| Dmitry Teselkin | af730f9 | 2018-08-16 11:29:55 +0300 | [diff] [blame] | 1 | # 3.2.1 Ensure source routed packets are not accepted |
| 2 | # |
| 3 | # Description |
| 4 | # =========== |
| 5 | # In networking, source routing allows a sender to partially or fully specify |
| 6 | # the route packets take through a network. In contrast, non-source routed |
| 7 | # packets travel a path determined by routers in the network. In some cases, |
| 8 | # systems may not be routable or reachable from some locations (e.g. private |
| 9 | # addresses vs. Internet routable), and so source routed packets would need |
| 10 | # to be used. |
| 11 | # |
| 12 | # Rationale |
| 13 | # ========= |
| 14 | # Setting `net.ipv4.conf.all.accept_source_route` and |
| 15 | # `net.ipv4.conf.default.accept_source_route` to 0 disables the system from |
| 16 | # accepting source routed packets. Assume this system was capable of routing |
| 17 | # packets to Internet routable addresses on one interface and private addresses |
| 18 | # on another interface. Assume that the private addresses were not routable to |
| 19 | # the Internet routable addresses and vice versa. Under normal routing |
| 20 | # circumstances, an attacker from the Internet routable addresses could not use |
| 21 | # the system as a way to reach the private address systems. If, however, source |
| 22 | # routed packets were allowed, they could be used to gain access to the private |
| 23 | # address systems as the route could be specified, rather than rely on routing |
| 24 | # protocols that did not allow this routing. |
| 25 | # |
| 26 | # Audit |
| 27 | # ===== |
| 28 | # |
| 29 | # Run the following commands and verify output matches: |
| 30 | # |
| 31 | # # sysctl net.ipv4.conf.all.accept_source_route |
| 32 | # net.ipv4.conf.all.accept_source_route = 0 |
| 33 | # # sysctl net.ipv4.conf.default.accept_source_route |
| 34 | # net.ipv4.conf.default.accept_source_route = 0 |
| 35 | # |
| 36 | # Remediation |
| 37 | # =========== |
| 38 | # |
| 39 | # Set the following parameters in the /etc/sysctl.conf file: |
| 40 | # |
| 41 | # net.ipv4.conf.all.accept_source_route = 0 |
| 42 | # net.ipv4.conf.default.accept_source_route = 0 |
| 43 | # |
| 44 | # Run the following commands to set the active kernel parameters: |
| 45 | # |
| 46 | # # sysctl -w net.ipv4.conf.all.accept_source_route=0 |
| 47 | # # sysctl -w net.ipv4.conf.default.accept_source_route=0 |
| 48 | # # sysctl -w net.ipv4.route.flush=1 |
| 49 | |
| 50 | parameters: |
| 51 | linux: |
| 52 | system: |
| 53 | kernel: |
| 54 | sysctl: |
| 55 | net.ipv4.conf.all.accept_source_route: 0 |
| 56 | net.ipv4.conf.default.accept_source_route: 0 |