Public Release

dns_server.go

@@ -0,0 +1,125 @@
+package nebula
+
+import (
+	"fmt"
+	"net"
+	"strconv"
+	"sync"
+
+	"github.com/miekg/dns"
+)
+
+// This whole thing should be rewritten to use context
+
+var dnsR *dnsRecords
+
+type dnsRecords struct {
+	sync.RWMutex
+	dnsMap  map[string]string
+	hostMap *HostMap
+}
+
+func newDnsRecords(hostMap *HostMap) *dnsRecords {
+	return &dnsRecords{
+		dnsMap:  make(map[string]string),
+		hostMap: hostMap,
+	}
+}
+
+func (d *dnsRecords) Query(data string) string {
+	d.RLock()
+	if r, ok := d.dnsMap[data]; ok {
+		d.RUnlock()
+		return r
+	}
+	d.RUnlock()
+	return ""
+}
+
+func (d *dnsRecords) QueryCert(data string) string {
+	ip := net.ParseIP(data[:len(data)-1])
+	if ip == nil {
+		return ""
+	}
+	iip := ip2int(ip)
+	hostinfo, err := d.hostMap.QueryVpnIP(iip)
+	if err != nil {
+		return ""
+	}
+	q := hostinfo.GetCert()
+	if q == nil {
+		return ""
+	}
+	cert := q.Details
+	c := fmt.Sprintf("\"Name: %s\" \"Ips: %s\" \"Subnets %s\" \"Groups %s\" \"NotBefore %s\" \"NotAFter %s\" \"PublicKey %x\" \"IsCA %t\" \"Issuer %s\"", cert.Name, cert.Ips, cert.Subnets, cert.Groups, cert.NotBefore, cert.NotAfter, cert.PublicKey, cert.IsCA, cert.Issuer)
+	return c
+}
+
+func (d *dnsRecords) Add(host, data string) {
+	d.Lock()
+	d.dnsMap[host] = data
+	d.Unlock()
+}
+
+func parseQuery(m *dns.Msg, w dns.ResponseWriter) {
+	for _, q := range m.Question {
+		switch q.Qtype {
+		case dns.TypeA:
+			l.Debugf("Query for A %s", q.Name)
+			ip := dnsR.Query(q.Name)
+			if ip != "" {
+				rr, err := dns.NewRR(fmt.Sprintf("%s A %s", q.Name, ip))
+				if err == nil {
+					m.Answer = append(m.Answer, rr)
+				}
+			}
+		case dns.TypeTXT:
+			a, _, _ := net.SplitHostPort(w.RemoteAddr().String())
+			b := net.ParseIP(a)
+			// We don't answer these queries from non nebula nodes or localhost
+			//l.Debugf("Does %s contain %s", b, dnsR.hostMap.vpnCIDR)
+			if !dnsR.hostMap.vpnCIDR.Contains(b) && a != "127.0.0.1" {
+				return
+			}
+			l.Debugf("Query for TXT %s", q.Name)
+			ip := dnsR.QueryCert(q.Name)
+			if ip != "" {
+				rr, err := dns.NewRR(fmt.Sprintf("%s TXT %s", q.Name, ip))
+				if err == nil {
+					m.Answer = append(m.Answer, rr)
+				}
+			}
+		}
+	}
+}
+
+func handleDnsRequest(w dns.ResponseWriter, r *dns.Msg) {
+	m := new(dns.Msg)
+	m.SetReply(r)
+	m.Compress = false
+
+	switch r.Opcode {
+	case dns.OpcodeQuery:
+		parseQuery(m, w)
+	}
+
+	w.WriteMsg(m)
+}
+
+func dnsMain(hostMap *HostMap) {
+
+	dnsR = newDnsRecords(hostMap)
+
+	// attach request handler func
+	dns.HandleFunc(".", handleDnsRequest)
+
+	// start server
+	port := 53
+	server := &dns.Server{Addr: ":" + strconv.Itoa(port), Net: "udp"}
+	l.Debugf("Starting DNS responder at %d\n", port)
+	err := server.ListenAndServe()
+	defer server.Shutdown()
+	if err != nil {
+		l.Errorf("Failed to start server: %s\n ", err.Error())
+	}
+}