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Date: Thu, 18 Aug 2016 14:48:45 +0200
From: Florian Westphal <fw@...len.de>
To: <netdev@...r.kernel.org>
Cc: Florian Westphal <fw@...len.de>
Subject: [RFC 1/3] tcp: randomize tcp timestamp offsets for each connection
commit ceaa1fef65a7c2e ("tcp: adding a per-socket timestamp offset")
added the main infrastructure that is needed for per-connection
randomization, in particular writing/reading the on-wire tcp header
format takes the offset into account so rest of stack can use normal
tcp_time_stamp (jiffies).
So only two items are left:
- add a tsoffset for request sockets
- extend the tcp isn generator to also return another 32bit number
in addition to the ISN.
Re-use of ISN generator also means timestamps are still monotonically
increasing for same connection quadruple.
Signed-off-by: Florian Westphal <fw@...len.de>
---
include/linux/tcp.h | 1 +
include/net/secure_seq.h | 13 +++++++++----
include/net/tcp.h | 2 +-
net/core/secure_seq.c | 19 +++++++++++++------
net/ipv4/syncookies.c | 1 +
net/ipv4/tcp_input.c | 7 ++++++-
net/ipv4/tcp_ipv4.c | 30 ++++++++++++++++++++----------
net/ipv4/tcp_minisocks.c | 4 +++-
net/ipv4/tcp_output.c | 2 +-
net/ipv6/syncookies.c | 1 +
net/ipv6/tcp_ipv6.c | 28 ++++++++++++++++++----------
11 files changed, 74 insertions(+), 34 deletions(-)
diff --git a/include/linux/tcp.h b/include/linux/tcp.h
index 7be9b12..edad1a1 100644
--- a/include/linux/tcp.h
+++ b/include/linux/tcp.h
@@ -122,6 +122,7 @@ struct tcp_request_sock {
u32 txhash;
u32 rcv_isn;
u32 snt_isn;
+ u32 ts_off;
u32 last_oow_ack_time; /* last SYNACK */
u32 rcv_nxt; /* the ack # by SYNACK. For
* FastOpen it's the seq#
diff --git a/include/net/secure_seq.h b/include/net/secure_seq.h
index 3f36d45..3d576f7 100644
--- a/include/net/secure_seq.h
+++ b/include/net/secure_seq.h
@@ -3,13 +3,18 @@
#include <linux/types.h>
+struct secure_tcp_seq {
+ u32 seq;
+ u32 tsoff;
+};
+
u32 secure_ipv4_port_ephemeral(__be32 saddr, __be32 daddr, __be16 dport);
u32 secure_ipv6_port_ephemeral(const __be32 *saddr, const __be32 *daddr,
__be16 dport);
-__u32 secure_tcp_sequence_number(__be32 saddr, __be32 daddr,
- __be16 sport, __be16 dport);
-__u32 secure_tcpv6_sequence_number(const __be32 *saddr, const __be32 *daddr,
- __be16 sport, __be16 dport);
+struct secure_tcp_seq secure_tcp_sequence_number(__be32 saddr, __be32 daddr,
+ __be16 sport, __be16 dport);
+struct secure_tcp_seq secure_tcpv6_sequence_number(const __be32 *saddr, const __be32 *daddr,
+ __be16 sport, __be16 dport);
u64 secure_dccp_sequence_number(__be32 saddr, __be32 daddr,
__be16 sport, __be16 dport);
u64 secure_dccpv6_sequence_number(__be32 *saddr, __be32 *daddr,
diff --git a/include/net/tcp.h b/include/net/tcp.h
index c00e7d5..5707361 100644
--- a/include/net/tcp.h
+++ b/include/net/tcp.h
@@ -1749,7 +1749,7 @@ struct tcp_request_sock_ops {
struct dst_entry *(*route_req)(const struct sock *sk, struct flowi *fl,
const struct request_sock *req,
bool *strict);
- __u32 (*init_seq)(const struct sk_buff *skb);
+ __u32 (*init_seq)(const struct sk_buff *skb, u32 *tsoff);
int (*send_synack)(const struct sock *sk, struct dst_entry *dst,
struct flowi *fl, struct request_sock *req,
struct tcp_fastopen_cookie *foc,
diff --git a/net/core/secure_seq.c b/net/core/secure_seq.c
index fd3ce46..613f2fd 100644
--- a/net/core/secure_seq.c
+++ b/net/core/secure_seq.c
@@ -40,11 +40,13 @@ static u32 seq_scale(u32 seq)
#endif
#if IS_ENABLED(CONFIG_IPV6)
-__u32 secure_tcpv6_sequence_number(const __be32 *saddr, const __be32 *daddr,
- __be16 sport, __be16 dport)
+struct secure_tcp_seq
+secure_tcpv6_sequence_number(const __be32 *saddr, const __be32 *daddr,
+ __be16 sport, __be16 dport)
{
u32 secret[MD5_MESSAGE_BYTES / 4];
u32 hash[MD5_DIGEST_WORDS];
+ struct secure_tcp_seq seq;
u32 i;
net_secret_init();
@@ -58,7 +60,9 @@ __u32 secure_tcpv6_sequence_number(const __be32 *saddr, const __be32 *daddr,
md5_transform(hash, secret);
- return seq_scale(hash[0]);
+ seq.seq = seq_scale(hash[0]);
+ seq.tsoff = hash[1];
+ return seq;
}
EXPORT_SYMBOL(secure_tcpv6_sequence_number);
@@ -86,10 +90,11 @@ EXPORT_SYMBOL(secure_ipv6_port_ephemeral);
#ifdef CONFIG_INET
-__u32 secure_tcp_sequence_number(__be32 saddr, __be32 daddr,
- __be16 sport, __be16 dport)
+struct secure_tcp_seq secure_tcp_sequence_number(__be32 saddr, __be32 daddr,
+ __be16 sport, __be16 dport)
{
u32 hash[MD5_DIGEST_WORDS];
+ struct secure_tcp_seq seq;
net_secret_init();
hash[0] = (__force u32)saddr;
@@ -99,7 +104,9 @@ __u32 secure_tcp_sequence_number(__be32 saddr, __be32 daddr,
md5_transform(hash, net_secret);
- return seq_scale(hash[0]);
+ seq.seq = seq_scale(hash[0]);
+ seq.tsoff = hash[1];
+ return seq;
}
u32 secure_ipv4_port_ephemeral(__be32 saddr, __be32 daddr, __be16 dport)
diff --git a/net/ipv4/syncookies.c b/net/ipv4/syncookies.c
index e3c4043..5db13f7 100644
--- a/net/ipv4/syncookies.c
+++ b/net/ipv4/syncookies.c
@@ -334,6 +334,7 @@ struct sock *cookie_v4_check(struct sock *sk, struct sk_buff *skb)
treq = tcp_rsk(req);
treq->rcv_isn = ntohl(th->seq) - 1;
treq->snt_isn = cookie;
+ treq->ts_off = 0;
req->mss = mss;
ireq->ir_num = ntohs(th->dest);
ireq->ir_rmt_port = th->source;
diff --git a/net/ipv4/tcp_input.c b/net/ipv4/tcp_input.c
index 3ebf45b..092f2dd 100644
--- a/net/ipv4/tcp_input.c
+++ b/net/ipv4/tcp_input.c
@@ -6249,6 +6249,7 @@ int tcp_conn_request(struct request_sock_ops *rsk_ops,
goto drop;
tcp_rsk(req)->af_specific = af_ops;
+ tcp_rsk(req)->ts_off = 0;
tcp_clear_options(&tmp_opt);
tmp_opt.mss_clamp = af_ops->mss_clamp;
@@ -6269,6 +6270,9 @@ int tcp_conn_request(struct request_sock_ops *rsk_ops,
if (security_inet_conn_request(sk, skb, req))
goto drop_and_free;
+ if (isn && tmp_opt.tstamp_ok) /* retrans? recompute tsoff */
+ af_ops->init_seq(skb, &tcp_rsk(req)->ts_off);
+
if (!want_cookie && !isn) {
/* VJ's idea. We save last timestamp seen
* from the destination in peer table, when entering
@@ -6309,7 +6313,7 @@ int tcp_conn_request(struct request_sock_ops *rsk_ops,
goto drop_and_release;
}
- isn = af_ops->init_seq(skb);
+ isn = af_ops->init_seq(skb, &tcp_rsk(req)->ts_off);
}
if (!dst) {
dst = af_ops->route_req(sk, &fl, req, NULL);
@@ -6321,6 +6325,7 @@ int tcp_conn_request(struct request_sock_ops *rsk_ops,
if (want_cookie) {
isn = cookie_init_sequence(af_ops, sk, skb, &req->mss);
+ tcp_rsk(req)->ts_off = 0;
req->cookie_ts = tmp_opt.tstamp_ok;
if (!tmp_opt.tstamp_ok)
inet_rsk(req)->ecn_ok = 0;
diff --git a/net/ipv4/tcp_ipv4.c b/net/ipv4/tcp_ipv4.c
index 32b048e..47683c7 100644
--- a/net/ipv4/tcp_ipv4.c
+++ b/net/ipv4/tcp_ipv4.c
@@ -66,6 +66,7 @@
#include <net/net_namespace.h>
#include <net/icmp.h>
#include <net/inet_hashtables.h>
+#include <net/secure_seq.h>
#include <net/tcp.h>
#include <net/transp_v6.h>
#include <net/ipv6.h>
@@ -96,12 +97,16 @@ static int tcp_v4_md5_hash_hdr(char *md5_hash, const struct tcp_md5sig_key *key,
struct inet_hashinfo tcp_hashinfo;
EXPORT_SYMBOL(tcp_hashinfo);
-static __u32 tcp_v4_init_sequence(const struct sk_buff *skb)
+static u32 tcp_v4_init_sequence(const struct sk_buff *skb, u32 *tsoff)
{
- return secure_tcp_sequence_number(ip_hdr(skb)->daddr,
- ip_hdr(skb)->saddr,
- tcp_hdr(skb)->dest,
- tcp_hdr(skb)->source);
+ struct secure_tcp_seq s;
+
+ s = secure_tcp_sequence_number(ip_hdr(skb)->daddr,
+ ip_hdr(skb)->saddr,
+ tcp_hdr(skb)->dest,
+ tcp_hdr(skb)->source);
+ *tsoff = s.tsoff;
+ return s.seq;
}
int tcp_twsk_unique(struct sock *sk, struct sock *sktw, void *twp)
@@ -234,11 +239,16 @@ int tcp_v4_connect(struct sock *sk, struct sockaddr *uaddr, int addr_len)
sk->sk_gso_type = SKB_GSO_TCPV4;
sk_setup_caps(sk, &rt->dst);
- if (!tp->write_seq && likely(!tp->repair))
- tp->write_seq = secure_tcp_sequence_number(inet->inet_saddr,
- inet->inet_daddr,
- inet->inet_sport,
- usin->sin_port);
+ if (!tp->write_seq && likely(!tp->repair)) {
+ struct secure_tcp_seq seq;
+
+ seq = secure_tcp_sequence_number(inet->inet_saddr,
+ inet->inet_daddr,
+ inet->inet_sport,
+ usin->sin_port);
+ tp->write_seq = seq.seq;
+ tp->tsoffset = seq.tsoff;
+ }
inet->inet_id = tp->write_seq ^ jiffies;
diff --git a/net/ipv4/tcp_minisocks.c b/net/ipv4/tcp_minisocks.c
index 4b95ec4..b43ca7e 100644
--- a/net/ipv4/tcp_minisocks.c
+++ b/net/ipv4/tcp_minisocks.c
@@ -530,7 +530,7 @@ struct sock *tcp_create_openreq_child(const struct sock *sk,
newtp->rx_opt.ts_recent_stamp = 0;
newtp->tcp_header_len = sizeof(struct tcphdr);
}
- newtp->tsoffset = 0;
+ newtp->tsoffset = treq->ts_off;
#ifdef CONFIG_TCP_MD5SIG
newtp->md5sig_info = NULL; /*XXX*/
if (newtp->af_specific->md5_lookup(sk, newsk))
@@ -579,6 +579,8 @@ struct sock *tcp_check_req(struct sock *sk, struct sk_buff *skb,
if (tmp_opt.saw_tstamp) {
tmp_opt.ts_recent = req->ts_recent;
+ if (tmp_opt.rcv_tsecr)
+ tmp_opt.rcv_tsecr -= tcp_rsk(req)->ts_off;
/* We do not store true stamp, but it is not required,
* it can be estimated (approximately)
* from another data.
diff --git a/net/ipv4/tcp_output.c b/net/ipv4/tcp_output.c
index bdaef7f..e0e478e 100644
--- a/net/ipv4/tcp_output.c
+++ b/net/ipv4/tcp_output.c
@@ -640,7 +640,7 @@ static unsigned int tcp_synack_options(struct request_sock *req,
}
if (likely(ireq->tstamp_ok)) {
opts->options |= OPTION_TS;
- opts->tsval = tcp_skb_timestamp(skb);
+ opts->tsval = tcp_skb_timestamp(skb) + tcp_rsk(req)->ts_off;
opts->tsecr = req->ts_recent;
remaining -= TCPOLEN_TSTAMP_ALIGNED;
}
diff --git a/net/ipv6/syncookies.c b/net/ipv6/syncookies.c
index 59c4839..241d40e 100644
--- a/net/ipv6/syncookies.c
+++ b/net/ipv6/syncookies.c
@@ -209,6 +209,7 @@ struct sock *cookie_v6_check(struct sock *sk, struct sk_buff *skb)
treq->snt_synack.v64 = 0;
treq->rcv_isn = ntohl(th->seq) - 1;
treq->snt_isn = cookie;
+ treq->ts_off = 0;
/*
* We need to lookup the dst_entry to get the correct window size.
diff --git a/net/ipv6/tcp_ipv6.c b/net/ipv6/tcp_ipv6.c
index 33df8b8..5cf7aa9 100644
--- a/net/ipv6/tcp_ipv6.c
+++ b/net/ipv6/tcp_ipv6.c
@@ -101,12 +101,16 @@ static void inet6_sk_rx_dst_set(struct sock *sk, const struct sk_buff *skb)
}
}
-static __u32 tcp_v6_init_sequence(const struct sk_buff *skb)
+static u32 tcp_v6_init_sequence(const struct sk_buff *skb, u32 *tsoff)
{
- return secure_tcpv6_sequence_number(ipv6_hdr(skb)->daddr.s6_addr32,
- ipv6_hdr(skb)->saddr.s6_addr32,
- tcp_hdr(skb)->dest,
- tcp_hdr(skb)->source);
+ struct secure_tcp_seq s;
+
+ s = secure_tcpv6_sequence_number(ipv6_hdr(skb)->daddr.s6_addr32,
+ ipv6_hdr(skb)->saddr.s6_addr32,
+ tcp_hdr(skb)->dest,
+ tcp_hdr(skb)->source);
+ *tsoff = s.tsoff;
+ return s.seq;
}
static int tcp_v6_connect(struct sock *sk, struct sockaddr *uaddr,
@@ -278,12 +282,16 @@ static int tcp_v6_connect(struct sock *sk, struct sockaddr *uaddr,
sk_set_txhash(sk);
- if (!tp->write_seq && likely(!tp->repair))
- tp->write_seq = secure_tcpv6_sequence_number(np->saddr.s6_addr32,
- sk->sk_v6_daddr.s6_addr32,
- inet->inet_sport,
- inet->inet_dport);
+ if (!tp->write_seq && likely(!tp->repair)) {
+ struct secure_tcp_seq seq;
+ seq = secure_tcpv6_sequence_number(np->saddr.s6_addr32,
+ sk->sk_v6_daddr.s6_addr32,
+ inet->inet_sport,
+ inet->inet_dport);
+ tp->write_seq = seq.seq;
+ tp->tsoffset = seq.tsoff;
+ }
err = tcp_connect(sk);
if (err)
goto late_failure;
--
2.7.3
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