Keep the colleague's microbu-esp32c5 tree in this repository

obu-firmware builds against vanetza-idf from microbu-esp32c5/external, but
that tree was gitignored, so a clone of this repository could not build the
firmware it ships. It is now committed here as ordinary files in its own
folder, microbu-esp32c5/: the colleague's commit cf4b99f plus the V2X2MAP
bridge's signature verification (--trust) used on the bench. Nothing is
fetched from or pushed to the colleague's repository; this repository and
its remotes carry everything. The folder's own .gitignore keeps build output,
downloaded components and private key material out, as it did there; the
committed file set is identical to that repository's tracked files.

The ESP32-C5 is still flashed from obu-firmware/, which only takes
vanetza-idf from microbu-esp32c5/, so the two stay separate folders.
FLASHING.md says how to take a newer version of the colleague's tree (copy
it over the folder, rebuild, test, commit).

microbu-esp32c5/external/vanetza-idf/vanetza/security/v2/verification.cpp

@@ -0,0 +1,94 @@
+#include <vanetza/security/v2/verification.hpp>
+
+namespace vanetza
+{
+namespace security
+{
+namespace v2
+{
+
+bool check_generation_time(const SecuredMessage& message, Clock::time_point now)
+{
+    using namespace std::chrono;
+
+    bool valid = false;
+    const Time64* generation_time = message.header_field<HeaderFieldType::Generation_Time>();
+    if (generation_time) {
+        // Values are picked from C2C-CC Basic System Profile v1.1.0, see RS_BSP_168
+        static const auto generation_time_future = milliseconds(40);
+        static const Clock::duration generation_time_past_default = minutes(10);
+        static const Clock::duration generation_time_past_ca = seconds(2);
+        auto generation_time_past = generation_time_past_default;
+
+        const IntX* its_aid = message.header_field<HeaderFieldType::Its_Aid>();
+        if (its_aid && aid::CA == *its_aid) {
+            generation_time_past = generation_time_past_ca;
+        }
+
+        if (*generation_time > convert_time64(now + generation_time_future)) {
+            valid = false;
+        } else if (*generation_time < convert_time64(now - generation_time_past)) {
+            valid = false;
+        } else {
+            valid = true;
+        }
+    }
+
+    return valid;
+}
+
+bool check_generation_location(const SecuredMessage& message, const Certificate& cert)
+{
+    const IntX* its_aid = message.header_field<HeaderFieldType::Its_Aid>();
+    if (its_aid && aid::CA == *its_aid) {
+        return true; // no check required for CAMs, field not even allowed
+    }
+
+    const ThreeDLocation* generation_location = message.header_field<HeaderFieldType::Generation_Location>();
+    if (generation_location) {
+        auto region = cert.get_restriction<ValidityRestrictionType::Region>();
+
+        if (!region || get_type(*region) == RegionType::None) {
+            return true;
+        }
+
+        return is_within(TwoDLocation(*generation_location), *region);
+    }
+
+    return false;
+}
+
+bool check_certificate_time(const Certificate& certificate, Clock::time_point now)
+{
+    auto time = certificate.get_restriction<ValidityRestrictionType::Time_Start_And_End>();
+    auto time_now = convert_time32(now);
+
+    if (!time) {
+        return false; // must be present
+    }
+
+    if (time->start_validity > time_now || time->end_validity < time_now) {
+        return false; // premature or outdated
+    }
+
+    return true;
+}
+
+bool check_certificate_region(const Certificate& certificate, const PositionFix& position)
+{
+    auto region = certificate.get_restriction<ValidityRestrictionType::Region>();
+
+    if (!region || get_type(*region) == RegionType::None) {
+        return true;
+    }
+
+    if (!position.confidence) {
+        return false; // cannot check region restrictions without good position fix
+    }
+
+    return is_within(TwoDLocation(position.latitude, position.longitude), *region);
+}
+
+} // namespace v2
+} // namespace security
+} // namespace vanetza