openstack/octavia
Code Issues Proposed changes

Make SSH bind to management net only

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Our present amphora image create scripts set up the ssh daemon on the
amphora to bind to the wildcard interface (which is the default).
However, this causes problems for anyone who tries to set up a listener
on TCP port 22, since haproxy will not be able to bind to the same IP.

This patch introduces a dhclient post-bind script to the amphora image
to gracefully rebind the SSH-daemon to only the load balancer management
net IP when it comes up on the network, solving the above use case. This
patch has the secondary benefit of making the amphora's SSH daemon only
respond to requests on the management network, which incrementally
increases the security of the amphora.

Change-Id: Iab93cec1f4dc4a2e37ad3cb8a92c132383dcda6a
Closes-Bug: #1551505
This commit is contained in:
Stephen Balukoff 2016-03-04 01:15:15 -08:00
parent 5c8ebf0784
commit 81c73bd1b5
3 changed files with 20 additions and 0 deletions
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1
diskimage-create/diskimage-create.sh
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@ -329,6 +329,7 @@ fi
# Add the Octavia keepalived, Amphora Agent and Pyroute elements
if [ "$AMP_BASEOS" = "ubuntu" ]; then
AMP_element_sequence="$AMP_element_sequence rebind-sshd"
AMP_element_sequence="$AMP_element_sequence no-resolvconf"
AMP_element_sequence="$AMP_element_sequence amphora-agent-ubuntu"
AMP_element_sequence="$AMP_element_sequence pyroute2"

8
elements/rebind-sshd/README.rst Normal file
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@ -0,0 +1,8 @@
This element adds a post-BOUND script to the dhclient configuration to rebind
the ssh daemon to listen only on the management network interface. The reason
for doing this is that some use cases require load balancing services on TCP
port 22 to work, and if SSH binds to the wildcard address on port 22, then
haproxy can't.
This also has the secondary benefit of making the amphora slightly more secure
as its SSH daemon will only respond to requests on the management network.

11
elements/rebind-sshd/finalise.d/98-rebind-sshd-after-dhcp Executable file
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@ -0,0 +1,11 @@
#!/bin/bash
echo '#!/bin/sh
if [ "$reason" = "BOUND" ]; then
if `grep -q "#ListenAddress 0.0.0.0" /etc/ssh/sshd_config`; then
/bin/sed -i "s/^#ListenAddress 0.0.0.0.*$/ListenAddress $new_ip_address/g" /etc/ssh/sshd_config
if `/bin/ps -ef|/bin/grep -v grep|/bin/grep -q sshd`; then
/usr/sbin/service ssh restart
fi
fi
fi' > /etc/dhcp/dhclient-enter-hooks.d/rebind-sshd
chmod +x /etc/dhcp/dhclient-enter-hooks.d/rebind-sshd