don't require full login information on patch server

src/License.cc

@@ -127,6 +127,14 @@ shared_ptr<License> LicenseIndex::get(uint32_t serial_number) const {
   }
 }
 
+shared_ptr<License> LicenseIndex::get_by_bb_username(const string& bb_username) const {
+  try {
+    return this->bb_username_to_license.at(bb_username);
+  } catch (const out_of_range&) {
+    throw missing_license();
+  }
+}
+
 vector<shared_ptr<License>> LicenseIndex::all() const {
   vector<shared_ptr<License>> ret;
   ret.reserve(this->serial_number_to_license.size());

src/License.hh

@@ -100,6 +100,7 @@ public:
 
   size_t count() const;
   std::shared_ptr<License> get(uint32_t serial_number) const;
+  std::shared_ptr<License> get_by_bb_username(const std::string& bb_username) const;
   std::vector<std::shared_ptr<License>> all() const;
 
   void add(std::shared_ptr<License> l);

src/ReceiveCommands.cc

@@ -5003,8 +5003,16 @@ static void on_04_P(shared_ptr<Client> c, uint16_t, uint32_t, string& data) {
   const auto& cmd = check_size_t<C_Login_Patch_04>(data);
   auto s = c->require_server_state();
 
+  string username = cmd.username.decode();
+  string password = cmd.password.decode();
+
+  // There are 3 cases here:
+  // - No login information at all: just proceed without checking license
+  // - Username only: check that license exists if allow_unregistered_users is off
+  // - Username and password: call verify_bb
+  if (!username.empty() && !password.empty()) {
     try {
-    auto l = s->license_index->verify_bb(cmd.username.decode(), cmd.password.decode());
+      auto l = s->license_index->verify_bb(username, password);
       c->set_license(l);
 
     } catch (const LicenseIndex::incorrect_password& e) {
@@ -5033,6 +5041,24 @@ static void on_04_P(shared_ptr<Client> c, uint16_t, uint32_t, string& data) {
       }
     }
 
+  } else if (!username.empty() && !s->allow_unregistered_users) {
+    try {
+      auto l = s->license_index->get_by_bb_username(username);
+      c->set_license(l);
+    } catch (const LicenseIndex::missing_license& e) {
+      send_message_box(c, string_printf("Login failed: %s", e.what()));
+      c->should_disconnect = true;
+      return;
+    }
+
+  } else {
+    auto l = s->license_index->create_temporary_license();
+    l->serial_number = random_object<uint32_t>() & 0x7FFFFFFF;
+    l->bb_username = "__unknown__";
+    l->bb_password = "__unknown__";
+    c->set_license(l);
+  }
+
   // On BB we can use colors and newlines should be \n; on PC we can't use
   // colors, the text is auto-word-wrapped, and newlines should be \r\n.
   bool is_bb_patch = (c->version() == Version::BB_PATCH);