AdGuardHome/helpers.go

276 lines
7.5 KiB
Go

package main
import (
"bufio"
"errors"
"fmt"
"io"
"io/ioutil"
"math/rand"
"net"
"net/http"
"os"
"path"
"path/filepath"
"runtime"
"strconv"
"strings"
)
// ----------------------------------
// helper functions for working with files
// ----------------------------------
// Writes data first to a temporary file and then renames it to what's specified in path
func safeWriteFile(path string, data []byte) error {
dir := filepath.Dir(path)
err := os.MkdirAll(dir, 0755)
if err != nil {
return err
}
tmpPath := path + ".tmp"
err = ioutil.WriteFile(tmpPath, data, 0644)
if err != nil {
return err
}
return os.Rename(tmpPath, path)
}
// ----------------------------------
// helper functions for HTTP handlers
// ----------------------------------
func ensure(method string, handler func(http.ResponseWriter, *http.Request)) func(http.ResponseWriter, *http.Request) {
return func(w http.ResponseWriter, r *http.Request) {
if r.Method != method {
http.Error(w, "This request must be "+method, http.StatusMethodNotAllowed)
return
}
handler(w, r)
}
}
func ensurePOST(handler func(http.ResponseWriter, *http.Request)) func(http.ResponseWriter, *http.Request) {
return ensure("POST", handler)
}
func ensureGET(handler func(http.ResponseWriter, *http.Request)) func(http.ResponseWriter, *http.Request) {
return ensure("GET", handler)
}
func ensurePUT(handler func(http.ResponseWriter, *http.Request)) func(http.ResponseWriter, *http.Request) {
return ensure("PUT", handler)
}
func ensureDELETE(handler func(http.ResponseWriter, *http.Request)) func(http.ResponseWriter, *http.Request) {
return ensure("DELETE", handler)
}
func optionalAuth(handler func(http.ResponseWriter, *http.Request)) func(http.ResponseWriter, *http.Request) {
return func(w http.ResponseWriter, r *http.Request) {
if config.AuthName == "" || config.AuthPass == "" {
handler(w, r)
return
}
user, pass, ok := r.BasicAuth()
if !ok || user != config.AuthName || pass != config.AuthPass {
w.Header().Set("WWW-Authenticate", `Basic realm="dnsfilter"`)
w.WriteHeader(http.StatusUnauthorized)
w.Write([]byte("Unauthorised.\n"))
return
}
handler(w, r)
}
}
type authHandler struct {
handler http.Handler
}
func (a *authHandler) ServeHTTP(w http.ResponseWriter, r *http.Request) {
optionalAuth(a.handler.ServeHTTP)(w, r)
}
func optionalAuthHandler(handler http.Handler) http.Handler {
return &authHandler{handler}
}
// -------------------
// first run / install
// -------------------
func detectFirstRun() bool {
configfile := config.ourConfigFilename
if !filepath.IsAbs(configfile) {
configfile = filepath.Join(config.ourWorkingDir, config.ourConfigFilename)
}
_, err := os.Stat(configfile)
if !os.IsNotExist(err) {
// do nothing, file exists
return false
}
return true
}
// preInstall lets the handler run only if firstRun is true, no redirects
func preInstall(handler func(http.ResponseWriter, *http.Request)) func(http.ResponseWriter, *http.Request) {
return func(w http.ResponseWriter, r *http.Request) {
if !config.firstRun {
// if it's not first run, don't let users access it (for example /install.html when configuration is done)
http.Error(w, http.StatusText(http.StatusForbidden), http.StatusForbidden)
return
}
handler(w, r)
}
}
// preInstallStruct wraps preInstall into a struct that can be returned as an interface where necessary
type preInstallHandlerStruct struct {
handler http.Handler
}
func (p *preInstallHandlerStruct) ServeHTTP(w http.ResponseWriter, r *http.Request) {
preInstall(p.handler.ServeHTTP)(w, r)
}
// preInstallHandler returns http.Handler interface for preInstall wrapper
func preInstallHandler(handler http.Handler) http.Handler {
return &preInstallHandlerStruct{handler}
}
// postInstall lets the handler run only if firstRun is false, and redirects to /install.html otherwise
func postInstall(handler func(http.ResponseWriter, *http.Request)) func(http.ResponseWriter, *http.Request) {
return func(w http.ResponseWriter, r *http.Request) {
if config.firstRun && !strings.HasPrefix(r.URL.Path, "/install.") {
http.Redirect(w, r, "/install.html", http.StatusSeeOther) // should not be cacheable
return
}
handler(w, r)
}
}
type postInstallHandlerStruct struct {
handler http.Handler
}
func (p *postInstallHandlerStruct) ServeHTTP(w http.ResponseWriter, r *http.Request) {
postInstall(p.handler.ServeHTTP)(w, r)
}
func postInstallHandler(handler http.Handler) http.Handler {
return &postInstallHandlerStruct{handler}
}
// -------------------------------------------------
// helper functions for parsing parameters from body
// -------------------------------------------------
func parseParametersFromBody(r io.Reader) (map[string]string, error) {
parameters := map[string]string{}
scanner := bufio.NewScanner(r)
for scanner.Scan() {
line := scanner.Text()
if len(line) == 0 {
// skip empty lines
continue
}
parts := strings.SplitN(line, "=", 2)
if len(parts) != 2 {
return parameters, errors.New("Got invalid request body")
}
parameters[strings.TrimSpace(parts[0])] = strings.TrimSpace(parts[1])
}
return parameters, nil
}
// ------------------
// network interfaces
// ------------------
type netInterface struct {
Name string `json:"name"`
MTU int `json:"mtu"`
HardwareAddr string `json:"hardware_address"`
Addresses []string `json:"ip_addresses"`
Flags string `json:"flags"`
}
// getValidNetInterfaces returns interfaces that are eligible for DNS and/or DHCP
// invalid interface is a ppp interface or the one that doesn't allow broadcasts
func getValidNetInterfaces() ([]net.Interface, error) {
ifaces, err := net.Interfaces()
if err != nil {
return nil, fmt.Errorf("Couldn't get list of interfaces: %s", err)
}
netIfaces := []net.Interface{}
for i := range ifaces {
if ifaces[i].Flags&net.FlagPointToPoint != 0 {
// this interface is ppp, we're not interested in this one
continue
}
iface := ifaces[i]
netIfaces = append(netIfaces, iface)
}
return netIfaces, nil
}
// checkPortAvailable is not a cheap test to see if the port is bindable, because it's actually doing the bind momentarily
func checkPortAvailable(host string, port int) error {
ln, err := net.Listen("tcp", net.JoinHostPort(host, strconv.Itoa(port)))
if err != nil {
return err
}
ln.Close()
return nil
}
func checkPacketPortAvailable(host string, port int) error {
ln, err := net.ListenPacket("udp", net.JoinHostPort(host, strconv.Itoa(port)))
if err != nil {
return err
}
ln.Close()
return err
}
// ------------------------
// random string generation
// ------------------------
const letterBytes = "abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ"
const (
letterIdxBits = 6 // 6 bits to represent a letter index
letterIdxMask = 1<<letterIdxBits - 1 // All 1-bits, as many as letterIdxBits
letterIdxMax = 63 / letterIdxBits // # of letter indices fitting in 63 bits
)
func RandStringBytesMaskImpr(n int) string {
b := make([]byte, n)
// A rand.Int63() generates 63 random bits, enough for letterIdxMax letters!
for i, cache, remain := n-1, rand.Int63(), letterIdxMax; i >= 0; {
if remain == 0 {
cache, remain = rand.Int63(), letterIdxMax
}
if idx := int(cache & letterIdxMask); idx < len(letterBytes) {
b[i] = letterBytes[idx]
i--
}
cache >>= letterIdxBits
remain--
}
return string(b)
}
// ---------------------
// debug logging helpers
// ---------------------
func _Func() string {
pc := make([]uintptr, 10) // at least 1 entry needed
runtime.Callers(2, pc)
f := runtime.FuncForPC(pc[0])
return path.Base(f.Name())
}