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@xxxxxxxxx>
---
Documentation/networking/ip-sysctl.rst | 6 ++++++
include/net/tcp_authopt.h | 1 +
net/ipv4/sysctl_net_ipv4.c | 10 ++++++++++
net/ipv4/tcp_authopt.c | 13 ++++++++++++-
4 files changed, 29 insertions(+), 1 deletion(-)
diff --git a/Documentation/networking/ip-sysctl.rst b/Documentation/networking/ip-sysctl.rst
index 16b8bf72feaf..3f00681f73d7 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 8bb76128ed11..a505db1dd67b 100644
--- a/include/net/tcp_authopt.h
+++ b/include/net/tcp_authopt.h
@@ -65,10 +65,11 @@ struct tcp_authopt_info {
/** @dst_isn: Remote Initial Sequence Number */
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 97eb54774924..cc34de6e4817 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;
@@ -583,10 +584,19 @@ 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_dointvec,
+ },
+#endif
{ }
};
static struct ctl_table ipv4_net_table[] = {
{
diff --git a/net/ipv4/tcp_authopt.c b/net/ipv4/tcp_authopt.c
index 5e80e5e5e36e..7c49dcce7d24 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);
EXPORT_SYMBOL(tcp_authopt_needed);
/* All current algorithms have a mac length of 12 but crypto API digestsize can be larger */
@@ -360,10 +365,12 @@ 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;
@@ -382,13 +389,15 @@ 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;
+ memset(opt, 0, sizeof(*opt));
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;
opt->flags = info->flags & TCP_AUTHOPT_KNOWN_FLAGS;
@@ -451,10 +460,12 @@ 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
