vanguards: init at 0.3.1

add derivation for vanguards, a set of scripts that increase security
for tor hidden services by protecting against guard discovery attacks

resources:
https://github.com/mikeperry-tor/vanguards
https://spec.torproject.org/vanguards-spec/index.html?highlight=vanguards

pkgs/by-name/va/vanguards/package.nix

@@ -0,0 +1,44 @@
+{ pkgs, lib }:
+let
+  vgpkgs = import (pkgs.fetchFromGitHub {
+    # required version for stem and ipaddress to work
+    owner = "NixOS";
+    repo = "nixpkgs";
+    rev = "f539a47dabe6fd614179ee7df12d596bdab1dff9";
+    sha256 = "sha256-wXhy+5YmZRaUUaZKnuRIfsOdHsPBQq2ewdMFDS2uRsw=";
+  }) { };
+in
+vgpkgs.python2Packages.buildPythonPackage rec {
+  pname = "vanguards";
+  version = "0.3.1";
+
+  #tries to access the network during the tests, which fails
+  doCheck = false;
+
+  src = pkgs.fetchFromGitHub {
+    owner = "mikeperry-tor";
+    repo = pname;
+    rev = "c3961ac40ca0bce67f79bc76021f5817730033b8";
+    sha256 = "sha256-y5WwDLn2asYcA5hTl++UVeH5KZ8VRP4sMIjRv9y7GVE=";
+  };
+
+  propagatedBuildInputs = with vgpkgs; [
+    (python2.withPackages (
+      ps: with ps; [
+        stem
+        ipaddress
+      ]
+    ))
+  ];
+
+  meta = {
+    maintainers = with lib.maintainers; [ ForgottenBeast ];
+    mainProgram = "vanguards";
+    license = lib.licenses.mit;
+    description = ''
+      Runs alongside tor and interacts with its control port
+      in order to protect and alert against guard node attacks on hidden services
+    '';
+  };
+
+}