Examples describe a network that will be configured with two interfaces Ethernet and Wireless. Ethernet interface will be configured as default route, wireless interface covered here is simple alternative to Ethernet connection.
If is first boot after install configure iptables and one of above described scripts then proceed to upgrade your system.
This example will use Chaos Computer Club server, edit /etc/resolv.conf and make it immutable;
# /etc/resolv.conf.head can replace this line
nameserver 213.73.91.35
# /etc/resolv.conf.tail can replace this line
# chattr +i /etc/resolv.conf
Current example of /etc/rc.d/net;
Address: 192.168.0.1 11000000.10101000.00000000 .00000001
Netmask: 255.255.255.0 = 24 11111111.11111111.11111111 .00000000
Wildcard: 0.0.0.255 00000000.00000000.00000000 .11111111
=>
Network: 192.168.0.0/24 11000000.10101000.00000000 .00000000 (Class C)
Broadcast: 192.168.0.255 11000000.10101000.00000000 .11111111
HostMin: 192.168.0.1 11000000.10101000.00000000 .00000001
HostMax: 192.168.0.254 11000000.10101000.00000000 .11111110
Hosts/Net: 254 (Private Internet)
Other IP class that can used for private network;
Address: 10.0.0.1 00001010.00000000.00000000 .00000001
Netmask: 255.255.255.0 = 24 11111111.11111111.11111111 .00000000
Wildcard: 0.0.0.255 00000000.00000000.00000000 .11111111
=>
Network: 10.0.0.0/24 00001010.00000000.00000000 .00000000 (Class A)
Broadcast: 10.0.0.255 00001010.00000000.00000000 .11111111
HostMin: 10.0.0.1 00001010.00000000.00000000 .00000001
HostMax: 10.0.0.254 00001010.00000000.00000000 .11111110
Hosts/Net: 254 (Private Internet)
Manual configuring like net script;
# DEV=enp8s0
# ADDR=192.168.1.9
# MASK=24
# GW=192.168.1.254
# ip addr flush dev ${DEV}
# ip route flush dev ${DEV}
# ip addr add ${ADDR}/${MASK} dev ${DEV} broadcast +
# ip link set ${DEV} up
# ip route add default via ${GW}
For more information about iptables read arch wiki. You can use /etc/iptables/rules.v4 as template, replace interface by the one facing the router/gateway. This configuration file is used at boot time by iptables-restore command, if you use a script or change the rules of running system you can use iptables-save command to save configuration to a file.
# mkdir /etc/iptables
# cp c9-doc/core/conf/iptables/rules.v4 /etc/iptables/
# cp c9-doc/core/conf/rc.d/iptables /etc/rc.d/
# chmod +x /etc/rc.d/iptables
Adjust rules.v4 to your needs, then;
# sh /etc/rc.d/iptables start
Copy init script, edit if you dont like to let drop when you call stop.
Re-configure your rc.conf and add iptables before (w)lan is up;
SERVICES=(lo iptables net crond)
There is more information on Wiki Wifi Start Scripts and see /etc/rc.d/wlan. Manual or first time configuration;
# ip link
# iwlist wlp2s0 scan
# iwconfig wlp2s0 essid NAME key s:ABCDE12345
Configure wpa supplicant edit;
# vim /etc/wpa_supplicant.conf
ctrl_interface=/var/run/wpa_supplicant
update_config=1
fast_reauth=1
ap_scan=1
# wpa_passphrase <ssid> <password> >> /etc/wpa_supplicant.conf
Now start wpa_supplicant with:
# wpa_supplicant -B -i wlp2s0 -c /etc/wpa_supplicant.conf
Successfully initialized wpa_supplicant
Use /etc/rc.d/wlan init script to auto load wpa configuration and dhcp client.
# wpa_cli
> status
> add_network
3
> set_network 3 ssid "Crux-Network"
OK
> set_network 3 psk "uber-secret-pass"
OK
> enable_network 3
OK
> list_networks
> select_network 3
> save_config
Sysctl references Arch TCP/IP stack hardening, Cyberciti Nginx Hardning, Cyberciti Security Hardening, edit /etc/sysctl.conf;
#
# /etc/sysctl.conf: configuration for system variables, see sysctl.conf(5)
#
kernel.printk = 1 4 1 7
# 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
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
# No source routed packets here
net.ipv4.conf.all.accept_source_route = 0
net.ipv4.conf.default.accept_source_route = 0
## 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
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
# Don't act as a router
net.ipv4.ip_forward = 0
net.ipv4.conf.all.send_redirects = 0
net.ipv4.conf.default.send_redirects = 0
kernel.shmmax = 500000000
# Turn on execshild
kernel.exec-shield = 1
kernel.randomize_va_space = 1
# Optimization for port usefor LBs
# Increase system file descriptor limit
fs.file-max = 65535
# Allow for more PIDs (to reduce rollover problems); may break some programs 32768
kernel.pid_max = 65536
# 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
# 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
# End of file
Change to act as a router (default of conf/sysctl.conf);
# Act as a router, necessary for Access Point
net.ipv4.ip_forward = 1
net.ipv4.conf.all.send_redirects = 1
net.ipv4.conf.default.send_redirects = 1
Load new settings;
# sysctl -p
Core OS Index
This is part of the c9-doc Manual. Copyright (C) 2016 c9 team. See the file Gnu Free Documentation License for copying conditions.