Add compress/lzw taint tracking

Author: gagliardetto

ql/src/semmle/go/frameworks/Stdlib.qll

@@ -10,6 +10,7 @@ import semmle.go.frameworks.stdlib.Bytes
 import semmle.go.frameworks.stdlib.CompressBzip2
 import semmle.go.frameworks.stdlib.CompressFlate
 import semmle.go.frameworks.stdlib.CompressGzip
+import semmle.go.frameworks.stdlib.CompressLzw
 
 /** A `String()` method. */
 class StringMethod extends TaintTracking::FunctionModel, Method {

ql/src/semmle/go/frameworks/stdlib/CompressLzw.qll

@@ -0,0 +1,27 @@
+/**
+ * Provides classes modeling security-relevant aspects of the `compress/lzw` package.
+ */
+
+import go
+
+/** Provides models of commonly used functions in the `compress/lzw` package. */
+module CompressLzw {
+  private class FunctionModels extends TaintTracking::FunctionModel {
+    FunctionInput inp;
+    FunctionOutput outp;
+
+    FunctionModels() {
+      // signature: func NewReader(r io.Reader, order Order, litWidth int) io.ReadCloser
+      hasQualifiedName("compress/lzw", "NewReader") and
+      (inp.isParameter(0) and outp.isResult())
+      or
+      // signature: func NewWriter(w io.Writer, order Order, litWidth int) io.WriteCloser
+      hasQualifiedName("compress/lzw", "NewWriter") and
+      (inp.isResult() and outp.isParameter(0))
+    }
+
+    override predicate hasTaintFlow(FunctionInput input, FunctionOutput output) {
+      input = inp and output = outp
+    }
+  }
+}