Make botan’s policy configurable from a file

fix #3244

tests/network.cpp

@@ -0,0 +1,42 @@
+#include "catch.hpp"
+#include <network/tls_policy.hpp>
+
+TEST_CASE("tls_policy")
+{
+  BiboumiTLSPolicy policy;
+  const auto default_minimum_signature_strength = policy.minimum_signature_strength();
+  const auto default_session_ticket_lifetime = policy.session_ticket_lifetime();
+  const auto default_minimum_rsa_bits = policy.minimum_rsa_bits();
+
+  policy.load("does not exist");
+  WHEN("we fail to load the file")
+    {
+      THEN("all values are the default ones")
+        {
+          CHECK(policy.minimum_signature_strength() == default_minimum_signature_strength);
+          CHECK(policy.minimum_rsa_bits() == default_minimum_rsa_bits);
+        }
+      AND_WHEN("we load a valid first file")
+        {
+          std::istringstream iss("minimum_signature_strength  =      128\nminimum_rsa_bits=12\n");
+          policy.load(iss);
+          THEN("the specified values are updated, and the rest is still the default")
+            {
+              CHECK(policy.minimum_signature_strength() == 128);
+              CHECK(policy.minimum_rsa_bits() == 12);
+              CHECK(policy.session_ticket_lifetime() == default_session_ticket_lifetime);
+            }
+          AND_WHEN("we load a second file")
+            {
+              std::istringstream iss("minimum_signature_strength  =      15");
+              policy.load(iss);
+              THEN("the specified values are updated, and the rest is untouched")
+                {
+                  CHECK(policy.minimum_signature_strength() == 15);
+                  CHECK(policy.minimum_rsa_bits() == 12);
+                  CHECK(policy.session_ticket_lifetime() == default_session_ticket_lifetime);
+                }
+            }
+        }
+    }
+}