http: Introduce TCivetwebSSL class for https-only servers

It is small sub-class, which allows to start http server like: 

    new THttpServer("https:4567?ssl_cert=certificate.pem");

Certificate should be provided in any case

net/http/inc/LinkDef.h

@@ -9,6 +9,7 @@
 #pragma link C++ class THttpWSHandler;
 #pragma link C++ class TFastCgi;
 #pragma link C++ class TCivetweb;
+#pragma link C++ class TCivetwebSSL;
 #pragma link C++ class THttpLongPollEngine;
 
 #pragma link C++ class THttpCallArg;

net/http/inc/TCivetweb.h

@@ -25,6 +25,8 @@ protected:
 
    virtual void Terminate() { fTerminating = kTRUE; }
 
+   virtual Bool_t IsSecured() const { return kFALSE; }
+
 public:
    TCivetweb();
    virtual ~TCivetweb();
@@ -42,4 +44,16 @@ public:
    ClassDef(TCivetweb, 0) // http server implementation, based on civetweb embedded server
 };
 
+//=========================================================================
+
+class TCivetwebSSL : public TCivetweb {
+protected:
+   virtual Bool_t IsSecured() const { return kTRUE; }
+
+public:
+   TCivetwebSSL() = default;
+
+   ClassDef(TCivetwebSSL, 0) // using only https protocol
+};
+
 #endif

net/http/src/TCivetweb.cxx

@@ -400,6 +400,7 @@ Int_t TCivetweb::ProcessLog(const char *message)
 /// Extra parameters like in URL string could be specified after '?' mark:
 ///    thrds=N   - there N is number of threads used by the civetweb (default is 10)
 ///    top=name  - configure top name, visible in the web browser
+///    ssl_certificate=filename - SSL certificate, see docs/OpenSSL.md from civetweb
 ///    auth_file=filename  - authentication file name, created with htdigets utility
 ///    auth_domain=domain   - authentication domain
 ///    websocket_timeout=tm  - set web sockets timeout in seconds (default 300)
@@ -417,17 +418,18 @@ Bool_t TCivetweb::Create(const char *args)
    memset(fCallbacks, 0, sizeof(struct mg_callbacks));
    //((struct mg_callbacks *) fCallbacks)->begin_request = begin_request_handler;
    ((struct mg_callbacks *)fCallbacks)->log_message = log_message_handler;
-   TString sport = "8080", num_threads = "10", websocket_timeout = "300000";
+   TString sport = IsSecured() ? "8480s" : "8080", num_threads = "10", websocket_timeout = "300000";
    TString auth_file, auth_domain, log_file, ssl_cert;
    Bool_t use_ws = kTRUE;
 
    // extract arguments
-   if ((args != 0) && (strlen(args) > 0)) {
+   if (args && (strlen(args) > 0)) {
 
       // first extract port number
       sport = "";
       while ((*args != 0) && (*args != '?') && (*args != '/'))
          sport.Append(*args++);
+      if (IsSecured() && (sport.Index("s")==kNPOS)) sport.Append("s");
 
       // than search for extra parameters
       while ((*args != 0) && (*args != '?'))
@@ -440,11 +442,11 @@ Bool_t TCivetweb::Create(const char *args)
             url.ParseOptions();
 
             const char *top = url.GetValueFromOptions("top");
-            if (top != 0)
+            if (top)
                fTopName = top;
 
             const char *log = url.GetValueFromOptions("log");
-            if (log != 0)
+            if (log)
                log_file = log;
 
             Int_t thrds = url.GetIntValueFromOptions("thrds");
@@ -452,15 +454,15 @@ Bool_t TCivetweb::Create(const char *args)
                num_threads.Form("%d", thrds);
 
             const char *afile = url.GetValueFromOptions("auth_file");
-            if (afile != 0)
+            if (afile)
                auth_file = afile;
 
             const char *adomain = url.GetValueFromOptions("auth_domain");
-            if (adomain != 0)
+            if (adomain)
                auth_domain = adomain;
 
             const char *sslc = url.GetValueFromOptions("ssl_cert");
-            if (sslc != 0)
+            if (sslc)
                ssl_cert = sslc;
 
             Int_t wtmout = url.GetIntValueFromOptions("websocket_timeout");
@@ -516,9 +518,9 @@ Bool_t TCivetweb::Create(const char *args)
    if (ssl_cert.Length() > 0) {
       options[op++] = "ssl_certificate";
       options[op++] = ssl_cert.Data();
-   }
+   } else if (IsSecured()) Error("Create", "No SSL certificate file configured");
 
-   options[op++] = 0;
+   options[op++] = nullptr;
 
    // Start the web server.
    fCtx = mg_start((struct mg_callbacks *)fCallbacks, this, options);
@@ -526,11 +528,11 @@ Bool_t TCivetweb::Create(const char *args)
    if (!fCtx)
       return kFALSE;
 
-   mg_set_request_handler((struct mg_context *)fCtx, "/", begin_request_handler, 0);
+   mg_set_request_handler((struct mg_context *)fCtx, "/", begin_request_handler, nullptr);
 
    if (use_ws)
       mg_set_websocket_handler((struct mg_context *)fCtx, "**root.websocket$", websocket_connect_handler,
-                               websocket_ready_handler, websocket_data_handler, websocket_close_handler, 0);
+                               websocket_ready_handler, websocket_data_handler, websocket_close_handler, nullptr);
 
    return kTRUE;
 }

net/http/src/THttpServer.cxx

@@ -355,10 +355,10 @@ Bool_t THttpServer::CreateEngine(const char *engine)
 
    if ((clname.Length() == 0) || (clname == "http") || (clname == "civetweb"))
       clname = "TCivetweb";
+   else if (clname == "https")
+      clname = "TCivetwebSSL";
    else if (clname == "fastcgi")
       clname = "TFastCgi";
-   else if (clname == "dabc")
-      clname = "TDabcEngine";
 
    // ensure that required engine class exists before we try to create it
    TClass *engine_class = gROOT->LoadClass(clname.Data());