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inet: stop leaking jiffies on the wire

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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: 1da177e4c3 ("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>
This commit is contained in:
Eric Dumazet 2019-11-01 10:32:19 -07:00 committed by David S. Miller
parent c8c2cd8102
commit a904a0693c
5 changed files with 6 additions and 6 deletions
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2
drivers/crypto/chelsio/chtls/chtls_cm.c
View File

@ -1297,7 +1297,7 @@ static void make_established(struct sock *sk, u32 snd_isn, unsigned int opt)
tp->write_seq = snd_isn;
tp->snd_nxt = snd_isn;
tp->snd_una = snd_isn;
inet_sk(sk)->inet_id = tp->write_seq ^ jiffies;
inet_sk(sk)->inet_id = prandom_u32();
assign_rxopt(sk, opt);
if (tp->rcv_wnd > (RCV_BUFSIZ_M << 10))

2
net/dccp/ipv4.c
View File

@ -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;

2
net/ipv4/datagram.c
View File

@ -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;

4
net/ipv4/tcp_ipv4.c
View File

@ -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);

2
net/sctp/socket.c
View File

@ -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;