On Mon, May 13, 2019 at 07:38:37PM +0800, Weilong Chen wrote: > > 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.
That does not really answer my question. Even if "CVE" meant much more back in 1999 than it does these days, none of the CVE-1999-0524 descriptions I found cares to explain why it's considered a problem that an attacker knows time on your machine. They just claim it is. If we assume it is a security problem, then we would have to consider having correct time a security problem which is something I certainly don't agree with. One idea is that there may be applications using current time as a seed for random number generator - but then such application is the real problem, not having correct time. Michal Kubecek
