194 lines
4.9 KiB
Go
194 lines
4.9 KiB
Go
package main
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import (
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"crypto/hmac"
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"crypto/sha512"
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"crypto/tls"
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"encoding/json"
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"errors"
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"fmt"
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"io/ioutil"
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"log"
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"net"
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"net/http"
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"os"
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"path"
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"strings"
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"text/template"
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"gopkg.in/ldap.v2"
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)
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var loginSalt string
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type loginChecker struct {
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students []Student
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ldapAddr string
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ldapPort int
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ldapIsTLS bool
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ldapBase string
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ldapBindUsername string
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ldapBindPassword string
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}
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type loginUpload struct {
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Username string
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Password string
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}
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func (l loginChecker) ldapAuth(username, password string) (res bool, err error) {
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tlsCnf := tls.Config{InsecureSkipVerify: true}
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var c *ldap.Conn
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if l.ldapIsTLS {
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c, err = ldap.DialTLS("tcp", fmt.Sprintf("%s:%d", l.ldapAddr, l.ldapPort), &tlsCnf)
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if err != nil {
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return false, err
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}
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} else {
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c, err = ldap.Dial("tcp", fmt.Sprintf("%s:%d", l.ldapAddr, l.ldapPort))
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if err != nil {
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return false, err
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}
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// Reconnect with TLS
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err = c.StartTLS(&tlsCnf)
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if err != nil {
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return false, err
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}
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}
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defer c.Close()
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if l.ldapBindUsername != "" {
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err = c.Bind(l.ldapBindUsername, l.ldapBindPassword)
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if err != nil {
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return false, err
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}
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}
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// Search for the given username
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searchRequest := ldap.NewSearchRequest(
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l.ldapBase,
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ldap.ScopeWholeSubtree, ldap.NeverDerefAliases, 0, 0, false,
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fmt.Sprintf("(&(objectClass=person)(uid=%s))", username),
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[]string{"dn"},
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nil,
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)
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sr, err := c.Search(searchRequest)
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if err != nil {
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return false, err
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}
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if len(sr.Entries) != 1 {
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return false, errors.New("User does not exist or too many entries returned")
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}
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userdn := sr.Entries[0].DN
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err = c.Bind(userdn, password)
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if err != nil {
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return false, err
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}
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return true, nil
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}
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func (l loginChecker) ServeHTTP(w http.ResponseWriter, r *http.Request) {
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if addr := r.Header.Get("X-Forwarded-For"); addr != "" {
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r.RemoteAddr = addr
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}
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log.Printf("%s \"%s %s\" [%s]\n", r.RemoteAddr, r.Method, r.URL.Path, r.UserAgent())
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w.Header().Set("Content-Type", "text/plain")
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// Check request type and size
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if r.Method != "POST" {
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http.Error(w,
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"Invalid request",
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http.StatusBadRequest)
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return
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} else if r.ContentLength < 0 || r.ContentLength > 1023 {
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http.Error(w,
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"Request entity too large",
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http.StatusRequestEntityTooLarge)
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return
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}
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dec := json.NewDecoder(r.Body)
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var lu loginUpload
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if err := dec.Decode(&lu); err != nil {
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http.Error(w,
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err.Error(),
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http.StatusBadRequest)
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return
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}
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// Perform login check
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canContinue := false
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for _, std := range l.students {
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if std.Login == lu.Username {
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canContinue = true
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}
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}
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if !canContinue {
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log.Println("Login not found:", lu.Username, "at", r.RemoteAddr)
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http.Error(w, "Login not found in whitelist.", http.StatusUnauthorized)
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return
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}
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if ok, err := l.ldapAuth(lu.Username, lu.Password); err != nil {
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log.Println("Unable to perform authentication for", lu.Username, ":", err, "at", r.RemoteAddr)
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http.Error(w, err.Error(), http.StatusUnauthorized)
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return
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} else if !ok {
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log.Println("Login failed:", lu.Username, "at", r.RemoteAddr)
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http.Error(w, "Invalid password", http.StatusUnauthorized)
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return
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}
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if err := l.lateLoginAction(lu.Username, r.RemoteAddr); err != nil {
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log.Println("Error on late login action:", err)
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http.Error(w, "Internal server error. Please retry in a few minutes", http.StatusInternalServerError)
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return
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}
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log.Println("Successful login of", lu.Username, "at", r.RemoteAddr)
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http.Error(w, "Success", http.StatusOK)
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}
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func (l loginChecker) lateLoginAction(username, remoteAddr string) error {
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// Find corresponding MAC
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var fname string
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spl := strings.SplitN(remoteAddr, ":", 2)
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if ip := net.ParseIP(spl[0]); ip == nil {
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return errors.New("Unable to parse given IPv4: " + spl[0])
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} else if arptable, err := ARPAnalyze(); err != nil {
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return err
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} else if arpent := ARPContainsIP(arptable, ip); arpent == nil {
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return errors.New("Unable to find MAC in ARP table")
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} else {
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fname = fmt.Sprintf("%02x-%02x-%02x-%02x-%02x-%02x-%02x", arpent.HWType, arpent.HWAddress[0], arpent.HWAddress[1], arpent.HWAddress[2], arpent.HWAddress[3], arpent.HWAddress[4], arpent.HWAddress[5])
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}
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if tpl, err := ioutil.ReadFile(path.Join(tftpDir, "pxelinux.cfg", "tpl")); err != nil {
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log.Println("Unable to open tpl: ", err)
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} else if file, err := os.OpenFile(path.Join(tftpDir, "pxelinux.cfg", fname), os.O_CREATE|os.O_WRONLY|os.O_TRUNC, os.FileMode(0644)); err != nil {
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log.Println("Unable to open destination file: ", err)
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} else {
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defer file.Close()
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mac := hmac.New(sha512.New512_224, []byte(loginSalt))
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if configTmpl, err := template.New("pxelinux.cfg").Parse(string(tpl)); err != nil {
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log.Println("Cannot create template: ", err)
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} else if err := configTmpl.Execute(file, map[string]string{"username": username, "remoteAddr": remoteAddr, "pkey": fmt.Sprintf("%x", mac.Sum([]byte(username))), "fname": fname}); err != nil {
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log.Println("An error occurs during template execution: ", err)
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}
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}
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return nil
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}
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