Add taint-tracking for crypto package

Author: gagliardetto

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

@@ -13,6 +13,7 @@ import semmle.go.frameworks.stdlib.CompressGzip
 import semmle.go.frameworks.stdlib.CompressLzw
 import semmle.go.frameworks.stdlib.CompressZlib
 import semmle.go.frameworks.stdlib.Fmt
+import semmle.go.frameworks.stdlib.Crypto
 import semmle.go.frameworks.stdlib.Mime
 import semmle.go.frameworks.stdlib.MimeMultipart
 import semmle.go.frameworks.stdlib.MimeQuotedprintable

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

@@ -0,0 +1,23 @@
+/**
+ * Provides classes modeling security-relevant aspects of the `crypto` package.
+ */
+
+import go
+
+/** Provides models of commonly used functions in the `crypto` package. */
+module Crypto {
+  private class MethodModels extends TaintTracking::FunctionModel, Method {
+    FunctionInput inp;
+    FunctionOutput outp;
+
+    MethodModels() {
+      // signature: func (Decrypter).Decrypt(rand io.Reader, msg []byte, opts DecrypterOpts) (plaintext []byte, err error)
+      this.implements("crypto", "Decrypter", "Decrypt") and
+      (inp.isParameter(1) and outp.isResult(0))
+    }
+
+    override predicate hasTaintFlow(FunctionInput input, FunctionOutput output) {
+      input = inp and output = outp
+    }
+  }
+}