OSP Module for Secure, Multi-Lateral Peering

Ulrich Abend

   FhG FOKUS

   <ullstar@iptel.org>

Edited by

Di-Shi Sun

   TransNexus, Inc.

   <support@transnexus.com>

   Copyright © 2003 FhG FOKUS
     __________________________________________________________________

   Table of Contents

   1. Admin Guide

        1. Overview
        2. Dependencies
        3. Parameters

              3.1. sp1_uri, sp2_uri, ..., sp16_uri
              3.2. sp1_weight, sp2_weight, ..., sp16_weight
              3.3. device_ip
              3.4. device_port
              3.5. token_format
              3.6. private_key, local_certificate, ca_certificates
              3.7. enable_crypto_hardware_support
              3.8. ssl_lifetime
              3.9. persistence
              3.10. retry_delay
              3.11. retry_limit
              3.12. timeout
              3.13. max_destinations
              3.14. validate_call_id
              3.15. use_rpid_for_calling_number
              3.16. redirection_uri_format
              3.17. source_networkid_avp

        4. Functions

              4.1. checkospheader()
              4.2. validateospheader()
              4.3. requestosprouting()
              4.4. checkosproute()
              4.5. prepareosproute()
              4.6. checkcallingtranslation()
              4.7. prepareallosproute()
              4.8. reportospusage()

   2. Developer Guide

   List of Examples

   1.1. Setting the OSP servers
   1.2. Setting the OSP server weights
   1.3. Setting the device IP address
   1.4. Setting the device port
   1.5. Setting the token format
   1.6. Set authorization files
   1.7. Setting the hardware support
   1.8. Setting the ssl lifetime
   1.9. Setting the persistence
   1.10. Setting the retry delay
   1.11. Setting the retry limit
   1.12. Setting the timeout
   1.13. Setting the number of destination
   1.14. Instructing the module to validate call id
   1.15. Instructing the module to use calling number in Remote-Party-ID
   1.16. Setting the redirection URI format
   1.17. Setting the source network ID AVP
   1.18. checkospheader usage
   1.19. validateospheader usage
   1.20. requestosprouting usage
   1.21. checkosproute usage
   1.22. prepareosproute usage
   1.23. checkcallingtranslation usage
   1.24. prepareallosproute usage
   1.25. reportospusage usage

Chapter 1. Admin Guide

   Table of Contents

   1. Overview
   2. Dependencies
   3. Parameters

        3.1. sp1_uri, sp2_uri, ..., sp16_uri
        3.2. sp1_weight, sp2_weight, ..., sp16_weight
        3.3. device_ip
        3.4. device_port
        3.5. token_format
        3.6. private_key, local_certificate, ca_certificates
        3.7. enable_crypto_hardware_support
        3.8. ssl_lifetime
        3.9. persistence
        3.10. retry_delay
        3.11. retry_limit
        3.12. timeout
        3.13. max_destinations
        3.14. validate_call_id
        3.15. use_rpid_for_calling_number
        3.16. redirection_uri_format
        3.17. source_networkid_avp

   4. Functions

        4.1. checkospheader()
        4.2. validateospheader()
        4.3. requestosprouting()
        4.4. checkosproute()
        4.5. prepareosproute()
        4.6. checkcallingtranslation()
        4.7. prepareallosproute()
        4.8. reportospusage()

1. Overview

   The OSP module enables Kamailio to support secure, multi-lateral
   peering using the OSP standard defined by ETSI (TS 101 321 V4.1.1).
   This module will enable your Kamailio to:
     * Send a peering authorization request to a peering server.
     * Validate a digitally signed peering authorization token received in
       a SIP INVITE message.
     * Report usage information to a peering server.

2. Dependencies

   The OSP module depends on the following modules which must be loaded
   before the OSP module.
     * sl -- stateless replier
     * tm -- stateful processing
     * rr -- Record-Route/Route operation
     * textops -- text based operation
     * siputils -- Remote-Party-ID operattion
     * OSP Toolkit -- The OSP Toolkit, available from
       http://sourceforge.net/projects/osp-toolkit, must be built before
       building Kamailio with the OSP Module. For instructions on building
       Kamailio with the OSP Toolkit, see
       http://www.transnexus.com/White%20Papers/Multi-Lateral_Peering_with
       _Kamailio_V1.4.pdf

3. Parameters

   3.1. sp1_uri, sp2_uri, ..., sp16_uri
   3.2. sp1_weight, sp2_weight, ..., sp16_weight
   3.3. device_ip
   3.4. device_port
   3.5. token_format
   3.6. private_key, local_certificate, ca_certificates
   3.7. enable_crypto_hardware_support
   3.8. ssl_lifetime
   3.9. persistence
   3.10. retry_delay
   3.11. retry_limit
   3.12. timeout
   3.13. max_destinations
   3.14. validate_call_id
   3.15. use_rpid_for_calling_number
   3.16. redirection_uri_format
   3.17. source_networkid_avp

3.1. sp1_uri, sp2_uri, ..., sp16_uri

   These sp_uri (string) parameters define peering servers to be used for
   requesting peering authorization and routing information. At least one
   peering server must be configured. Others are required only if there
   are more than one peering servers. Each peering server address takes
   the form of a standard URL, and consists of up to four components:
     * An optional indication of the protocol to be used for communicating
       with the peering server. Both HTTP and HTTP secured with SSL/TLS
       are supported and are indicated by "http://" and "https://"
       respectively. If the protocol is not explicitly indicated, the
       Kamailio defaults to HTTP secured with SSL.
     * The Internet domain name for the peering server. An IP address may
       also be used, provided it is enclosed in square brackets such as
       [172.16.1.1].
     * An optional TCP port number for communicating with the peering
       server. If the port number is omitted, the Kamailio defaults to
       port 1080 (for HTTP) or port 1443 (for HTTP secured with SSL).
       The uniform resource identifier for requests to the peering server.
       This component is not optional and must be included.

   Example 1.1. Setting the OSP servers
modparam("osp","sp1_uri","http://osptestserver.transnexus.com:1080/osp")
modparam("osp","sp2_uri","https://[1.2.3.4]:1443/osp")

3.2. sp1_weight, sp2_weight, ..., sp16_weight

   These sp_weight (integer) parameters are used for load balancing
   peering requests to peering servers. These parameters are most
   effective when configured as factors of 1000. For example, if sp1_uri
   should manage twice the traffic load of sp2_uri, then set sp1_weight to
   2000 and sp2_weight to 1000. Shared load balancing between peering
   servers is recommended. However, peering servers can be configured as
   primary and backup by assigning a sp_weight of 0 to the primary server
   and a non-zero sp_weight to the back-up server. The default values for
   sp1_weight and sp2_weight are 1000.

   Example 1.2. Setting the OSP server weights
modparam("osp","sp1_weight",1000)

3.3. device_ip

   The device_ip (string) is a recommended parameter that explicitly
   defines the IP address of Kamailio in a peering request message (as
   SourceAlternate type=transport). The IP address must be in brackets as
   shown in the example below.

   Example 1.3. Setting the device IP address
modparam("osp","device_ip","[1.1.1.1]")

3.4. device_port

   The device_port (string) parameter is an optional field which includes
   the SIP port being used by Kamailio in the peering request (as
   SourceAlternate type=network) to the peering server. If is not
   configured, this information is not included in the peering request.
   This field is useful if multiple Kamailio are running on the same Linux
   computer since it enables the peering server to administer different
   peering policies based on different SIP proxies. This parameter has not
   been implemented yet.

   Example 1.4. Setting the device port
modparam("osp","device_port","5060")

3.5. token_format

   When Kamailio receives a SIP INVITE with a peering token, the OSP
   Module will validate the token to determine whether or not the call has
   been authorized by a peering server. Peering tokens may, or may not, be
   digitally signed. The token_format (integer) parameter defines if
   Kamailio will validate signed or unsigned tokens or both. The values
   for token format are defined below. The default value is 2.

   0 - Validate only signed tokens. Calls with valid signed tokens are
   allowed.

   1 - Validate only unsigned tokens. Calls with valid unsigned tokens are
   allowed.

   2 - Validate both signed and unsigned tokens are allowed. Calls with
   valid tokens are allowed.

   Example 1.5. Setting the token format
modparam("osp","token_format",2)

3.6. private_key, local_certificate, ca_certificates

   These parameters identify files are used for validating peering
   authorization tokens and establishing a secure channel between Kamailio
   and a peering server using SSL. The files are generated using the
   'Enroll' utility from the OSP Toolkit. By default, the proxy will look
   for pkey.pem, localcert.pem, and cacart_0.pem in the default
   configuration directory. The default config directory is set at compile
   time using CFG_DIR and defaults to /usr/local/etc/kamailio/. The files
   may be copied to the expected file location or the parameters below may
   be changed.

   Example 1.6. Set authorization files

   If the default CFG_DIR value was used at compile time, the files will
   be loaded from:
modparam("osp","private_key","/usr/local/etc/kamailio/pkey.pem")
modparam("osp","local_certificate","/usr/local/etc/kamailio/localcert.pem")
modparam("osp","ca_certificates","/usr/local/etc/kamailio/cacert.pem")

3.7. enable_crypto_hardware_support

   The enable_crypto_hardware_support (integer) parameter is used to set
   the cryptographic hardware acceleration engine in the openssl library.
   The default value is 0 (no crypto hardware is present). If crypto
   hardware is used, the value should be set to 1.

   Example 1.7. Setting the hardware support
modparam("osp","enable_crypto_hardware_support",0)

3.8. ssl_lifetime

   The ssl_lifetime (integer) parameter defines the lifetime, in seconds,
   of a single SSL session key. Once this time limit is exceeded, the OSP
   Module will negotiate a new session key. Communication exchanges in
   progress will not be interrupted when this time limit expires. This is
   an optional field with default value is 200 seconds.

   Example 1.8. Setting the ssl lifetime
modparam("osp","ssl_lifetime",200)

3.9. persistence

   The persistence (integer) parameter defines the time, in seconds, that
   an HTTP connection should be maintained after the completion of a
   communication exchange. The OSP Module will maintain the connection for
   this time period in anticipation of future communication exchanges to
   the same peering server.

   Example 1.9. Setting the persistence
modparam("osp","persistence",1000)

3.10. retry_delay

   The retry_delay (integer) parameter defines the time, in seconds,
   between retrying connection attempts to an OSP peering server. After
   exhausting all peering servers the OSP Module will delay for this
   amount of time before resuming connection attempts. This is an optional
   field with default value is 1 second.

   Example 1.10. Setting the retry delay
modparam("osp","retry_delay",1)

3.11. retry_limit

   The retry_limit (integer) parameter defines the maximum number of
   retries for connection attempts to a peering server. If no connection
   is established after this many retry attempts to all peering servers,
   the OSP Module will cease connection attempts and return appropriate
   error codes. This number does not count the initial connection attempt,
   so that a retry_limit of 1 will result in a total of two connection
   attempts to every peering server. The default value is 2.

   Example 1.11. Setting the retry limit
modparam("osp","retry_limit",2)

3.12. timeout

   The timeout (integer) parameter defines the maximum time in
   milliseconds, to wait for a response from a peering server. If no
   response is received within this time, the current connection is
   aborted and the OSP Module attempts to contact the next peering server.
   The default value is 10 seconds.

   Example 1.12. Setting the timeout
modparam("osp","timeout",10)

3.13. max_destinations

   The max_destinations (integer) parameter defines the maximum number of
   destinations that Kamailio requests the peering server to return in a
   peering response. The default value is 5.

   Example 1.13. Setting the number of destination
modparam("osp","max_destinations",5)

3.14. validate_call_id

   The validate_call_id (integer) parameter instructs the OSP module to
   validate call id in the peering token. If this value is set to 1, the
   OSP Module validates that the call id in the SIP INVITE message matches
   the call id in the peering token. If they do not match the INVITE is
   rejected. If this value is set to 0, the OSP Module will not validate
   the call id in the peering token. The default value is 1.

   Example 1.14. Instructing the module to validate call id
modparam("osp","validate_call_id",1)

3.15. use_rpid_for_calling_number

   The use_rpid_for_calling_number (integer) parameter instructs the OSP
   module to use the calling number in the Remote-Party-ID of the SIP
   INVITE message. If this value is set to 1, the OSP Module uses the
   calling number in the Reomte-Party-ID header of the INVITE message when
   a Remote-Party-ID exists. If this value is set to 0, the OSP Module
   will use the calling number in the From header of the INVITE message.
   The default value is 1.

   Example 1.15. Instructing the module to use calling number in
   Remote-Party-ID
modparam("osp","use_rpid_calling_number",1)

3.16. redirection_uri_format

   The redirection_uri_format (integer) parameter instructs the OSP module
   to use the different URI format in the SIP redirection message. If this
   value is set to 0, the OSP Module uses "xxxxxxxxxx@xxx.xxx.xxx.xxx" URI
   in the SIP redirection messages. If this value is set to 1, the OSP
   Module will use “<xxxxxxxxxx@xxx.xxx.xxx.xxx>” URI in the SIP
   redirection messages. The default value is 0

   Example 1.16. Setting the redirection URI format
modparam("osp","redirection_uri_format",1)

3.17. source_networkid_avp

   The source_networkid_avp (string) parameter instructs the OSP module to
   use the defined AVP to pass the source network ID value. The default
   value is "$avp(s:_osp_source_networkid_)". Then the source network ID
   can be set by "$avp(s:_osp_source_networkid_) = pseudo-variables". All
   pseudo variables are described in
   http://kamailio.org/dokuwiki/doku.php/pseudovariables:1.3.x.

   Example 1.17. Setting the source network ID AVP
modparam("osp","source_networkid_avp","$avp(s:snid)")

4. Functions

   4.1. checkospheader()
   4.2. validateospheader()
   4.3. requestosprouting()
   4.4. checkosproute()
   4.5. prepareosproute()
   4.6. checkcallingtranslation()
   4.7. prepareallosproute()
   4.8. reportospusage()

4.1. checkospheader()

   This function checks for the existence of the OSP-Auth-Token header
   field.

   This function can be used from REQUEST_ROUTE and FAILURE_ROUTE.

   Example 1.18. checkospheader usage
...
if (checkospheader()) {
  log(1,"OSP header field found.\n");
} else {
  log(1,"no OSP header field present\n");
};
...

4.2. validateospheader()

   This function validates an OSP-Token specified in the
   OSP-Auth-Tokenheader field of the SIP message. If a peering token is
   present, it will be validated locally. If no OSP header is found or the
   header token is invalid or expired, -1 is returned; on successful
   validation 1 is returned.

   This function can be used from REQUEST_ROUTE and FAILURE_ROUTE.

   Example 1.19. validateospheader usage
...
if (validateospheader()) {
  log(1,"valid OSP header found\n");
} else {
  log(1,"OSP header not found, invalid or expired\n");
};
...

4.3. requestosprouting()

   This function launches a query to the peering server requesting the IP
   address of one or more destination peers serving the called party. If
   destination peers are available, the peering server will return the IP
   address and a peering authorization token for each destination peer.
   The OSP-Auth-Token Header field is inserted into the SIP message and
   the SIP uri is rewritten to the IP address of destination peer provided
   by the peering server.

   The address of the called party must be a valid E164 number, otherwise
   this function returns -1. If the transaction was accepted by the
   peering server, the uri is being rewritten and 1 returned, on errors
   (peering servers are not available, authentication failed or there is
   no route to destination or the route is blocked) -1 is returned.

   This function can be used from REQUEST_ROUTE and FAILURE_ROUTE.

   Example 1.20. requestosprouting usage
...
if (requestosprouting()) {
  log(1,"successfully queried OSP server, now relaying call\n");
} else {
  log(1,"Authorization request was rejected from OSP server\n");
};
...

4.4. checkosproute()

   This function is used to check if there is any route for the call.

   This function can be used from REQUEST_ROUTE and FAILURE_ROUTE.

   Example 1.21. checkosproute usage
...
if (checkosproute()) {
  log(1,"There is at least one route for the call\n");
} else {
  log(1,"There is not any route for the call\n");
};
...

4.5. prepareosproute()

   This function tries to prepare the INVITE to be forwarded using the
   destination in the list returned by the peering server. If the calling
   number is translated, a RPID value for the RPID AVP will be set. If the
   route could not be prepared, the function returns 'FALSE' back to the
   script, which can then decide how to handle the failure. Note, if
   checkosproute has been called and returns 'TRUE' before calling
   prepareosproute, prepareosproute should not return 'FALSE' because
   checkosproute has confirmed that there is at least one route.

   This function can be used from BRANCH_ROUTE.

   Example 1.22. prepareosproute usage
...
if (prepareosproute()) {
  log(1,"successfully prepared the route, now relaying call\n");
} else {
  log(1,"could not prepare the route, there is not route\n");
};
...

4.6. checkcallingtranslation()

   This function is used to check if the calling number is translated.
   Before calling checkcallingtranslation, prepareosproute should be
   called. If the calling number does been translated, the original
   Remote-Party-ID, if it exists, should be removed from the INVITE
   message. And a new Remote-Party-ID header should be added (a RPID value
   for the RPID AVP has been set by prepareosproute). If the calling
   number is not translated, nothing should be done.

   This function can be used from BRANCH_ROUTE.

   Example 1.23. checkcallingtranslation usage
...
if (checkcallingtranslation()) {
  # Remove the Remote_Party-ID from the received message
  # Otherwise it will be forwarded on to the next hop
  remove_hf("Remote-Party-ID");

  # Append a new Remote_Party
  append_rpid_hf();
}
...

4.7. prepareallosproute()

   This function tries to prepare all the routes in the list returned by
   the peering server. The message is then either forked off or redirected
   to the destination. If unsuccessful in preparing the routes a SIP 500
   is sent back and a trace message is logged.

   This function can be used from REQUEST_ROUTE and FAILURE_ROUTE.

   Example 1.24. prepareallosproute usage
...
if (prepareallosproute()) {
  log(1,"Routes are prepared, now either forking or redirecting the call\n");
} else {
  log(1,"Could not prepare the routes. No destination available\n");
};
...

4.8. reportospusage()

   This function should be called after receiving a BYE message. If the
   message contains an OSP cookie, the function will forward originating
   and/or terminating duration usage information to a peering server. The
   function returns TRUE if the BYE includes an OSP cookie. The actual
   usage message will be send on a different thread and will not delay BYE
   processing. The function should be called before relaying the message.

   Meaning of the parameter is as follows:
     * "0" - Source device releases the call.
     * "1" - Destination device releases the call.

   This function can be used from REQUEST_ROUTE.

   Example 1.25. reportospusage usage
...
if (is_direction("downstream")) {
  log(1,"This BYE message is from SOURCE\n");
  if (!reportospusage("0")) {
    log(1,"This BYE message does not include OSP usage information\n");
  }
} else {
  log(1,"This BYE message is from DESTINATION\n");
  if (!reportospusage("1")) {
    log(1,"This BYE message does not include OSP usage information\n");
  }
}
...

Chapter 2. Developer Guide

   The functions of the OSP modules are not used by other Kamailio
   modules.