From patchwork Tue Oct 27 13:51:23 2020 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Greg KH X-Patchwork-Id: 312983 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 CC3E4C55179 for ; Tue, 27 Oct 2020 14:17:45 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 9D72122202 for ; Tue, 27 Oct 2020 14:17:45 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1603808265; bh=bcfvIJmKlabq9204cn8GO6rrhDD6gspxG6dLQKMkS5E=; h=From:To:Cc:Subject:Date:In-Reply-To:References:List-ID:From; b=wNpkouYyquWual7JYq2lY5+gaI8NO19xUpj1lzdyV8ZFRlrCCWZfyy1D8M3E1b2PG IYW/zMHBumBCQP3Cxy06zYkn0QNXG/t3P1sxhXPtb5SPbVKY1vPVxaFUhsxtWiEGJ3 +Ewdfn8ohIFfx9MxyTdY+N3DaNK221bOuUyE7LE0= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1757294AbgJ0ORm (ORCPT ); Tue, 27 Oct 2020 10:17:42 -0400 Received: from mail.kernel.org ([198.145.29.99]:40812 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1757288AbgJ0ORl (ORCPT ); Tue, 27 Oct 2020 10:17:41 -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 65CC3206F7; Tue, 27 Oct 2020 14:17:40 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1603808260; bh=bcfvIJmKlabq9204cn8GO6rrhDD6gspxG6dLQKMkS5E=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=u5MS3zAlAGkQnK4NdL0L/hnMTzzYFA5qQ7S9Bhc3VWIHg+75iGMynICW57Dl1ic7v x7myF0dP/CJm+IW3qyYThklGi+vQtcdcrSHvyD9bE7tzjk1LTwG4eS04T6Hdx82w+f hfgG4fBUM0Ny+eVq+aNYZBmbTK0988tDQymBZ/Co= 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 4.19 025/264] icmp: randomize the global rate limiter Date: Tue, 27 Oct 2020 14:51:23 +0100 Message-Id: <20201027135431.836248747@linuxfoundation.org> X-Mailer: git-send-email 2.29.1 In-Reply-To: <20201027135430.632029009@linuxfoundation.org> References: <20201027135430.632029009@linuxfoundation.org> User-Agent: quilt/0.66 MIME-Version: 1.0 Precedence: bulk List-ID: X-Mailing-List: stable@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.txt | 4 +++- net/ipv4/icmp.c | 7 +++++-- 2 files changed, 8 insertions(+), 3 deletions(-) --- a/Documentation/networking/ip-sysctl.txt +++ b/Documentation/networking/ip-sysctl.txt @@ -934,12 +934,14 @@ 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 icmp_ratemask - INTEGER --- a/net/ipv4/icmp.c +++ b/net/ipv4/icmp.c @@ -244,7 +244,7 @@ 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 */ @@ -272,7 +272,10 @@ 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);