From patchwork Sun Aug 29 22:16:14 2021 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Eric Dumazet X-Patchwork-Id: 504220 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=-15.7 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,FREEMAIL_FORGED_FROMDOMAIN,FREEMAIL_FROM, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_CR_TRAILER,INCLUDES_PATCH, MAILING_LIST_MULTI, SPF_HELO_NONE, SPF_PASS, 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 D32A0C4320E for ; Sun, 29 Aug 2021 22:16:23 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id BCC0560F56 for ; Sun, 29 Aug 2021 22:16:23 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S235685AbhH2WRP (ORCPT ); Sun, 29 Aug 2021 18:17:15 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:54750 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S233919AbhH2WRO (ORCPT ); Sun, 29 Aug 2021 18:17:14 -0400 Received: from mail-pj1-x102c.google.com (mail-pj1-x102c.google.com [IPv6:2607:f8b0:4864:20::102c]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id E2112C061575 for ; Sun, 29 Aug 2021 15:16:21 -0700 (PDT) Received: by mail-pj1-x102c.google.com with SMTP id mq3so8176009pjb.5 for ; Sun, 29 Aug 2021 15:16:21 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20161025; h=from:to:cc:subject:date:message-id:in-reply-to:references :mime-version:content-transfer-encoding; bh=swelTAQtQxKqymGLqfC04nJtJBqlKXlaH5+mLMbRKuc=; b=CozOLFTAepnkrCzoC1YZ9qkwxkyAsZ0lwdWRlZCGX1hAdlawCzKct9WZw1m67778fk YUUldJbf7jSToZwUoE2VHKAF6OnzpkrpTre8iaqHwBJ5G05aBJXTWVd56/sgbn43HVwd 8lapT37/8oelEtkWbqhN5UpxL+mf9MKl+xCfhHgmCmrr3ylgQOoMkPJX+ORADAAjyuPm hrxnDz2HjPveFkYAxUhHfdmUlC3LkDZ003tytsZQGFAVUKpPRKpGriuyuYaaIR4ZD4Zz tKDo0JxmH+zNdPd20uJBCkPD7VG7IwkRRk5x+Xo5bwWr7TbjrkzFy1p9tG35LE/GtKkC V5Mw== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:from:to:cc:subject:date:message-id:in-reply-to :references:mime-version:content-transfer-encoding; bh=swelTAQtQxKqymGLqfC04nJtJBqlKXlaH5+mLMbRKuc=; b=CssWXOSzyLxnpluo7WOBBL3XnlZrRD98wNjqIIwGqhqN8EmKFWVez1ONRWY7d+TNDz ZPqaN5zhUuTVq31/tmPeXM1Zgedv/b9Nu1Y88XAxJL6kLuz3QBYMspd6jWxBDM4Rq/cY aDVcrM+V4UeUIHlVWgItuc1Rk0bSfOzakQiVfCsmUsTMMQJGm6TaHH4y6p9dVMRQ8pHP 0pFSnMmvkIFyJXlhfkzx5p6dL8NrJQTkkNWOQeeKosQVUCnQfz8IyFg6IRsvgyEVJE2U 8onmUxobuXjIaW+LNMKvL23mkVPBbcllAV/dk12VRa9LrLn2GGt/Y5nVMWU/M6d1OFCP QE8A== X-Gm-Message-State: AOAM532pgTWGJiQb7LBBZY7Egigo+QLTazHoaTnQpSbJ6qAu6yY6/reC CRPJ8BfKgLmPTAmIpNU6cKk= X-Google-Smtp-Source: ABdhPJyG3Cx3ltOOY/Znnh/xy/2hW8r2SDWi+MXBqk0KCiMbl120xg9GMZVBOStUrUSSWZoRf5fESg== X-Received: by 2002:a17:902:e8c2:b029:123:25ba:e443 with SMTP id v2-20020a170902e8c2b029012325bae443mr19106215plg.29.1630275381532; Sun, 29 Aug 2021 15:16:21 -0700 (PDT) Received: from edumazet1.svl.corp.google.com ([2620:15c:2c4:201:3934:d27b:77de:86b7]) by smtp.gmail.com with ESMTPSA id o15sm1162735pjr.0.2021.08.29.15.16.20 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Sun, 29 Aug 2021 15:16:21 -0700 (PDT) From: Eric Dumazet To: "David S . Miller" , Jakub Kicinski Cc: netdev , Eric Dumazet , Eric Dumazet , Willy Tarreau , Keyu Man , David Ahern , Wei Wang , Martin KaFai Lau Subject: [PATCH net 1/2] ipv6: make exception cache less predictible Date: Sun, 29 Aug 2021 15:16:14 -0700 Message-Id: <20210829221615.2057201-2-eric.dumazet@gmail.com> X-Mailer: git-send-email 2.33.0.259.gc128427fd7-goog In-Reply-To: <20210829221615.2057201-1-eric.dumazet@gmail.com> References: <20210829221615.2057201-1-eric.dumazet@gmail.com> MIME-Version: 1.0 Precedence: bulk List-ID: X-Mailing-List: netdev@vger.kernel.org From: Eric Dumazet Even after commit 4785305c05b2 ("ipv6: use siphash in rt6_exception_hash()"), an attacker can still use brute force to learn some secrets from a victim linux host. One way to defeat these attacks is to make the max depth of the hash table bucket a random value. Before this patch, each bucket of the hash table used to store exceptions could contain 6 items under attack. After the patch, each bucket would contains a random number of items, between 6 and 10. The attacker can no longer infer secrets. This is slightly increasing memory size used by the hash table, we do not expect this to be a problem. Following patch is dealing with the same issue in IPv4. Fixes: 35732d01fe31 ("ipv6: introduce a hash table to store dst cache") Signed-off-by: Eric Dumazet Reported-by: Keyu Man Cc: Wei Wang Cc: Martin KaFai Lau Reviewed-by: David Ahern Reviewed-by: Wei Wang --- net/ipv6/route.c | 5 ++++- 1 file changed, 4 insertions(+), 1 deletion(-) diff --git a/net/ipv6/route.c b/net/ipv6/route.c index c5e8ecb96426bda619fe242351e40dcf6ff68bcf..60334030210192660a7fa141163f36af7489d0ae 100644 --- a/net/ipv6/route.c +++ b/net/ipv6/route.c @@ -1657,6 +1657,7 @@ static int rt6_insert_exception(struct rt6_info *nrt, struct in6_addr *src_key = NULL; struct rt6_exception *rt6_ex; struct fib6_nh *nh = res->nh; + int max_depth; int err = 0; spin_lock_bh(&rt6_exception_lock); @@ -1711,7 +1712,9 @@ static int rt6_insert_exception(struct rt6_info *nrt, bucket->depth++; net->ipv6.rt6_stats->fib_rt_cache++; - if (bucket->depth > FIB6_MAX_DEPTH) + /* Randomize max depth to avoid some side channels attacks. */ + max_depth = FIB6_MAX_DEPTH + prandom_u32_max(FIB6_MAX_DEPTH); + while (bucket->depth > max_depth) rt6_exception_remove_oldest(bucket); out: