Asterisk VoIP Security

I leave here a link to the webinar on security in asterisk that took place last Friday. The speakers were an FBI agent, an expert from VOIPSA and two employee of the company Digium.

very interesting ..


Provisioning Linksys SPA922

When I started in the world of Asterisk, one of the important things to deploy a VoIP network is the segmentation of the network VLANs to separate voice and data. When I started two years ago, only knew two options:

– Use different network but this implies duplicate the number of the switches (much money and in my opinion unprofessional).
– Use VLAN’s to separate the networks. This option is better although requires much administrative work whenever there is change a site computer or telephone.

I was investigating the way this is done automatically and it seems that something went.

Here I leave an example implementation.

In this scenario We are going to configure a system to provisioning Linksys Phones (SPA922). Firts We have to configure our network LAN with 2 vlans (or more) to separate the data and voice network. We have used Cisco Switches (Catalyst 2960 and 3750).


The IP range ov Vlans are this:

Vlan 1 -> data network ->
Vlan 2 -> voice network ->

We need to have two DHCP servers, one in each vlan. In the vlan 1 we have configured one DHCP server (Windows 2003 Server) which will be the principal DHCP server. This is the configuration:

003 Router
006 DNS Servers
015 DNS Domain Name
044 WINS/NBNS Servers
046 WINS/NBNS Node Type 0x8
066 Boot Server Host Name (TFTP Server)

In the other Vlan (voIP), we have Asterisk server with DHCP server and TFTP Server. These are the configs:

apt-get install dhcpd

/etc/dhcp3# vim dhcpd.conf

subnet netmask
option domain-name-servers;
option routers;
option subnet-mask;
option broadcast-address;
option tftp-server-name "";
default-lease-time 600;
max-lease-time 7200;


apt-get install atftpd

/etc/default# vim atftpd

OPTIONS="--daemon --port 69 --tftpd-timeout 300 --retry-timeout 5 --mcast-port 1758 --mcast-addr --mcast-ttl 1 --maxthread 100 --verbose=5 /tftpboot"

The tftp server configuration file indicates that the config are int tftpboot directory where we have configured the general config file for all phones and the especific config files to the phones too.

/etc/tftpboot# vim spa922.cfg


<Profile_Rule ua="na">/spa922-MAC/spa922-$MA.cfg</Profile_Rule>

<!-- SYSTEM -->
<Primary_NTP_Server ua="na"></Primary_NTP_Server>
<Time_Zone ua="na">GMT+01:00</Time_Zone>

<!-- TIMERS -->
<Interdigit_Long_Timer ua="na">25</Interdigit_Long_Timer>

<!-- SIP -->

<Use_Auth_ID_1_ ua="na">No</Use_Auth_ID_1_>

<Dial_Plan_1_ ua="na">([1345]xxxS0|6xxxxxxxxS0|9xxxxxxxxS0|xx.)</Dial_Plan_1_>
<Enable_IP_Dialing_1_ ua="na">No</Enable_IP_Dialing_1_>

<Enable_VLAN ua="rw"> yes </Enable_VLAN>
<VLAN_ID ua="rw"> 2 </VLAN_ID>


Network Link Redundancy

Folow these steps to create a Link redundancy in a server with two ethernet cards in Debian 4.0Etch.

– 1. apt-get install ifenslave (ifenslave-2.6)

– 2. Create a file called aliases-bond in /etc/modprobe.d/ with the next content:

|alias bond0 bonding|

|options bond0 mode=1 arp_internal=2000 arp_ip_target=”the gateway”|

– 3. load bonding with this command -> modprobe bonding

– 4. add “bonding” to /etc/modules

– 5. Edit /etc/network/interfaces

|auto bond0|

|iface bond0 inet static|

|pre-up modprobe bond0|

|hwaddress ether “the mac address of one of the ethernet card”|

|address “ip address”|

|netmask “subnet mask”|

|gateway “gateway”|

|dns-nameservers X.X.X.X  X.X.X.X|
|up ifenslave bond0 eth0 eth1|

|down ifenslave -d bond0 eth0 eth1|

It Works!!


OMA (Outlook Mobile Access) in Symbian OS

This Howto is to use Symbian Mobiles with Microsoft Outlook Mobile Access (OMA)

686px-Symbian_OS_logosvgWe Suppose that OMA server is installed and configured.

First we have to convert the Exchange certificate from extension .cer to extension .der to works in symbian OS. (certificates with .cer extension doesn´t work in symbian OS)

Download and install OpenSSL Software:

Execute this commands in the shell to convert the certificate:

Convert CER (.crt .der) to PEM

openssl x509 -inform der -in “MYCERT.cer” -out “MYCERT.pem”

Convert PEM to DER

openssl x509 -outform der -in “MYCERT.pem” -out “MYCERT.der”

Copy and install the certificate with the extension .der to the mobile.

Download the software “Mail For Exchange” to synchronize the mobile with the exchange server.

Install this software in the mobile and configure with the settings of the Exchange Server.

It Works!!.

Debian “Etch” + Asterisk + Asterisk-Addons + Zaptel + Libpri + mISDN + Asterisk-GUI

This Howto is to install Asterisk on a fresh Debian “Etch” system.
After download a netinstall image of Debian 4.0r1 and configure localization, language, partitions and so on, in the final steps, debian should now be asking you what packages you want installed.

Choose base system only.

After finish installation and first reboot, login with root and:

aptitude update
aptitude upgrade


aptitude install ssh ntp

From here, the next steps were done from a ssh session with putty client.

Compiling New Custom Kernel *** Optional ***

aptitude install kernel-package libncurses5-dev fakeroot wget bzip2 build-essential

cd /usr/src


tar xjf linux-2.6.*

ln -s /usr/src/linux- /usr/src/linux

cd /usr/src/linux

Copy the current kernel configuration to /usr/src/linux

make clean && make mrproper

cp /boot/config-`uname -r` ./.config

make menuconfig

In the configuration menu, we select “Load alternate configuration…” and choose the config file that we have copy in the /usr/src/linux directory. /usr/src/linux/.config

We are going to modify some parameters in the kernel configuration:

In the subsection “Processor type and features” we check:

“Enable IRQ balancing” is disabled
“Timer frequency” change the value 250 Hz by 1000 Hz.
“High Resolution Timer Option” and “HPET Timer Support” as built-in.
For users with NVidia SATA drives unchek “Paravirtualization Support”.

And under “Library Routines” subsection, “CONFIG_CRC_CCITT” must be enabled.

When we had made this changes we save the configuration and exit.

Building the new .deb kernel and headers packages :

make-kpkg clean
fakeroot make-kpkg –initrd –append-to-version=-custom kernel_image kernel_headers

After the compilation will be two .deb packages under directory /usr/src/

Install the new packages.

cd /usr/src
dpkg -i linux-image-
dpkg -i linux-headers-


Test the new kernel is loaded.

uname -a

The output must be something similar to “Linux asterisk

*** Finish *** Optional *** Compiling Custom Kernel

Go for dependencies…

aptitude install build-essential libcurl3-dev libvorbis-dev libspeex-dev unixodbc unixodbc-dev libiksemel-dev flex xsltproc

aptitude install linux-headers-`uname -r` g++ libncurses5-dev libnewt-dev libusb-dev subversion git-core

Downloading and untarring…

cd /usr/src


tar xvzf asterisk-1.4-current.tar.gz && tar xvzf zaptel-1.4-current.tar.gz && tar xvzf libpri-1.4-current.tar.gz && tar xvzf mISDN.tar.gz && tar xvzf mISDNuser.tar.gz && tar xvzf asterisk-addons-1.4.5.tar.gz

Installing Zaptel

cd /usr/src/zaptel-1.4*
./install_prereq test
./install_prereq install

make install
make config
modprobe ztdummy

Installing Libpri

cd /usr/src/libpri-1.4*
make && make install

Installing mISDN

Note: The current version (1.1.7) not compile with the last kernel ( The ( is tested that works.

cd /usr/src/mISDN
make install
cd /usr/src/mISDNuser/
make && make install


mISDN scan
mISDN config

This creates the file /etc/mISDN.conf which you should review and/or edit.

vi /etc/mISDN.conf

If everything looks good, going to start mISDN

mISDN start

and check everything is right,


Running on startup…

/usr/sbin/update-rc.d mISDN defaults 15 30

Installing Asterisk

cd /usr/src/asterisk-1.4*

The next step is not mandatory. For install core and extra sounds in different languages:

make menuselect

select the core-sounds you would like to play and extra sounds. Exit with “x” to save.

make install
make samples
make config
asterisk -vvvc
stop now
echo “ztdummy” >> /etc/modules

Note: If you make a mistake and/or fail compilation, you need to run:

make clean then ./configure and make install again.

Going to reboot for test the system startup is correct.


asterisk -r

Install Asterisk-Addons

cd /usr/src/asterisk-addons*

./configure && make && make install

make samples

Install Asterisk-GUI

If you have asterisk config files (no new install), backup it…

cp -r /etc/asterisk /etc/asterisk.bak

Download and install Asterisk-GUI

cd /usr/src
svn checkout asterisk-gui
cd /usr/src/asterisk-gui
./configure && make && make install
make samples

Some tweaks to configuration files…

cat << EOF >/etc/asterisk/http.conf

cat << EOF >/etc/asterisk/manager.conf
displaysystemname = yes
enabled = yes
webenabled = yes
port = 5038
;httptimeout = 60
bindaddr =

secret = admin
read = system,call,log,verbose,command,agent,config
write = system,call,log,verbose,command,agent,config

Checking configuration…

make checkconfig

asterisk -r

Try, configure and enjoy your new system… with admin/admin login or your setup config…


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