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Message-Id: <b0abf2b789220708011a862a892c37b0fd76dc25.1632240523.git.cdleonard@gmail.com>
Date: Tue, 21 Sep 2021 19:14:51 +0300
From: Leonard Crestez <cdleonard@...il.com>
To: Dmitry Safonov <0x7f454c46@...il.com>,
David Ahern <dsahern@...nel.org>, Shuah Khan <shuah@...nel.org>
Cc: Eric Dumazet <edumazet@...gle.com>,
"David S. Miller" <davem@...emloft.net>,
Herbert Xu <herbert@...dor.apana.org.au>,
Kuniyuki Iwashima <kuniyu@...zon.co.jp>,
Hideaki YOSHIFUJI <yoshfuji@...ux-ipv6.org>,
Jakub Kicinski <kuba@...nel.org>,
Yuchung Cheng <ycheng@...gle.com>,
Francesco Ruggeri <fruggeri@...sta.com>,
Mat Martineau <mathew.j.martineau@...ux.intel.com>,
Christoph Paasch <cpaasch@...le.com>,
Ivan Delalande <colona@...sta.com>,
Priyaranjan Jha <priyarjha@...gle.com>,
Menglong Dong <dong.menglong@....com.cn>,
netdev@...r.kernel.org, linux-crypto@...r.kernel.org,
linux-kselftest@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: [PATCH 08/19] tcp: authopt: Disable via sysctl by default
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 <cdleonard@...il.com>
---
Documentation/networking/ip-sysctl.rst | 6 ++++++
include/net/tcp_authopt.h | 1 +
net/ipv4/sysctl_net_ipv4.c | 10 ++++++++++
net/ipv4/tcp_authopt.c | 11 +++++++++++
4 files changed, 28 insertions(+)
diff --git a/Documentation/networking/ip-sysctl.rst b/Documentation/networking/ip-sysctl.rst
index d91ab28718d4..16e34268ecb4 100644
--- a/Documentation/networking/ip-sysctl.rst
+++ b/Documentation/networking/ip-sysctl.rst
@@ -995,10 +995,16 @@ tcp_rx_skb_cache - BOOLEAN
on systems with a lot of TCP sockets, since it increases
memory usage.
Default: 0 (disabled)
+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 263f98c3a1a8..422f0034d32b 100644
--- a/include/net/tcp_authopt.h
+++ b/include/net/tcp_authopt.h
@@ -51,10 +51,11 @@ struct tcp_authopt_info {
u32 src_isn;
u32 dst_isn;
};
#ifdef CONFIG_TCP_AUTHOPT
+extern int sysctl_tcp_authopt;
DECLARE_STATIC_KEY_FALSE(tcp_authopt_needed);
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);
diff --git a/net/ipv4/sysctl_net_ipv4.c b/net/ipv4/sysctl_net_ipv4.c
index 4680268f2e59..365466fbca8b 100644
--- a/net/ipv4/sysctl_net_ipv4.c
+++ b/net/ipv4/sysctl_net_ipv4.c
@@ -17,10 +17,11 @@
#include <net/udp.h>
#include <net/cipso_ipv4.h>
#include <net/ping.h>
#include <net/protocol.h>
#include <net/netevent.h>
+#include <net/tcp_authopt.h>
static int two = 2;
static int three __maybe_unused = 3;
static int four = 4;
static int thousand = 1000;
@@ -595,10 +596,19 @@ static struct ctl_table ipv4_table[] = {
.procname = "tcp_tx_skb_cache",
.data = &tcp_tx_skb_cache_key.key,
.mode = 0644,
.proc_handler = proc_do_static_key,
},
+#ifdef CONFIG_TCP_AUTHOPT
+ {
+ .procname = "tcp_authopt",
+ .data = &sysctl_tcp_authopt,
+ .maxlen = sizeof(int),
+ .mode = 0644,
+ .proc_handler = proc_dointvec,
+ },
+#endif
{ }
};
static struct ctl_table ipv4_net_table[] = {
{
diff --git a/net/ipv4/tcp_authopt.c b/net/ipv4/tcp_authopt.c
index 0c32b8fb1d41..41f844d5d49a 100644
--- a/net/ipv4/tcp_authopt.c
+++ b/net/ipv4/tcp_authopt.c
@@ -3,10 +3,15 @@
#include <linux/kernel.h>
#include <net/tcp.h>
#include <net/tcp_authopt.h>
#include <crypto/hash.h>
+/* 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);
/* only for CONFIG_IPV6=m */
EXPORT_SYMBOL(tcp_authopt_needed);
@@ -361,10 +366,12 @@ 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);
+ if (!sysctl_tcp_authopt)
+ return -EPERM;
err = _copy_from_sockptr_tolerant((u8*)&opt, sizeof(opt), optval, optlen);
if (err)
return err;
@@ -384,10 +391,12 @@ int tcp_get_authopt_val(struct sock *sk, struct tcp_authopt *opt)
{
struct tcp_sock *tp = tcp_sk(sk);
struct tcp_authopt_info *info;
sock_owned_by_me(sk);
+ if (!sysctl_tcp_authopt)
+ return -EPERM;
memset(opt, 0, sizeof(*opt));
info = rcu_dereference_check(tp->authopt_info, lockdep_sock_is_held(sk));
if (!info)
return -ENOENT;
@@ -452,10 +461,12 @@ int tcp_set_authopt_key(struct sock *sk, sockptr_t optval, unsigned int optlen)
struct tcp_authopt_key_info *key_info, *old_key_info;
struct tcp_authopt_alg_imp *alg;
int err;
sock_owned_by_me(sk);
+ if (!sysctl_tcp_authopt)
+ return -EPERM;
err = _copy_from_sockptr_tolerant((u8*)&opt, sizeof(opt), optval, optlen);
if (err)
return err;
--
2.25.1
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