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

auth.go

@@ -1,37 +0,0 @@
-package main
-
-import (
-	"golang.org/x/crypto/bcrypt"
-	"database/sql"
-	"fmt"
-	"net/http"
-)
-
-func authenticateUser(db *sql.DB, username, password string) bool {
-	hashedPassword, ok := getPasswordForUser(db, username)
-	if ok {
-		err := bcrypt.CompareHashAndPassword(hashedPassword, []byte(password))
-		//TODO: print error message?
-		return err == nil
-	} else {
-		return false
-	}
-}
-
-func basicAuth(db *sql.DB) http.HandlerFunc {
-	return func(w http.ResponseWriter, r *http.Request) {
-		user, pass, ok := r.BasicAuth()
-		if !ok || !authenticateUser(db, user, pass) {
-			w.Header().Set("WWW-Authenticate", `Basic realm="dyndns"`)
-			w.WriteHeader(401)
-			w.Write([]byte("badauth"))
-			return
-		}
-
-		userdata, err := getDataForUser(db, user)
-		if err != nil {
-			fmt.Println(err)
-		}
-		handleRequest(w, r, userdata)
-	}
-}

backend.go

@@ -1,68 +0,0 @@
-package main
-
-import (
-	"fmt"
-	"net"
-	"net/http"
-	"strings"
-)
-
-// check if net.ParseIP returns nil!!
-func getIP(r *http.Request) net.IP {
-	addr := r.URL.Query().Get("myip")
-	if len(addr) > 0 {
-		return net.ParseIP(addr)
-	}
-
-	addr = r.Header.Get(http.CanonicalHeaderKey("X-Forwarded-For"))
-	if len(addr) > 0 {
-		end := strings.Index(addr, ", ")
-		if end == -1 {
-			end = len(addr)
-		}
-		return net.ParseIP(addr[:end])
-	}
-
-	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 {
-		panic(err)
-	}
-	return net.ParseIP(addr)
-}
-
-func handleRequest(w http.ResponseWriter, r *http.Request, data userData) {
-	msg := "good"
-	defer func() {
-		w.Write([]byte(msg))
-	}()
-
-	hostname := r.URL.Query().Get("hostname")
-	if len(hostname) <= 0 || hostname != data.hostname {
-		msg = "nohost"
-		return
-	}
-
-	ipaddr := getIP(r)
-	if ipaddr == nil {
-		//TODO:
-		msg = "error"
-		return
-	}
-	msg = "Hostname: " + hostname + " , IP: " + ipaddr.String()
-
-	updated, err := updateNameserver(data, ipaddr)
-	if err != nil {
-		msg = "dnserr"
-		fmt.Println(err)
-		return
-	}
-	if !updated {
-		msg = "nochg"
-		return
-	}
-}

config.example.toml

@@ -1,6 +1,9 @@
-[database]
-host = "127.0.0.1"
 port = 5432
-user = "username"
+
-pass = "password"
+[[rrconfig]]
-name = "database"
+username = "username"
+password = "password"
+nameserver = "ns1.example.org"
+zonename = "example.org"
+hostname = "somerecord.example.org"
+tsigkey = "<tsig-key>"

config.go

@@ -0,0 +1,48 @@
+package main
+
+import (
+	"fmt"
+	"github.com/pelletier/go-toml"
+	"os"
+)
+
+type Config struct {
+	ServerPort uint16     `toml:"port"`
+	RRConfigs  []RRConfig `toml:"rrconfig"`
+
+	rrconfigs map[string]*RRConfig
+}
+
+type RRConfig struct {
+	Username   string `toml:"username"`
+	Password   string `toml:"password"`
+	Nameserver string `toml:"nameserver"`
+	Zonename   string `toml:"zonename"`
+	Hostname   string `toml:"hostname"`
+	Tsigkey    string `toml:"tsigkey"`
+	Ttl        int    `toml:"ttl" default:"60"`
+}
+
+func LoadConfig(path string) (*Config, error) {
+	var cfg Config
+
+	f, err := os.Open(path)
+	if err != nil {
+		return nil, err
+	}
+
+	decoder := toml.NewDecoder(f).Strict(true)
+	err = decoder.Decode(&cfg)
+	if err != nil {
+		return nil, err
+	}
+
+	cfg.rrconfigs = map[string]*RRConfig{}
+	for _, entry := range cfg.RRConfigs {
+		if _, ok := cfg.rrconfigs[entry.Username]; ok {
+			return nil, fmt.Errorf("Duplicate username detected")
+		}
+		cfg.rrconfigs[entry.Username] = &entry
+	}
+	return &cfg, nil
+}

data.go

@@ -1,72 +0,0 @@
-package main
-
-import (
-	"fmt"
-	"database/sql"
-	_ "github.com/lib/pq"
-)
-
-type databaseConfig struct {
-	Host string
-	Port int
-	User string
-	Pass string
-	Name string
-}
-
-type userData struct {
-	nameserver string
-	zonename string
-	hostname string
-	tsigkey string
-}
-
-func prepareDatabase() (*sql.DB, error) {
-	dbconf := config.Database
-	psqlInfo := fmt.Sprintf("host=%s port=%d user=%s password=%s dbname=%s " +
-							"sslmode=disable", dbconf.Host, dbconf.Port,
-							dbconf.User, dbconf.Pass, dbconf.Name)
-	db, err := sql.Open("postgres", psqlInfo)
-	if err != nil {
-		return nil, err
-	}
-
-	_, err = db.Exec("CREATE TABLE IF NOT EXISTS users " +
-					 "(id SERIAL PRIMARY KEY, username VARCHAR(255) NULL, " +
-					 "password VARCHAR(255) NULL, salt VARCHAR(255) NULL, " +
-					 "nameserver VARCHAR(255) NULL, zone VARCHAR(255) NULL, " +
-					 "hostname VARCHAR(255) NULL, tsig VARCHAR(255) NULL)")
-	if err != nil {
-		db.Close()
-		return nil, err
-	}
-	return db, nil
-}
-
-func getPasswordForUser(db *sql.DB, username string) ([]byte, bool) {
-	var password []byte
-
-	row := db.QueryRow("SELECT password FROM users WHERE username=$1", username)
-	err := row.Scan(&password)
-	if err != nil {
-		if err == sql.ErrNoRows {
-			return nil, false
-		} else {
-			panic(err)
-		}
-	}
-	return password, true
-}
-
-func getDataForUser(db *sql.DB, username string) (userData, error) {
-	var data userData
-
-	row := db.QueryRow("SELECT nameserver, zone, hostname, tsig " +
-					   "FROM users WHERE username=$1", username)
-	err := row.Scan(&data.nameserver, &data.zonename, &data.hostname,
-					&data.tsigkey)
-	if err != nil {
-		return data, err
-	}
-	return data, nil
-}

go.mod

@@ -0,0 +1,8 @@
+module git.preisner.eu/preisi/dyndns
+
+go 1.16
+
+require (
+	github.com/pelletier/go-toml v1.9.3
+	golang.org/x/crypto v0.0.0-20210711020723-a769d52b0f97
+)

go.sum

@@ -0,0 +1,12 @@
+github.com/pelletier/go-toml v1.9.3 h1:zeC5b1GviRUyKYd6OJPvBU/mcVDVoL1OhT17FCt5dSQ=
+github.com/pelletier/go-toml v1.9.3/go.mod h1:u1nR/EPcESfeI/szUZKdtJ0xRNbUoANCkoOuaOx1Y+c=
+golang.org/x/crypto v0.0.0-20210616213533-5ff15b29337e h1:gsTQYXdTw2Gq7RBsWvlQ91b+aEQ6bXFUngBGuR8sPpI=
+golang.org/x/crypto v0.0.0-20210616213533-5ff15b29337e/go.mod h1:GvvjBRRGRdwPK5ydBHafDWAxML/pGHZbMvKqRZ5+Abc=
+golang.org/x/crypto v0.0.0-20210711020723-a769d52b0f97 h1:/UOmuWzQfxxo9UtlXMwuQU8CMgg1eZXqTRwkSQJWKOI=
+golang.org/x/crypto v0.0.0-20210711020723-a769d52b0f97/go.mod h1:GvvjBRRGRdwPK5ydBHafDWAxML/pGHZbMvKqRZ5+Abc=
+golang.org/x/net v0.0.0-20210226172049-e18ecbb05110/go.mod h1:m0MpNAwzfU5UDzcl9v0D8zg8gWTRqZa9RBIspLL5mdg=
+golang.org/x/sys v0.0.0-20201119102817-f84b799fce68/go.mod h1:h1NjWce9XRLGQEsW7wpKNCjG9DtNlClVuFLEZdDNbEs=
+golang.org/x/sys v0.0.0-20210615035016-665e8c7367d1/go.mod h1:oPkhp1MJrh7nUepCBck5+mAzfO9JrbApNNgaTdGDITg=
+golang.org/x/term v0.0.0-20201126162022-7de9c90e9dd1/go.mod h1:bj7SfCRtBDWHUb9snDiAeCFNEtKQo2Wmx5Cou7ajbmo=
+golang.org/x/text v0.3.3/go.mod h1:5Zoc/QRtKVWzQhOtBMvqHzDpF6irO9z98xDceosuGiQ=
+golang.org/x/tools v0.0.0-20180917221912-90fa682c2a6e/go.mod h1:n7NCudcB/nEzxVGmLbDWY5pfWTLqBcC2KZ6jyYvM4mQ=

main.go

@@ -2,34 +2,22 @@ package main
 
 import (
 	"flag"
+	"fmt"
 	"net/http"
-	"github.com/BurntSushi/toml"
 )
 
-type tomlConfig struct {
-	Database databaseConfig
-}
-
-var config tomlConfig
-
 func main() {
 	var configPath string
 	flag.StringVar(&configPath, "config", "config.toml", "path to config file")
 	flag.Parse()
 
-	_, err := toml.DecodeFile(configPath, &config)
+	cfg, err := LoadConfig(configPath)
 	if err != nil {
 		panic(err)
 	}
 
-	db, err := prepareDatabase()
+	http.HandleFunc("/", RequestHandler(cfg))
-	if err != nil {
+	err = http.ListenAndServe(fmt.Sprintf(":%d", cfg.ServerPort), nil)
-		panic(err)
-	}
-	defer db.Close()
-
-	http.HandleFunc("/", basicAuth(db))
-	err = http.ListenAndServe(":3002", nil)
 	if err != nil {
 		panic(err)
 	}

nameserver.go

@@ -1,70 +1,59 @@
 package main
 
 import (
-	"bytes"
 	"fmt"
+	"log"
 	"net"
 	"os/exec"
 	"strings"
 )
 
-func createQuery(data userData, addr net.IP, deleteRecord bool) string {
+func requiresRRUpdate(entry *RRConfig, addr net.IP) bool {
-	var query strings.Builder
+	// TODO: use custom resolver to query authoritive nameserver instead of
-
+	// local resolver
-	query.WriteString(fmt.Sprintf("key %s\n", data.tsigkey))
+	addrs, err := net.LookupIP(entry.Hostname)
-	query.WriteString(fmt.Sprintf("server %s\n", data.nameserver))
+	if err != nil {
-	query.WriteString(fmt.Sprintf("zone %s\n", data.zonename))
+		log.Printf("dns lookup failed: %s", err)
-	if deleteRecord {
+		// enforce update, it's better than not trying at all
-		query.WriteString(fmt.Sprintf("update delete %s. A\n", data.hostname))
+		return true
 	}
-	query.WriteString(fmt.Sprintf("update add %s. A %s\n", data.hostname,
-								  addr.String()))
-	query.WriteString("show\n")
-	query.WriteString("send\n")
 
-	return query.String()
+	// check if the current ip matches
+	for _, ip := range addrs {
+		if ip.Equal(addr) {
+			// the ip seems to be still up-to-date -> no update required
+			return false
+		}
+	}
+	return true
 }
 
-func queryNameserver(query string) error {
+func updateRR(entry *RRConfig, addr net.IP) error {
-	var (
+	query := generateQuery(entry, addr)
-		stdout bytes.Buffer
+	return executeQuery(query)
-		stderr bytes.Buffer
+}
-	)
 
+func generateQuery(entry *RRConfig, addr net.IP) string {
+	var q strings.Builder
+
+	fmt.Fprintf(&q, "key %s\n", entry.Tsigkey)
+	fmt.Fprintf(&q, "server %s\n", entry.Nameserver)
+	fmt.Fprintf(&q, "zone %s\n", entry.Zonename)
+	// TODO: check if addr is ipv4 or ipv6 (-> update A or AAAA)
+	fmt.Fprintf(&q, "add %s. %d A %s\n", entry.Hostname, entry.Ttl, addr.String())
+	fmt.Fprintf(&q, "send\n")
+
+	return q.String()
+}
+
+func executeQuery(query string) error {
 	cmd := exec.Command("knsupdate", "-v")
 	cmd.Stdin = strings.NewReader(query)
-	cmd.Stdout = &stdout
+	output, err := cmd.CombinedOutput()
-	cmd.Stderr = &stderr
+	// TODO: is outputting stdout+stderr on failure even necessary?
-	err := cmd.Run()
+	if err != nil {
-	fmt.Printf(stdout.String())
+		log.Printf("executeQuery failed: %s", output)
-	fmt.Printf(stderr.String())
+	}
 
 	return err
 }
-
-func updateNameserver(data userData, addr net.IP) (bool, error) {
-	updateRecord := true
-	deleteRecord := true
-
-	addrs, err := net.LookupIP(data.hostname)
-	if err != nil {
-		deleteRecord = false
-	} else {
-		for _, ip := range addrs {
-			if ip.Equal(addr) {
-				updateRecord = false
-				break
-			}
-		}
-	}
-	if !updateRecord {
-		return false, nil
-	} else {
-		query := createQuery(data, addr, deleteRecord)
-		err = queryNameserver(query)
-		if err != nil {
-			return true, err
-		}
-		return true, nil
-	}
-}

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())
+	}
+}