From: Eric Dumazet edumazet@google.com
[ 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 --- net/dccp/ipv4.c | 2 +- net/ipv4/datagram.c | 2 +- net/ipv4/tcp_ipv4.c | 4 ++-- net/sctp/socket.c | 2 +- 4 files changed, 5 insertions(+), 5 deletions(-)
--- a/net/dccp/ipv4.c +++ b/net/dccp/ipv4.c @@ -121,7 +121,7 @@ int dccp_v4_connect(struct sock *sk, str 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; --- a/net/ipv4/datagram.c +++ b/net/ipv4/datagram.c @@ -75,7 +75,7 @@ int __ip4_datagram_connect(struct sock * 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; --- a/net/ipv4/tcp_ipv4.c +++ b/net/ipv4/tcp_ipv4.c @@ -239,7 +239,7 @@ int tcp_v4_connect(struct sock *sk, stru inet->inet_sport, usin->sin_port);
- inet->inet_id = tp->write_seq ^ jiffies; + inet->inet_id = prandom_u32();
err = tcp_connect(sk);
@@ -1307,7 +1307,7 @@ struct sock *tcp_v4_syn_recv_sock(const 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); --- a/net/sctp/socket.c +++ b/net/sctp/socket.c @@ -7734,7 +7734,7 @@ void sctp_copy_sock(struct sock *newsk, 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;