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README
H350 Module Christian Schlatter University of North Carolina <cs@unc.edu> Copyright � 2007 University of North Carolina Revision History Revision 0.1 05-17-2007 __________________________________________________________ Table of Contents 1. Admin Guide 1.1. Overview 1.1.1. Example H.350 commObject LDAP Entry 1.2. Dependencies 1.2.1. Kamailio Modules 1.2.2. External Libraries or Applications 1.3. Exported Parameters 1.3.1. ldap_session (string) 1.3.2. base_dn (string) 1.3.3. search_scope (string) 1.4. Exported Functions 1.4.1. h350_sipuri_lookup(sip_uri) 1.4.2. h350_auth_lookup(auth_username, "username_avp_spec/pwd_avp_spec") 1.4.3. h350_result_call_preferences(avp_name_prefix) 1.4.4. h350_result_service_level(avp_name_prefix) Resources List of Examples 1.1. Example H.350 commObject storing SIP account data 1.2. ldap_session parameter usage 1.3. base_dn parameter usage 1.4. search_scope parameter usage 1.5. Example Usage 1.6. Example Usage 1.7. Example H.350 callPreferenceURI simple call forwarding rules 1.8. Example Usage 1.9. Example SIPIdentityServiceLevel values and resulting AVPs 1.10. Example Usage Chapter 1. Admin Guide 1.1. Overview The Kamailio H350 module enables an Kamailio SIP proxy server to access SIP account data stored in an LDAP [RFC4510] directory containing H.350 [H.350] commObjects. ITU-T Recommendation H.350 standardizes LDAP object classes to store Real-Time Communication (RTC) account data. In particular, H.350.4 [H.350.4] defines an object class called sipIdentity that includes attribute specifications for SIP account data like SIP URI, SIP digest username/password, or service level. This allows to store SIP account data in a vendor neutral way and lets different entities, like SIP proxies, provisioning, or billing applications, access the data in a standardized format. The ViDe H.350 Cookbook [vide-h.350-cb] is a good reference for deploying an H.350 directory. Besides general information on H.350, LDAP, and related standards, this document explains how to set up an H.350/LDAP directory and discusses different deployment scenarios. The H350 module uses the Kamailio LDAP module to import H.350 attribute values into the Kamailio routing script variable space. The module exports functions to parse and store the H.350 attribute values from the Kamailio routing script. It allows a script writer to implement H.350 based SIP digest authentication, call forwarding, SIP URI alias to AOR rewriting, and service level parsing. 1.1.1. Example H.350 commObject LDAP Entry The following example shows a typical H.350 commObject LDAP entry storing SIP account data. Example 1.1. Example H.350 commObject storing SIP account data Attribute Name Attribute Value(s) -------------- ----------------- # LDAP URI identifying the owner of this commObject, typically # points to an entry in the enterprise directory commOwner ldap://dir.example.com/dc=example,dc=com??one?(uid=bob) # Unique identifier for this commObject, used for referencing # this object e.g. from the enterprise directory commUniqueId 298217asdjgj213 # Determines if this commObject should be listed on white pages commPrivate false # Valid SIP URIs for this account (can be used to store alias SIP URIs # like DIDs as well) SIPIdentitySIPURI sip:bob@example.com sip:bob@alias.example.com sip:+1919123456@alias.example.com # SIP digest username SIPIdentityUserName bob # SIP digest password SIPIdentityPassword pwd # SIP proxy address SIPIdentityProxyAddress sip.example.com # SIP registrar address SIPIdentityRegistrarAddress sip.example.com # Call preferences: Forward to voicemail on no response # after 20 seconds and on busy callPreferenceURI sip:bob@voicemail.example.com n:20000 sip:bob@voicemail.example.com b # Account service level(s) SIPIdentityServiceLevel long_distance conferencing # H.350 object classes objectClass top commObject SIPIdentity callPreferenceURIObject 1.2. Dependencies 1.2.1. Kamailio Modules The module depends on the following modules (the listed modules must be loaded before this module): * LDAP 1.2.2. External Libraries or Applications The following libraries or applications must be installed before running Kamailio with this module loaded: * OpenLDAP library (libldap), libldap header files (libldap-dev) are needed for compilation 1.3. Exported Parameters 1.3.1. ldap_session (string) Name of the LDAP session to be used for H.350 queries, as defined in the LDAP module configuration file. Default value: "" Example 1.2. ldap_session parameter usage modparam("h350", "ldap_session", "h350"); 1.3.2. base_dn (string) Base LDAP DN to start LDAP search for H.350 entries. For best performance, this should be set to the direct ancestor of the H.350 objects. Default value: "" Example 1.3. base_dn parameter usage modparam("h350", "base_dn", "ou=h350,dc=example,dc=com"); 1.3.3. search_scope (string) LDAP search scope for H.350 queries, one of "one", "base", or "sub". Default value: "one" Example 1.4. search_scope parameter usage modparam("h350", "search_scope", "sub"); 1.4. Exported Functions 1.4.1. h350_sipuri_lookup(sip_uri) This function performs an LDAP search query for an H.350 commObject with a SIPIdentitySIPURI of sip_uri. The sip_uri parameter first gets escaped according the rules for LDAP filter strings. The result of the LDAP search is stored internally and can be accessed either by one of the h350_result* or one of the ldap_result* functions from the Kamailio LDAP module. The function returns -1 (FALSE) for internal errors, and -2 (FALSE) if no H.350 commObject was found with a matching sip_uri. n > 0 (TRUE) is returned if n H.350 commObjects were found. This function can be used from REQUEST_ROUTE, ONREPLY_ROUTE, FAILURE_ROUTE and BRANCH_ROUTE. Function Parameters: sip_uri H.350 SIPIdentitySIPURI to search for in directory. Included Kamailio variables do get expanded. Return Values: n > 0 (TRUE): + n H.350 commObjects found. -1 (FALSE): + Internal error occurred. -2 (FALSE): + No H.350 commObject found. This function can be used from REQUEST_ROUTE, FAILURE_ROUTE, BRANCH_ROUTE, and ONREPLY_ROUTE. Example 1.5. Example Usage # # H.350 lookup for callee # if (!h350_sipuri_lookup("sip:$rU@$rd")) { switch ($retcode) { case -2: xlog("L_INFO", "h350 callee lookup: no entry found in H.350 directory"); exit; case -1: sl_send_reply("500", "Internal server error"); exit; } } # now h350_result* or ldap_result* functions can be used 1.4.2. h350_auth_lookup(auth_username, "username_avp_spec/pwd_avp_spec") This function performs an LDAP search query for SIP digest authentication credentials in an H.350 directory. The H.350 directory is searched for a commObject with SIPIdentityUserName of auth_username. If such a commObject is found, the SIP digest authentication username and password are stored in AVPs username_avp_spec and pwd_avp_spec, respectively. pv_*_authorize functions from AUTH module can then be used to perform SIP digest authentication. The function returns 1 (TRUE) if an H.350 commObject was found, -1 (FALSE) in case of an internal error, and -2 (FALSE) if no matching commObject was found. This function can be used from REQUEST_ROUTE, ONREPLY_ROUTE, FAILURE_ROUTE and BRANCH_ROUTE. Function Parameters: auth_username H.350 SIPIdentityUserName to search for in directory. Included Kamailio variables do get expanded. username_avp_spec Specification for authentication username AVP, e.g. $avp(s:username). pwd_avp_spec Specification for authentication password AVP, e.g. $avp(s:pwd). Return Values: 1 (TRUE): + H.350 commObject found and SIP digest authentication credentials stored in username_avp_spec and pwd_avp_spec. -1 (FALSE): + Internal error occurred. -2 (FALSE): + No H.350 commObject found. This function can be used from REQUEST_ROUTE, FAILURE_ROUTE, BRANCH_ROUTE, and ONREPLY_ROUTE. Example 1.6. Example Usage # -- auth params -- modparam("auth", "username_spec", "$avp(s:auth_user)") modparam("auth", "password_spec", "$avp(s:auth_pwd)") modparam("auth", "calculate_ha1", 1) # -- h350 params -- modparam("h350", "ldap_session", "h350") modparam("h350", "base_dn", "ou=h350,dc=example,dc=com") modparam("h350", "search_scope", "one") route[1] { # # H.350 based SIP digest authentication # # challenge all requests not including an Auth header if (!(is_present_hf("Authorization") || is_present_hf("Proxy-Authorization"))) { if (is_method("REGISTER")) { www_challenge("example.com", "0"); exit; } proxy_challenge("example.com", "0"); exit; } # get digest password from H.350 using auth username ($au) if (!h350_auth_lookup("$au", "$avp(s:auth_user)/$avp(s:auth_pwd)")) { switch ($retcode) { case -2: sl_send_reply("401", "Unauthorized"); exit; case -1: sl_send_reply("500", "Internal server error"); exit; } } # REGISTER requests if (is_method("REGISTER")) { if (!pv_www_authorize("example.com")) { if ($retcode == -5) { sl_send_reply("500", "Internal server error"); exit; } else { www_challenge("example.com", "0"); exit; } } consume_credentials(); xlog("L_INFO", "REGISTER request successfully authenticated"); return(1); } # non-REGISTER requests if (!pv_proxy_authorize("example.com")) { if ($retcode == -5) { sl_send_reply("500", "Internal server error"); exit; } else { proxy_challenge("example.com", "0"); exit; } } consume_credentials(); xlog("L_INFO", "$rm request successfully authenticated"); return(1); } 1.4.3. h350_result_call_preferences(avp_name_prefix) This function parses the callPreferenceURI attribute of an H.350 commObject, which must have been fetched through h350_*_lookup or ldap_search. callPreferenceURI is a multi-valued attribute that stores call preference rules like e.g. forward-on-busy or forward-unconditionally. Directory services architecture for call forwarding and preferences [H.350.6] defines a format for simple call forwarding rules: target_uri type[:argument] In a SIP environment, target_uri is typically the call forwarding rule's target SIP URI, although it could be any type of URI, e.g. an HTTP pointer to a CPL script. Four different values are specified for type: b for "forward on busy", n for "forward on no answer", u for "forward unconditionally", and f for "forward on destination not found". The optional argument is a string indicating the time in milliseconds after which the call forwarding should occur. Example 1.7. Example H.350 callPreferenceURI simple call forwarding rules # Example 1: # forward to sip:voicemail@example.com on no answer after 15 seconds: callPreferenceURI: sip:voicemail@example.com n:15000 # Example 2: # unconditionally forward to sip:alice@example.com: callPreferenceURI: sip:alice@example.com u # Example 3: # forward to sip:bob@example.com and sip:alice@example.com # (forking) on destination not found: callPreferenceURI: sip:bob@example.com f callPreferenceURI: sip:alice@example.com f h350_result_call_preferences stores these call forwarding rules as AVPs according to the following rules: # # AVP storing a forwarding rule's target URI # AVP name = avp_name_prefix + '_' + type AVP value = target_uri # # AVP storing a forwarding rule's argument # AVP name = avp_name_prefix + '_' + type + '_t' AVP value = argument / 1000 Example 1 from above would result in two AVPs: $avp("s:prefix_n") = "sip:voicemail@example.com" and $avp("s:prefix_n_t") = 15. Example 2: $avp("s:prefix_u") = "sip:alice@example.com". Example 3: $avp("s:prefix_f[1]") = "sip:bob@example.com" and $avp("s:prefix_f[2]]") = "sip:alice@example.com". These AVPs can then be used to implement the desired behavior in the Kamailio routing script. This function returns the number of successfully parsed simple call forwarding rules (TRUE), in case the H.350 callPreferenceURI attribute contained one or multiple values matching the simple call forwarding rule syntax described above. It returns -1 (FALSE) for internal errors, and -2 (FALSE) if none of the rules matched or if no callPreferenceURI attribute was found. This function can be used from REQUEST_ROUTE, ONREPLY_ROUTE, FAILURE_ROUTE and BRANCH_ROUTE. Function Parameters: avp_name_prefix Name prefix for call forwarding rule AVPs, as described above. Return Values: n > 0 (TRUE): + n simple call forwarding rules found. -1 (FALSE): + Internal error occurred. -2 (FALSE): + No simple call forwarding rule found, or callPreferenceURI not present. This function can be used from REQUEST_ROUTE, FAILURE_ROUTE, BRANCH_ROUTE, and ONREPLY_ROUTE. Example 1.8. Example Usage # # H.350 lookup for callee # ... h350_sipuri_lookup("sip:$rU@$rd") ... # # store H.350 call preferences in AVP # if (!h350_result_call_preferences("callee_pref_") && ($retcode == -1)) { sl_send_reply("500", "Internal server error"); exit; } # $avp(s:callee_pref_u) == CFU URI(s) # $avp(s:callee_pref_n) == CFNR URI(s) # $avp(s:callee_pref_n_t) == CFNR timeout in seconds # $avp(s:callee_pref_b) == CFB URI(s) # $avp(s:callee_pref_f) == CFOFFLINE URI(s) # # Example for forward-unconditionally (CFU) # if (is_avp_set("$avp(s:callee_pref_u)")) { # replace R-URI with CFU URI, g will fetch all CFU URIs # --> request can fork if (avp_pushto("$ru", "$avp(s:callee_pref_u)/g")) { avp_delete("$avp(s:callee_pref_u)"); } else { sl_send_reply("500", "Internal server error"); exit; } sl_send_reply("181", "Call is being forwarded"); t_relay(); exit; } 1.4.4. h350_result_service_level(avp_name_prefix) Directory services architecture for SIP [H.350.4] defines a multi-valued LDAP attribute named SIPIdentityServiceLevel, which can be used to store SIP account service level values in an LDAP directory. This function parses the SIPIdentityServiceLevel attribute and stores all service level values as AVPs for later retrieval in the Kamailio routing script. The function accesses the H.350 commObject fetched by a call to h350_*_lookup or ldap_search. The resulting AVPs have a name of the form avp_name_prefix + SIPIdentityServiceLevel attribute value, and an integer value of 1. Example 1.9. Example SIPIdentityServiceLevel values and resulting AVPs SIPIdentityServiceLevel: longdistance SIPIdentityServiceLevel: international SIPIdentityServiceLevel: 900 after calling h350_result_service_level("sl_"), the following AVPs will be available in the routing script: $avp("s:sl_longdistance") = 1 $avp("s:sl_international") = 1 $avp("s:sl_900") = 1 This function returns the number of added AVPs (TRUE), -1 (FALSE)for internal errors, and -2 (FALSE)if no SIPIdentityServiceLevel attribute was found. The function can be used from REQUEST_ROUTE, ONREPLY_ROUTE, FAILURE_ROUTE and BRANCH_ROUTE. Function Parameters: avp_name_prefix Name prefix for service level AVPs, as described above. Return Values: n > 0 (TRUE): + n AVPs added. -1 (FALSE): + Internal error occurred. -2 (FALSE): + No SIPIdentityServiceLevel attribute found. This function can be used from REQUEST_ROUTE, FAILURE_ROUTE, BRANCH_ROUTE, and ONREPLY_ROUTE. Example 1.10. Example Usage # # H.350 SIP digest authentication for caller # ... h350_auth_lookup("$au", ...) ... # # store caller's service level as AVP # if (!h350_result_service_level("caller_sl_") && ($retcode == -1)) { sl_send_reply("500", "Internal server error"); exit; } # # make routing decision based on service level AVPs # if (is_avp_set("$avp(s:caller_sl_international)")) { t_relay(); } else { sl_send_reply("403", "Forbidden"); } exit; Resources [H.350] Directory Services Architecture for Multimedia Conferencing. August 2003. ITU-T. [H.350.4] Directory services architecture for SIP. August 2003. ITU-T. [H.350.6] Directory services architecture for call forwarding and preferences. March 2004. ITU-T. [ViDe-H.350-Cookbook] ViDe H.350 Cookbook. 2005. ViDe. [RFC4510] Lightweight Directory Access Protocol (LDAP): Technical Specification Road Map. June 2006. Internet Engineering Task Force.