Detections
Analytics
3.3.2.5 Ensure net.ipv6.conf.all.accept_source_route is configured
Information
The accept_source_route option causes network interfaces to accept packets with the Strict Source Route (SSR) or Loose Source Routing (LSR) option set.net.ipv6.conf.all.accept_source_route controls accepting of all IPv6 packets with the SSR or LSR option set on all interfaces.
In networking, source routing allows a sender to partially or fully specify the route packets take through a 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.
More information about the kernel parameter configuration files, their location, and load preference is available in the "Configure Network Kernel Parameters" section overview.
Note: If IPv6 has been disabled this recommendation is not applicable.
Setting net.ipv6.conf.all.accept_source_route to 0 disables the system from accepting source routed packets. Assume this system was capable of routing packets to Internet routable addresses on one interface and private addresses on another interface. Assume that the private addresses were not routable to the Internet routable addresses and vice versa. Under normal routing circumstances, an attacker from the Internet routable addresses could not use the system as a way to reach the private address systems. If, however, source routed packets were allowed, they could be used to gain access to the private address systems as the route could be specified, rather than rely on routing protocols that did not allow this routing.
Solution
- Run the following command to comment out net.ipv6.conf.all.accept_source_route lines returned by the audit procedure that are not net.ipv6.conf.all.accept_source_route = 0 :# sed -ri '^\s*net.ipv6.conf.all.accept_source_route\s*=\s*1/s/^/#/g' "path/to/file/in/audit/filename"
Example:
# sed -ri '/^\s*net.ipv6.conf.all.accept_source_route\s*=\s*1/s/^/#/g' /etc/sysctl.d/99-sysctl.conf
- Create or edit a file in the /etc/sysctl.d/ directory ending in .conf and edit or add the following line:
net.ipv6.conf.all.accept_source_route = 0
Example:
# [ ! -d "/etc/sysctl.d/" ] && mkdir -p /etc/sysctl.d/
# printf '%s\n' "" "net.ipv6.conf.all.accept_source_route = 0" >> /etc/sysctl.d/60-ipv6_sysctl.conf
- Run the following command to load all sysctl configuration files:
# sysctl --system
See Also
Item Details
Audit Name: CIS Amazon Linux 2 v4.0.0 L1 Server
Category: CONFIGURATION MANAGEMENT
References: 800-53|CM-6b., CCI|CCI-000366, CSCv7|9.2, Rule-ID|SV-230538r1017300_rule, Rule-ID|SV-235015r991589_rule, Rule-ID|SV-248880r991589_rule, Rule-ID|SV-257973r991589_rule, Rule-ID|SV-269259r1050141_rule, Rule-ID|SV-271879r1092349_rule
Plugin: Unix
Control ID: 671757fb2af17330ea53a1ec571500feeaab1bc7799626d6d29288766d09a2a5