Require that server names must be hostnames, and nicks cannot be hostnames

irc/config.go

@@ -110,6 +110,9 @@ func LoadConfig(filename string) (config *Config, err error) {
 	if config.Server.Name == "" {
 		return nil, errors.New("Server name missing")
 	}
+	if !IsHostname(config.Server.Name) {
+		return nil, errors.New("Server name must match the format of a hostname")
+	}
 	if config.Server.Database == "" {
 		return nil, errors.New("Server database missing")
 	}

irc/net.go

@@ -27,3 +27,28 @@ func LookupHostname(addr Name) Name {
 	hostname := strings.TrimSuffix(names[0], ".")
 	return Name(hostname)
 }
+
+var allowedHostnameChars = "abcdefghijklmnopqrstuvwxyz1234567890-."
+
+func IsHostname(name string) bool {
+	// IRC hostnames specifically require a period
+	if !strings.Contains(name, ".") || len(name) < 1 || len(name) > 253 {
+		return false
+	}
+
+	// ensure each part of hostname is valid
+	for _, part := range strings.Split(name, ".") {
+		if len(part) < 1 || len(part) > 63 || strings.HasPrefix(part, "-") || strings.HasSuffix(part, "-") {
+			return false
+		}
+	}
+
+	// ensure all chars of hostname are valid
+	for _, char := range strings.Split(strings.ToLower(name), "") {
+		if !strings.Contains(allowedHostnameChars, char) {
+			return false
+		}
+	}
+
+	return true
+}

irc/strings.go

@@ -47,6 +47,10 @@ func (name Name) IsNickname() bool {
 		strings.Contains(namestr, "!") || strings.Contains(namestr, "@") {
 		return false
 	}
+	// names that look like hostnames are restricted to servers, as with other ircds
+	if IsHostname(namestr) {
+		return false
+	}
 	return NicknameExpr.MatchString(namestr)
 }