Don't list security groups by default, add 'public <yes|no>'

* [Security group blocks](https://www.unrealircd.org/docs/Security-group_block)
  are now hidden in lists by default. If you want the security group to be shown
  in things like `MODE #channel +b ~security-group:x` (which shows a list)
  then you need to use `public yes;`. The default security groups
  like known-users, webirc-users, etc. are public by default.

doc/RELEASE-NOTES.md

@@ -55,6 +55,11 @@ in progress and may not always be a stable version.
 * Update shipped libraries: c-ares to 1.33.1
 * Move +/- 1000 lines of code from core to modules (regarding
   throttling, maxperip, vhost, exit_client).
+* [Security group blocks](https://www.unrealircd.org/docs/Security-group_block)
+  are now hidden in lists by default. If you want the security group to be shown
+  in things like `MODE #channel +b ~security-group:x` (which shows a list)
+  then you need to use `public yes;`. The default security groups
+  like known-users, webirc-users, etc. are public by default.
 
 ### Fixes:
 * In some circumstances users could hang during the handshake when

include/struct.h

@@ -2198,6 +2198,7 @@ struct SecurityGroup {
 	SecurityGroup *prev, *next;
 	int priority;
 	char name[SECURITYGROUPLEN+1];
+	int public;
 	NameValuePrioList *printable_list;
 	int printable_list_counter;
 	/* Include */

src/modules/extbans/securitygroup.c

@@ -122,7 +122,8 @@ int extban_securitygroup_is_ok(BanContext *b)
 			sendnotice(b->client, "ERROR: Unknown security-group '%s'. Syntax: +b ~security-group:securitygroup or +b ~security-group:!securitygroup", b->banstr);
 			sendnotice(b->client, "Available security groups:");
 			for (s = securitygroups; s; s = s->next)
-				sendnotice(b->client, "%s", s->name);
+				if (s->public)
+					sendnotice(b->client, "%s", s->name);
 			sendnotice(b->client, "unknown-users");
 			sendnotice(b->client, "End of security group list.");
 			return 0;

src/securitygroup.c

@@ -368,6 +368,12 @@ int _test_security_group(ConfigFile *conf, ConfigEntry *ce)
 
 	for (cep = ce->items; cep; cep = cep->next)
 	{
+		if (cep->name && !strcmp(cep->name, "public"))
+		{
+		} else
+		if (cep->name && !strcmp(cep->name, "priority"))
+		{
+		} else
 		if (!test_match_item(conf, cep, &errors))
 		{
 			config_error_unknown(cep->file->filename, cep->line_number,
@@ -555,7 +561,12 @@ int _conf_security_group(ConfigFile *conf, ConfigEntry *ce)
 			DelListItem(s, securitygroups);
 			AddListItemPrio(s, securitygroups, s->priority);
 		} else
+		if (cep->name && !strcmp(cep->name, "public"))
+		{
+			s->public = config_checkval(cep->value, CFG_YESNO);
+		} else {
 			conf_match_item(conf, cep, &s);
+		}
 	}
 	return 1;
 }
@@ -700,20 +711,24 @@ void set_security_group_defaults(void)
 
 	/* Default group: webirc */
 	s = add_security_group("webirc-users", 50);
+	s->public = 1;
 	s->webirc = 1;
 
 	/* Default group: websocket */
 	s = add_security_group("websocket-users", 51);
+	s->public = 1;
 	s->websocket = 1;
 
 	/* Default group: known-users */
 	s = add_security_group("known-users", 100);
+	s->public = 1;
 	s->identified = 1;
 	s->reputation_score = 25;
 	s->webirc = 0;
 
 	/* Default group: tls-users */
 	s = add_security_group("tls-users", 300);
+	s->public = 1;
 	s->tls = 1;
 }