add a config switch to accept hostnames from WEBIRC

See #1686; this allows i2pd to pass the i2p address to Ergo, which may be
useful for moderation under some circumstances.

default.yaml

@@ -218,6 +218,10 @@ server:
                 # - "192.168.1.1"
                 # - "192.168.10.1/24"
 
+            # whether to accept the hostname parameter on the WEBIRC line as the IRC hostname
+            # (the default/recommended Ergo configuration will use cloaks instead)
+            accept-hostname: false
+
     # maximum length of clients' sendQ in bytes
     # this should be big enough to hold bursts of channel/direct messages
     max-sendq: 96k

irc/client.go

@@ -165,6 +165,7 @@ type Session struct {
 	realIP            net.IP
 	proxiedIP         net.IP
 	rawHostname       string
+	hostnameFinalized bool
 	isTor             bool
 	hideSTS           bool
 
@@ -488,12 +489,21 @@ func (client *Client) resizeHistory(config *Config) {
 	}
 }
 
-// resolve an IP to an IRC-ready hostname, using reverse DNS, forward-confirming if necessary,
+// once we have the final IP address (from the connection itself or from proxy data),
-// and sending appropriate notices to the client
+// compute the various possibilities for the hostname:
-func (client *Client) lookupHostname(session *Session, overwrite bool) {
+// * In the default/recommended configuration, via the cloak algorithm
+// * If hostname lookup is enabled, via (forward-confirmed) reverse DNS
+// * If WEBIRC was used, possibly via the hostname passed on the WEBIRC line
+func (client *Client) finalizeHostname(session *Session) {
+	// only allow this once, since registration can fail (e.g. if the nickname is in use)
+	if session.hostnameFinalized {
+		return
+	}
+	session.hostnameFinalized = true
+
 	if session.isTor {
 		return
-	} // else: even if cloaking is enabled, look up the real hostname to show to operators
+	}
 
 	config := client.server.Config()
 	ip := session.realIP
@@ -501,6 +511,8 @@ func (client *Client) lookupHostname(session *Session, overwrite bool) {
 		ip = session.proxiedIP
 	}
 
+	// even if cloaking is enabled, we may want to look up the real hostname to show to operators:
+	if session.rawHostname == "" {
 		var hostname string
 		lookupSuccessful := false
 		if config.Server.lookupHostnames {
@@ -514,17 +526,12 @@ func (client *Client) lookupHostname(session *Session, overwrite bool) {
 		} else {
 			hostname = utils.IPStringToHostname(ip.String())
 		}
-
 		session.rawHostname = hostname
-	cloakedHostname := config.Server.Cloaks.ComputeCloak(ip)
-	client.stateMutex.Lock()
-	defer client.stateMutex.Unlock()
-	// update the hostname if this is a new connection, but not if it's a reattach
-	if overwrite || client.rawHostname == "" {
-		client.rawHostname = hostname
-		client.cloakedHostname = cloakedHostname
-		client.updateNickMaskNoMutex()
 	}
+
+	// these will be discarded if this is actually a reattach:
+	client.rawHostname = session.rawHostname
+	client.cloakedHostname = config.Server.Cloaks.ComputeCloak(ip)
 }
 
 func (client *Client) doIdentLookup(conn net.Conn) {

irc/gateways.go

@@ -32,6 +32,7 @@ type webircConfig struct {
 	Fingerprint    *string // legacy name for certfp, #1050
 	Certfp         string
 	Hosts          []string
+	AcceptHostname bool `yaml:"accept-hostname"`
 	allowedNets    []net.IPNet
 }
 

irc/handlers.go

@@ -3512,8 +3512,9 @@ func webircHandler(server *Server, client *Client, msg ircmsg.Message, rb *Respo
 		}
 	}
 
+	config := server.Config()
 	givenPassword := []byte(msg.Params[0])
-	for _, info := range server.Config().Server.WebIRC {
+	for _, info := range config.Server.WebIRC {
 		if utils.IPInNets(client.realIP, info.allowedNets) {
 			// confirm password and/or fingerprint
 			if 0 < len(info.Password) && bcrypt.CompareHashAndPassword(info.Password, givenPassword) != nil {
@@ -3523,11 +3524,23 @@ func webircHandler(server *Server, client *Client, msg ircmsg.Message, rb *Respo
 				continue
 			}
 
-			err, quitMsg := client.ApplyProxiedIP(rb.session, net.ParseIP(msg.Params[3]), secure)
+			candidateIP := msg.Params[3]
+			err, quitMsg := client.ApplyProxiedIP(rb.session, net.ParseIP(candidateIP), secure)
 			if err != nil {
 				client.Quit(quitMsg, rb.session)
 				return true
 			} else {
+				if info.AcceptHostname {
+					candidateHostname := msg.Params[2]
+					if candidateHostname != candidateIP {
+						if utils.IsHostname(candidateHostname) {
+							rb.session.rawHostname = candidateHostname
+						} else {
+							// log this at debug level since it may be spammy
+							server.logger.Debug("internal", "invalid hostname from WEBIRC", candidateHostname)
+						}
+					}
+				}
 				return false
 			}
 		}

irc/server.go

@@ -314,9 +314,7 @@ func (server *Server) checkBanScriptExemptSASL(config *Config, session *Session)
 func (server *Server) tryRegister(c *Client, session *Session) (exiting bool) {
 	// XXX PROXY or WEBIRC MUST be sent as the first line of the session;
 	// if we are here at all that means we have the final value of the IP
-	if session.rawHostname == "" {
+	c.finalizeHostname(session)
-		session.client.lookupHostname(session, false)
-	}
 
 	// try to complete registration normally
 	// XXX(#1057) username can be filled in by an ident query without the client

traditional.yaml

@@ -192,6 +192,9 @@ server:
                 # - "192.168.1.1"
                 # - "192.168.10.1/24"
 
+            # whether to accept the hostname parameter on the WEBIRC line as the IRC hostname
+            accept-hostname: true
+
     # maximum length of clients' sendQ in bytes
     # this should be big enough to hold bursts of channel/direct messages
     max-sendq: 96k