cyberstrikeus CIS Ubuntu Linux 18.04 LTS Benchmark v2.2.0 - Control 3.3.8
Description
In networking, source routing allows a sender to partially or fully specify the route packets take through the network. In contrast, non-source routed packets travel a path determined by routers in the network. In some cases, systems may not be routable or reachable from some locations (e.g. private addresses vs. internet routable), and so source routed packets would need to be used.
Rationale
Setting net.ipv4.conf.all.accept_source_route, net.ipv4.conf.default.accept_source_route, net.ipv6.conf.all.accept_source_route and net.ipv6.conf.default.accept_source_route to 0 disables the system from accepting source routed packets. Assume this system was capable of routing packets to the internet, an attacker could be redirected through the system to an internal private address using source routed packets.
Impact
None.
Audit Procedure
Command Line
Run the following commands to verify source routed packets are not accepted:
sysctl net.ipv4.conf.all.accept_source_route
sysctl net.ipv4.conf.default.accept_source_route
sysctl net.ipv6.conf.all.accept_source_route
sysctl net.ipv6.conf.default.accept_source_route
Expected Result
net.ipv4.conf.all.accept_source_route = 0
net.ipv4.conf.default.accept_source_route = 0
net.ipv6.conf.all.accept_source_route = 0
net.ipv6.conf.default.accept_source_route = 0
Remediation
Command Line
Set the following parameters in /etc/sysctl.conf or a /etc/sysctl.d/* file:
net.ipv4.conf.all.accept_source_route = 0
net.ipv4.conf.default.accept_source_route = 0
net.ipv6.conf.all.accept_source_route = 0
net.ipv6.conf.default.accept_source_route = 0
Run the following commands to set the active kernel parameters:
sysctl -w net.ipv4.conf.all.accept_source_route=0
sysctl -w net.ipv4.conf.default.accept_source_route=0
sysctl -w net.ipv6.conf.all.accept_source_route=0
sysctl -w net.ipv6.conf.default.accept_source_route=0
sysctl -w net.ipv4.route.flush=1
sysctl -w net.ipv6.route.flush=1
Default Value
net.ipv4.conf.all.accept_source_route = 0, net.ipv4.conf.default.accept_source_route = 0, net.ipv6.conf.all.accept_source_route = 0, net.ipv6.conf.default.accept_source_route = 0
References
- NIST SP 800-53 Rev. 5: CM-7, SC-5, SC-7
- CIS Ubuntu Linux 18.04 LTS Benchmark v2.2.0
CIS Controls
Version 8
4.1 Establish and Maintain a Secure Configuration Process - Establish and maintain a secure configuration process for enterprise assets.
Version 7
5.1 Establish Secure Configurations - Maintain documented, standard security configuration standards for all authorized operating systems and software.
Profile Applicability
- Level 1 - Server
- Level 1 - Workstation
Assessment Status
Automated