Add taint-tracking for encoding/base64

Author: gagliardetto

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

@@ -19,6 +19,7 @@ import semmle.go.frameworks.stdlib.Encoding
 import semmle.go.frameworks.stdlib.EncodingAscii85
 import semmle.go.frameworks.stdlib.EncodingAsn1
 import semmle.go.frameworks.stdlib.EncodingBase32
+import semmle.go.frameworks.stdlib.EncodingBase64
 import semmle.go.frameworks.stdlib.Path
 import semmle.go.frameworks.stdlib.PathFilepath
 import semmle.go.frameworks.stdlib.Reflect

ql/src/semmle/go/frameworks/stdlib/EncodingBase64.qll

@@ -0,0 +1,54 @@
+/**
+ * Provides classes modeling security-relevant aspects of the `encoding/base64` package.
+ */
+
+import go
+
+/** Provides models of commonly used functions in the `encoding/base64` package. */
+module EncodingBase64 {
+  private class FunctionModels extends TaintTracking::FunctionModel {
+    FunctionInput inp;
+    FunctionOutput outp;
+
+    FunctionModels() {
+      // signature: func NewDecoder(enc *Encoding, r io.Reader) io.Reader
+      hasQualifiedName("encoding/base64", "NewDecoder") and
+      (inp.isParameter(1) and outp.isResult())
+      or
+      // signature: func NewEncoder(enc *Encoding, w io.Writer) io.WriteCloser
+      hasQualifiedName("encoding/base64", "NewEncoder") and
+      (inp.isResult() and outp.isParameter(1))
+    }
+
+    override predicate hasTaintFlow(FunctionInput input, FunctionOutput output) {
+      input = inp and output = outp
+    }
+  }
+
+  private class MethodModels extends TaintTracking::FunctionModel, Method {
+    FunctionInput inp;
+    FunctionOutput outp;
+
+    MethodModels() {
+      // signature: func (*Encoding).Decode(dst []byte, src []byte) (n int, err error)
+      this.hasQualifiedName("encoding/base64", "Encoding", "Decode") and
+      (inp.isParameter(1) and outp.isParameter(0))
+      or
+      // signature: func (*Encoding).DecodeString(s string) ([]byte, error)
+      this.hasQualifiedName("encoding/base64", "Encoding", "DecodeString") and
+      (inp.isParameter(0) and outp.isResult(0))
+      or
+      // signature: func (*Encoding).Encode(dst []byte, src []byte)
+      this.hasQualifiedName("encoding/base64", "Encoding", "Encode") and
+      (inp.isParameter(1) and outp.isParameter(0))
+      or
+      // signature: func (*Encoding).EncodeToString(src []byte) string
+      this.hasQualifiedName("encoding/base64", "Encoding", "EncodeToString") and
+      (inp.isParameter(0) and outp.isResult())
+    }
+
+    override predicate hasTaintFlow(FunctionInput input, FunctionOutput output) {
+      input = inp and output = outp
+    }
+  }
+}