inet: stop leaking jiffies on the wire

Historically linux tried to stick to RFC 791, 1122, 2003
for IPv4 ID field generation.

RFC 6864 made clear that no matter how hard we try,
we can not ensure unicity of IP ID within maximum
lifetime for all datagrams with a given source
address/destination address/protocol tuple.

Linux uses a per socket inet generator (inet_id), initialized
at connection startup with a XOR of 'jiffies' and other
fields that appear clear on the wire.

Thiemo Nagel pointed that this strategy is a privacy
concern as this provides 16 bits of entropy to fingerprint
devices.

Let's switch to a random starting point, this is just as
good as far as RFC 6864 is concerned and does not leak
anything critical.

Fixes: 1da177e4c3f4 ("Linux-2.6.12-rc2")
Signed-off-by: Eric Dumazet <edumazet@google.com>
Reported-by: Thiemo Nagel <tnagel@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

4 files changed, 5 insertions, 5 deletions

diff --git a/net/dccp/ipv4.c b/net/dccp/ipv4.c
index d9b4200ed12d..0d8f782c25cc 100644
--- a/net/dccp/ipv4.c
+++ b/net/dccp/ipv4.c
@@ -117,7 +117,7 @@ int dccp_v4_connect(struct sock *sk, struct sockaddr *uaddr, int addr_len)
                                                     inet->inet_daddr,
                                                     inet->inet_sport,
                                                     inet->inet_dport);
-        inet->inet_id = dp->dccps_iss ^ jiffies;
+        inet->inet_id = prandom_u32();
 
         err = dccp_connect(sk);
         rt = NULL;
diff --git a/net/ipv4/datagram.c b/net/ipv4/datagram.c
index 9a0fe0c2fa02..4a8550c49202 100644
--- a/net/ipv4/datagram.c
+++ b/net/ipv4/datagram.c
@@ -73,7 +73,7 @@ int __ip4_datagram_connect(struct sock *sk, struct sockaddr *uaddr, int addr_len
         reuseport_has_conns(sk, true);
         sk->sk_state = TCP_ESTABLISHED;
         sk_set_txhash(sk);
-        inet->inet_id = jiffies;
+        inet->inet_id = prandom_u32();
 
         sk_dst_set(sk, &rt->dst);
         err = 0;
diff --git a/net/ipv4/tcp_ipv4.c b/net/ipv4/tcp_ipv4.c
index b74192695955..67b2dc7a1727 100644
--- a/net/ipv4/tcp_ipv4.c
+++ b/net/ipv4/tcp_ipv4.c
@@ -303,7 +303,7 @@ int tcp_v4_connect(struct sock *sk, struct sockaddr *uaddr, int addr_len)
                                                  inet->inet_daddr);
         }
 
-        inet->inet_id = tp->write_seq ^ jiffies;
+        inet->inet_id = prandom_u32();
 
         if (tcp_fastopen_defer_connect(sk, &err))
                 return err;
@@ -1450,7 +1450,7 @@ struct sock *tcp_v4_syn_recv_sock(const struct sock *sk, struct sk_buff *skb,
         inet_csk(newsk)->icsk_ext_hdr_len = 0;
         if (inet_opt)
                 inet_csk(newsk)->icsk_ext_hdr_len = inet_opt->opt.optlen;
-        newinet->inet_id = newtp->write_seq ^ jiffies;
+        newinet->inet_id = prandom_u32();
 
         if (!dst) {
                 dst = inet_csk_route_child_sock(sk, newsk, req);
diff --git a/net/sctp/socket.c b/net/sctp/socket.c
index ca81e06df165..ffd3262b7a41 100644
--- a/net/sctp/socket.c
+++ b/net/sctp/socket.c
@@ -9306,7 +9306,7 @@ void sctp_copy_sock(struct sock *newsk, struct sock *sk,
         newinet->inet_rcv_saddr = inet->inet_rcv_saddr;
         newinet->inet_dport = htons(asoc->peer.port);
         newinet->pmtudisc = inet->pmtudisc;
-        newinet->inet_id = asoc->next_tsn ^ jiffies;
+        newinet->inet_id = prandom_u32();
 
         newinet->uc_ttl = inet->uc_ttl;
         newinet->mc_loop = 1;