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Message-ID: <20190513121145.GE22349@unicorn.suse.cz> Date: Mon, 13 May 2019 14:11:45 +0200 From: Michal Kubecek <mkubecek@...e.cz> To: netdev@...r.kernel.org Cc: Weilong Chen <chenweilong@...wei.com>, davem@...emloft.net, kuznet@....inr.ac.ru, yoshfuji@...ux-ipv6.org Subject: Re: [PATCH net-next] ipv4: Add support to disable icmp timestamp On Mon, May 13, 2019 at 08:06:37PM +0800, Weilong Chen wrote: > On 2019/5/13 19:49, Michal Kubecek wrote: > > 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. > > > Yes, the target computer responded to an ICMP timestamp request. By > accurately determining the target's clock state, an attacker can more > effectively attack certain time-based pseudorandom number generators (PRNGs) > and the authentication systems that rely on them. > > So, the 'time' may become sensitive information. The OS should not leak it > out. So you are effectively saying that having correct time is a security vulnerability? I'm sorry but I cannot agree with that. Seeding PRNG with current time is known to be a bad practice and if some application does it, the solution is to fix the application, not obfuscating system time. Michal Kubecek
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