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dns: fixed a bug in parseQuestion which may leads to a panic

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This commit is contained in:
nadoo 2018-01-10 12:25:57 +08:00
parent 2e10672c3b
commit bebfa0e48e
1 changed files with 12 additions and 7 deletions
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19
dns.go
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@ -196,9 +196,9 @@ func (s *DNS) ListenAndServeUDP() {
continue
}
b = b[:n]
reqMsg := b[:n]
go func() {
_, respMsg := s.handleReqMsg(reqLen, b)
_, respMsg := s.Exchange(reqLen, reqMsg)
_, err = c.WriteTo(respMsg, clientAddr)
if err != nil {
logf("proxy-dns error in local write: %s", err)
@ -246,7 +246,7 @@ func (s *DNS) ServeTCP(c net.Conn) {
}
if reqLen <= DNSHeaderLen {
logf("proxy-dns not enough data")
logf("proxy-dns-tcp not enough data")
return
}
@ -257,7 +257,7 @@ func (s *DNS) ServeTCP(c net.Conn) {
return
}
respLen, respMsg := s.handleReqMsg(reqLen, reqMsg)
respLen, respMsg := s.Exchange(reqLen, reqMsg)
if err := binary.Write(c, binary.BigEndian, respLen); err != nil {
logf("proxy-dns-tcp error in local write respLen: %s\n", err)
}
@ -268,8 +268,8 @@ func (s *DNS) ServeTCP(c net.Conn) {
// logf("proxy-dns-tcp %s <-> %s, type: %d, %s: %s", c.RemoteAddr(), dnsServer, query.QueryType, domain, ip)
}
// handle request msg and return response msg
func (s *DNS) handleReqMsg(reqLen uint16, reqMsg []byte) (respLen uint16, respMsg []byte) {
// Exchange handles request msg and return response msg
func (s *DNS) Exchange(reqLen uint16, reqMsg []byte) (respLen uint16, respMsg []byte) {
// fmt.Printf("dns req len %d:\n%s\n\n", reqLen, hex.Dump(reqMsg[:]))
query, err := parseQuestion(reqMsg)
if err != nil {
@ -367,10 +367,11 @@ func (s *DNS) AddAnswerHandler(h DNSAnswerHandler) {
func parseQuestion(p []byte) (*DNSQuestion, error) {
q := &DNSQuestion{}
lenP := len(p)
var i int
var domain []byte
for i = DNSHeaderLen; i < len(p); {
for i = DNSHeaderLen; i < lenP; {
l := int(p[i])
if l == 0 {
@ -378,6 +379,10 @@ func parseQuestion(p []byte) (*DNSQuestion, error) {
break
}
if lenP <= i+l+1 {
return nil, errors.New("parseQuestion error, not enough data for QNAME")
}
domain = append(domain, p[i+1:i+l+1]...)
domain = append(domain, '.')