Java: Refactor part of TaintTrackingUtil.qll

java/ql/src/semmle/code/java/dataflow/FlowSteps.qll

@@ -0,0 +1,141 @@
+/**
+ * Provides classes representing various flow steps for taint tracking.
+ */
+
+private import java
+private import semmle.code.java.dataflow.DataFlow
+
+/**
+ * A module importing the frameworks that implement additional flow steps,
+ * ensuring that they are visible to the taint tracking library.
+ */
+module Frameworks {
+  private import semmle.code.java.frameworks.jackson.JacksonSerializability
+  private import semmle.code.java.frameworks.android.Intent
+  private import semmle.code.java.frameworks.android.SQLite
+  private import semmle.code.java.frameworks.Guice
+  private import semmle.code.java.frameworks.Protobuf
+}
+
+/**
+ * A unit class for adding additional taint steps.
+ *
+ * Extend this class to add additional taint steps that should apply to all
+ * taint configurations.
+ */
+class AdditionalTaintStep extends Unit {
+  /**
+   * Holds if the step from `node1` to `node2` should be considered a taint
+   * step for all configurations.
+   */
+  abstract predicate step(DataFlow::Node node1, DataFlow::Node node2);
+}
+
+/**
+ * A method or constructor that preserves taint.
+ *
+ * Extend this class and override at least one of `returnsTaintFrom` or `transfersTaint`
+ * to add additional taint steps through a method that should apply to all taint configurations.
+ */
+abstract class TaintPreservingCallable extends Callable {
+  /**
+   * Holds if this callable returns tainted data when `arg` tainted.
+   * `arg` is a parameter index, or is -1 to indicate the qualifier.
+   */
+  predicate returnsTaintFrom(int arg) { none() }
+
+  /**
+   * Holds if this callable writes tainted data to `sink` when `src` is tainted.
+   * `src` and `sink` are parameter indices, or -1 to indicate the qualifier.
+   */
+  predicate transfersTaint(int src, int sink) { none() }
+}
+
+private class StringTaintPreservingMethod extends TaintPreservingCallable {
+  StringTaintPreservingMethod() {
+    this.getDeclaringType() instanceof TypeString and
+    this
+        .hasName(["concat", "copyValueOf", "endsWith", "format", "formatted", "getBytes", "indent",
+              "intern", "join", "repeat", "split", "strip", "stripIndent", "stripLeading",
+              "stripTrailing", "substring", "toCharArray", "toLowerCase", "toString", "toUpperCase",
+              "trim"])
+  }
+
+  override predicate returnsTaintFrom(int arg) {
+    arg = -1 and not this.isStatic()
+    or
+    this.hasName(["concat", "copyValueOf"]) and arg = 0
+    or
+    this.hasName(["format", "formatted", "join"]) and arg = [0 .. getNumberOfParameters()]
+  }
+}
+
+private class StringTaintPreservingConstructor extends Constructor, TaintPreservingCallable {
+  StringTaintPreservingConstructor() { this.getDeclaringType() instanceof TypeString }
+
+  override predicate returnsTaintFrom(int arg) { arg = 0 }
+}
+
+private class NumberTaintPreservingCallable extends TaintPreservingCallable {
+  int argument;
+
+  NumberTaintPreservingCallable() {
+    this.getDeclaringType().getASupertype*().hasQualifiedName("java.lang", "Number") and
+    (
+      this instanceof Constructor and
+      argument = 0
+      or
+      this.getName().matches(["to%String", "toByteArray", "%Value"]) and
+      argument = -1
+      or
+      this.getName().matches(["parse%", "valueOf%", "to%String", "decode"]) and
+      argument = 0
+    )
+  }
+
+  override predicate returnsTaintFrom(int arg) { arg = argument }
+}
+
+/** Holds for the types `StringBuilder`, `StringBuffer`, and `StringWriter`. */
+private predicate stringBuilderType(RefType t) {
+  t.hasQualifiedName("java.lang", "StringBuilder") or
+  t.hasQualifiedName("java.lang", "StringBuffer") or
+  t.hasQualifiedName("java.io", "StringWriter")
+}
+
+private class StringBuilderTaintPreservingCallable extends TaintPreservingCallable {
+  StringBuilderTaintPreservingCallable() {
+    exists(Method m |
+      this.(Method).overrides*(m) and
+      stringBuilderType(m.getDeclaringType()) and
+      m.hasName(["append", "insert", "replace", "toString", "write"])
+    )
+    or
+    this.(Constructor).getParameterType(0) instanceof RefType and
+    stringBuilderType(this.getDeclaringType())
+  }
+
+  override predicate returnsTaintFrom(int arg) {
+    arg = -1 and
+    not this instanceof Constructor
+    or
+    this instanceof Constructor and arg = 0
+    or
+    this.hasName("append") and arg = 0
+    or
+    this.hasName("insert") and arg = 1
+    or
+    this.hasName("replace") and arg = 2
+  }
+
+  override predicate transfersTaint(int src, int sink) {
+    returnsTaintFrom(src) and
+    sink = -1 and
+    src != -1 and
+    not this instanceof Constructor
+    or
+    this.hasName("write") and
+    src = 0 and
+    sink = -1
+  }
+}