From: Eric Dumazet <edumazet@google.com>
Date: Fri, 1 Nov 2019 17:32:19 +0000 (-0700)
Subject: inet: stop leaking jiffies on the wire
X-Git-Url: https://git.stricted.de/?a=commitdiff_plain;h=4fa6002a34db62f5a5d536f30fc9dedd1ce7ee84;p=GitHub%2FLineageOS%2Fandroid_kernel_motorola_exynos9610.git

inet: stop leaking jiffies on the wire

[ Upstream commit a904a0693c189691eeee64f6c6b188bd7dc244e9 ]

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>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---

diff --git a/net/dccp/ipv4.c b/net/dccp/ipv4.c
index 17afa03cab3a..176bddacc16e 100644
--- a/net/dccp/ipv4.c
+++ b/net/dccp/ipv4.c
@@ -121,7 +121,7 @@ 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 f915abff1350..d3eddfd13875 100644
--- a/net/ipv4/datagram.c
+++ b/net/ipv4/datagram.c
@@ -75,7 +75,7 @@ int __ip4_datagram_connect(struct sock *sk, struct sockaddr *uaddr, int addr_len
 	inet->inet_dport = usin->sin_port;
 	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 0569718e3656..44a41ac2b0ca 100644
--- a/net/ipv4/tcp_ipv4.c
+++ b/net/ipv4/tcp_ipv4.c
@@ -245,7 +245,7 @@ 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;
@@ -1368,7 +1368,7 @@ 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 d1c917851b0c..09cda66d0567 100644
--- a/net/sctp/socket.c
+++ b/net/sctp/socket.c
@@ -8136,7 +8136,7 @@ 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;