "com.hubspot.jinjava;Jinjava;true;render;;;Argument[0];ssti;manual",
         "org.thymeleaf;ITemplateEngine;true;process;;;Argument[0];ssti;manual",
         "org.thymeleaf;ITemplateEngine;true;processThrottled;;;Argument[0];ssti;manual",
-        "org.apache.velocity.app;Velocity;true;evaluate;;;Argument[0];ssti;manual",
         "org.apache.velocity.app;Velocity;true;evaluate;;;Argument[3];ssti;manual",
         "org.apache.velocity.app;Velocity;true;mergeTemplate;;;Argument[2];ssti;manual",
-        "org.apache.velocity.app;VelocityEngine;true;evaluate;;;Argument[0];ssti;manual",
         "org.apache.velocity.app;VelocityEngine;true;evaluate;;;Argument[3];ssti;manual",
         "org.apache.velocity.app;VelocityEngine;true;mergeTemplate;;;Argument[2];ssti;manual",
         "org.apache.velocity.runtime.resource.util;StringResourceRepository;true;putStringResource;;;Argument[1];ssti;manual",
-        "org.apache.velocity.runtime;RuntimeServices;true;evaluate;;;Argument[0];ssti;manual",
         "org.apache.velocity.runtime;RuntimeServices;true;evaluate;;;Argument[3];ssti;manual",
         "org.apache.velocity.runtime;RuntimeServices;true;parse;;;Argument[0];ssti;manual",
-        "org.apache.velocity.runtime;RuntimeSingleton;true;parse;;;Argument[0];ssti;manual",
-        "org.apache.velocity;Template;true;merge;;;Argument[0];ssti;manual"
+        "org.apache.velocity.runtime;RuntimeSingleton;true;parse;;;Argument[0];ssti;manual"
       ]
   }
 }

java/ql/lib/semmle/code/java/security/TemplateInjection.qll

@@ -61,8 +61,8 @@ public void bad3(HttpServletRequest request) {
 		runtimeServices.parse(reader, new Template()); // $hasTemplateInjection
 	}
 
-	@GetMapping(value = "bad4")
-	public void bad4(HttpServletRequest request) {
+	@GetMapping(value = "good1")
+	public void good1(HttpServletRequest request) {
 		String name = "ttemplate";
 		String code = request.getParameter("code");
 
@@ -72,7 +72,7 @@ public void bad4(HttpServletRequest request) {
 		StringWriter w = new StringWriter();
 		StringReader reader = new StringReader("test");
 
-		Velocity.evaluate(context, w, "mystring", reader); // $hasTemplateInjection
+		Velocity.evaluate(context, w, "mystring", reader); // Safe
 	}
 
 	@GetMapping(value = "bad5")
@@ -85,15 +85,17 @@ public void bad5(HttpServletRequest request) {
 
 		StringWriter w = new StringWriter();
 		VelocityEngine engine = null;
-		engine.mergeTemplate("testtemplate.vm", "UTF-8", context, w); // $hasTemplateInjection
+		engine.mergeTemplate("testtemplate.vm", "UTF-8", context, w); // Safe
 		AbstractContext ctx = null;
 		ctx.put("key", code);
-		engine.evaluate(ctx, null, null, null); // $hasTemplateInjection
+		engine.evaluate(ctx, null, null, (String) null); // Safe
+		engine.evaluate(ctx, null, null, (Reader) null); // Safe
 		engine.evaluate(null, null, null, code); // $hasTemplateInjection
+		engine.evaluate(null, null, null, new StringReader(code)); // $hasTemplateInjection
 	}
 
-	@GetMapping(value = "bad6")
-	public void bad6(HttpServletRequest request) {
+	@GetMapping(value = "good2")
+	public void good2(HttpServletRequest request) {
 		String name = "ttemplate";
 		String code = request.getParameter("code");
 
@@ -102,24 +104,13 @@ public void bad6(HttpServletRequest request) {
 
 		StringWriter w = new StringWriter();
 		Template t = new Template();
-		t.merge(context, w); // $hasTemplateInjection
-	}
-
-	@GetMapping(value = "bad7")
-	public void bad7(HttpServletRequest request) {
-		String name = "ttemplate";
-		String code = request.getParameter("code");
+		t.merge(context, w); // Safe
+		t.merge(context, w, new LinkedList<String>()); // Safe
 
-		VelocityContext context = new VelocityContext();
-		context.put("code", code);
-
-		StringWriter w = new StringWriter();
-		Template t = new Template();
-		t.merge(context, w, new LinkedList<String>()); // $hasTemplateInjection
 	}
 
-	@GetMapping(value = "bad8")
-	public void bad8(HttpServletRequest request) {
+	@GetMapping(value = "bad6")
+	public void bad6(HttpServletRequest request) {
 		String code = request.getParameter("code");
 
 		StringResourceRepository repo = new StringResourceRepositoryImpl();