Add signature to cipher operation

Author: bdrodes

shared/cryptography/codeql/cryptography/Model.qll

@@ -792,6 +792,7 @@ module CryptographyBase<LocationSig Location, InputSig<Location> Input> {
     TDecryptionMode() or
     TWrapMode() or
     TUnwrapMode() or
+    TSignatureMode() or
     TUnknownCipherOperationMode()
 
   abstract class CipherOperationSubtype extends TCipherOperationSubtype {
@@ -814,6 +815,10 @@ module CryptographyBase<LocationSig Location, InputSig<Location> Input> {
     override string toString() { result = "Unwrap" }
   }
 
+  class SignatureSubtype extends CipherOperationSubtype, TSignatureMode {
+    override string toString() { result = "Sign" }
+  }
+
   class UnknownCipherOperationSubtype extends CipherOperationSubtype, TUnknownCipherOperationMode {
     override string toString() { result = "Unknown" }
   }