Add taint-tracking for crypto package

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
+    }
+  }
+}

ql/test/library-tests/semmle/go/frameworks/StdlibTaintFlow/Crypto.go

@@ -0,0 +1,20 @@
+// Code generated by https://github.com/gagliardetto/codebox. DO NOT EDIT.
+
+package main
+
+import "crypto"
+
+func TaintStepTest_CryptoDecrypterDecrypt_B0I0O0(sourceCQL interface{}) interface{} {
+	fromByte656 := sourceCQL.([]byte)
+	var mediumObjCQL crypto.Decrypter
+	intoByte414, _ := mediumObjCQL.Decrypt(nil, fromByte656, nil)
+	return intoByte414
+}
+
+func RunAllTaints_Crypto() {
+	{
+		source := newSource(0)
+		out := TaintStepTest_CryptoDecrypterDecrypt_B0I0O0(source)
+		sink(0, out)
+	}
+}