Fix splitting of IP:PORT endpoints

Split on the first colon *from the right* to avoid badly spllitting IPv6-based
endpoints like ``[2001:db8::1]:443``.

src/client.cpp

@@ -458,7 +458,7 @@ void setup_ssl_context( ssl::context& ssl_context
 static
 string base_domain_from_target(const beast::string_view& target)
 {
-    auto full_host = target.substr(0, target.find(':'));
+    auto full_host = target.substr(0, target.rfind(':'));
     size_t dot0, dot1 = 0;
     if ((dot0 = full_host.find('.')) != full_host.rfind('.'))
         // Two different dots were found

src/injector.cpp

@@ -80,7 +80,7 @@ void handle_connect_request( GenericConnection& client_c
 
     // Split CONNECT target in host and port (443 i.e. HTTPS by default).
     auto hp = req["host"];
-    auto pos = hp.find(':');
+    auto pos = hp.rfind(':');
     string host, port;
     if (pos != string::npos) {
         host = hp.substr(0, pos).to_string();

src/util.h

@@ -21,7 +21,7 @@ asio::ip::tcp::endpoint
 parse_tcp_endpoint(const std::string& s, sys::error_code& ec)
 {
     using namespace std;
-    auto pos = s.find(':');
+    auto pos = s.rfind(':');
 
     ec = sys::error_code();