rewrite most code; removes database to solely rely on config file

web.go

@@ -0,0 +1,126 @@
+package main
+
+import (
+	"fmt"
+	"golang.org/x/crypto/bcrypt"
+	"log"
+	"net"
+	"net/http"
+	"strings"
+)
+
+func isAuthenticated(cfg *Config, r *http.Request) *RRConfig {
+	user, pw, ok := r.BasicAuth()
+	if !ok {
+		// no basic auth header detected
+		return nil
+	}
+
+	entry, ok := cfg.rrconfigs[user]
+	if !ok {
+		// non-existent username
+		return nil
+	}
+
+	err := bcrypt.CompareHashAndPassword([]byte(entry.Password), []byte(pw))
+	if err != nil {
+		log.Printf("Config contains invalid password hash for user %q", user)
+		return nil
+	}
+	return entry
+}
+
+func getIpAddress(r *http.Request) net.IP {
+	addr := r.URL.Query().Get("myip")
+	if len(addr) > 0 {
+		// If myip was supplied, parse it and return the result regardless of
+		// success, failure will be handled later.
+		return net.ParseIP(addr)
+	}
+
+	// check http headers and request for other possible ip address sources
+	addr = r.Header.Get(http.CanonicalHeaderKey("X-Forwarded-For"))
+	if len(addr) > 0 {
+		tokens := strings.Split(addr, ", ")
+		// tokens is always at least 1 element long
+		// -> return first element as it contains the client's ip address
+		return net.ParseIP(tokens[0])
+	}
+	// TODO: support newer standarized "Forwarded"-Header
+
+	addr = r.Header.Get(http.CanonicalHeaderKey("X-Real-IP"))
+	if len(addr) > 0 {
+		return net.ParseIP(addr)
+	}
+
+	addr, _, err := net.SplitHostPort(r.RemoteAddr)
+	if err != nil {
+		log.Printf("Retrieving IP-Address failed: %s", err)
+		return nil
+	}
+	return net.ParseIP(addr)
+}
+
+// returns api-response on failure
+func verifyHostname(entry *RRConfig, hostname string) string {
+	if len(hostname) <= 0 {
+		return "nohost"
+	}
+
+	// TODO: allow single user to update multiple hostnames
+	// TODO: return ntfqdn -> differentiate between 'hostname doesnt exist' and
+	// 'hostname is not fqdn'
+	if hostname != entry.Hostname {
+		return "nohost"
+	}
+	return ""
+}
+
+func RequestHandler(cfg *Config) func(w http.ResponseWriter, r *http.Request) {
+	return func(w http.ResponseWriter, r *http.Request) {
+		userdata := isAuthenticated(cfg, r)
+		if userdata == nil {
+			w.Header().Set("WWW-Authenticate", `Basic realm="dyndns"`)
+			w.WriteHeader(http.StatusUnauthorized)
+			w.Write([]byte("badauth"))
+			fmt.Fprintln(w, "badauth")
+			return
+		}
+
+		// all remaining responses should come with status code 200
+		w.WriteHeader(http.StatusOK)
+
+		// check for 'valid' useragent, should not be strictly necessary but
+		// the protocol demands it
+		if len(r.UserAgent()) <= 0 {
+			fmt.Fprintln(w, "badagent")
+			return
+		}
+
+		hostname := r.URL.Query().Get("hostname")
+		response := verifyHostname(userdata, hostname)
+		if response != "" {
+			fmt.Fprintln(w, response)
+			return
+		}
+
+		ipaddr := getIpAddress(r)
+		if ipaddr == nil {
+			fmt.Fprintln(w, "911")
+			return
+		}
+
+		if !requiresRRUpdate(userdata, ipaddr) {
+			fmt.Fprintf(w, "nochg %s\n", ipaddr.String())
+			return
+		}
+
+		err := updateRR(userdata, ipaddr)
+		if err != nil {
+			log.Printf("updating RR failed: %s", err)
+			fmt.Fprintln(w, "911")
+			return
+		}
+		fmt.Fprintf(w, "good %s\n", ipaddr.String())
+	}
+}