| Dmitry Teselkin | af730f9 | 2018-08-16 11:29:55 +0300 | [diff] [blame] | 1 | # 3.2.2 Ensure ICMP redirects are not accepted |
| 2 | # |
| 3 | # Description |
| 4 | # =========== |
| 5 | # ICMP redirect messages are packets that convey routing information and tell |
| 6 | # your host (acting as a router) to send packets via an alternate path. It is |
| 7 | # a way of allowing an outside routing device to update your system routing |
| 8 | # tables. By setting net.ipv4.conf.all.accept_redirects to 0, the system will |
| 9 | # not accept any ICMP redirect messages, and therefore, won't allow outsiders |
| 10 | # to update the system's routing tables. |
| 11 | # |
| 12 | # Rationale |
| 13 | # ========= |
| 14 | # Attackers could use bogus ICMP redirect messages to maliciously alter the |
| 15 | # system routing tables and get them to send packets to incorrect networks and |
| 16 | # allow your system packets to be captured. |
| 17 | # |
| 18 | # Audit |
| 19 | # ===== |
| 20 | # |
| 21 | # Run the following commands and verify output matches: |
| 22 | # |
| 23 | # # sysctl net.ipv4.conf.all.accept_redirects |
| 24 | # net.ipv4.conf.all.accept_redirects = 0 |
| 25 | # # sysctl net.ipv4.conf.default.accept_redirects |
| 26 | # net.ipv4.conf.default.accept_redirects = 0 |
| 27 | # |
| 28 | # Remediation |
| 29 | # =========== |
| 30 | # |
| 31 | # Set the following parameters in the /etc/sysctl.conf file: |
| 32 | # |
| 33 | # net.ipv4.conf.all.accept_redirects = 0 |
| 34 | # net.ipv4.conf.default.accept_redirects = 0 |
| 35 | # |
| 36 | # Run the following commands to set the active kernel parameters: |
| 37 | # |
| 38 | # # sysctl -w net.ipv4.conf.all.accept_redirects=0 |
| 39 | # # sysctl -w net.ipv4.conf.default.accept_redirects=0 |
| 40 | # # sysctl -w net.ipv4.route.flush=1 |
| 41 | |
| 42 | parameters: |
| 43 | linux: |
| 44 | system: |
| 45 | kernel: |
| 46 | sysctl: |
| 47 | net.ipv4.conf.all.accept_redirects: 0 |
| 48 | net.ipv4.conf.default.accept_redirects: 0 |