Presence Tutorial

This tutorial describes how to setup OpenSIPS Presence Agent together with OpenXCAP Presence Policy server and Blink SIP client. The interactions with Blink client are described here:

http://projects.ag-projects.com/news/15

OpenXCAP setup

Database setup

Both OpenXCAP backends (Database and OpenSIPS) depend on a database engine to store service subscribers and XCAP resources. The database creation scripts are found in the scripts/ directory, but it's tipically created using the opensipsdbctl tool provided by OpenSIPS.

Create Tables

If you use OpenSIPS backend, you do not need to create any tables and configure OpenXCAP to use the same database as OpenSIPS.

If you want to setup OpenXCAP to use its own database, create the database:

mysqladmin create openxcap

and the tables using the script:

source:scripts/mysql-create-tables.sql

This script creates two tables:
  1. subscriber, which is used to authenticate XCAP requests
  2. xcap, where the XCAP documents are actually stored

The subscriber table is a subset of the subscriber table from OpenSIPS, xcap table is the same as the one from OpenSIPS.

Add MySQL user

Use the following script as template, edit it first and run it against on your database:

source:scripts/mysql-create-user.sql

Server configuration

If you have installed the debian package copy /etc/openxcap/config.ini.sample to /etc/openxcap/config.ini. For other Linux OS copy config.ini.sample from the tar archive to the same directory. Edit config.ini with your settings.

source:"config.ini.sample"

The specific settings for an installation must be set from the configuration file, which is split in several configuration sections.

The [Server] section contains global settings: the IP address and port where OpenXCAP listens for client requests.

The XCAP root is the context that contains all the documents across all applications and users that are managed by the server. Only the client requests that address the root defined here are accepted. If the root URI has the "https" scheme, the server will listen for requests in TLS mode. The X509 certificate and private key that will identify the server are loaded using the values in the [TLS] section.

OpenXCAP support multiple, interchangeable backend modules. Each backend knows where and how to authorize and authenticate XCAP users and where to store the XCAP documents. Currently, supported values are "Database" and "OpenSIPS", the specific settings will be taken the corresponding sections, [Database] or [OpenSIPS].

An XCAP request must be authenticated before it's handled, and the various settings are found in the [Authentication] section.

A trusted peer IP list can be defined, requests matching this list will be accepted without authentication.

Client requests must be authenticated in the context of a realm that is the same as the SIP domain. This realm is derived in real time for each request using the following logic:

  • if the user section of the XCAP URI (the section following the "users" path segment) is in the form of username@domain, the realm is taken from the domain part
  • some XCAP clients (e.g. CounterPath's Eyebeam), only put the username in the XCAP URI, so there is the need for a convention to determine the realm: it must be included in the XCAP root URI on the client side. For example, if the XCAP root of the server is http://example.com/xcap-root, the client should be provisioned with http://example.com/xcap-root@domain/
  • if the above logic does not provide the realm, the realm will be taken from the default_realm setting of [Authentication]

The Database section contains the database connection URI to the database where the service subscribers are kept (authentication_db_uri) and the database connection URI to the database where XCAP documents are stored. Currently, only MySQL database engine has been implemented.

The OpenSIPS section contains all the settings of the Database section, plus the URL where OpenSIPS's XMLRPC management interface is listening for commands. The refreshWatchers and rls_update_subscriptions commands are sent to OpenSIPS management interface to inform the server that the XCAP documents have been changed for a user so that OpenSIPS can send notifications out according to the new policy in real-time.

When using TLS you must generate an X.509 certificate and a key. Consult Internet resources for how to do this. The procedure is the same as for any other TLS server like Apache web server.

Running

For non Debian systems copy the openxcap startup script from the debian directory present in the tar file to /etc/init.d/ and edit it to match your system.

Start OpenXCAP server:

sudo /etc/init.d/openxcap start

You can also start OpenXCAP in no fork mode, which is useful to debug the configuration. This will not put the server in the background and will log its messages in the console where it was started:

adigeo@ag-imac3:~/work/openxcap$sudo ./openxcap --no-fork
Starting OpenXCAP 2.1.0
Listening on: 0.0.0.0:80
XCAP root: http://xcap.example.com/xcap-root
xcap.server.HTTPFactory starting on 80

Logging

OpenXCAP logs its start, stop and error messages to /var/log/syslog. Client access requests are logged in /var/log/openxcap/access.log. You can configure the logging of the headers and bodies of client requests and responses in the Logging section of the configuration file.

Adding Accounts

The accounts used for authentication of XCAP requests are stored in OpenSIPS subscriber table. You can add subscribers by using your favorite OpenSIPS subscriber management tool (OpenSIPS provides the opensipsctl command line script with the default installation). The following script that can also be used to manually add accounts to opensips subscriber table:

source:scripts/add-openxcap-user.py

After completing this chapter, go to Testing section.

OpenSIPS setup

The following OpenSIPS configuration example enables OpenSIPS to act like a dedicated SIP Presence agent that accepts messages from a trusted SIP Proxy with XCAP authorization enabled using OpenXCAP as policy server. The SIP Proxies defined as trusted peers must be configured to authenticate and authorize the PUBLISH and SUBSCRIBE methods and deal with NAT traversal.

Is advisable to consult http://opensips.org web site, documentation section for up to date settings documentation.

Settings (save as settings.m4):

divert(-1)
define(`SERVER_IP',`127.0.0.1')
define(`UDP_PORT', `5060')
define(`TCP_PORT', `5060')
define(`TLS_PORT', `5061')
define(`XMLRPC_PORT', `8000')
define(`ENABLE_TCP', `no')             # OpenSIPS will listen on TCP for SIP requests
define(`ENABLE_TLS', `no')             # OpenSIPS will listen on TLS for SIP requests
define(`TRUSTED_PEERS_GROUP', `42')    # ID of the group containing the trusted peers
define(`DB_URL', `mysql://opensips:opensipsrw@localhost/opensips')     # Database address
# Helpers
define(`PRESENCE_SERVER_ADDRESS', `sip:presence@SERVER_IP:UDP_PORT')
define(`RLS_SERVER_ADDRESS', `sip:rls@SERVER_IP:UDP_PORT')
divert

OpenSIPS configuration (save as opensips.m4):

#
# OpenSIPS Presence Agent script
#     by AG Projects <support@ag-projects.com>
#
# This OpenSIPS configuration example enables OpenSIPS to act like a dedicated SIP Presence agent that accepts messages
# from a trusted SIP Proxy with XCAP authorization enabled using OpenXCAP as policy server. The SIP Proxies defined as trusted
# peers must be configured to authenticate and authorize the PUBLISH and SUBSCRIBE methods and deal with NAT traversal.
#
# You can enable / disable more features / functionalities by
#   re-generating the scenario with different options.
#
# Please refer to the Core CookBook at:
#      http://www.opensips.org/Resources/DocsCookbooks
# for a explanation of possible statements, functions and parameters.
#

####### Global Parameters #########

debug=3
log_stderror=no
log_facility=LOG_LOCAL0

fork=yes
children=4

/* uncomment the following lines to enable debugging */
#debug=6
#fork=no
#log_stderror=yes

/* uncomment the next line to enable the auto temporary blacklisting of
   not available destinations (default disabled) */
#disable_dns_blacklist=no

/* uncomment the next line to enable IPv6 lookup after IPv4 dns
   lookup failures (default disabled) */
#dns_try_ipv6=yes

/* comment the next line to enable the auto discovery of local aliases
   based on revers DNS on IPs */
auto_aliases=no

listen=udp:SERVER_IP:UDP_PORT

ifelse(ENABLE_TCP, `yes', `disable_tcp=no
listen=tcp:SERVER_IP:TCP_PORT' , `
ifelse(ENABLE_TLS,`yes',`disable_tcp=no
',`disable_tcp=yes')')

ifelse(ENABLE_TLS,`yes',`disable_tls=no
listen=tls:SERVER_IP:TLS_PORT
tls_verify_server=1
tls_verify_client = 1
tls_require_client_certificate = 0
tls_method = TLSv1
tls_certificate = "/usr/local/etc/opensips/tls/user/user-cert.pem" 
tls_private_key = "/usr/local/etc/opensips/tls/user/user-privkey.pem" 
tls_ca_list = "/usr/local/etc/opensips/tls/user/user-calist.pem" 
', `disable_tls=yes')

####### Modules Section ########

#set module path
mpath="/usr/local/lib/opensips/modules/" 

#### SIGNALING module
loadmodule "signaling.so" 

#### StateLess module
loadmodule "sl.so" 

#### Transaction Module
loadmodule "tm.so" 

#### Record Route Module
loadmodule "rr.so" 

#### MAX ForWarD module
loadmodule "maxfwd.so" 

#### FIFO Management Interface
loadmodule "mi_fifo.so" 
modparam("mi_fifo", "fifo_name", "/tmp/opensips_presence_fifo")
modparam("mi_fifo", "fifo_mode", 0666)

#### XMLRPC Management Interface
loadmodule "mi_xmlrpc.so" 
modparam("mi_xmlrpc", "port", XMLRPC_PORT)

#### URI module
loadmodule "uri.so" 

#### DB MySQL module
loadmodule "db_mysql.so" 

#### DOMAIN module
loadmodule "domain.so" 
modparam("domain", "db_url", "DB_URL")
modparam("domain", "db_mode", 1)
modparam("usrloc|uri", "use_domain", 1)

#### PERMISSIONS module
loadmodule "permissions.so" 
modparam("permissions", "db_url", "DB_URL")

#### PRESENCE modules
loadmodule "presence.so" 
loadmodule "xcap.so" 
loadmodule "presence_xml.so" 
loadmodule "rls.so" 
modparam("presence|pua|xcap", "db_url", "DB_URL")
modparam("presence", "server_address", "PRESENCE_SERVER_ADDRESS")
modparam("presence", "fallback2db", 1)
modparam("presence", "notify_offline_body", 0)
modparam("presence_xml", "pres_rules_auid", "org.openmobilealliance.pres-rules")
modparam("presence_xml", "force_active", 0)
modparam("presence_xml", "pidf_manipulation", 1)
modparam("presence_xml", "generate_offline_body",  0)
modparam("xcap", "integrated_xcap_server", 1)
modparam("rls", "server_address", "RLS_SERVER_ADDRESS")
modparam("rls", "to_presence_code", 5)
modparam("rls", "waitn_time", 10)

####### Routing Logic ########

# main request routing logic

route{
    if (!mf_process_maxfwd_header("10")) {
        sl_send_reply("483","Too Many Hops");
        exit;
    }

    if (!(check_source_address("TRUSTED_PEERS_GROUP")) || (uri==myself && !is_present_hf("Self-Forwarded"))) {
        sl_send_reply("403", "Forbidden");
        exit;
    }

    if(!is_method("PUBLISH|SUBSCRIBE|NOTIFY")) {
        sl_send_reply("503", "Service Unavailable");
        exit;
    }

    if (is_method("SUBSCRIBE")) {
        if (has_totag()) {
            if (uri=="PRESENCE_SERVER_ADDRESS" || uri=="RLS_SERVER_ADDRESS" || !loose_route()) {
                if (t_newtran()) {
                    rls_handle_subscribe();
                    if ($retcode==5) {
                        handle_subscribe();
                    }
                } else {
                    sl_reply_error();
                }
            } else {
                sl_send_reply("503", "Service Unavailable");
                exit;
            }
        } else {
            if (loose_route()) {
                xlog("Rejecting incorrectly formatted request\n");
                sl_send_reply("400", "Bad request");
                exit;
            }

            # only process presence for local users
            if (!is_uri_host_local()) {
                send_reply("403","Forbidden");
                exit;
            }

            rls_handle_subscribe();

            switch ($retcode) {
            case 5:
                # RLS indicated that message should be processed by presence
                if (db_does_uri_exist()) {
                    handle_subscribe();
                } else {
                    t_reply("404", "User not found");
                }
                exit;
            default:
                exit;
            }
        }
    }

    if (is_method("PUBLISH")) {
        if (!is_from_local()) {
            sl_send_reply("403", "PUBLISH forbidden for outside domains");
            exit;
        }

        if (t_newtran()) {
            handle_publish();
        } else {
            sl_reply_error();
        }
        exit;
    }

    if (is_method("NOTIFY")) {
        if (!has_totag()) {
            sl_send_reply("405", "Method Not Allowed");
            exit;
        }

        if (!loose_route()) {
            if (!t_newtran()) {
                sl_reply_error();
                exit;
            }
            rls_handle_notify();
            switch ($retcode) {
            case 1:
                # Notify processed by rls
                xlog("$rm processed by RLS\n");
                exit;
            case -1:
                # Error
                xlog("$rm processed by RLS but has error\n");
                t_reply("500", "Server error while processing RLS NOTIFY");
                exit;
            default:
                if (uri == "RLS_SERVER_ADDRESS") {
                    xlog("$rm should be processed by RLS but was not recognized, dropping\n");
                    t_reply("481", "Server error while processing RLS NOTIFY");
                }
                exit;
            }
        }

    }

}

local_route {
    if (is_method("SUBSCRIBE")) {
        xlog("Locally generated SUBSCRIBE due to RLS to $tu\n");
        # Send it back to ourselves, so that we can do handle_subscribe on
        append_hf("Self-Forwarded: Yes\r\n");
        $du = "sip:SERVER_IP:UDP_PORT";
    }
}

In order to build a working opensips.cfg file adjust settings.m4 to your needs and run the following command:

m4 settings.m4 opensips.m4 > opensips.cfg

Blink Client setup

The only setting required by Blink is the XCAP Root, it must match the XCAP root from OpenXCAP server configuration.

Alternatively, the owner of the SIP domain can add the following record into the DNS:

xcap.example.com. 3600 IN TXT "https://xcap.example.net/xcap-root/"

Replace example.com with your domain and the xcap root accordingly. If this DNS TXT record exists, Blink will discover the XCAP root in the DNS response.