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* dhcp: don't process Discover/Request packets with empty client HW address

This commit is contained in:
Simon Zolin 2019-03-07 14:06:35 +03:00
parent 92cf7c1aca
commit d832d7ce95
1 changed files with 19 additions and 0 deletions
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19
dhcpd/dhcpd.go
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@ -325,6 +325,17 @@ func (s *Server) ServeDHCP(p dhcp4.Packet, msgType dhcp4.MessageType, options dh
return nil return nil
} }
// Return TRUE if DHCP packet is correct
func isValidPacket(p dhcp4.Packet) bool {
hw := p.CHAddr()
zeroes := make([]byte, len(hw))
if bytes.Equal(hw, zeroes) {
log.Tracef("Packet has empty CHAddr")
return false
}
return true
}
func (s *Server) handleDiscover(p dhcp4.Packet, options dhcp4.Options) dhcp4.Packet { func (s *Server) handleDiscover(p dhcp4.Packet, options dhcp4.Options) dhcp4.Packet {
// find a lease, but don't update lease time // find a lease, but don't update lease time
var lease *Lease var lease *Lease
@ -335,6 +346,10 @@ func (s *Server) handleDiscover(p dhcp4.Packet, options dhcp4.Options) dhcp4.Pac
log.Tracef("Message from client: Discover. ReqIP: %s HW: %s Hostname: %s", log.Tracef("Message from client: Discover. ReqIP: %s HW: %s Hostname: %s",
reqIP, p.CHAddr(), hostname) reqIP, p.CHAddr(), hostname)
if !isValidPacket(p) {
return nil
}
lease = s.findLease(p) lease = s.findLease(p)
for lease == nil { for lease == nil {
lease, err = s.reserveLease(p) lease, err = s.reserveLease(p)
@ -360,6 +375,10 @@ func (s *Server) handleDHCP4Request(p dhcp4.Packet, options dhcp4.Options) dhcp4
log.Tracef("Message from client: Request. IP: %s ReqIP: %s HW: %s", log.Tracef("Message from client: Request. IP: %s ReqIP: %s HW: %s",
p.CIAddr(), reqIP, p.CHAddr()) p.CIAddr(), reqIP, p.CHAddr())
if !isValidPacket(p) {
return nil
}
server := options[dhcp4.OptionServerIdentifier] server := options[dhcp4.OptionServerIdentifier]
if server != nil && !net.IP(server).Equal(s.ipnet.IP) { if server != nil && !net.IP(server).Equal(s.ipnet.IP) {
log.Tracef("Request message not for this DHCP server (%v vs %v)", server, s.ipnet.IP) log.Tracef("Request message not for this DHCP server (%v vs %v)", server, s.ipnet.IP)