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diff --git a/linux/sysctl.html b/linux/sysctl.html new file mode 100644 index 0000000..3b1d492 --- /dev/null +++ b/linux/sysctl.html @@ -0,0 +1,177 @@ +<!DOCTYPE html> +<html dir="ltr" lang="en"> + <head> + <meta charset='utf-8'> + <title>2.6.2. Sysctl</title> + </head> + <body> + + <a href="index.html">Core OS Index</a> + + <h1 id="sysctl">2.6.2. Sysctl</h1> + + <p>Sysctl references + <a href="https://wiki.archlinux.org/index.php/sysctl#TCP.2FIP_stack_hardening">Arch TCP/IP stack hardening</a>, + <a href="http://www.cyberciti.biz/tips/linux-unix-bsd-nginx-webserver-security.html">Cyberciti Nginx Hardning</a>, + <a href="http://www.cyberciti.biz/faq/linux-kernel-etcsysctl-conf-security-hardening/">Cyberciti Security Hardening</a>.</p> + + <pre> + # + # /etc/sysctl.conf: configuration for system variables, see sysctl.conf(5) + # + + kernel.printk = 7 1 1 4 + + kernel.randomize_va_space = 2 + + # Shared Memory + #kernel.shmmax = 500000000 + # Total allocated file handlers that can be allocated + # fs.file-nr= + vm.mmap_min_addr=65536 + + # Allow for more PIDs (to reduce rollover problems); may break some programs 32768 + kernel.pid_max = 65536 + + #Yama LSM by default + kernel.yama.ptrace_scope = 1 + + # + # Filesystem Protections + # + + # Optimization for port usefor LBs + # Increase system file descriptor limit + fs.file-max = 65535 + + # Hide symbol addresses in /proc/kallsyms + kernel.kptr_restrict = 2 + + # + # Network Protections + # + + net.core.bpf_jit_enable = 0 + + # Increase Linux auto tuning TCP buffer limits + # min, default, and max number of bytes to use + # set max to at least 4MB, or higher if you use very high BDP paths + # Tcp Windows etc + net.core.rmem_max = 8388608 + net.core.wmem_max = 8388608 + net.core.netdev_max_backlog = 5000 + net.ipv4.tcp_window_scaling = 1 + + #A sequence of SACKs may be crafted such that one can trigger an integer overflow, leading to a kernel panic. + net.ipv4.tcp_sack = 0 + + # Both ports linux-blob and linux-libre don't build with ipv6 + # Disable ipv6 + net.ipv6.conf.all.disable_ipv6 = 1 + net.ipv6.conf.default.disable_ipv6 = 1 + net.ipv6.conf.lo.disable_ipv6 = 1 + + # Tuen IPv6 + #net.ipv6.conf.default.router_solicitations = 0 + #net.ipv6.conf.default.accept_ra_rtr_pref = 0 + #net.ipv6.conf.default.accept_ra_pinfo = 0 + #net.ipv6.conf.default.accept_ra_defrtr = 0 + #net.ipv6.conf.default.autoconf = 0 + #net.ipv6.conf.default.dad_transmits = 0 + #net.ipv6.conf.default.max_addresses = 0 + + # Avoid a smurf attack, ping scanning + net.ipv4.icmp_echo_ignore_broadcasts = 1 + + # Turn on protection for bad icmp error messages + net.ipv4.icmp_ignore_bogus_error_responses = 1 + + # Turn on syncookies for SYN flood attack protection + net.ipv4.tcp_syncookies = 1 + + ## protect against tcp time-wait assassination hazards + ## drop RST packets for sockets in the time-wait state + ## (not widely supported outside of linux, but conforms to RFC) + net.ipv4.tcp_rfc1337 = 1 + + ## tcp timestamps + ## + protect against wrapping sequence numbers (at gigabit speeds) + ## + round trip time calculation implemented in TCP + ## - causes extra overhead and allows uptime detection by scanners like nmap + ## enable @ gigabit speeds + net.ipv4.tcp_timestamps = 0 + #net.ipv4.tcp_timestamps = 1 + + # Turn on and log spoofed, source routed, and redirect packets + net.ipv4.conf.all.log_martians = 1 + net.ipv4.conf.default.log_martians = 1 + + ## ignore echo broadcast requests to prevent being part of smurf attacks (default) + net.ipv4.icmp_echo_ignore_broadcasts = 1 + + ## sets the kernels reverse path filtering mechanism to value 1(on) + ## will do source validation of the packet's recieved from all the interfaces on the machine + ## protects from attackers that are using ip spoofing methods to do harm + net.ipv4.conf.all.rp_filter = 1 + net.ipv4.conf.default.rp_filter = 1 + #net.ipv6.conf.default.rp_filter = 1 + #net.ipv6.conf.all.rp_filter = 1 + + + # Make sure no one can alter the routing tables + # Act as a router, necessary for Access Point + net.ipv4.conf.all.accept_redirects = 0 + net.ipv4.conf.default.accept_redirects = 0 + net.ipv4.conf.all.secure_redirects = 0 + net.ipv4.conf.default.secure_redirects = 0 + # No source routed packets here + # Discard packets with source routes, ip spoofing + net.ipv4.conf.all.accept_source_route = 0 + net.ipv4.conf.default.accept_source_route = 0 + + + net.ipv4.conf.all.send_redirects = 0 + net.ipv4.conf.default.send_redirects = 0 + + net.ipv4.ip_forward = 0 + + # Increase system IP port limits + net.ipv4.ip_local_port_range = 2000 65000 + + # Increase TCP max buffer size setable using setsockopt() + net.ipv4.tcp_rmem = 4096 87380 8388608 + net.ipv4.tcp_wmem = 4096 87380 8388608 + + # Disable proxy_arp + net.ipv4.conf.default.proxy_arp = 0 + net.ipv4.conf.all.proxy_arp = 0 + + # Disable bootp_relay + net.ipv4.conf.default.bootp_relay = 0 + net.ipv4.conf.all.bootp_relay = 0 + + # Decrease TCP fin timeout + net.ipv4.tcp_fin_timeout = 30 + # Decrease TCP keep alive time + net.ipv4.tcp_keepalive_time = 1800 + # Sen SynAck retries to 3 + net.ipv4.tcp_synack_retries = 3 + + # End of file + </pre> + + <p>Reload sysctl settings;</p> + + <pre> + # sysctl --system + </pre> + + <a href="index.html">Core OS Index</a> + <p>This is part of the Tribu System Documentation. + Copyright (C) 2020 + Tribu Team. + See the file <a href="../fdl-1.3-standalone.html">Gnu Free Documentation License</a> + for copying conditions.</p> + + </body> +</html> |