Re: [PATCH net-next] ipv4: Add support to disable icmp timestamp

Weilong Chen [off-list ref] wrote:

On 2019/5/13 15:49, Michal Kubecek wrote:

quoted

On Mon, May 13, 2019 at 09:33:13AM +0800, Weilong Chen wrote:

quoted

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.

These are not the same.

TCP timestamps (before pseudo-randomized offset were added) used to leaked
system uptime.

ICMP timestamps "leak" milliseconds since midnight. Don't see how thats
a problem.