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package server
import (
"crypto/md5" //nolint:gosec,gci
"fmt"
"io"
"math/rand"
"net"
"strconv"
"time"
"github.com/pion/stun"
"github.com/pion/turn/v2/internal/proto"
)
const (
maximumAllocationLifetime = time.Hour // https://tools.ietf.org/html/rfc5766#section-6.2 defines 3600 seconds recommendation
nonceLifetime = time.Hour // https://tools.ietf.org/html/rfc5766#section-4
)
func randSeq(n int) string {
letters := []rune("abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ")
b := make([]rune, n)
for i := range b {
b[i] = letters[rand.Intn(len(letters))] //nolint:gosec
}
return string(b)
}
func buildNonce() (string, error) {
/* #nosec */
h := md5.New()
if _, err := io.WriteString(h, strconv.FormatInt(time.Now().Unix(), 10)); err != nil {
return "", fmt.Errorf("%w: %v", errFailedToGenerateNonce, err)
}
if _, err := io.WriteString(h, strconv.FormatInt(rand.Int63(), 10)); err != nil { //nolint:gosec
return "", fmt.Errorf("%w: %v", errFailedToGenerateNonce, err)
}
return fmt.Sprintf("%x", h.Sum(nil)), nil
}
func buildAndSend(conn net.PacketConn, dst net.Addr, attrs ...stun.Setter) error {
msg, err := stun.Build(attrs...)
if err != nil {
return err
}
_, err = conn.WriteTo(msg.Raw, dst)
return err
}
// Send a STUN packet and return the original error to the caller
func buildAndSendErr(conn net.PacketConn, dst net.Addr, err error, attrs ...stun.Setter) error {
if sendErr := buildAndSend(conn, dst, attrs...); sendErr != nil {
err = fmt.Errorf("%w %v %v", errFailedToSendError, sendErr, err)
}
return err
}
func buildMsg(transactionID [stun.TransactionIDSize]byte, msgType stun.MessageType, additional ...stun.Setter) []stun.Setter {
return append([]stun.Setter{&stun.Message{TransactionID: transactionID}, msgType}, additional...)
}
func authenticateRequest(r Request, m *stun.Message, callingMethod stun.Method) (stun.MessageIntegrity, bool, error) {
respondWithNonce := func(responseCode stun.ErrorCode) (stun.MessageIntegrity, bool, error) {
nonce, err := buildNonce()
if err != nil {
return nil, false, err
}
// Nonce has already been taken
if _, keyCollision := r.Nonces.LoadOrStore(nonce, time.Now()); keyCollision {
return nil, false, errDuplicatedNonce
}
return nil, false, buildAndSend(r.Conn, r.SrcAddr, buildMsg(m.TransactionID,
stun.NewType(callingMethod, stun.ClassErrorResponse),
&stun.ErrorCodeAttribute{Code: responseCode},
stun.NewNonce(nonce),
stun.NewRealm(r.Realm),
)...)
}
if !m.Contains(stun.AttrMessageIntegrity) {
return respondWithNonce(stun.CodeUnauthorized)
}
nonceAttr := &stun.Nonce{}
usernameAttr := &stun.Username{}
realmAttr := &stun.Realm{}
badRequestMsg := buildMsg(m.TransactionID, stun.NewType(callingMethod, stun.ClassErrorResponse), &stun.ErrorCodeAttribute{Code: stun.CodeBadRequest})
if err := nonceAttr.GetFrom(m); err != nil {
return nil, false, buildAndSendErr(r.Conn, r.SrcAddr, err, badRequestMsg...)
}
// Assert Nonce exists and is not expired
nonceCreationTime, ok := r.Nonces.Load(string(*nonceAttr))
if !ok || time.Since(nonceCreationTime.(time.Time)) >= nonceLifetime {
r.Nonces.Delete(nonceAttr)
return respondWithNonce(stun.CodeStaleNonce)
}
if err := realmAttr.GetFrom(m); err != nil {
return nil, false, buildAndSendErr(r.Conn, r.SrcAddr, err, badRequestMsg...)
} else if err := usernameAttr.GetFrom(m); err != nil {
return nil, false, buildAndSendErr(r.Conn, r.SrcAddr, err, badRequestMsg...)
}
ourKey, ok := r.AuthHandler(usernameAttr.String(), realmAttr.String(), r.SrcAddr)
if !ok {
return nil, false, buildAndSendErr(r.Conn, r.SrcAddr, fmt.Errorf("%w %s", errNoSuchUser, usernameAttr.String()), badRequestMsg...)
}
if err := stun.MessageIntegrity(ourKey).Check(m); err != nil {
return nil, false, buildAndSendErr(r.Conn, r.SrcAddr, err, badRequestMsg...)
}
return stun.MessageIntegrity(ourKey), true, nil
}
func allocationLifeTime(m *stun.Message) time.Duration {
lifetimeDuration := proto.DefaultLifetime
var lifetime proto.Lifetime
if err := lifetime.GetFrom(m); err == nil {
if lifetime.Duration < maximumAllocationLifetime {
lifetimeDuration = lifetime.Duration
}
}
return lifetimeDuration
}
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