RFC 1337 describes various TCP (side channel) attacks against prematurely closed connections stalling in TIME-WAIT state, such as DoS or injecting arbitrary TCP segments, and recommends to silently discard RST packets for sockets in this state.
While applications still tied to such sockets should tolerate invalid input (thanks to Jon Postel), there is little legitimate reason to send such RST packets altogether.
At the time of writing, no collateral damage related to active RFC 1337 implementations is known. Measuerements in productive environments did not reveal any side effects either, which is why I consider enabling RFC 1337 implementation to be a safe change.
See also: https://tools.ietf.org/html/rfc1337
Signed-off-by: Peter Müller peter.mueller@ipfire.org --- config/etc/sysctl.conf | 11 ++++++++--- 1 file changed, 8 insertions(+), 3 deletions(-)
diff --git a/config/etc/sysctl.conf b/config/etc/sysctl.conf index 7e7ebee44..d48c7734e 100644 --- a/config/etc/sysctl.conf +++ b/config/etc/sysctl.conf @@ -32,7 +32,7 @@ net.ipv6.conf.all.disable_ipv6 = 1 net.ipv6.conf.default.disable_ipv6 = 1
# Enable netfilter accounting -net.netfilter.nf_conntrack_acct=1 +net.netfilter.nf_conntrack_acct = 1
# Disable netfilter on bridges. net.bridge.bridge-nf-call-ip6tables = 0 @@ -86,10 +86,15 @@ net.ipv4.tcp_wmem = 4096 16384 16777216 net.ipv4.udp_mem = 3145728 4194304 16777216
# Prefer low latency over higher throughput -net.ipv4.tcp_low_latency=1 +net.ipv4.tcp_low_latency = 1
# Reserve more socket space for the TCP window -net.ipv4.tcp_adv_win_scale=2 +net.ipv4.tcp_adv_win_scale = 2
# Enable TCP fast-open net.ipv4.tcp_fastopen = 3 + +# Drop RST packets for sockets in TIME-WAIT state, as described in RFC 1337. +# This protects against various TCP attacks, such as DoS against or injection +# of arbitrary segments into prematurely closed connections. +net.ipv4.tcp_rfc1337 = 1
Thank you.
Would you please propose the same for IPFire 3?
-Michael
On 30 Sep 2020, at 15:46, Peter Müller peter.mueller@ipfire.org wrote:
RFC 1337 describes various TCP (side channel) attacks against prematurely closed connections stalling in TIME-WAIT state, such as DoS or injecting arbitrary TCP segments, and recommends to silently discard RST packets for sockets in this state.
While applications still tied to such sockets should tolerate invalid input (thanks to Jon Postel), there is little legitimate reason to send such RST packets altogether.
At the time of writing, no collateral damage related to active RFC 1337 implementations is known. Measuerements in productive environments did not reveal any side effects either, which is why I consider enabling RFC 1337 implementation to be a safe change.
See also: https://tools.ietf.org/html/rfc1337
Signed-off-by: Peter Müller peter.mueller@ipfire.org
config/etc/sysctl.conf | 11 ++++++++--- 1 file changed, 8 insertions(+), 3 deletions(-)
diff --git a/config/etc/sysctl.conf b/config/etc/sysctl.conf index 7e7ebee44..d48c7734e 100644 --- a/config/etc/sysctl.conf +++ b/config/etc/sysctl.conf @@ -32,7 +32,7 @@ net.ipv6.conf.all.disable_ipv6 = 1 net.ipv6.conf.default.disable_ipv6 = 1
# Enable netfilter accounting -net.netfilter.nf_conntrack_acct=1 +net.netfilter.nf_conntrack_acct = 1
# Disable netfilter on bridges. net.bridge.bridge-nf-call-ip6tables = 0 @@ -86,10 +86,15 @@ net.ipv4.tcp_wmem = 4096 16384 16777216 net.ipv4.udp_mem = 3145728 4194304 16777216
# Prefer low latency over higher throughput -net.ipv4.tcp_low_latency=1 +net.ipv4.tcp_low_latency = 1
# Reserve more socket space for the TCP window -net.ipv4.tcp_adv_win_scale=2 +net.ipv4.tcp_adv_win_scale = 2
# Enable TCP fast-open net.ipv4.tcp_fastopen = 3
+# Drop RST packets for sockets in TIME-WAIT state, as described in RFC 1337. +# This protects against various TCP attacks, such as DoS against or injection +# of arbitrary segments into prematurely closed connections.
+net.ipv4.tcp_rfc1337 = 1
2.26.2
-
Michael Tremer -
Peter Müller