Add taint-tracking for crypto/x509 package

Author: gagliardetto

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

@@ -17,6 +17,7 @@ import semmle.go.frameworks.stdlib.Crypto
 import semmle.go.frameworks.stdlib.CryptoCipher
 import semmle.go.frameworks.stdlib.CryptoRsa
 import semmle.go.frameworks.stdlib.CryptoTls
+import semmle.go.frameworks.stdlib.CryptoX509
 import semmle.go.frameworks.stdlib.Mime
 import semmle.go.frameworks.stdlib.MimeMultipart
 import semmle.go.frameworks.stdlib.MimeQuotedprintable

ql/src/semmle/go/frameworks/stdlib/CryptoX509.qll

@@ -0,0 +1,23 @@
+/**
+ * Provides classes modeling security-relevant aspects of the `crypto/x509` package.
+ */
+
+import go
+
+/** Provides models of commonly used functions in the `crypto/x509` package. */
+module CryptoX509 {
+  private class FunctionModels extends TaintTracking::FunctionModel {
+    FunctionInput inp;
+    FunctionOutput outp;
+
+    FunctionModels() {
+      // signature: func DecryptPEMBlock(b *encoding/pem.Block, password []byte) ([]byte, error)
+      hasQualifiedName("crypto/x509", "DecryptPEMBlock") and
+      (inp.isParameter(0) and outp.isResult(0))
+    }
+
+    override predicate hasTaintFlow(FunctionInput input, FunctionOutput output) {
+      input = inp and output = outp
+    }
+  }
+}