Add a trailing dot to DNS domains by default to speed up discovery when a search domain is configured

cli/cmd/dns.go

@@ -76,6 +76,11 @@ func parseDNSOptions() (*libgobuster.Options, *gobusterdns.OptionsDNS, error) {
 		return nil, nil, fmt.Errorf("invalid value for resolver: %w", err)
 	}
 
+	pluginOpts.NoFQDN, err = cmdDNS.Flags().GetBool("no-fqdn")
+	if err != nil {
+		return nil, nil, fmt.Errorf("invalid value for no-fqdn: %w", err)
+	}
+
 	if pluginOpts.Resolver != "" && runtime.GOOS == "windows" {
 		return nil, nil, fmt.Errorf("currently can not set custom dns resolver on windows. See https://golang.org/pkg/net/#hdr-Name_Resolution")
 	}
@@ -96,6 +101,7 @@ func init() {
 	cmdDNS.Flags().BoolP("show-cname", "c", false, "Show CNAME records (cannot be used with '-i' option)")
 	cmdDNS.Flags().DurationP("timeout", "", time.Second, "DNS resolver timeout")
 	cmdDNS.Flags().BoolP("wildcard", "", false, "Force continued operation when wildcard found")
+	cmdDNS.Flags().BoolP("no-fqdn", "", false, "Do not automatically add a trailing dot to the domain, so the resolver uses the DNS search domain")
 	cmdDNS.Flags().StringP("resolver", "r", "", "Use custom DNS server (format server.com or server.com:port)")
 	if err := cmdDNS.MarkFlagRequired("domain"); err != nil {
 		log.Fatalf("error on marking flag as required: %v", err)

gobusterdns/gobusterdns.go

@@ -111,6 +111,9 @@ func (d *GobusterDNS) PreRun(ctx context.Context, progress *libgobuster.Progress
 // ProcessWord is the process implementation of gobusterdns
 func (d *GobusterDNS) ProcessWord(ctx context.Context, word string, progress *libgobuster.Progress) error {
 	subdomain := fmt.Sprintf("%s.%s", word, d.options.Domain)
+	if !d.options.NoFQDN && !strings.HasSuffix(subdomain, ".") {
+		subdomain += "."
+	}
 	ips, err := d.dnsLookup(ctx, subdomain)
 	if err == nil {
 		if !d.isWildcard || !d.wildcardIps.ContainsAny(ips) {
@@ -119,6 +122,7 @@ func (d *GobusterDNS) ProcessWord(ctx context.Context, word string, progress *li
 				Found:     true,
 				ShowIPs:   d.options.ShowIPs,
 				ShowCNAME: d.options.ShowCNAME,
+				NoFQDN:    d.options.NoFQDN,
 			}
 			if d.options.ShowIPs {
 				result.IPs = ips

gobusterdns/options.go

@@ -11,6 +11,7 @@ type OptionsDNS struct {
 	ShowCNAME      bool
 	WildcardForced bool
 	Resolver       string
+	NoFQDN         bool
 	Timeout        time.Duration
 }
 

gobusterdns/result.go

@@ -19,6 +19,7 @@ type Result struct {
 	ShowCNAME bool
 	Found     bool
 	Subdomain string
+	NoFQDN    bool
 	IPs       []netip.Addr
 	CNAME     string
 }
@@ -29,6 +30,9 @@ func (r Result) ResultToString() (string, error) {
 
 	c := green
 
+	if !r.NoFQDN {
+		r.Subdomain = strings.TrimSuffix(r.Subdomain, ".")
+	}
 	if r.Found {
 		c(buf, "Found: ")
 	} else {