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Eric Dumazet 04ca6973f7 ip: make IP identifiers less predictable 
In "Counting Packets Sent Between Arbitrary Internet Hosts", Jeffrey and
Jedidiah describe ways exploiting linux IP identifier generation to
infer whether two machines are exchanging packets.

With commit 73f156a6e8 ("inetpeer: get rid of ip_id_count"), we
changed IP id generation, but this does not really prevent this
side-channel technique.

This patch adds a random amount of perturbation so that IP identifiers
for a given destination [1] are no longer monotonically increasing after
an idle period.

Note that prandom_u32_max(1) returns 0, so if generator is used at most
once per jiffy, this patch inserts no hole in the ID suite and do not
increase collision probability.

This is jiffies based, so in the worst case (HZ=1000), the id can
rollover after ~65 seconds of idle time, which should be fine.

We also change the hash used in __ip_select_ident() to not only hash
on daddr, but also saddr and protocol, so that ICMP probes can not be
used to infer information for other protocols.

For IPv6, adds saddr into the hash as well, but not nexthdr.

If I ping the patched target, we can see ID are now hard to predict.

21:57:11.008086 IP (...)
    A > target: ICMP echo request, seq 1, length 64
21:57:11.010752 IP (... id 2081 ...)
    target > A: ICMP echo reply, seq 1, length 64

21:57:12.013133 IP (...)
    A > target: ICMP echo request, seq 2, length 64
21:57:12.015737 IP (... id 3039 ...)
    target > A: ICMP echo reply, seq 2, length 64

21:57:13.016580 IP (...)
    A > target: ICMP echo request, seq 3, length 64
21:57:13.019251 IP (... id 3437 ...)
    target > A: ICMP echo reply, seq 3, length 64

[1] TCP sessions uses a per flow ID generator not changed by this patch.

Signed-off-by: Eric Dumazet <edumazet@google.com>
Reported-by: Jeffrey Knockel <jeffk@cs.unm.edu>
Reported-by: Jedidiah R. Crandall <crandall@cs.unm.edu>
Cc: Willy Tarreau <w@1wt.eu>
Cc: Hannes Frederic Sowa <hannes@redhat.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
 		2014-07-28 18:46:34 -07:00
..
netfilter Merge git://git.kernel.org/pub/scm/linux/kernel/git/pablo/nf-next 2014-05-30 17:54:47 -07:00
Kconfig net: neighbour: Remove CONFIG_ARPD 2013-09-03 21:41:43 -04:00
Makefile xfrm4: Add IPsec protocol multiplexer 2014-02-25 07:04:16 +01:00
af_inet.c net-gre-gro: Fix a bug that breaks the forwarding path 2014-07-16 14:45:26 -07:00
ah4.c ah4: Use the IPsec protocol multiplexer API 2014-02-25 07:04:17 +01:00
arp.c ipv4: arp: update neighbour address when a gratuitous arp is received and arp_accept is set 2014-01-02 00:08:38 -05:00
cipso_ipv4.c ipv4: ERROR: code indent should use tabs where possible 2013-12-26 13:43:21 -05:00
datagram.c ipv4: fix a race in ip4_datagram_release_cb() 2014-06-11 15:39:18 -07:00
devinet.c ipv4: minor spelling fix 2014-05-18 21:10:29 -04:00
esp4.c esp4: Use the IPsec protocol multiplexer API 2014-02-25 07:04:17 +01:00
fib_frontend.c ipv4, fib: pass LOOPBACK_IFINDEX instead of 0 to flowi4_iif 2014-04-16 15:05:11 -04:00
fib_lookup.h ipv4: make fib_detect_death static 2013-12-28 17:01:46 -05:00
fib_rules.c inet: fix NULL pointer Oops in fib(6)_rule_suppress 2013-12-10 17:54:23 -05:00
fib_semantics.c ipv4: fib_semantics: increment fib_info_cnt after fib_info allocation 2014-05-07 17:14:32 -04:00
fib_trie.c net: Revert "fib_trie: use seq_file_net rather than seq->private" 2014-06-04 15:11:41 -07:00
gre_demux.c GRE: enable offloads for GRE 2014-07-11 13:53:39 -07:00
gre_offload.c net-gre-gro: Fix a bug that breaks the forwarding path 2014-07-16 14:45:26 -07:00
icmp.c ipv4: icmp: Fix pMTU handling for rare case 2014-07-07 17:22:57 -07:00
igmp.c igmp: fix the problem when mc leave group 2014-07-07 21:30:55 -07:00
inet_connection_sock.c ipv4: make ip_local_reserved_ports per netns 2014-05-14 15:31:45 -04:00
inet_diag.c inet_diag: fix inet_diag_dump_icsk() to use correct state for timewait sockets 2014-01-13 22:35:46 -08:00
inet_fragment.c inet: frag: make sure forced eviction removes all frags 2014-03-06 15:28:45 -05:00
inet_hashtables.c net: Use a more standard macro for INET_ADDR_COOKIE 2014-05-14 16:07:23 -04:00
inet_lro.c lro: remove dead code 2013-12-29 16:34:25 -05:00
inet_timewait_sock.c tcp/dccp: remove twchain 2013-10-08 23:19:24 -04:00
inetpeer.c Merge git://git.kernel.org/pub/scm/linux/kernel/git/davem/net-next 2014-06-12 14:27:40 -07:00
ip_forward.c net: rename local_df to ignore_df 2014-05-12 14:03:41 -04:00
ip_fragment.c ipv4: fix "conntrack zones" support for defrag user check in ip_expire 2014-05-05 16:02:59 +02:00
ip_gre.c gre: allow changing mac address when device is up 2014-06-10 22:46:42 -07:00
ip_input.c net: Fix memory leak if TPROXY used with TCP early demux 2014-01-27 16:22:11 -08:00
ip_options.c ipv4: fix buffer overflow in ip_options_compile() 2014-07-21 20:16:26 -07:00
ip_output.c inetpeer: get rid of ip_id_count 2014-06-02 11:00:41 -07:00
ip_sockglue.c ipv4: yet another new IP_MTU_DISCOVER option IP_PMTUDISC_OMIT 2014-02-26 15:51:00 -05:00
ip_tunnel.c ip_tunnel: fix ip_tunnel_lookup 2014-07-08 19:35:09 -07:00
ip_tunnel_core.c net: Support for multiple checksums with gso 2014-06-04 22:46:38 -07:00
ip_vti.c ip_vti: Fix 'ip tunnel add' with 'key' parameters 2014-06-11 00:30:52 -07:00
ipcomp.c ipcomp4: Use the IPsec protocol multiplexer API 2014-02-25 07:04:17 +01:00
ipconfig.c ipv4: ipconfig.c: add parentheses in an if statement 2014-02-14 00:14:23 -05:00
ipip.c Merge git://git.kernel.org/pub/scm/linux/kernel/git/davem/net 2014-06-11 16:02:55 -07:00
ipmr.c inetpeer: get rid of ip_id_count 2014-06-02 11:00:41 -07:00
netfilter.c netfilter: remove double colon 2014-02-19 11:41:25 +01:00
ping.c ping: move ping_group_range out of CONFIG_SYSCTL 2014-05-08 22:50:47 -04:00
proc.c net: clean up snmp stats code 2014-05-07 16:06:05 -04:00
protocol.c net: remove outdated comment for ipv4 and ipv6 protocol handler 2013-11-28 18:47:51 -05:00
raw.c inetpeer: get rid of ip_id_count 2014-06-02 11:00:41 -07:00
route.c ip: make IP identifiers less predictable 2014-07-28 18:46:34 -07:00
syncookies.c net: support marking accepting TCP sockets 2014-05-13 18:35:09 -04:00
sysctl_net_ipv4.c ipv4: make ip_local_reserved_ports per netns 2014-05-14 15:31:45 -04:00
tcp.c tcp: Fix divide by zero when pushing during tcp-repair 2014-07-02 18:21:03 -07:00
tcp_bic.c tcp: remove in_flight parameter from cong_avoid() methods 2014-05-03 19:23:07 -04:00
tcp_cong.c tcp: remove in_flight parameter from cong_avoid() methods 2014-05-03 19:23:07 -04:00
tcp_cubic.c Merge git://git.kernel.org/pub/scm/linux/kernel/git/davem/net 2014-05-12 13:19:14 -04:00
tcp_diag.c inet_diag: Rename inet_diag_req into inet_diag_req_v2 2012-01-11 12:56:06 -08:00
tcp_fastopen.c tcp: remove unnecessary tcp_sk assignment. 2014-06-16 21:35:00 -07:00
tcp_highspeed.c tcp: remove in_flight parameter from cong_avoid() methods 2014-05-03 19:23:07 -04:00
tcp_htcp.c tcp: remove in_flight parameter from cong_avoid() methods 2014-05-03 19:23:07 -04:00
tcp_hybla.c tcp: remove in_flight parameter from cong_avoid() methods 2014-05-03 19:23:07 -04:00
tcp_illinois.c tcp: remove in_flight parameter from cong_avoid() methods 2014-05-03 19:23:07 -04:00
tcp_input.c tcp: fix false undo corner cases 2014-07-07 21:40:48 -07:00
tcp_ipv4.c net: support marking accepting TCP sockets 2014-05-13 18:35:09 -04:00
tcp_lp.c tcp: remove in_flight parameter from cong_avoid() methods 2014-05-03 19:23:07 -04:00
tcp_memcontrol.c cgroup: replace cftype->trigger() with cftype->write() 2014-05-13 12:16:21 -04:00
tcp_metrics.c net: use the new API kvfree() 2014-06-05 00:49:51 -07:00
tcp_minisocks.c tcp: use tcp_v4_send_synack on first SYN-ACK 2014-05-13 17:53:02 -04:00
tcp_offload.c net-gre-gro: Fix a bug that breaks the forwarding path 2014-07-16 14:45:26 -07:00
tcp_output.c tcp: fix false undo corner cases 2014-07-07 21:40:48 -07:00
tcp_probe.c tcp: switch rtt estimations to usec resolution 2014-02-26 17:08:40 -05:00
tcp_scalable.c tcp: remove in_flight parameter from cong_avoid() methods 2014-05-03 19:23:07 -04:00
tcp_timer.c tcp: snmp stats for Fast Open, SYN rtx, and data pkts 2014-03-03 15:58:03 -05:00
tcp_vegas.c tcp: remove in_flight parameter from cong_avoid() methods 2014-05-03 19:23:07 -04:00
tcp_vegas.h net: ipv4/ipv6: Remove extern from function prototypes 2013-10-19 19:12:11 -04:00
tcp_veno.c tcp: remove in_flight parameter from cong_avoid() methods 2014-05-03 19:23:07 -04:00
tcp_westwood.c tcp: remove unused min_cwnd member of tcp_congestion_ops 2014-02-13 18:22:34 -05:00
tcp_yeah.c tcp: remove in_flight parameter from cong_avoid() methods 2014-05-03 19:23:07 -04:00
tunnel4.c net: Convert printks to pr_<level> 2012-03-11 23:42:51 -07:00
udp.c udp: Add MIB counters for rcvbuferrors 2014-06-27 00:20:55 -07:00
udp_diag.c netlink: rename ssk to sk in struct netlink_skb_params 2013-04-19 14:57:56 -04:00
udp_impl.h net: ipv4/ipv6: Remove extern from function prototypes 2013-10-19 19:12:11 -04:00
udp_offload.c net: Add skb_gro_postpull_rcsum to udp and vxlan 2014-06-11 15:46:13 -07:00
udplite.c net: Eliminate no_check from protosw 2014-05-23 16:28:53 -04:00
xfrm4_input.c xfrm4: Add IPsec protocol multiplexer 2014-02-25 07:04:16 +01:00
xfrm4_mode_beet.c ipv4: ERROR: code indent should use tabs where possible 2013-12-26 13:43:21 -05:00
xfrm4_mode_transport.c
…
xfrm4_mode_tunnel.c inetpeer: get rid of ip_id_count 2014-06-02 11:00:41 -07:00
xfrm4_output.c Merge git://git.kernel.org/pub/scm/linux/kernel/git/davem/net 2014-05-24 00:32:30 -04:00
xfrm4_policy.c xfrm: Introduce xfrm_input_afinfo to access the the callbacks properly 2014-03-14 07:28:07 +01:00
xfrm4_protocol.c xfrm4: Properly handle unsupported protocols 2014-04-29 08:41:12 +02:00
xfrm4_state.c inet: make no_pmtu_disc per namespace and kill ipv4_config 2013-12-18 16:58:20 -05:00
xfrm4_tunnel.c sit: add IPv4 over IPv4 support 2013-05-31 17:19:05 -07:00