I was auditing one of our customer again and this time round, i managed to come up with a 7 step guide to better secure the TCP stack for Solaris. Well, you guys can add on for more.
1. Configure for more random TCP sequence number generation. Check that in(/etc/default/inetinit), the TCP_STRONG_ISS is set to 2. For instance, TCP_STRONG_ISS=2
2. IP forwarding is to be turned off to prevent the machine acting as a router. To disable IP forwarding, a file "/etc/notrouter" need to be present. If the file is missing, issue the following command to create one : touch /etc/notrouter
To prevent dynamic routes updates via the network, move "in.routed" and "in.rdisc" away from "/usr/sbin" directory by perform the following commands :
mv /usr/sbin/in.routed /export/home/cfgh/base
mv /usr/sbin/in.rdisc /export/home/cfgh/base
3. Change default kernel IP settings for better security. Following the following steps to change the kernel IP defaults values :
Setup files and environment:
touch /etc/init.d/exconfig
ln -s /etc/init.d/exconfig /etc/rc2.d/S70exconfig
chmod 744 /etc/init.d/exconfig /etc/rc2.d/S70exconfig
Edit file "/etc/init.d/exconfig" and add the following lines:
#!/bin/sh
# /etc/init.d/exconfig
RELEASE=`/usr/bin/uname -r`
release7 ()
{
/usr/sbin/ex -set /dev/ip ip_forwarding 0
/usr/sbin/ex -set /dev/ip ip_strict_dst_multihoming 1
/usr/sbin/ex -set /dev/ip ip_send_redirects 0
/usr/sbin/ex -set /dev/ip ip_ignore_redirect 1
/usr/sbin/ex -set /dev/ip ip_forward_src_routed 0
/usr/sbin/ex -set /dev/ip ip_forward_directed_broadcasts 0
/usr/sbin/ex -set /dev/ip ip_respond_to_echo_broadcast 0
/usr/sbin/ex -set /dev/tcp tcp_conn_req_max_q0 4096
/usr/sbin/ex -set /dev/tcp tcp_ip_abort_cinterval 60000
/usr/sbin/ex -set /dev/ip ip_respond_to_timestamp 0
/usr/sbin/ex -set /dev/ip ip_respond_to_timestamp_broadcast 0
/usr/sbin/ex -set /dev/ip ip_respond_to_address_mask_broadcast 0
/usr/sbin/ex -set /dev/arp arp_cleanup_interval 60000
id -a mqm > /dev/null 2>&1
if [ \$? -eq 0 ]
then
/usr/sbin/ex -set /dev/tcp tcp_keepalive_interval 600000
fi
}
release8 ()
{
/usr/sbin/ex -set /dev/ip ip6_forwarding 0
/usr/sbin/ex -set /dev/ip ip6_strict_dst_multihoming 1
/usr/sbin/ex -set /dev/ip ip6_send_redirects 0
/usr/sbin/ex -set /dev/ip ip6_ignore_redirect 1
/usr/sbin/ex -set /dev/ip ip6_forward_src_routed 0
/usr/sbin/ex -set /dev/ip ip_ire_arp_interval 60000
}
release6 ()
{
/usr/sbin/ex -set /dev/ip ip_respond_to_echo_broadcast 0
/usr/sbin/ex -set /dev/ip ip_forward_directed_broadcasts 0
/usr/sbin/ex -set /dev/ip ip_strict_dst_multihoming 1
/usr/sbin/ex -set /dev/ip ip_ignore_redirect 1
/usr/sbin/ex -set /dev/ip ip_forward_src_routed 0
}
if [ \$RELEASE = "5.7" ]
then
release7
elif [ \$RELEASE = "5.8" ] || [ \$RELEASE = "5.10" ] || [ \$RELEASE = "5.9" ]
then
release7
release8
elif [ \$RELEASE = "5.6" ]
then
release6
fi
4. Disable multicast from the server, edit the file "/etc/rc2.d/S72inetsvc" and comment out/remove the following lines :
#(
#if [ "$_INIT_NET_STRATEGY" = "dhcp" ]; then
# mcastif=`/sbin/dhcpinfo Yiaddr` || mcastif=$_INIT_UTS_NODENAME
#else
# mcastif=$_INIT_UTS_NODENAME
#fi
#
#echo "Setting default Ipv4 interface for multicase:" \
# "add net 224.0/4: gateway $mcastif
#
#/usr/sbin/route -n add -interface "224.0/4" "$mcastif" >/dev/null
#)&
For Solaris 10
Multicast would be disabled using /etc/rc2.d/S72inetsvc-os10
5. Denial of Service Prevention System Settings.
Services that must be disabled on all servers, unless required by business function from /etc/services. Services include: ftp-data ftp tftp pop2 pop3 pop-2 nntp chargen daytime discard echo finger talk who whois new-rwho klogin eklogin telnet systat netstat time
6. Prevent "core dump" generated by inetd as it may contain login information. This could be achieved by editing the file "/etc/rc2.d/S72inetsvc". Change the line :
/usr/sbin/inetd -s &
to /usr/bin/ulimit -c 0; /usr/sbin/inetd -s -t &
Note :
ulimit -c 0 : set the core file size to 0 byte
inetd -s -t : stand-alone server with tracing of all tcp connections
For Solaris 10
Create the script /etc/rc2.d/S72inetsvc-os10 as per below.
#cat /etc/rc2.d/S72inetsvc-os10
IPADDR=`netstat -nr | grep -w 224.0.0.0 | awk '{print $2}'`
/usr/sbin/route -n delete -interface "224.0/4" $IPADDR
/usr/sbin/svcadm enable inetd
/usr/sbin/inetadm -M tcp_trace=TRUE
#chmod 555 /etc/rc2.d/S72inetsvc-os10
7. .netrc files System Settings (.netrc files, .netrc files in root's home directory). Files are not permitted, remove the files if any, issue command find / -name .netrc -print
