From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-9.8 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI, SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED,USER_AGENT_GIT autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 15D92C388F9 for ; Tue, 27 Oct 2020 15:21:40 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id CA83622264 for ; Tue, 27 Oct 2020 15:21:39 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1603812099; bh=nstPzUardyPZb8ENdyhzbw1WAnRVrR9xXGc9+0Og5QY=; h=From:To:Cc:Subject:Date:In-Reply-To:References:List-ID:From; b=sfbef1fceEDfTxq6bFB9Az2WVcWK+1ng9PA3jTbRTQ/CuqB4a7jxmCRCo0B6aWpWg f6upwTL/0BhlRPoRVbciDES9Z9+XjaBZfbwVJQ5D1pcLfeOcfIvxoF/74VRd1bVL3P 4zxZzv9Ph9BQiPpsHCzhg1Jkh+6boO86BgHubnk4= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1797106AbgJ0PVi (ORCPT ); Tue, 27 Oct 2020 11:21:38 -0400 Received: from mail.kernel.org ([198.145.29.99]:56730 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1796512AbgJ0PTJ (ORCPT ); Tue, 27 Oct 2020 11:19:09 -0400 Received: from localhost (83-86-74-64.cable.dynamic.v4.ziggo.nl [83.86.74.64]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPSA id 7186521D41; Tue, 27 Oct 2020 15:19:08 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1603811949; bh=nstPzUardyPZb8ENdyhzbw1WAnRVrR9xXGc9+0Og5QY=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=xmFiqkgPwt6CUv3Dp4RBTZ8XvJMNzIxYNaogQxGwvQrcb7lp8yGY8T+joctrU7Pu1 ce0ZrLmUreqo8g3VcqGTBDSDMLwRRbrrYxCwkGga/UI6sHgxgf9BgtQzeL44UEHX3I t30yKOwUnHAjbzc7qXu3qA3f27DTs8I6FiiYoanU= From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, Eric Dumazet , Keyu Man , Jakub Kicinski Subject: [PATCH 5.9 038/757] icmp: randomize the global rate limiter Date: Tue, 27 Oct 2020 14:44:48 +0100 Message-Id: <20201027135452.311960829@linuxfoundation.org> X-Mailer: git-send-email 2.29.1 In-Reply-To: <20201027135450.497324313@linuxfoundation.org> References: <20201027135450.497324313@linuxfoundation.org> User-Agent: quilt/0.66 MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org From: Eric Dumazet [ Upstream commit b38e7819cae946e2edf869e604af1e65a5d241c5 ] Keyu Man reported that the ICMP rate limiter could be used by attackers to get useful signal. Details will be provided in an upcoming academic publication. Our solution is to add some noise, so that the attackers no longer can get help from the predictable token bucket limiter. Fixes: 4cdf507d5452 ("icmp: add a global rate limitation") Signed-off-by: Eric Dumazet Reported-by: Keyu Man Signed-off-by: Jakub Kicinski Signed-off-by: Greg Kroah-Hartman --- Documentation/networking/ip-sysctl.rst | 4 +++- net/ipv4/icmp.c | 7 +++++-- 2 files changed, 8 insertions(+), 3 deletions(-) --- a/Documentation/networking/ip-sysctl.rst +++ b/Documentation/networking/ip-sysctl.rst @@ -1142,13 +1142,15 @@ icmp_ratelimit - INTEGER icmp_msgs_per_sec - INTEGER Limit maximal number of ICMP packets sent per second from this host. Only messages whose type matches icmp_ratemask (see below) are - controlled by this limit. + controlled by this limit. For security reasons, the precise count + of messages per second is randomized. Default: 1000 icmp_msgs_burst - INTEGER icmp_msgs_per_sec controls number of ICMP packets sent per second, while icmp_msgs_burst controls the burst size of these packets. + For security reasons, the precise burst size is randomized. Default: 50 --- a/net/ipv4/icmp.c +++ b/net/ipv4/icmp.c @@ -239,7 +239,7 @@ static struct { /** * icmp_global_allow - Are we allowed to send one more ICMP message ? * - * Uses a token bucket to limit our ICMP messages to sysctl_icmp_msgs_per_sec. + * Uses a token bucket to limit our ICMP messages to ~sysctl_icmp_msgs_per_sec. * Returns false if we reached the limit and can not send another packet. * Note: called with BH disabled */ @@ -267,7 +267,10 @@ bool icmp_global_allow(void) } credit = min_t(u32, icmp_global.credit + incr, sysctl_icmp_msgs_burst); if (credit) { - credit--; + /* We want to use a credit of one in average, but need to randomize + * it for security reasons. + */ + credit = max_t(int, credit - prandom_u32_max(3), 0); rc = true; } WRITE_ONCE(icmp_global.credit, credit);