Ruby: Model Sinatra

Adds some very basic modeling of Sinatra applications.
We recognise the `params` call in Sinatra routes as an HTTP request
input access.

Author: hmac

ruby/ql/lib/codeql/ruby/frameworks/Sinatra.qll

@@ -0,0 +1,44 @@
+/** Provides modeling for the Sinatra library. */
+
+private import codeql.ruby.controlflow.CfgNodes::ExprNodes
+private import codeql.ruby.DataFlow
+private import codeql.ruby.Concepts
+
+/** Provides modeling for the Sinatra library. */
+module Sinatra {
+  private class App extends DataFlow::ClassNode {
+    App() { this = DataFlow::getConstant("Sinatra").getConstant("Base").getADescendentModule() }
+
+    Route getRoute() { result.getApp() = this }
+  }
+
+  private class Route extends DataFlow::CallNode {
+    private App app;
+
+    Route() {
+      this =
+        app.getAModuleLevelCall([
+            "get", "post", "put", "patch", "delete", "options", "link", "unlink"
+          ])
+    }
+
+    App getApp() { result = app }
+
+    DataFlow::BlockNode getBody() { result = this.getBlock() }
+  }
+
+  private class Params extends DataFlow::CallNode, Http::Server::RequestInputAccess::Range {
+    private Route route;
+
+    Params() {
+      this.asExpr().getExpr().getEnclosingCallable() = route.getBody().asCallableAstNode() and
+      this.getMethodName() = "params"
+    }
+
+    override string getSourceType() { result = "Sinatra::Base#params" }
+
+    override Http::Server::RequestInputKind getKind() {
+      result = Http::Server::parameterInputKind()
+    }
+  }
+}