Categoriearchief: Networking

Setting up a PPTP VPN to a Windows 2008 Server

Requirements

Linux
KDE
A Windows server to connect to.

Step 1: Install required software

yum install kde-plasma-networkmanagement-pptp NetworkManager-pptp

Step 2: Configure the network

In the KDE Network Manager plasma module, go to the tab VPN, click add and choose PPTP.

Enter and connection name you like. In the field "gateway" type the hostname or IP number of the Windows server you're connecting to. Under Login, Password and NT Domain, fill in your authentication data. Then click advanced.

In the advanced window, disable EAP and enable MPPE. Then click OK.

Go to the tab IPv4. Under method, I chose Automatic (VPN). But Automatic (VPN) addresses only is also a nice option: it sets the IPs but no DNS settings.

Go to the routes sub-tab. Switch on Ignore automatically obtained routes and Use only for resources on this connection to make sure the connection doesn't steal your traffic. Then I entered a manual route: 192.168.178.0/255.255.255.0 to gateway 0.0.0.0 (it is a ppp device after all).

You may want to configure IPv6 as well, but I don't at this moment, so I'm not documenting this.

Step 3: Connect

Click on the icon in the tray and connect.

Ubuntu/Debian

I'm running RedHat-based software on all of my machines. Above information may be useful for Ubuntu/Debian users, but it's not tested and I'm not supporting it.

Servers: RedHat Enterprise Linux/CentOS is more suitable for servers, as there's a lot of professional level support available. I think that's important, because if I say, get a car accident, I want the servers to be managable by another professional.

Desktops/Laptops: RPM packages are pretty exchangable between RedHat-based platforms. That's a good reason to run Fedora on the desktop.
© GeekLabInfo Setting up a PPTP VPN to a Windows 2008 Server is a post from GeekLab.info. You are free to copy materials from GeekLab.info, but you are required to link back to http://www.geeklab.info
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Playing with the sockets: socat and netcat

Connect two netcats to each other

mkfifo backpipe
nc localhost 55545 0backpipe

Telnet with readline and a history:

socat -d -d READLINE,history=$HOME/.http_history \
TCP4:www.domain.org:www,crnl

Talk to your modem in raw mode:

socat - /dev/ttyS0,raw,echo=0,crnl

Simulate tail -f:

socat -u /var/log/messages,seek-end=0,ignoreeof -

Give a random interactive program, such as nslookup, a history:

socat readline,history=.nslookup_hist exec:"nslookup",pty,ctty,setsid,echo=0

Use your modem with a non-persistent history:

socat readline /dev/ttyS0,raw,echo=0,crlf,nonblock

Use your modem with a persistent history:

socat READLINE,history:/tmp/serial.cmds \
  OPEN:/dev/ttyS0,ispeed=9600,ospeed=9600,crnl,raw,sane,echo=false

To dos (as in tofrodos):

socat -u - -,crlf

From dos (as in tofrodos):

socat -u -,cr -

Run sendmail daemon with your favorite network options

Warning: using this wrong may result in becoming an open relay!

socat TCP-LISTEN:25,fork,ip-ttl=4,ip-tos=7,tcp-maxseg=576 EXEC:"/usr/sbin/sendmail -bs",nofork

Send a mail using chat (from ppp package):

socat -d -d system:'/usr/sbin/chat "220 " "HELO loopback" "250 " "MAIL FROM: <root@localhost>" "250 " "RCPT TO: root" "250 " "DATA" "354 " "test'$(echo -e "\r.")'" "250 " "QUIT"',pty,echo=0,cr tcp:localhost:25,crlf,nodelay

Connect remote X :1 to local X :0

socat exec:'ssh root@troas socat unix-l\:/tmp/.X11-unix/X1 -' unix:/tmp/.X11-unix/X0

Note the escaping of the colon in the remote command.

Sending a file - Server sending the file

server$ socat -u FILE:test.dat TCP-LISTEN:9876,reuseaddr
client$ socat -u TCP:127.0.0.1:9876 OPEN:out.dat,creat

Sending a file - Server receiving the file

server$ socat -u TCP-LISTEN:9876,reuseaddr OPEN:out.txt,creat
client$ socat -u FILE:test.txt TCP:127.0.0.1:9876

Be a syslog server:

socat -u UDP4-LISTEN:5140,reuseaddr,fork OPEN:/tmp/syslog.msg,creat,append

I can't figure out how to put a newline after each message...

Send syslog messages to screen:

socat -t0 -T0 -u UDP4-LISTEN:514,reuseaddr,fork -

To get time from time server:

socat TCP:time.nist.gov:13 -

Really sick - use socat as a VPN solution:

socat -d -d  \
    TUN:192.168.99.2/24,up \
    SYSTEM:"ssh root@remote-server socat -d -d  - 'TUN:192.168.99.1/24,up'"

This must be run as a user that can modify tap/tun devices on both sides of the tunnel.

Use a remote modem

On the side with the modem

socat /dev/ttyS0,raw,echo=0 tcp4-listen:3334

On the side where you want the modem transferred

socat PTY,link=$HOME/vmodem0,raw,echo=0 TCP:servername:3334

You can now access remote /dev/ttyS0 through local $HOME/vmodem0

Use a remote modem over SSH

socat PTY,link=$HOME/vmodem0,waitslave \
 EXEC:"ssh root@remote-server socat - /dev/ttyS0"

You can now access remote /dev/ttyS0 through local $HOME/vmodem0. Remove waitslave to keep alive after local client disconnect.

Using OpenSSL over UDP

This uses a chaining method I believe to be only available in socat2.
On the listening side:

socat2 - "OPENSSL-SERVER,cert=client.pem,cafile=server.crt|UDP4-LISTEN:4430,fork"

On the connecting side:

socat2 exec:ls "OPENSSL-CLIENT,cert=server.pem,cafile=client.crt|UDP4:localhost:4430"

OpenSSL Tunnel

First, generate certificates and distribute them to either side:

FILENAME=server
openssl genrsa -out $FILENAME.key 1024 
openssl req -new -key $FILENAME.key -x509 -days 3653 -out $FILENAME.crt 
cat $FILENAME.key $FILENAME.crt >$FILENAME.pem 
chmod 600 $FILENAME.key $FILENAME.pem 
 
FILENAME=client
openssl genrsa -out $FILENAME.key 1024 
openssl req -new -key $FILENAME.key -x509 -days 3653 -out $FILENAME.crt 
cat $FILENAME.key $FILENAME.crt >$FILENAME.pem 
chmod 600 $FILENAME.key $FILENAME.pem

On the listening side:

socat openssl-listen:4433,reuseaddr,cert=server.pem,cafile=client.crt tcp-connect:localhost

On the connecting side:

socat - openssl-connect:server.domain.org:4433,cert=client.pem,cafile=server.crt

More information:
1 2

© GeekLabInfo Playing with the sockets: socat and netcat is a post from GeekLab.info. You are free to copy materials from GeekLab.info, but you are required to link back to http://www.geeklab.info
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X11 over SSH

CentOS 5's and Fedora 15's base installations are pretty good prepared to use X11 over SSH. You just need to install one more package on the server you're connecting to: xorg-x11-xauth. According to yum info, the purpose of this package is:
xauth is used to edit and display the authorization information used in connecting to an X server.
This editting probably means synchronising X11 authority cookies between SSH peers.

Installing is done using:
yum install xorg-x11-xauth

Then ssh into the box using:
ssh -X [servername]

© GeekLabInfo X11 over SSH is a post from GeekLab.info. You are free to copy materials from GeekLab.info, but you are required to link back to http://www.geeklab.info
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Native IPv6: First steps

Today I made my first native IPv6 connection. I've been running Teredo/Miredo on my laptop for quite a while now, and I thought it was time to get a real IPv6 connection. I could use IPv6 autoconfiguration, but on a server you need a fixed IP.

Needed software

Install required packages that are not included in the Fedora default install:
yum install iproute2 ndisc6

Configuring manually

Configuring the network is not that much different from configuring an IPv4 address.

IPv4 IPv6
ip addr add 1.2.3.4/24 dev eth0 ip addr add 2001:1BE8:DEAD:BEEF::1a1a/64 dev eth0
ip route add default via 1.2.3.254 ip route add default via 2001:1BE8:DEAD:BEEF::1

Now test it by pinging/tracerouting some known IPv6 services:


[root@localhost ~]# ping6 ipv6.google.com
PING ipv6.google.com(2a00:1450:8003::69) 56 data bytes
64 bytes from 2a00:1450:8003::69: icmp_seq=1 ttl=58 time=7.19 ms
64 bytes from 2a00:1450:8003::69: icmp_seq=2 ttl=58 time=7.52 ms
64 bytes from 2a00:1450:8003::69: icmp_seq=3 ttl=58 time=6.98 ms
64 bytes from 2a00:1450:8003::69: icmp_seq=4 ttl=58 time=7.44 ms
^C
--- ipv6.google.com ping statistics ---
4 packets transmitted, 4 received, 0% packet loss, time 3003ms
rtt min/avg/max/mdev = 6.989/7.287/7.525/0.227 ms
[root@localhost ~]# tracert6 ipv6.google.com
traceroute to ipv6.google.com (2a00:1450:8003::69) from 2001:1be8:dead:beef::1a1a, 30 hops max, 60 bytes packets
1  2001:1be8:dead:beef::1 (2001:1be8:3f03:541::1)  1.024 ms  0.970 ms  1.036 ms
2  2001:1be8::310:1 (2001:1be8::310:1)  2.618 ms  2001:1be8::300:1 (2001:1be8::300:1)  2.583 ms  2001:1be8::310:1 (2001:1be8::310:1)  2.527 ms
3  pr61.ams04.net.google.com (2001:7f8:1::a501:5169:1)  2.865 ms  2.536 ms  2.184 ms
4  2001:4860::1:0:4b3 (2001:4860::1:0:4b3)  2.801 ms  3.156 ms  24.731 ms
5  2001:4860::2:0:66e (2001:4860::2:0:66e)  7.021 ms  6.830 ms  96.541 ms
6  2001:4860:0:1::31 (2001:4860:0:1::31)  7.092 ms  7.367 ms  12.089 ms
7  2a00:1450:8003::69 (2a00:1450:8003::69)  6.996 ms  7.550 ms  7.341 ms

Configure at boot time

Step 1. Enable IPv6 networking

vim /etc/sysconfig/network
then add (or replace):
NETWORKING_IPV6=yes

Step 2. Configure IPv6 addresses

vim /etc/sysconfig/network-scripts/ifcfg-eth0
then add the following lines:

IPV6INIT=yes
IPV6ADDR=2001:1BE8:DEAD:BEEF::1a1a/64
IPV6_DEFAULTGW=2001:1BE8:DEAD:BEEF::1

Step 3. Test

Run service network restart or reboot to test.
Warning: if you do this remotely, you may lose the connection. I first locked myself out of my test machine, but I always got a KVM switch attached or VMWare console.

Security

Please remember that using IPv6 also means that there's a new entrance to your network. Use ip6tables to set up a firewall.

Ubuntu/Debian

I'm running RedHat-based software on all of my machines. Above information may be useful for Ubuntu/Debian users, but it's not tested and I'm not supporting it.

Servers: RedHat Enterprise Linux/CentOS is more suitable for servers, as there's a lot of professional level support available. I think that's important, because if I say, get a car accident, I want the servers to be managable by another professional.

Desktops/Laptops: RPM packages are pretty exchangable between RedHat-based platforms. That's a good reason to run Fedora on the desktop.
© GeekLabInfo Native IPv6: First steps is a post from GeekLab.info. You are free to copy materials from GeekLab.info, but you are required to link back to http://www.geeklab.info
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Firewall your Exchange 2007 server

Software that is not reachable, can't be hacked. Easy as that. So if you have an cloud-based anti-spam/anti-virus filter, you can block your smtp server for badguys.

In my situation, I'm using a Windows 2008 SBS server with Exchange 2007.

  1. Start wf.msc
  2. Go to inbound rules
  3. Find MSExchangeTransportWorker and double-click it to open the properties
  4. On the tab "scope", select "These IP addresses" and add the following IPs: 'Local subnet', 127.0.0.0/8, 192.168.0.0/16, fe80::/16
  5. Also add the IPs of your anti-spam servers as well
  6. Then click OK
  7. Don't forget to check that the changes actually work by both checking an IP that can connect and one that doesn't
© GeekLabInfo Firewall your Exchange 2007 server is a post from GeekLab.info. You are free to copy materials from GeekLab.info, but you are required to link back to http://www.geeklab.info
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Squid active directory authentication on Centos 5.6

Step 1. Install ntp and synchronize clocks

We'll be using winbind, kerberos and ntlm to authenticate the user. This requires the clocks of the AD server and the proxy server to be synchronized.

rpm -qa ntp || yum -y install ntp
sed -i "s/^server /#server /g" /etc/ntp.conf
echo "server YOURSERVERNAME" >> /etc/ntp.conf
ntpdate YOURSERVERNAME   #synchronize right now
service ntpd start                #and keep in sync
chkconfig ntpd on       #after reboot as well

Step 2. Install required software

yum install krb5-workstation samba-common authconfig squid
chkconfig squid on

Step 3. Connect to active directory

Please note that MYCOMPANY.local and mycompany.local may be different domains due to the upper/lowercase.

ADSERVER=sbs.MYCOMPANY.local
DOMAIN=MYCOMPANY.local
WORKGROUP=MYCOMPANY
authconfig --enableshadow --enablemd5 --passalgo=md5 --krb5kdc=$ADSERVER \
--krb5realm=$DOMAIN --smbservers=$ADSERVER --smbworkgroup=$WORKGROUP \
--enablewinbind --enablewinbindauth --smbsecurity=ads --smbrealm=$DOMAIN \
--smbidmapuid="16777216-33554431" --smbidmapgid="16777216-33554431" --winbindseparator="+" \
--winbindtemplateshell="/bin/false" --enablewinbindusedefaultdomain --disablewinbindoffline \
--winbindjoin=Administrator --disablewins --disablecache --enablelocauthorize --updateall

I found some information saying that /var/cache/samba/winbindd_privileged should be chowned 750 to root:squid or that you should add user squid to group wbpriv. Also, squid.conf should not have cache_effective_group defined. However, this part was not relevant on my Centos 5.6. The reason could be that I installed 5.4, then upgraded, i'm not sure. Just leaving it as a note.

Now check your winbind connection using the following commands:
wbinfo -u
wbinfo -g

Step 4. Configure squid

auth_param ntlm program /usr/bin/ntlm_auth --helper-protocol=squid-2.5-ntlmssp 
auth_param ntlm children 5
auth_param ntlm keep_alive on
acl our_networks src 192.168.0.0/16
acl ntlm proxy_auth REQUIRED
http_access allow our_networks ntlm
authenticate_ip_ttl 900 seconds

This will allow all valid, logged in users to surf the web. You could also limit which users can surf by adding
--require-membership-of=ADGROUPNAME to the ntlm_auth command

Start Squid using /sbin/service squid restart and you're good to go.

You may want to check what else I'm writing on Squid. I'm planning to document a lot more in the next few weeks.

© GeekLabInfo Squid active directory authentication on Centos 5.6 is a post from GeekLab.info. You are free to copy materials from GeekLab.info, but you are required to link back to http://www.geeklab.info
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Useful VPN Services

Say you're living in China, and you have no web freedom whatsoever. Or in the Netherlands, and your favorite linux distro download site has been blocked by the corrupt "elite". Then having a tunnel to outside the country could be very useful.

I found two VPN services that seem very promising:
ItsHidden.com
MacroVPN.com

© GeekLabInfo Useful VPN Services is a post from GeekLab.info. You are free to copy materials from GeekLab.info, but you are required to link back to http://www.geeklab.info
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Share one VPN connection

My personal Linux laptop is a real spider in the web. It's got OpenVPN connections to the office, to the datacenter, to serveral family members, etcetera. I love it. But sometimes, there are some tasks that Linux simply can't do, like running a vSphere client.

For those situations, I use the second (Windows) computer on my desk to perform those tasks. However, this computer does not have a VPN connection right to the place I'm connecting to.
Lees verder

© GeekLabInfo Share one VPN connection is a post from GeekLab.info. You are free to copy materials from GeekLab.info, but you are required to link back to http://www.geeklab.info
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PXE Boot with old-style dhcp and tftp

In this article I'm covering the use of old-style dhcp and tftp, which is useful for company networks that have/need a complete dhcp server running. Personally, for smaller setups, I now prefer dnsmasq to do the job.

Booting from PXE

With most modern onboard and PCI network interface cards (NICs), it's possible to boot from the network. This system is called PXE.

Why would I want to boot from the network?

  • For installation of a computer without using CDs/DVD's
  • For thin clients
  • For booting diagnostic software
  • What is needed for PXE Boot?

  • a network card that supports PXE
  • a bios that supports plugin boot cards
  • a DHCP server
  • a TFTP server
  • some (open source) software you want to run
  • How to set up PXE boot?

    As I'm running (a variant of) RedHat Linux, I only cover how to set up PXE boot using Linux components. But there are Windows solutions as well. (Google it!)

    Step 1: set up DHCP

    When the NIC boots, it needs to get IP settings. Setup dhcp as usual. Now add these lines to the configuration:

    next-server <em>192.168.1.254</em>;
    filename "/pxelinux.0";

    In the place of 192.168.1.254, you need to enter your own tftp server address.

    On my RH system, I installed the dhcp server using yum install dhcp, then configured /etc/dhcpd.conf as follows:


    ddns-update-style ad-hoc;
    authoritative;
    log-facility local0;
    default-lease-time 86400;
    max-lease-time 86400;
    subnet 192.168.1.0 netmask 255.255.255.0{
        range 192.168.1.100 192.168.1.200; <em>#limited range</em>
       option subnet-mask 255.255.255.0;
        option broadcast-address 192.168.1.255;
        option routers 192.168.1.254;
        option domain-name-servers 192.168.1.254;
        option domain-name "lan";
        next-server 192.168.1.254;
        filename "/pxelinux.0";
    }

    Step 2: set up TFTP

    Download and install a tftp server. Most Linuxes ship their own, which you can install using yum (RedHat), yast (SuSE), apt-get (debian/ubuntu) or similar.

    On my RedHat, I install a tftp server by running yum install tftp-server. Then I enable it using /sbin/chkconfig tftp on and reload xinetd: /sbin/service xinetd restart.

    Step 3: download and install syslinux

    On my RedHat system, I install syslinux by running yum install syslinux. I then copy the syslinux.0 file to /tftpboot: cp /usr/lib/syslinux/pxelinux.0 /tftpboot

    Optional: Firewall

    On a default RedHat installation, the firewall is enabled. You may need to open port 67-69 for dhcpd and tftp to function and port 53 for DNS.

    Links

    More details are described on
    http://syslinux.zytor.com/wiki/index.php/PXELINUX

    © GeekLabInfo PXE Boot with old-style dhcp and tftp is a post from GeekLab.info. You are free to copy materials from GeekLab.info, but you are required to link back to http://www.geeklab.info
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