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 FreeBSD firewalls › ipfw -- IP firewall and traffic shaper control program  ipfw(8) › ipf (IP Filter) - alters packet filtering lists for IP packet.

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Presentation on theme: " FreeBSD firewalls › ipfw -- IP firewall and traffic shaper control program  ipfw(8) › ipf (IP Filter) - alters packet filtering lists for IP packet."— Presentation transcript:

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2  FreeBSD firewalls › ipfw -- IP firewall and traffic shaper control program  ipfw(8) › ipf (IP Filter) - alters packet filtering lists for IP packet input and output  ipf(8) › pf -- packet filter  pf(4) http://www.freebsd.org/doc/en/books/handbook/firewalls.html

3  Using ipfw 1. Add these options in kernel configuration file and recompile the kernel 2. Edit /etc/rc.conf to enable firewall  "firewall" keyword in rc.conf options IPFIREWALL options IPFIREWALL_VERBOSE options IPFIREWALL_FORWARD options IPFIREWALL_DEFAULT_TO_ACCEPT # firewall firewall_enable="YES" firewall_script="/etc/firewalls/rules" firewall_quiet="YES"

4 3. Edit ipfw command script that you specify in rc.conf  Ex: /etc/firewall/rules › ipfw command  # ipfw list(show current firewall rules)  # ipfw flush(delete all firewall rules)  # ipfw add {pass|deny} {udp|tcp|all} from where to where

5  Example (Head part) #!/bin/sh fwcmd="/sbin/ipfw -q“ myip=“140.113.17.215” ${fwcmd} -f flush ${fwcmd} add pass all from ${myip} to any # Allow TCP through if setup succeeded ${fwcmd} add pass tcp from any to any established ${fwcmd} add deny log all from any to any frag echo -n "Established “ # Allow icmp (ping only) ${fwcmd} add pass icmp from any to any icmptypes 0,3,8,11 icmp(4)

6  Example (service part) # Allow Samba ${fwcmd} add pass tcp from 140.113.17.0/24 to ${myip} 137-139 setup echo -n "Samba " # Allow HTTP/HTTPS ${fwcmd} add pass tcp from any to ${myip} 80 setup ${fwcmd} add pass tcp from any to ${myip} 443 setup echo -n "HTTP/HTTPS " # SSH ${fwcmd} add pass tcp from any to any 22 setup echo -n "SSH " # open any system port that your system provide

7  Example (Tail part) # Default to deny ${fwcmd} add 65500 reset log tcp from any to any ${fwcmd} add 65501 reject udp from any to any ${fwcmd} add 65502 reject log icmp from any to any ${fwcmd} add 65534 deny log all from any to any

8  Manual reset firewall rules › Edit the script and › # sh /etc/firewall/rules  When you install new service and wondering why it can not use … › # ipfw flush › Delete all firewall rules to remove problems caused by firewall

9  Debug your system via log file › /var/log/security Dec 25 11:25:36 sabsd last message repeated 2 times Dec 25 11:45:06 sabsd kernel: ipfw: 65500 Reset TCP 211.48.52.58:1997 140.113.17.215:5554 in via fxp0 Dec 25 11:45:07 sabsd kernel: ipfw: 65500 Reset TCP 211.48.52.58:1997 140.113.17.215:5554 in via fxp0 Dec 25 11:45:07 sabsd kernel: ipfw: 65500 Reset TCP 211.48.52.58:4062 140.113.17.215:1023 in via fxp0 Dec 25 11:45:08 sabsd kernel: ipfw: 65500 Reset TCP 211.48.52.58:4062 140.113.17.215:1023 in via fxp0 Dec 25 11:45:09 sabsd kernel: ipfw: 65500 Reset TCP 211.48.52.58:4246 140.113.17.215:9898 in via fxp0 Dec 25 12:05:44 sabsd kernel: ipfw: 65500 Reset TCP 204.100.126.30:2188 140.113.17.215:445 in via fxp0 Dec 25 12:05:45 sabsd last message repeated 2 times

10  /usr/share/examples  ipfw/ › /usr/share/examples/ipfw/change_rules.sh  ipfilter/  pf/

11  Trusted remote host and user name DB › Allow user to login (via rlogin) and copy files (rcp) between machines without passwords › Format:  Simple: hostname [username]  Complex: [+-][hostname|@netgroup] [[+-][username|@netgorup]] › Example  bar.com foo(trust user “ foo ” from host “ bar.com ” )  +@adm_cs_cc(trust all from amd_cs_cc group)  +@adm_cs_cc -@chwong  Do not use this unless you know what you are doing exactly

12  TCP Wrapper › Provide support for every server daemon under its control

13 › To see what daemons are controlled by inetd, see /etc/inetd.conf › TCP wrapper should not be considered a replacement of a good firewall. Instead, it should be used in conjunction with a firewall or other security tools #ftp stream tcp nowait root /usr/libexec/ftpd ftpd -l #ftp stream tcp6 nowait root /usr/libexec/ftpd ftpd -l #telnet stream tcp nowait root /usr/libexec/telnetd telnetd #telnet stream tcp6 nowait root /usr/libexec/telnetd telnetd shell stream tcp nowait root /usr/libexec/rshd rshd #shell stream tcp6 nowait root /usr/libexec/rshd rshd login stream tcp nowait root /usr/libexec/rlogind rlogind #login stream tcp6 nowait root /usr/libexec/rlogind rlogind

14  To use TCP wrapper 1. inetd daemon must start up with " -Ww" option (default) Or edit /etc/rc.conf › Edit /etc/hosts.allow  Format: daemon : address : action  daemon is the daemon name which inetd started  address can be hostname, IPv4 addr, IPv6 addr  action can be “ allow ” or “ deny ”  Keyword “ ALL ” can be used in daemon and address fields to means everything inetd_enable="YES" inetd_flags="-wW"

15 › First rule match semantic  Meaning that the configuration file is scanned in ascending order for a matching rule  When a match is found, the rule is applied and the search process will stop  Example: ALL: localhost, loghost @adm_cc_cs : allow sshd : @sun_cc_cs, @bsd_cc_cs, @linux_cc_cs : allow identd : ALL : allow rpcbind : 140.113.209. 140.113.235. 140.113.23..cs.nctu.edu.tw : allow rpc.rstatd rpc.rusersd : 140.113.209. 140.113.235. 140.113.23. : allow rpc.lockd rpc.statd : 140.113.209. 140.113.235. 140.113.23. : allow mountd : 140.113.209. 140.113.235. 140.113.23. : allow rpc.rusersd : @all_cc_cs 140.113.17.203: allow ALL : ALL : deny

16  Advance configuration › External commands (twist option)  twist will be called to execute a shell command or script › External commands (spawn option)  spawn is like twist, but it will not send a reply back to the client # The rest of the daemons are protected. telnet : ALL \ : severity auth.info \ : twist /bin/echo "You are not welcome to use %d from %h." # We do not allow connections from example.com: ALL :.example.com \ : spawn (/bin/echo %a from %h attempted to access %d >> \ /var/log/connections.log) \ : deny

17 › Wildcard (PARANOID option)  Match any connection that is made from an IP address that differs from its hostname # Block possibly spoofed requests to sendmail: sendmail : PARANOID : deny hosts_access(5) hosts_options(5)

18  FreeBSD Security Information › http://security.freebsd.org/ › http://www.freebsd.org/security/advisories.html  Security Notifications List › freebsd-security-notifications@freebsd.org  See supplicant: › “The FreeBSD Security Officer function”  http://people.freebsd.org/~simon/presentations/

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