Public bug reported: A Nexpose scan of Ubuntu 16.04 lists a number of insecure configurations, including ICMP redirection, source routing, and forwarding. Inspection shows that net.ipv4.conf.default enables these things.
RHEL 6 documentation suggests shutting down source routing, forwarding, and ICMP redirects of any kind, as per the below: https://access.redhat.com/documentation/en- US/Red_Hat_Enterprise_Linux/6/html/Security_Guide/sect-Security_Guide- Server_Security-Disable-Source-Routing.html Adjusting these settings can have detrimental effects on a live system. For example: disabling forwarding over the docker0 interface breaks Docker. As a sane default, I recommend loading default settings during system boot, which will create network interfaces with those settings and allow later processes to enable these features as-needed. I recommend the following settings in /etc/sysctl.conf: # Disable forwarding by default net.ipv4.conf.default.forwarding=0 net.ipv6.conf.default.forwarding=0 # Multicast forwarding net.ipv4.conf.default.mc_forwarding=0 net.ipv6.conf.default.mc_forwarding=0 # Do not accept ICMP redirects (prevent MITM attacks) net.ipv4.conf.default.accept_redirects = 0 net.ipv6.conf.default.accept_redirects = 0 net.ipv4.conf.default.secure_redirects = 0 net.ipv6.conf.default.secure_redirects = 0 # Do not send ICMP redirects (we are not a router) net.ipv4.conf.default.send_redirects = 0 net.ipv6.conf.default.send_redirects = 0 # Do not accept IP source route packets (we are not a router) net.ipv4.conf.default.accept_source_route = 0 net.ipv6.conf.default.accept_source_route = 0 net.ipv4.conf.default.rp_filter=1 Take note: Setting net.ipv4.conf.default.forarding=0 here somehow doesn't have any effect; the other settings do. Perhaps bug #84537 is in effect? ** Affects: procps (Ubuntu) Importance: Undecided Status: New -- You received this bug notification because you are a member of Ubuntu Bugs, which is subscribed to Ubuntu. https://bugs.launchpad.net/bugs/1676540 Title: Enable secure networking defaults in sysctl.conf To manage notifications about this bug go to: https://bugs.launchpad.net/ubuntu/+source/procps/+bug/1676540/+subscriptions -- ubuntu-bugs mailing list [email protected] https://lists.ubuntu.com/mailman/listinfo/ubuntu-bugs
