C#: Include CompositeFormat.Parse as Format like method.

Author: michaelnebel

csharp/ql/lib/semmle/code/csharp/frameworks/Format.qll

@@ -289,3 +289,31 @@ class FormatCall extends MethodCall {
     result = this.getArgument(this.getFirstArgument() + index)
   }
 }
+
+/**
+ * A method call to a method that parses a format string, for example a call
+ * to `string.Format()`.
+ */
+abstract private class FormatStringParseCallImpl extends MethodCall {
+  /**
+   * Gets the expression used as the format string.
+   */
+  abstract Expr getFormatExpr();
+}
+
+final class FormatStringParseCall = FormatStringParseCallImpl;
+
+private class OrdinaryFormatCall extends FormatStringParseCallImpl instanceof FormatCall {
+  override Expr getFormatExpr() { result = FormatCall.super.getFormatExpr() }
+}
+
+/**
+ * A method call to `System.Text.CompositeFormat.Parse`.
+ */
+class ParseFormatStringCall extends FormatStringParseCallImpl {
+  ParseFormatStringCall() {
+    this.getTarget() = any(SystemTextCompositeFormatClass x).getParseMethod()
+  }
+
+  override Expr getFormatExpr() { result = this.getArgument(0) }
+}

csharp/ql/src/API Abuse/FormatInvalid.ql

@@ -15,22 +15,6 @@ import semmle.code.csharp.frameworks.system.Text
 import semmle.code.csharp.frameworks.Format
 import FormatFlow::PathGraph
 
-abstract class FormatStringParseCall extends MethodCall {
-  abstract Expr getFormatExpr();
-}
-
-class OrdinaryFormatCall extends FormatStringParseCall instanceof FormatCall {
-  override Expr getFormatExpr() { result = FormatCall.super.getFormatExpr() }
-}
-
-class ParseFormatStringCall extends FormatStringParseCall {
-  ParseFormatStringCall() {
-    this.getTarget() = any(SystemTextCompositeFormatClass x).getParseMethod()
-  }
-
-  override Expr getFormatExpr() { result = this.getArgument(0) }
-}
-
 module FormatInvalidConfig implements DataFlow::ConfigSig {
   predicate isSource(DataFlow::Node n) { n.asExpr() instanceof StringLiteral }
 

csharp/ql/src/Security Features/CWE-134/UncontrolledFormatString.ql

@@ -20,7 +20,7 @@ module FormatStringConfig implements DataFlow::ConfigSig {
   predicate isSource(DataFlow::Node source) { source instanceof ActiveThreatModelSource }
 
   predicate isSink(DataFlow::Node sink) {
-    sink.asExpr() = any(FormatCall call | call.hasInsertions()).getFormatExpr()
+    sink.asExpr() = any(FormatStringParseCall call).getFormatExpr()
   }
 }