From patchwork Thu Dec 23 15:40:02 2021 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Leonard Crestez X-Patchwork-Id: 527491 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id C9BE8C433EF for ; Thu, 23 Dec 2021 15:41:25 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1349255AbhLWPlY (ORCPT ); Thu, 23 Dec 2021 10:41:24 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:33808 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1349080AbhLWPk5 (ORCPT ); Thu, 23 Dec 2021 10:40:57 -0500 Received: from mail-ed1-x534.google.com (mail-ed1-x534.google.com [IPv6:2a00:1450:4864:20::534]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id AD2D6C061763; Thu, 23 Dec 2021 07:40:50 -0800 (PST) Received: by mail-ed1-x534.google.com with SMTP id o6so22974342edc.4; Thu, 23 Dec 2021 07:40:50 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20210112; h=from:to:cc:subject:date:message-id:in-reply-to:references :mime-version:content-transfer-encoding; bh=D9NCFWuovE5/gne38khmJwHLjO1KbxvtMh1bmnt68Y8=; b=p092mNJqUcXIERjF1bU0yMXrGueKvKfHmiFQ+kpFtp+kEInGvyYy6jk3Vfnkimowu2 qFXyHxML4DT9+d5NxS7Xh3Cx//7Hi/8V1Fesfux5CdenO9J6ICXes2VvuaTrpHGoSGwi 68Ucvp1dQdzoMr4EcmWTYewoNi8KVo5GJo1JGt0Npjy4zBvFHN2+bld076Kbp6NTObiK vQXOtFqVaafRbgyHfORwuRjMDIs1cTO2N4/qeZqH3k23jPKUans5Mx+xyjD3rfZirZGX yQS1FWJwZZeoUaAGxUVxbLzQScCMZRDOZiAf3XMsXYBVsurdb0Pmif+QC3Ru/8ajFM2x 0jrA== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20210112; h=x-gm-message-state:from:to:cc:subject:date:message-id:in-reply-to :references:mime-version:content-transfer-encoding; bh=D9NCFWuovE5/gne38khmJwHLjO1KbxvtMh1bmnt68Y8=; b=jhoumE3M0s6818otvN6BcG3TTjdw54a9KlygQJmtc82pctPybSo0dO6y+MNA4puYLA 9VlKjyvPAEcV5MHMMfdiZfiW+7XUsON+JNZFhB0zqHJtJYGiuj9YvNrianqnree7Sso6 3m11NM1KXM5PN9PX4pwWMe5gyb2spCZRrKcumMK1x825IftTzighSh2w9T8kV6lalgyb 1kOM/qnHjktySKhjyBR+s+zbaYWUnKnrQ/wH8LPP94mak9oarRIpFfNzMHmWjxc7TnGb 2pQ3TM2a2QhTadsEi88Ghhv3h+LF46YKrv+uuQrNoAbBVBEqwi6CCADvk0Kjseo/LmTP Gm2Q== X-Gm-Message-State: AOAM530DFC/1Qh+OLoXw7qS8iXRwY+rOJKWTExkoJ1DNtJ8RzwChFp4D WF6435Qyg+9uPxHREIYOsnw= X-Google-Smtp-Source: ABdhPJyTCjyZ/as3+omHCjOhOt7qp4EcKlC6BQjiLKryJvs57IpQZCPF+NvfGVRvcupgZNpglKZU2Q== X-Received: by 2002:aa7:cfd5:: with SMTP id r21mr2464790edy.98.1640274049264; Thu, 23 Dec 2021 07:40:49 -0800 (PST) Received: from ponky.lan ([2a04:241e:501:3870:7c02:dfc6:b554:ab10]) by smtp.gmail.com with ESMTPSA id bx6sm2088617edb.78.2021.12.23.07.40.47 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Thu, 23 Dec 2021 07:40:48 -0800 (PST) From: Leonard Crestez To: David Ahern , Eric Dumazet , Philip Paeps , Dmitry Safonov <0x7f454c46@gmail.com> Cc: Shuah Khan , "David S. Miller" , Herbert Xu , Kuniyuki Iwashima , Hideaki YOSHIFUJI , Jakub Kicinski , Yuchung Cheng , Francesco Ruggeri , Mat Martineau , Christoph Paasch , Ivan Delalande , Priyaranjan Jha , netdev@vger.kernel.org, linux-crypto@vger.kernel.org, linux-kselftest@vger.kernel.org, linux-kernel@vger.kernel.org Subject: [PATCH v4 07/19] tcp: authopt: Disable via sysctl by default Date: Thu, 23 Dec 2021 17:40:02 +0200 Message-Id: X-Mailer: git-send-email 2.25.1 In-Reply-To: References: MIME-Version: 1.0 Precedence: bulk List-ID: X-Mailing-List: linux-crypto@vger.kernel.org This is mainly intended to protect against local privilege escalations through a rarely used feature so it is deliberately not namespaced. Enforcement is only at the setsockopt level, this should be enough to ensure that the tcp_authopt_needed static key never turns on. No effort is made to handle disabling when the feature is already in use. Signed-off-by: Leonard Crestez --- Documentation/networking/ip-sysctl.rst | 6 ++++ include/net/tcp_authopt.h | 1 + net/ipv4/sysctl_net_ipv4.c | 39 ++++++++++++++++++++++++++ net/ipv4/tcp_authopt.c | 27 +++++++++++++++++- 4 files changed, 72 insertions(+), 1 deletion(-) diff --git a/Documentation/networking/ip-sysctl.rst b/Documentation/networking/ip-sysctl.rst index c04431144f7a..2fa992ef4e02 100644 --- a/Documentation/networking/ip-sysctl.rst +++ b/Documentation/networking/ip-sysctl.rst @@ -987,10 +987,16 @@ tcp_limit_output_bytes - INTEGER tcp_challenge_ack_limit - INTEGER Limits number of Challenge ACK sent per second, as recommended in RFC 5961 (Improving TCP's Robustness to Blind In-Window Attacks) Default: 1000 +tcp_authopt - BOOLEAN + Enable the TCP Authentication Option (RFC5925), a replacement for TCP + MD5 Signatures (RFC2835). + + Default: 0 + UDP variables ============= udp_l3mdev_accept - BOOLEAN Enabling this option allows a "global" bound socket to work diff --git a/include/net/tcp_authopt.h b/include/net/tcp_authopt.h index 7096e3ad59a6..4c9ec1f39932 100644 --- a/include/net/tcp_authopt.h +++ b/include/net/tcp_authopt.h @@ -80,10 +80,11 @@ struct tcphdr_authopt { }; #ifdef CONFIG_TCP_AUTHOPT DECLARE_STATIC_KEY_FALSE(tcp_authopt_needed_key); #define tcp_authopt_needed (static_branch_unlikely(&tcp_authopt_needed_key)) +extern int sysctl_tcp_authopt; void tcp_authopt_free(struct sock *sk, struct tcp_authopt_info *info); void tcp_authopt_clear(struct sock *sk); int tcp_set_authopt(struct sock *sk, sockptr_t optval, unsigned int optlen); int tcp_get_authopt_val(struct sock *sk, struct tcp_authopt *key); diff --git a/net/ipv4/sysctl_net_ipv4.c b/net/ipv4/sysctl_net_ipv4.c index 97eb54774924..07de2666314c 100644 --- a/net/ipv4/sysctl_net_ipv4.c +++ b/net/ipv4/sysctl_net_ipv4.c @@ -17,10 +17,11 @@ #include #include #include #include #include +#include static int two = 2; static int three __maybe_unused = 3; static int four = 4; static int thousand = 1000; @@ -472,10 +473,37 @@ static int proc_fib_multipath_hash_fields(struct ctl_table *table, int write, return ret; } #endif +#ifdef CONFIG_TCP_AUTHOPT +static int proc_tcp_authopt(struct ctl_table *ctl, + int write, void *buffer, size_t *lenp, + loff_t *ppos) +{ + int val = sysctl_tcp_authopt; + struct ctl_table tmp = { + .data = &val, + .mode = ctl->mode, + .maxlen = sizeof(val), + .extra1 = SYSCTL_ZERO, + .extra2 = SYSCTL_ONE, + }; + int err; + + err = proc_dointvec_minmax(&tmp, write, buffer, lenp, ppos); + if (err) + return err; + if (sysctl_tcp_authopt && !val) { + net_warn_ratelimited("Enabling TCP Authentication Option is permanent\n"); + return -EINVAL; + } + sysctl_tcp_authopt = val; + return 0; +} +#endif + static struct ctl_table ipv4_table[] = { { .procname = "tcp_max_orphans", .data = &sysctl_tcp_max_orphans, .maxlen = sizeof(int), @@ -583,10 +611,21 @@ static struct ctl_table ipv4_table[] = { .mode = 0644, .proc_handler = proc_douintvec_minmax, .extra1 = &sysctl_fib_sync_mem_min, .extra2 = &sysctl_fib_sync_mem_max, }, +#ifdef CONFIG_TCP_AUTHOPT + { + .procname = "tcp_authopt", + .data = &sysctl_tcp_authopt, + .maxlen = sizeof(int), + .mode = 0644, + .proc_handler = proc_tcp_authopt, + .extra1 = SYSCTL_ZERO, + .extra2 = SYSCTL_ONE, + }, +#endif { } }; static struct ctl_table ipv4_net_table[] = { { diff --git a/net/ipv4/tcp_authopt.c b/net/ipv4/tcp_authopt.c index ba20a70359ee..6be5dbcd530e 100644 --- a/net/ipv4/tcp_authopt.c +++ b/net/ipv4/tcp_authopt.c @@ -4,10 +4,15 @@ #include #include #include #include +/* This is mainly intended to protect against local privilege escalations through + * a rarely used feature so it is deliberately not namespaced. + */ +int sysctl_tcp_authopt; + /* This is enabled when first struct tcp_authopt_info is allocated and never released */ DEFINE_STATIC_KEY_FALSE(tcp_authopt_needed_key); EXPORT_SYMBOL(tcp_authopt_needed_key); /* All current algorithms have a mac length of 12 but crypto API digestsize can be larger */ @@ -425,17 +430,30 @@ static int _copy_from_sockptr_tolerant(u8 *dst, memset(dst + srclen, 0, dstlen - srclen); return err; } +static int check_sysctl_tcp_authopt(void) +{ + if (!sysctl_tcp_authopt) { + net_warn_ratelimited("TCP Authentication Option disabled by sysctl.\n"); + return -EPERM; + } + + return 0; +} + int tcp_set_authopt(struct sock *sk, sockptr_t optval, unsigned int optlen) { struct tcp_authopt opt; struct tcp_authopt_info *info; int err; sock_owned_by_me(sk); + err = check_sysctl_tcp_authopt(); + if (err) + return err; err = _copy_from_sockptr_tolerant((u8 *)&opt, sizeof(opt), optval, optlen); if (err) return err; @@ -453,14 +471,18 @@ int tcp_set_authopt(struct sock *sk, sockptr_t optval, unsigned int optlen) int tcp_get_authopt_val(struct sock *sk, struct tcp_authopt *opt) { struct tcp_sock *tp = tcp_sk(sk); struct tcp_authopt_info *info; + int err; + memset(opt, 0, sizeof(*opt)); sock_owned_by_me(sk); + err = check_sysctl_tcp_authopt(); + if (err) + return err; - memset(opt, 0, sizeof(*opt)); info = rcu_dereference_check(tp->authopt_info, lockdep_sock_is_held(sk)); if (!info) return -ENOENT; opt->flags = info->flags & TCP_AUTHOPT_KNOWN_FLAGS; @@ -481,10 +503,13 @@ int tcp_set_authopt_key(struct sock *sk, sockptr_t optval, unsigned int optlen) struct netns_tcp_authopt *net = sock_net_tcp_authopt(sk); struct tcp_authopt_alg_imp *alg; int err; sock_owned_by_me(sk); + err = check_sysctl_tcp_authopt(); + if (err) + return err; if (!ns_capable(sock_net(sk)->user_ns, CAP_NET_ADMIN)) return -EPERM; err = _copy_from_sockptr_tolerant((u8 *)&opt, sizeof(opt), optval, optlen); if (err)