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login.go
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login.go
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package main
import (
"crypto/md5"
"errors"
"fmt"
"github.com/PuerkitoBio/goquery"
"golang.org/x/term"
"io"
"math"
"net/http"
"strings"
"syscall"
)
const FailedAttempt = "no SID cookie found in response header"
type LoginCommand struct {
Address string `required:"" help:"the Netgear switch's IP address or host name to connect to" short:"a"`
Password string `optional:"" help:"the admin console's password; if omitted, it will be prompted for" short:"p"`
}
func (login *LoginCommand) Run(args *GlobalOptions) error {
if len(login.Password) < 1 {
pwd, err := promptForPassword(login.Address)
if err != nil {
return err
}
login.Password = pwd
}
if len(login.Password) < 1 {
return errors.New("no password given")
}
model, err := detectNetgearModel(args, login.Address)
if err != nil {
return err
}
args.model = model
seedValue, err := getSeedValueFromSwitch(args, login.Address)
if err != nil {
return err
}
encryptedPwd := encryptPassword(login.Password, seedValue)
err = doLogin(args, login.Address, encryptedPwd)
if err != nil {
return err
}
return nil
}
func promptForPassword(serverName string) (string, error) {
fmt.Printf("Please enter password for '%s' (input hidden) :> ", serverName)
// the int conversion is required for the windows build to succeed
password, err := term.ReadPassword(int(syscall.Stdin))
println()
return string(password), err
}
func doLogin(args *GlobalOptions, host string, encryptedPwd string) error {
var url string
if isModel30x(args.model) {
url = fmt.Sprintf("http://%s/login.cgi", host)
} else if isModel316(args.model) {
url = fmt.Sprintf("http://%s/redirect.html", host)
} else {
return errors.New("Unknown model not supported, please contact the developers ")
}
if args.Verbose {
println("login attempt: " + url)
}
var formData string
if isModel30x(args.model) {
formData = "password=" + encryptedPwd
} else if isModel316(args.model) {
formData = "LoginPassword=" + encryptedPwd
}
resp, err := http.Post(url, "application/x-www-form-urlencoded", strings.NewReader(formData))
if err != nil {
return err
}
defer resp.Body.Close()
if args.Verbose {
println(resp.Status)
}
body, err := io.ReadAll(resp.Body)
if err != nil {
return err
}
var token string
if isModel30x(args.model) {
token = getSessionToken(resp)
if token == FailedAttempt && resp.StatusCode == http.StatusOK {
return errors.New("login request returned 200 OK, but response did not contain a session token ('SID' cookie). " +
"this is known behaviour from the switch. please, wait some minutes and tray again later")
}
}
if isModel316(args.model) {
token = findGambitTokenInResponseHtml(strings.NewReader(string(body)))
if token == FailedAttempt && resp.StatusCode == http.StatusOK {
return errors.New("login request returned 200 OK, but response did not contain a token ('Gambit' value in input field) ")
}
}
err = storeToken(args, host, token)
if err != nil {
return err
}
return nil
}
func checkIsLoginRequired(httpResponseBody string) bool {
return len(httpResponseBody) < 10 ||
strings.Contains(httpResponseBody, "/login.cgi") ||
strings.Contains(httpResponseBody, "/wmi/login") ||
strings.Contains(httpResponseBody, "/redirect.html")
}
func getSessionToken(resp *http.Response) string {
cookie := resp.Header.Get("Set-Cookie")
var sessionIdPrefixes = [...]string{
// can be extended, once GS316 will also use this pattern
"SID=", // GS305EPx, GS308EPx
}
for _, sessionIdPrefix := range sessionIdPrefixes {
if strings.HasPrefix(cookie, sessionIdPrefix) {
sidVal := cookie[len(sessionIdPrefix):]
split := strings.Split(sidVal, ";")
return split[0]
}
}
return FailedAttempt
}
func findGambitTokenInResponseHtml(reader io.Reader) (gambitToken string) {
gambitToken = FailedAttempt
doc, err := goquery.NewDocumentFromReader(reader)
if err == nil {
doc.Find("form").Each(func(i int, s *goquery.Selection) {
name, okName := s.Find("input[type=hidden]").Attr("name")
value, okValue := s.Find("input[type=hidden]").Attr("value")
if okName && name == "Gambit" && okValue {
gambitToken = value
}
})
}
return gambitToken
}
func getSeedValueFromSwitch(args *GlobalOptions, host string) (string, error) {
var url string
if isModel30x(args.model) {
url = fmt.Sprintf("http://%s/login.cgi", host)
} else if isModel316(args.model) {
url = fmt.Sprintf("http://%s/wmi/login", host)
} else {
return "", errors.New("Unknown model not supported, please contact the developers ")
}
if args.Verbose {
println("fetch seed value from: " + url)
}
resp, err := http.Get(url)
if err != nil {
return "", err
}
if args.Verbose {
println(resp.Status)
}
defer resp.Body.Close()
seedValue, err := findSeedValueInLoginHtml(resp.Body)
if err != nil {
return "", err
}
return seedValue, nil
}
func findSeedValueInLoginHtml(reader io.Reader) (string, error) {
doc, err := goquery.NewDocumentFromReader(reader)
if err != nil {
return "", err
}
randVal, exists := doc.Find("#rand").First().Attr("value")
if exists {
return randVal, nil
}
return "", errors.New("random seed value not found in login.cgi response. " +
"An element with id=rand and an attribute 'value' is expected")
}
// encryptPassword re-implements some logic from Netgear's GS305EP frontend component, see login.js
func encryptPassword(password string, seedValue string) string {
mergedStr := specialMerge(password, seedValue)
hash := md5.New()
_, _ = io.WriteString(hash, mergedStr)
return fmt.Sprintf("%x", hash.Sum(nil))
}
func specialMerge(password string, seedValue string) string {
result := strings.Builder{}
maxLen := int(math.Max(float64(len(password)), float64(len(seedValue))))
for i := 0; i < maxLen; i++ {
if i < len(password) {
result.WriteString(string([]rune(password)[i]))
}
if i < len(seedValue) {
result.WriteString(string([]rune(seedValue)[i]))
}
}
return result.String()
}