Add taint-tracking for package encoding

Author: gagliardetto

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

@@ -15,6 +15,7 @@ import semmle.go.frameworks.stdlib.CompressZlib
 import semmle.go.frameworks.stdlib.Mime
 import semmle.go.frameworks.stdlib.MimeMultipart
 import semmle.go.frameworks.stdlib.MimeQuotedprintable
+import semmle.go.frameworks.stdlib.Encoding
 import semmle.go.frameworks.stdlib.Path
 import semmle.go.frameworks.stdlib.PathFilepath
 import semmle.go.frameworks.stdlib.Reflect

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

@@ -0,0 +1,35 @@
+/**
+ * Provides classes modeling security-relevant aspects of the `encoding` package.
+ */
+
+import go
+
+/** Provides models of commonly used functions in the `encoding` package. */
+module Encoding {
+  private class MethodModels extends TaintTracking::FunctionModel, Method {
+    FunctionInput inp;
+    FunctionOutput outp;
+
+    MethodModels() {
+      // signature: func (BinaryMarshaler).MarshalBinary() (data []byte, err error)
+      this.implements("encoding", "BinaryMarshaler", "MarshalBinary") and
+      (inp.isReceiver() and outp.isResult(0))
+      or
+      // signature: func (TextMarshaler).MarshalText() (text []byte, err error)
+      this.implements("encoding", "TextMarshaler", "MarshalText") and
+      (inp.isReceiver() and outp.isResult(0))
+      or
+      // signature: func (BinaryUnmarshaler).UnmarshalBinary(data []byte) error
+      this.implements("encoding", "BinaryUnmarshaler", "UnmarshalBinary") and
+      (inp.isParameter(0) and outp.isReceiver())
+      or
+      // signature: func (TextUnmarshaler).UnmarshalText(text []byte) error
+      this.implements("encoding", "TextUnmarshaler", "UnmarshalText") and
+      (inp.isParameter(0) and outp.isReceiver())
+    }
+
+    override predicate hasTaintFlow(FunctionInput input, FunctionOutput output) {
+      input = inp and output = outp
+    }
+  }
+}