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OSP User Guide for Asterisk V1.6

9 February 2007

Table of Contents

Revision History
#1 Introduction
#2 OSP Toolkit
#2.1 Build OSP Toolkit
#2.1.1 Unpacking the Toolkit
#2.1.2 Preparing to build the OSP Toolkit
#2.1.3 Building the OSP Toolkit
#2.1.4 Installing the OSP Toolkit
#2.1.5 Building the Enrollment Utility
#2.2 Obtain Crypto Files
#3 Asterisk
#3.1 Configure for OSP Support
#3.1.1 Build Asterisk with OSP Toolkit
#3.1.2 osp.conf
#3.1.3 extensions.conf
#3.1.4 dahdi/sip/iax/h323/ooh323.conf
#3.2 OSP Dial Plan Functions
#3.2.1 OSPAuth
#3.2.2 OSPLookup
#3.2.3 OSPNext
#3.2.4 OSPFinish
#3.3 extensions.conf Examples
#3.3.1 Source Gateway
#3.3.2 Destination Gateway
#3.3.3 Proxy

Asterisk is a trademark of Digium, Inc.
TransNexus and OSP Secures are trademarks of TransNexus, Inc.

Revision History
Revision Date of Issue Description

1        26 Jul 2005   OSP Module User Guide for Asterisk V1.2
1.4      16 Jun 2006   OSP Module User Guide for Asterisk V1.4
1.6.0    13 Dec 2006   OSP Module User Guide for Asterisk V1.6
1.6.1    4 Jan 2007    Clarifying edits, add revision history, add general 
                       purpose extensions.conf example
1.6.2    9 Feb 2007    Replace OSP Toolkit site from SIPfoundry with 
                       SourceForge


1 Introduction
This document provides instructions on how to build and configure Asterisk V1.6 with the OSP Toolkit to enable secure, multi-lateral peering. This document is also available in the Asterisk source package as doc/osp.txt. The OSP Toolkit is an open source implementation of the OSP peering protocol and is freely available from https://sourceforge.net/projects/osp-toolkit. The OSP standard defined by the European Telecommunications Standards Institute (ETSI TS 101 321) www.etsi.org. If you have questions or need help, building Asterisk with the OSP Toolkit, please post your question on the OSP mailing list at https://lists.sourceforge.net/lists/listinfo/osp-toolkit-client.


2 OSP Toolkit
Please reference the OSP Toolkit document "How to Build and Test the OSP Toolkit” available from https://sourceforge.net/projects/osp-toolkit.


2.1 Build OSP Toolkit
The software listed below is required to build and use the OSP Toolkit:

  • OpenSSL (required for building) - Open Source SSL protocol and Cryptographic Algorithms (version 0.9.7g recommended) from www.openssl.org. Pre-compiled OpenSSL binary packages are not recommended because of the binary compatibility issue.
  • Perl (required for building) - A programming language used by OpenSSL for compilation. Any version of Perl should work. One version of Perl is available from www.activestate.com/Products/ActivePer. If pre-compiled OpenSSL packages are used, Perl package is not required.
  • C compiler (required for building) - Any C compiler should work. The GNU Compiler Collection from www.gnu.org is routinely used for building the OSP Toolkit for testing.


2.1.1 Unpacking the Toolkit
After downloading the OSP Toolkit (version 3.3.6 or later release) from www.sourceforge.net, perform the following steps in order:

  • Copy the OSP Toolkit distribution into the directory where it will reside. The default directory for the OSP Toolkit is /usr/src.

*Un-package the distribution file by executing the following command:

Where ### is the version number separated by underlines. For example, if the version is 3.3.6, then the above command would be:

A new directory (TK-3_3_6-20060303) will be created within the same directory as the tar file.

  • Go to the TK-3_3_6-20060303 directory by running this command:

Within this directory, you will find directories and files similar to what is listed below if the command "ls -F" is executed):

ls -F
enroll/
RelNotes.txt				lib/
README.txt				license.txt
bin/					src/
crypto/					test/
include/


2.1.2 Preparing to build the OSP Toolkit

  • Compile OpenSSL according to the instructions provided with the OpenSSL distribution (You would need to do this only if you don’t have openssl already).
  • Copy the OpenSSL header files (the *.h files) into the crypto/openssl directory within the osptoolkit directory. The OpenSSL header files are located under the openssl/include/openssl directory.
  • Copy the OpenSSL library files (libcrypto.a and libssl.a) into the lib directory within the osptoolkit directory. The OpenSSL library files are located under the openssl directory.
    Note: Since the Asterisk requires the OpenSSL package. If the OpenSSL package has been installed, steps 4 through 6 are not necessary.
  • Optionally, change the install directory of the OSP Toolkit. Open the Makefile in the /usr/src/TK-3_3_6-20060303/src directory, look for the install path variable – INSTALL_PATH, and edit it to be anywhere you want (defaults /usr/local).
    Note: Please change the install path variable only if you are familiar with both the OSP Toolkit and the Asterisk.


2.1.3 Building the OSP Toolkit

  • From within the OSP Toolkit directory (/usr/src/TK-3_3_6-20060303), start the compilation script by executing the following commands:


2.1.4 Installing the OSP Toolkit

The header files and the library of the OSP Toolkit should be installed. Otherwise, you must specify the OSP Toolkit path for the Asterisk.

  • Use the make script to install the Toolkit.

The make script is also used to install the OSP Toolkit header files and the library into the INSTALL_PATH specified in the Makefile.

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Please make sure you have the rights to access the INSTALL_PATH directory. For example, in order to access /usr/local directory, root privileges are required.


2.1.5 Building the Enrollment Utility

Device enrollment is the process of establishing a trusted cryptographic relationship between the VoIP device and the OSP Server. The Enroll program is a utility application for establishing a trusted relationship between an OSP client and an OSP server. Please see the document "Device Enrollment" at http://www.transnexus.com/OSP%20Toolkit/OSP%20Toolkit%20Documents/Device_Enrollment.pdf for more information about the enroll application.

  • From within the OSP Toolkit directory (example: /usr/src/TK-3_3_6-20060303), execute the following commands at the command prompt:

Compilation is successful if there are no errors in the compiler output. The enroll program is now located in the OSP Toolkit/bin directory (example: /usr/src/ TK-3_3_6-20060303/bin).


2.2 Obtain Crypto Files

The OSP module in Asterisk requires three crypto files containing a local certificate (localcert.pem), private key (pkey.pem), and CA certificate (cacert_0.pem). Asterisk will try to load the files from the Asterisk public/private key directory - /var/lib/asterisk/keys. If the files are not present, the OSP module will not start and the Asterisk will not support the OSP protocol. Use the enroll.sh script from the toolkit distribution to enroll Asterisk with an OSP server and obtain the crypto files. Documentation explaining how to use the enroll.sh script (Device Enrollment) to enroll with an OSP server is available at http://www.transnexus.com/OSP%20Toolkit/OSP%20Toolkit%20Documents/Device_Enrollment.pdf. Copy the files generated by the enrollment process to the Asterisk /var/lib/asterisk/keys directory.

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The osptestserver.transnexus.com is configured only for sending and receiving non-SSL messages, and issuing signed tokens. If you need help, post a message on the OSP mailing list at https://lists.sourceforge.net/lists/listinfo/osp-toolkit-client

The enroll.sh script takes the domain name or IP addresses of the OSP servers that the OSP Toolkit needs to enroll with as arguments, and then generates pem files – cacert_#.pem, certreq.pem, localcert.pem, and pkey.pem. The ‘#’ in the cacert file name is used to differentiate the ca certificate file names for the various SP’s (OSP servers). If only one address is provided at the command line, cacert_0.pem will be generated. If 2 addresses are provided at the command line, 2 files will be generated – cacert_0.pem and cacert_1.pem, one for each SP (OSP server). The example below shows the usage when the client is registering with osptestserver.transnexus.com.

The files generated should be copied to the /var/lib/asterisk/keys directory.

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The script enroll.sh requires AT&T korn shell (ksh) or any of its compatible variants. The /usr/src/TK-3_3_6-20060303/bin directory should be in the PATH variable. Otherwise, enroll.sh cannot find the enroll file.


3 Asterisk

In Asterisk, all OSP support is implemented as dial plan functions. In Asterisk V1.6, all combinations of routing between OSP and non-OSP enabled networks using any combination of SIP, H.323 and IAX protocols are fully supported. Section
3.1 describes the three easy steps to add OSP support to Asterisk:

  1. Build Asterisk with OSP Toolkit
  2. Configure osp.conf file
  3. Cut and paste to extensions.conf

Sections 3.2 and 3.3 provide a detailed explanation of OSP dial plan functions and configuration examples. The detailed information provided in Sections 3.2 and 3.3 is not required for operating Asterisk with OSP, but may be helpful to developers who want to customize their Asterisk OSP implementation.


3.1 Configure for OSP Support


3.1.1 Build Asterisk with OSP Toolkit

The first step is to build Asterisk with the OSP Toolkit. If the OSP Toolkit is installed in the default install directory, /usr/local, no additional configuration is required. Compile Asterisk according to the instructions provided with the Asterisk distribution.

If the OSP Toolkit is installed in another directory, such as /myosp, Asterisk must be configured with the location of the OSP Toolkit. See the example below.

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Please change the install path only if you familiar with both the OSP Toolkit and the Asterisk. Otherwise, the change may result in Asterisk not supporting the OSP protocol.


3.1.2 osp.conf

The /etc/asterisk/osp.conf file, shown below, contains configuration parameters for using OSP. Two parameters, servicepoint and source must be configured. The default values for all other parameters will work well for standard OSP implementations.


3.1.3 extensions.conf

OSP functions are implemented as dial plan functions in the extensions.conf file. To add OSP support to your Asterisk server, simply copy and paste the text box below to your extensions.conf file. These functions will enable your Asterisk server to support all OSP call scenarios. Configuration of your Asterisk server for OSP is now complete.


3.1.4 dahdi/sip/iax/h323/ooh323.conf

There is no configuration required for OSP.


3.2 OSP Dial Plan Functions

This section provides a description of each OSP dial plan function.


3.2.1 OSPAuth

OSP token validation function.
Input:

  • OSPPEERIP: last hop IP address
  • OSPINTOKEN: inbound OSP token
  • provider: OSP service provider configured in osp.conf. If it is empty, default provider is used.
  • priority jump

Output:

  • OSPINHANDLE: inbound OSP transaction handle
  • OSPINTIMELIMIT: inbound call duration limit
  • OSPAUTHSTATUS: OSPAuth return value. SUCCESS/FAILED/ERROR


3.2.2 OSPLookup

OSP lookup function.

Input:

  • OSPPEERIP: last hop IP address
  • OSPINHANDLE: inbound OSP transaction handle
  • OSPINTIMELIMIT: inbound call duration limit
  • exten: called number
  • provider: OSP service provider configured in osp.conf. If it is empty, default provider is used.
  • priority jump
  • callidtypes: Generate call ID for the outbound call. h: H.323; s: SIP; i: IAX. Only h, H.323, has been implemented.

Output:

  • OSPOUTHANDLE: outbound transaction handle
  • OSPTECH: outbound protocol
  • OSPDEST: outbound destination IP address
  • OSPCALLED: outbound called nummber
  • OSPCALLING: outbound calling number
  • OSPOUTTOKEN: outbound OSP token
  • OSPRESULTS: number of remaining destinations
  • OSPOUTTIMELIMIT: outbound call duration limit
  • OSPOUTCALLIDTYPES: same as input callidtypes
  • OSPOUTCALLID: outbound call ID. Only for H.323
  • OSPDIALSTR: outbound dial string
  • OSPLOOKUPSTATUS: OSPLookup return value. SUCCESS/FAILED/ERROR


3.2.3 OSPNext

OSP lookup next function.

Input:

  • OSPINHANDLE: inbound transaction handle
  • OSPOUTHANDLE: outbound transaction handle
  • OSPINTIMELIMIT: inbound call duration limit
  • OSPOUTCALLIDTYPES: types of call ID generated by Asterisk.
  • OSPRESULTS: number of remain destinations
  • cause: last destination disconnect cause
  • priority jump

Output:

  • OSPTECH: outbound protocol
  • OSPDEST: outbound destination IP address
  • OSPCALLED: outbound called number
  • OSPCALLING: outbound calling number
  • OSPOUTTOKEN: outbound OSP token
  • OSPRESULTS: number of remain destinations
  • OSPOUTTIMELIMIT: outbound call duration limit
  • OSPOUTCALLID: outbound call ID. Only for H.323
  • OSPDIALSTR: outbound dial string
  • OSPNEXTSTATUS: OSPLookup return value. SUCCESS/FAILED/ERROR


3.2.4 OSPFinish

OSP report usage function.

Input:

  • OSPINHANDLE: inbound transaction handle
  • OSPOUTHANDLE: outbound transaction handle
  • OSPAUTHSTATUS: OSPAuth return value
  • OSPLOOKUPTSTATUS: OSPLookup return value
  • OSPNEXTSTATUS: OSPNext return value
  • cause: last destination disconnect cause
  • priority jump

Output:

  • OSPFINISHSTATUS: OSPLookup return value. SUCCESS/FAILED/ERROR


3.3 extensions.conf Examples

The extensions.conf file example provided in Section 3.1 is designed to handle all OSP call scenarios when Asterisk is used as a source or destination gateway to the PSTN or as a proxy between VoIP networks. The extenstion.conf examples in this section are designed for specific use cases only.


3.3.1 Source Gateway

The examples in this section apply when the Asterisk server is being used as a TDM to VoIP gateway. Calls originate on the TDM network and are converted to VoIP by Asterisk. In these cases, the Asterisk server queries an OSP server to find a route to a VoIP destination. When the call ends, Asterisk sends a CDR to the OSP server.
For SIP protocol.

For IAX protocol.

For H.323 protocol.


3.3.2 Destination Gateway
The examples in this section apply when Asterisk is being used as a VoIP to TDM gateway. VoIP calls are received by Asterisk which validates the OSP peering token and completes to the TDM network. After the call ends, Asterisk sends a CDR to the OSP server.

For SIP protocol

For IAX protocol

For H.323 protocol


3.3.3 Proxy

The example in this section applies when Asterisk is a proxy between two VoIP networks.

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