Added java-kotlin Sensitive Logging barriers (substrings)

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

@@ -6,10 +6,14 @@ import semmle.code.java.dataflow.TaintTracking
 import semmle.code.java.security.SensitiveActions
 import semmle.code.java.frameworks.android.Compose
 private import semmle.code.java.security.Sanitizers
+import semmle.code.java.Constants
 
 /** A data flow source node for sensitive logging sources. */
 abstract class SensitiveLoggerSource extends DataFlow::Node { }
 
+/** A data flow barrier node for sensitive logging sanitizers. */
+abstract class SensitiveLoggerBarrier extends DataFlow::Node { }
+
 /** A variable that may hold sensitive information, judging by its name. */
 class VariableWithSensitiveName extends Variable {
   VariableWithSensitiveName() {
@@ -40,21 +44,128 @@ private class TypeType extends RefType {
   }
 }
 
+/**
+ * A sanitizer that may remove sensitive information from a string before logging.
+ *
+ *  It allows for substring operations taking the first N (or last N, for Kotlin) characters, limited to 7 or fewer.
+ */
+private class SensitiveLoggerSanitizerCalled extends SensitiveLoggerBarrier {
+  SensitiveLoggerSanitizerCalled() {
+    exists(MethodCall mc, Method m, int limit |
+      limit = 7 and
+      mc.getMethod() = m and
+      (
+        // substring in Java
+        (
+          m.hasQualifiedName("java.lang", "String", "substring") or
+          m.hasQualifiedName("java.lang", "StringBuffer", "substring") or
+          m.hasQualifiedName("java.lang", "StringBuilder", "substring")
+        ) and
+        twoArgLimit(mc, limit, false) and
+        this.asExpr() = mc.getQualifier()
+        or
+        // Kotlin string operations, which use extension methods (so the string is the first argument)
+        (
+          m.hasQualifiedName("kotlin.text", "StringsKt", "substring") and
+          twoArgLimit(mc, limit, true)
+          or
+          m.hasQualifiedName("kotlin.text", "StringsKt", ["take", "takeLast"]) and
+          singleArgLimit(mc, limit, true)
+        ) and
+        this.asExpr() = mc.getArgument(0)
+      )
+    )
+  }
+}
+
+/** A predicate to check single-argument method calls for a constant integer below a set limit. */
+bindingset[limit, isKotlin]
+private predicate singleArgLimit(MethodCall mc, int limit, boolean isKotlin) {
+  exists(int argIndex, int staticInt |
+    (if isKotlin = true then argIndex = 1 else argIndex = 0) and
+    (
+      staticInt <= limit and
+      staticInt > 0 and
+      mc.getArgument(argIndex).getUnderlyingExpr().(CompileTimeConstantExpr).getIntValue() =
+        staticInt
+      or
+      exists(CompileTimeConstantExpr cte, DataFlow::Node source, DataFlow::Node sink |
+        source.asExpr() = cte and
+        cte.getIntValue() = staticInt and
+        sink.asExpr() = mc.getArgument(argIndex) and
+        IntegerToArgFlow::flow(source, sink)
+      )
+    )
+  )
+}
+
+/** A predicate to check two-argument method calls for zero and a constant integer below a set limit. */
+bindingset[limit, isKotlin]
+private predicate twoArgLimit(MethodCall mc, int limit, boolean isKotlin) {
+  exists(int firstArgIndex, int secondArgIndex, int staticInt |
+    staticInt <= limit and
+    staticInt > 0 and
+    (
+      isKotlin = true and firstArgIndex = 1 and secondArgIndex = 2
+      or
+      isKotlin = false and firstArgIndex = 0 and secondArgIndex = 1
+    ) and
+    mc.getArgument(firstArgIndex).getUnderlyingExpr().(CompileTimeConstantExpr).getIntValue() = 0 and
+    (
+      mc.getArgument(secondArgIndex).getUnderlyingExpr().(CompileTimeConstantExpr).getIntValue() =
+        staticInt
+      or
+      exists(CompileTimeConstantExpr cte, DataFlow::Node source, DataFlow::Node sink |
+        source.asExpr() = cte and
+        cte.getIntValue() = staticInt and
+        sink.asExpr() = mc.getArgument(secondArgIndex) and
+        IntegerToArgFlow::flow(source, sink)
+      )
+    )
+  )
+}
+
+/** A data-flow configuration for identifying flow from a constant integer to a use in a method argument. */
+private module IntegerToArgConfig implements DataFlow::ConfigSig {
+  predicate isSource(DataFlow::Node source) {
+    source.asExpr().getUnderlyingExpr() instanceof CompileTimeConstantExpr and
+    source.asExpr().getType() instanceof IntegralType and
+    source.asExpr().(CompileTimeConstantExpr).getIntValue() > 0
+  }
+
+  predicate isSink(DataFlow::Node sink) {
+    exists(MethodCall mc |
+      sink.asExpr() = mc.getAnArgument() and
+      sink.asExpr().getType() instanceof IntegralType
+    )
+  }
+
+  predicate isBarrier(DataFlow::Node sanitizer) { none() }
+
+  predicate isBarrierIn(DataFlow::Node node) { none() }
+}
+
+private class GenericSanitizer extends SensitiveLoggerBarrier {
+  GenericSanitizer() {
+    this.asExpr() instanceof LiveLiteral or
+    this instanceof SimpleTypeSanitizer or
+    this.getType() instanceof TypeType
+  }
+}
+
 /** A data-flow configuration for identifying potentially-sensitive data flowing to a log output. */
 module SensitiveLoggerConfig implements DataFlow::ConfigSig {
   predicate isSource(DataFlow::Node source) { source instanceof SensitiveLoggerSource }
 
   predicate isSink(DataFlow::Node sink) { sinkNode(sink, "log-injection") }
 
-  predicate isBarrier(DataFlow::Node sanitizer) {
-    sanitizer.asExpr() instanceof LiveLiteral or
-    sanitizer instanceof SimpleTypeSanitizer or
-    sanitizer.getType() instanceof TypeType
-  }
+  predicate isBarrier(DataFlow::Node sanitizer) { sanitizer instanceof SensitiveLoggerBarrier }
 
   predicate isBarrierIn(DataFlow::Node node) { isSource(node) }
 
   predicate observeDiffInformedIncrementalMode() { any() }
 }
 
 module SensitiveLoggerFlow = TaintTracking::Global<SensitiveLoggerConfig>;
+
+module IntegerToArgFlow = TaintTracking::Global<IntegerToArgConfig>;