Implement new configuration option "MaxPenaltyTime" (#251)

This option configures the maximum penalty time increase in seconds, per
penalty event. Set to -1 for no limit (the default), 0 to disable
penalties altogether. ngIRCd doesn't use penalty increases higher than 2
seconds during normal operation, so values higher than 1 rarely make
sense.

Disabling (or reducing) penalties can greatly speed up "make check" runs
for example, see below, but are mostly a debugging feature and normally
not meant to be used on production systems!

Some example timings running "make check" from my macOS workstation:

- MaxPenaltyTime not set: 4:41,79s
- "MaxPenaltyTime = 1":   3:14,71s
- "MaxPenaltyTime = 0":     25,46s

Closes #249.

src/ngircd/conf.c

@@ -388,6 +388,7 @@ Conf_Test( void )
 	printf("  MaxConnectionsIP = %d\n", Conf_MaxConnectionsIP);
 	printf("  MaxJoins = %d\n", Conf_MaxJoins > 0 ? Conf_MaxJoins : -1);
 	printf("  MaxNickLength = %u\n", Conf_MaxNickLength - 1);
+	printf("  MaxPenaltyTime = %ld\n", Conf_MaxPenaltyTime);
 	printf("  MaxListSize = %d\n", Conf_MaxListSize);
 	printf("  PingTimeout = %d\n", Conf_PingTimeout);
 	printf("  PongTimeout = %d\n", Conf_PongTimeout);
@@ -765,6 +766,7 @@ Set_Defaults(bool InitServers)
 	Conf_MaxConnectionsIP = 5;
 	Conf_MaxJoins = 10;
 	Conf_MaxNickLength = CLIENT_NICK_LEN_DEFAULT;
+	Conf_MaxPenaltyTime = -1;
 	Conf_MaxListSize = 100;
 	Conf_PingTimeout = 120;
 	Conf_PongTimeout = 20;
@@ -1641,6 +1643,12 @@ Handle_LIMITS(const char *File, int Line, char *Var, char *Arg)
 			Config_Error_NaN(File, Line, Var);
 		return;
 	}
+	if (strcasecmp(Var, "MaxPenaltyTime") == 0) {
+		Conf_MaxPenaltyTime = atol(Arg);
+		if (Conf_MaxPenaltyTime < -1)
+			Conf_MaxPenaltyTime = -1;	/* "unlimited" */
+		return;
+	}
 	if (strcasecmp(Var, "PingTimeout") == 0) {
 		Conf_PingTimeout = atoi(Arg);
 		if (Conf_PingTimeout < 5) {
@@ -2281,6 +2289,11 @@ Validate_Config(bool Configtest, bool Rehash)
 			     "This server uses PAM, \"Password\" in [Global] section will be ignored!");
 #endif
 
+	if (Conf_MaxPenaltyTime != -1)
+		Config_Error(LOG_WARNING,
+			     "Maximum penalty increase ('MaxPenaltyTime') is set to %ld, this is not recommended!",
+			     Conf_MaxPenaltyTime);
+
 #ifdef DEBUG
 	servers = servers_once = 0;
 	for (i = 0; i < MAX_SERVERS; i++) {

src/ngircd/conf.h

@@ -239,6 +239,9 @@ GLOBAL unsigned int Conf_MaxNickLength;
 /** Maximum number of channels returned to /list */
 GLOBAL int Conf_MaxListSize;
 
+/** Maximium seconds to add per "penalty". -1 = unlimited. */
+GLOBAL time_t Conf_MaxPenaltyTime;
+
 #ifndef STRICT_RFC
 
 /** Require "AUTH PING-PONG" on login */

src/ngircd/conn-func.c

@@ -26,6 +26,7 @@
 #endif
 #include "conn.h"
 
+#include "conf.h"
 #include "conn-func.h"
 
 /**
@@ -97,6 +98,14 @@ Conn_SetPenalty(CONN_ID Idx, time_t Seconds)
 	assert(Idx > NONE);
 	assert(Seconds >= 0);
 
+	/* Limit new penalty to maximum configured, when less than 10 seconds. *
+	   The latter is used to limit brute force attacks, therefore we don't *
+	   want to limit that! */
+	if (Conf_MaxPenaltyTime >= 0
+	    && Seconds > Conf_MaxPenaltyTime
+	    && Seconds < 10)
+		Seconds = Conf_MaxPenaltyTime;
+
 	t = time(NULL);
 	if (My_Connections[Idx].delaytime < t)
 		My_Connections[Idx].delaytime = t;

src/testsuite/ngircd-test1.conf

@@ -12,6 +12,7 @@
 [Limits]
 	MaxConnectionsIP = 0
 	MaxJoins = 4
+	MaxPenaltyTime = 1
 
 [Options]
 	OperCanUseMode = yes

src/testsuite/ngircd-test2.conf

@@ -12,6 +12,7 @@
 [Limits]
 	MaxConnectionsIP = 0
 	MaxJoins = 4
+	MaxPenaltyTime = 1
 
 [Options]
 	OperCanUseMode = yes