As soon as you have packets arriving on your sip:carrier server, it will require a bit of time of your CPU. Denial of Service attacks are aimed to break down your system by sending floods of SIP messages in a very short period of time and keep your system busy to handle such huge amount of requests. sip:carrier allows you to block such kind of attacks quite easily, by configuring the following section in your /etc/ngcp-config/config.yml :

security:
  dos_ban_enable: 'yes'
  dos_ban_time: 3600
  dos_reqs_density_per_unit: 50
  dos_sampling_time_unit: 2
  dos_whitelisted_ips: []
  dos_whitelisted_subnets: []

Basically, as soon as sip:carrier receives more than 50 messages from the same IP in a time window of 2 seconds, that IP will be blocked for 3600 sec, and you will see in the the kamailio-lb.log a line saying:

Nov 9 00:11:53 sp1 lb[41958]: WARNING: <script>: IP '1.2.3.4' is blocked and banned - R=<null> ID=304153-3624477113-19168@tedadg.testlab.local

The banned IP will be stored in kamailio memory, you can check the list via web interface or via the following command:

# ngcp-kamctl lb fifo sht_dump ipban

	You have to run this command on ACTIVE load balancer node.

Excluding SIP endpoints from banning

There may be some SIP endpoints that send a huge traffic towards NGCP from a specific IP address. A typical example is a SIP Peering Server.

	sip:carrier supports handling such situations by excluding all defined SIP Peering Servers from DoS protection mechanism.

The NGCP platform administrator may also add whitelisted IP addresses manually in /etc/ngcp-config/config.yml at kamailio.lb.security.dos_whitelisted_ips and kamailio.lb.security.dos_whitelisted_subnets parameters.

This is a very common attack you can easily detect checking your /var/log/ngcp/kamailio-proxy.log. You will see INVITE/REGISTER messages coming in with strange usernames. Attackers is trying to spoof/guess subscriber’s credentials, which allow them to call out. The very first protection against these attacks is: ALWAYS USE STRONG PASSWORD. Nevertheless sip:carrier allow you to detect and block such attacks quite easily, by configuring the following /etc/ngcp-config/config.yml section:

  failed_auth_attempts: 3
  failed_auth_ban_enable: 'yes'
  failed_auth_ban_time: 3600

You may increase the number of failed attempt if you want (in same cases it’s better to be safed, some users can be banned accidentally because they are not writing the right password) and adjust the ban time. If a user try to authenticate an INVITE (or REGISTER) for example and it fails more then 3 times, the "user@domain" (not the IP as for Denial of Service attack) will be block for 3600 seconds. In this case you will see in your /var/log/ngcp/kamailio-lb.log the following lines:

Nov 9 13:31:56 sp1 lb[41952]: WARNING: <script>: Consecutive Authentication Failure for 'sipvicous@mydomain.com' UA='sipvicous-client' IP='1.2.3.4' - R=<null> ID=313793-3624525116-589163@testlab.local

Both the banned IPs and banned users are shown in the Admin web interface, you can check them by accessing the Security Bans section in the main menu. You can check the banned user as well by retrieving the same info directly from kamailio memory, using the following commands:

# ngcp-kamctl lb fifo sht_dump auth

	You have to run this command on ACTIVE load balancer node.

The term "topology hiding" in SIP is used to describe the measures taken by typically an SBC (Session Border Controller) to hide detailed information of the internal network at the border of which it is located. Pieces of information such as IP addresses and port numbers used by SIP endpoints and intermediaries within the network are considered sensitive, as these can give some hints to potential attackers about the topology of the network.

In a typical SIP session the mandatory headers may carry that sensitive information, for example: Contact, Via, Record-Route, To, From, Call-ID. An SBC applying topology hiding will mangle the content of those headers.

Concealment of sensitive information is achieved through encoding the original content of selected SIP headers. Then NGCP will create a new SIP URI using a preselected IP address and the encoded content as URI parameter, finally re-assembling the SIP header.

Examples for encoded SIP headers:

Record-Route: <sip:127.0.0.8;line=sr-NvaAlWtecghucEhu6WtAcu...>
Contact: <sip:127.0.0.8;line=sr-NvaAli-1VeL.kRxLcbN86W...>

The load-balancer element of the Sipwise NGCP has an SBC role, from the SIP peers point of view. The LB offers topology hiding function that can be simply activated through a configuration change. By default the function is disabled.

Activating topology hiding function is possible through the modification of the following configuration parameters in /etc/ngcp-config/config.yml file (shown below with default values of parameters):

kamailio:
  lb:
    security:
      topoh:
        enable: no
        mask_callid: no
        mask_ip: 127.0.0.8

Meaning of the configuration parameters:

Although hiding sensitive information about a SIP provider’s network is desired, there are some potential side effects caused by topology hiding.

The most common example is the consequence that SIP message size may grow when applying topology hiding. The fact that SIP messages become larger may even prevent NGCP from communicating successfully with another SIP entity (a peer SBC, for example). This can be expected under following circumstances:

In such a case the IP packets carrying SIP messages with encoded headers will have a size exceeding the MTU, that will cause loss of data.

The recommended solution in such a case is to use TCP transport for SIP messages.

The easiest way to fetch information about a single call among the log files is the search for the SIP CallID (a unique identifier for a SIP dialog). The call ID is used as call marker in almost all the voip related log file, such as /var/log/ngcp/kamailio-lb.log , /var/log/ngcp/kamailio-proxy.log , /var/log/ngcp/sems.log or /var/log/ngcp/rtp.log. Example of kamailio-proxy.log line:

Nov 19 00:35:56 sp1 proxy[7475]: NOTICE: <script>: New request on proxy - M=REGISTER R=sip:sipwise.local
F=sip:jdoe@sipwise.local T=sip:jdoe@sipwise.local IP=10.10.1.10:5060 (127.0.0.1:5060) ID=364e4676776621034977934e055d19ea@127.0.0.1 UA='SIP-UA 1.2.3.4'

The above line shows the SIP information you can find in a general line contained in /var/log/ngcp/kamailio-*:

In order to collect the full log related to a single call, it’s necessary to "grep" the /var/log/ngcp/kamailio-proxy.log using the ID= string, for example:

# grep "364e4676776621034977934e055d19ea@127.0.0.1" /var/log/ngcp/kamailio-proxy.log

The sip:carrier platform provides several tools to collect SIP traces. It can be used the sip:carrier ngrep-sip tool to collect SIP traces, for example to fetch traffic in text format from outbound and among load balancer, proxy and sems :

# ngrep-sip b

see the manual to know all the options:

# man ngrep-sip

The ngrep debian tool can be used in order to make a SIP trace and save it into a .pcap file :

# ngrep -s0 -Wbyline -d any -O /tmp/SIP_trace_file_name.pcap port 5062 or port 5060

The sngrep debian graphic tool as well can be used to visualize SIP trace and save them in a .pcap file :

# sngrep