move key generation functions into Pleroma.Keys module

lib/pleroma/keys.ex

@@ -0,0 +1,44 @@
+# Pleroma: A lightweight social networking server
+# Copyright © 2017-2019 Pleroma Authors <https://pleroma.social/>
+# SPDX-License-Identifier: AGPL-3.0-only
+
+defmodule Pleroma.Keys do
+  # Native generation of RSA keys is only available since OTP 20+ and in default build conditions
+  # We try at compile time to generate natively an RSA key otherwise we fallback on the old way.
+  try do
+    _ = :public_key.generate_key({:rsa, 2048, 65_537})
+
+    def generate_rsa_pem do
+      key = :public_key.generate_key({:rsa, 2048, 65_537})
+      entry = :public_key.pem_entry_encode(:RSAPrivateKey, key)
+      pem = :public_key.pem_encode([entry]) |> String.trim_trailing()
+      {:ok, pem}
+    end
+  rescue
+    _ ->
+      def generate_rsa_pem do
+        port = Port.open({:spawn, "openssl genrsa"}, [:binary])
+
+        {:ok, pem} =
+          receive do
+            {^port, {:data, pem}} -> {:ok, pem}
+          end
+
+        Port.close(port)
+
+        if Regex.match?(~r/RSA PRIVATE KEY/, pem) do
+          {:ok, pem}
+        else
+          :error
+        end
+      end
+  end
+
+  def keys_from_pem(pem) do
+    [private_key_code] = :public_key.pem_decode(pem)
+    private_key = :public_key.pem_entry_decode(private_key_code)
+    {:RSAPrivateKey, _, modulus, exponent, _, _, _, _, _, _, _} = private_key
+    public_key = {:RSAPublicKey, modulus, exponent}
+    {:ok, private_key, public_key}
+  end
+end