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tcp: randomize tcp timestamp offsets for each connection

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jiffies based timestamps allow for easy inference of number of devices
behind NAT translators and also makes tracking of hosts simpler.

commit ceaa1fef65 ("tcp: adding a per-socket timestamp offset")
added the main infrastructure that is needed for per-connection ts
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, i.e. PAWS will still work.

Includes fixes from Eric Dumazet.

Signed-off-by: Florian Westphal <fw@strlen.de>
Acked-by: Eric Dumazet <edumazet@google.com>
Acked-by: Yuchung Cheng <ycheng@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
This commit is contained in:
Florian Westphal 2016-12-01 11:32:06 +01:00 committed by David S. Miller
parent 7df5358d47
commit 95a22caee3
11 changed files with 35 additions and 20 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

1
include/linux/tcp.h
View File

@ -123,6 +123,7 @@ 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#

8
include/net/secure_seq.h
View File

@ -6,10 +6,10 @@
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);
u32 secure_tcp_sequence_number(__be32 saddr, __be32 daddr,
__be16 sport, __be16 dport, u32 *tsoff);
u32 secure_tcpv6_sequence_number(const __be32 *saddr, const __be32 *daddr,
__be16 sport, __be16 dport, u32 *tsoff);
u64 secure_dccp_sequence_number(__be32 saddr, __be32 daddr,
__be16 sport, __be16 dport);
u64 secure_dccpv6_sequence_number(__be32 *saddr, __be32 *daddr,

2
include/net/tcp.h
View File

@ -1827,7 +1827,7 @@ 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,

10
net/core/secure_seq.c
View File

@ -40,8 +40,8 @@ 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)
u32 secure_tcpv6_sequence_number(const __be32 *saddr, const __be32 *daddr,
__be16 sport, __be16 dport, u32 *tsoff)
{
u32 secret[MD5_MESSAGE_BYTES / 4];
u32 hash[MD5_DIGEST_WORDS];
@ -58,6 +58,7 @@ __u32 secure_tcpv6_sequence_number(const __be32 *saddr, const __be32 *daddr,
md5_transform(hash, secret);
*tsoff = hash[1];
return seq_scale(hash[0]);
}
EXPORT_SYMBOL(secure_tcpv6_sequence_number);
@ -86,8 +87,8 @@ EXPORT_SYMBOL(secure_ipv6_port_ephemeral);
#ifdef CONFIG_INET
__u32 secure_tcp_sequence_number(__be32 saddr, __be32 daddr,
__be16 sport, __be16 dport)
u32 secure_tcp_sequence_number(__be32 saddr, __be32 daddr,
__be16 sport, __be16 dport, u32 *tsoff)
{
u32 hash[MD5_DIGEST_WORDS];
@ -99,6 +100,7 @@ __u32 secure_tcp_sequence_number(__be32 saddr, __be32 daddr,
md5_transform(hash, net_secret);
*tsoff = hash[1];
return seq_scale(hash[0]);
}

1
net/ipv4/syncookies.c
View File

@ -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;

7
net/ipv4/tcp_input.c
View File

@ -6307,6 +6307,7 @@ 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;
@ -6328,6 +6329,9 @@ 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)
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
@ -6368,7 +6372,7 @@ 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);
@ -6380,6 +6384,7 @@ 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;

9
net/ipv4/tcp_ipv4.c
View File

@ -95,12 +95,12 @@ 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);
tcp_hdr(skb)->source, tsoff);
}
int tcp_twsk_unique(struct sock *sk, struct sock *sktw, void *twp)
@ -237,7 +237,8 @@ int tcp_v4_connect(struct sock *sk, struct sockaddr *uaddr, int addr_len)
tp->write_seq = secure_tcp_sequence_number(inet->inet_saddr,
inet->inet_daddr,
inet->inet_sport,
usin->sin_port);
usin->sin_port,
&tp->tsoffset);
inet->inet_id = tp->write_seq ^ jiffies;
@ -824,7 +825,7 @@ static void tcp_v4_reqsk_send_ack(const struct sock *sk, struct sk_buff *skb,
tcp_v4_send_ack(sk, skb, seq,
tcp_rsk(req)->rcv_nxt,
req->rsk_rcv_wnd >> inet_rsk(req)->rcv_wscale,
tcp_time_stamp,
tcp_time_stamp + tcp_rsk(req)->ts_off,
req->ts_recent,
0,
tcp_md5_do_lookup(sk, (union tcp_md5_addr *)&ip_hdr(skb)->daddr,

4
net/ipv4/tcp_minisocks.c
View File

@ -532,7 +532,7 @@ 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))
@ -581,6 +581,8 @@ 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.

2
net/ipv4/tcp_output.c
View File

@ -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;
}

1
net/ipv6/syncookies.c
View File

@ -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.

10
net/ipv6/tcp_ipv6.c
View File

@ -101,12 +101,12 @@ 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);
tcp_hdr(skb)->source, tsoff);
}
static int tcp_v6_connect(struct sock *sk, struct sockaddr *uaddr,
@ -283,7 +283,8 @@ static int tcp_v6_connect(struct sock *sk, struct sockaddr *uaddr,
tp->write_seq = secure_tcpv6_sequence_number(np->saddr.s6_addr32,
sk->sk_v6_daddr.s6_addr32,
inet->inet_sport,
inet->inet_dport);
inet->inet_dport,
&tp->tsoffset);
err = tcp_connect(sk);
if (err)
@ -956,7 +957,8 @@ static void tcp_v6_reqsk_send_ack(const struct sock *sk, struct sk_buff *skb,
tcp_rsk(req)->snt_isn + 1 : tcp_sk(sk)->snd_nxt,
tcp_rsk(req)->rcv_nxt,
req->rsk_rcv_wnd >> inet_rsk(req)->rcv_wscale,
tcp_time_stamp, req->ts_recent, sk->sk_bound_dev_if,
tcp_time_stamp + tcp_rsk(req)->ts_off,
req->ts_recent, sk->sk_bound_dev_if,
tcp_v6_md5_do_lookup(sk, &ipv6_hdr(skb)->daddr),
0, 0);
}