On 2019/5/13 15:49, Michal Kubecek wrote:
On Mon, May 13, 2019 at 09:33:13AM +0800, Weilong Chen wrote:
The remote host answers to an ICMP timestamp request.
This allows an attacker to know the time and date on your host.
Why is that a problem? If it is, does it also mean that it is a security
problem to have your time in sync (because then the attacker doesn't
even need ICMP timestamps to know the time and date on your host)?
It's a low risk vulnerability(CVE-1999-0524). TCP has
net.ipv4.tcp_timestamps = 0 to disable it.
This path is an another way contrast to iptables rules:
iptables -A input -p icmp --icmp-type timestamp-request -j DROP
iptables -A output -p icmp --icmp-type timestamp-reply -j DROP
Default is disabled to improve security.
If we need a sysctl for this (and I'm not convinced we do), I would
prefer preserving current behaviour by default.
Firewall is not applied to all scenarios.
Michal Kubecek
.
thanks.
