permissions Module

Miklos Tirpak

Edited by

Miklos Tirpak

Edited by

Bogdan-Andrei Iancu

Edited by

Juha Heinanen

   Copyright © 2003 Miklos Tirpak

   Copyright © 2006-2008 Juha Heinanen
     __________________________________________________________________

   Table of Contents

   1. Admin Guide

        1. Overview

              1.1. Call Routing
              1.2. Registration Permissions
              1.3. URI Permissions
              1.4. Address Permissions
              1.5. Trusted Requests

        2. Dependencies

              2.1. Kamailio Modules
              2.2. External Libraries or Applications

        3. Parameters

              3.1. default_allow_file (string)
              3.2. default_deny_file (string)
              3.3. check_all_branches (integer)
              3.4. allow_suffix (string)
              3.5. deny_suffix (string)
              3.6. db_url (string)
              3.7. address_table (string)
              3.8. grp_col (string)
              3.9. ip_addr_col (string)
              3.10. mask_col (string)
              3.11. port_col (string)
              3.12. db_mode (integer)
              3.13. trusted_table (string)
              3.14. source_col (string)
              3.15. proto_col (string)
              3.16. from_col (string)
              3.17. tag_col (string)
              3.18. peer_tag_avp (AVP string)
              3.19. peer_tag_mode (integer)

        4. Functions

              4.1. allow_routing()
              4.2. allow_routing(basename)
              4.3. allow_routing(allow_file,deny_file)
              4.4. allow_register(basename)
              4.5. allow_register(allow_file, deny_file)
              4.6. allow_uri(basename, pvar)
              4.7. allow_address(group_id, ip_addr_pvar, port_pvar)
              4.8. allow_source_address([group_id])
              4.9. allow_source_address_group()
              4.10. allow_address_group(addr, port)
              4.11. allow_trusted([src_ip_pvar, proto_pvar])

        5. MI Commands

              5.1. address_reload
              5.2. address_dump
              5.3. subnet_dump
              5.4. trusted_reload
              5.5. trusted_dump
              5.6. allow_uri

        6. RPC Commands

              6.1. addressReload
              6.2. addressDump
              6.3. subnetDump
              6.4. testUri basename uri contact
              6.5. trustedReload
              6.6. trustedDump

   List of Examples

   1.1. Set default_allow_file parameter
   1.2. Set default_deny_file parameter
   1.3. Set check_all_branches parameter
   1.4. Set allow_suffix parameter
   1.5. Set deny_suffix parameter
   1.6. Set db_url parameter
   1.7. Set address_table parameter
   1.8. Set grp_col parameter
   1.9. Set ip_addr_col parameter
   1.10. Set mask_col parameter
   1.11. Set port_col parameter
   1.12. Set db_mode parameter
   1.13. Set trusted_table parameter
   1.14. Set source_col parameter
   1.15. Set proto_col parameter
   1.16. Set from_col parameter
   1.17. Set tag_col parameter
   1.18. Set peer_tag_avp parameter
   1.19. Set peer_tag_mode parameter
   1.20. allow_routing usage
   1.21. allow_routing(basename) usage
   1.22. allow_routing(allow_file, deny_file) usage
   1.23. allow_register(basename) usage
   1.24. allow_register(allow_file, deny_file) usage
   1.25. allow_uri(basename, pvar) usage
   1.26. allow_address() usage
   1.27. allow_source_address(group_id) usage
   1.28. allow_source_address_group() usage
   1.29. allow_source_address_group() usage
   1.30. allow_trusted() usage

Chapter 1. Admin Guide

   Table of Contents

   1. Overview

        1.1. Call Routing
        1.2. Registration Permissions
        1.3. URI Permissions
        1.4. Address Permissions
        1.5. Trusted Requests

   2. Dependencies

        2.1. Kamailio Modules
        2.2. External Libraries or Applications

   3. Parameters

        3.1. default_allow_file (string)
        3.2. default_deny_file (string)
        3.3. check_all_branches (integer)
        3.4. allow_suffix (string)
        3.5. deny_suffix (string)
        3.6. db_url (string)
        3.7. address_table (string)
        3.8. grp_col (string)
        3.9. ip_addr_col (string)
        3.10. mask_col (string)
        3.11. port_col (string)
        3.12. db_mode (integer)
        3.13. trusted_table (string)
        3.14. source_col (string)
        3.15. proto_col (string)
        3.16. from_col (string)
        3.17. tag_col (string)
        3.18. peer_tag_avp (AVP string)
        3.19. peer_tag_mode (integer)

   4. Functions

        4.1. allow_routing()
        4.2. allow_routing(basename)
        4.3. allow_routing(allow_file,deny_file)
        4.4. allow_register(basename)
        4.5. allow_register(allow_file, deny_file)
        4.6. allow_uri(basename, pvar)
        4.7. allow_address(group_id, ip_addr_pvar, port_pvar)
        4.8. allow_source_address([group_id])
        4.9. allow_source_address_group()
        4.10. allow_address_group(addr, port)
        4.11. allow_trusted([src_ip_pvar, proto_pvar])

   5. MI Commands

        5.1. address_reload
        5.2. address_dump
        5.3. subnet_dump
        5.4. trusted_reload
        5.5. trusted_dump
        5.6. allow_uri

   6. RPC Commands

        6.1. addressReload
        6.2. addressDump
        6.3. subnetDump
        6.4. testUri basename uri contact
        6.5. trustedReload
        6.6. trustedDump

1. Overview

   1.1. Call Routing
   1.2. Registration Permissions
   1.3. URI Permissions
   1.4. Address Permissions
   1.5. Trusted Requests

   The Permissions module provides functions for handling IP based access
   control lists (ACL) in a number of ways.
     * Call Routing
     * Registration permissions
     * URI permissions
     * Address permissions
     * Trusted Requests

   The Address permissions and Trusted request handling supports using a
   database to load ACLs into RAM for fast processing.

1.1. Call Routing

   The module can be used to determine if a call has appropriate
   permission to be established. Permission rules are stored in plaintext
   configuration files similar to hosts.allow and hosts.deny files used by
   tcpd.

   When allow_routing function is called it tries to find a rule that
   matches selected fields of the message.

   Kamailio is a forking proxy and therefore a single message can be sent
   to different destinations simultaneously. When checking permissions all
   the destinations must be checked and if one of them fails, the
   forwarding will fail.

   The matching algorithm is as follows, first match wins:
     * Create a set of pairs of form (From, R-URI of branch 1), (From,
       R-URI of branch 2), etc.
     * Routing will be allowed when all pairs match an entry in the allow
       file.
     * Otherwise routing will be denied when one of pairs matches an entry
       in the deny file.
     * Otherwise, routing will be allowed.

   A non-existing permission control file is treated as if it were an
   empty file. Thus, permission control can be turned off by providing no
   permission control files.

   From header field and Request-URIs are always compared with regular
   expressions! For the syntax see the sample file:
   config/permissions.allow.

1.2. Registration Permissions

   In addition to call routing it is also possible to check REGISTER
   messages and decide--based on the configuration files--whether the
   message should be allowed and the registration accepted or not.

   Main purpose of the function is to prevent registration of "prohibited"
   IP addresses. One example, when a malicious user registers a contact
   containing IP address of a PSTN gateway, he might be able to bypass
   authorization checks performed by the SIP proxy. That is undesirable
   and therefore attempts to register IP address of a PSTN gateway should
   be rejected. Files config/register.allow and config/register.deny
   contain an example configuration.

   The function for registration checking is called allow_register and the
   algorithm is very similar to the algorithm described in Section 1.1,
   "Call Routing". The only difference is in the way how pairs are
   created.

   Instead of the From header field the function uses the To header field
   because th To header field in REGISTER messages contains the URI of the
   person being registered. Instead of the Request-URI of branches the
   function uses the Contact header field.

   Thus, the pairs used in matching will look like this: (To, Contact 1),
   (To, Contact 2), (To, Contact 3), and so on..

   The algorithm of matching is the same as described in Section 1.1,
   "Call Routing".

1.3. URI Permissions

   The module can be used to determine if a request to a destionation is
   allowed, based on an URI stored in a pvar. Permission rules are stored
   in plaintext configuration files similar to hosts.allow and hosts.deny
   used by tcpd.

   When the allow_uri function is called, it tries to find a rule that
   matches selected fields of the message. The matching algorithm is as
   follows, where the first match wins:
     * Create a pair <From URI, URI stored in pvar>.
     * Request will be allowed when the pair matches an entry in the allow
       file.
     * Request will be denied when the pair matches an entry in the deny
       file.
     * Otherwise, request will be allowed.

   A non-existing permission control file is treated as if it were an
   empty file. Thus, permission control can be turned off by providing no
   permission control files.

   The From URI and the URI stored in pvar are always compared with
   regular expressions! For the syntax see the sample file:
   config/permissions.allow.

1.4. Address Permissions

   The module can be used to determine if an address (IP address and port
   or DNS domain name) matches any of the addresses stored in a cached
   Kamailio database table. IP addresses in the database table can be
   subnet addresses. Port 0 in cached database table matches any port. The
   address and port to be matched can be either taken from the request
   (allow_source_address) or given as pvar arguments (allow_address).

   Addresses stored in the database table can be grouped together into one
   or more groups specified by a group identifier (positive integer value,
   i.e., equal or greater than 1). The group identifier is given as an
   argument to the allow_address() and allow_source_address() functions.
   One group can contain all of the three types of addresses: exact IP
   address, subnet IP address or DNS domain name.

   When the argument is an IP addess, it is tried to be matched with the
   records from that group that are of type exact IP or subnet. If the
   argument is not an IP it is tried to be matched with the records that
   are DNS domain names. No DNS lookup is performed, only strict matching.

   As a side effect of matching the address, non-NULL tag (see tag_col
   module parameter) is added as value to peer_tag AVP if peer_tag_avp
   module parameter has been defined.

1.5. Trusted Requests

   The module can be used to determine if an incoming request can be
   trusted without authentication.

   When the allow_trusted function is called, it tries to find a rule that
   matches the request. Rules contain the following fields: <source
   address, transport protocol, regular expression>.

   A requests is accepted if there exists a rule, where
     * source address is equal to the source address of the request or the
       source address given in pvar,
     * transport protocol is either "ANY" or equal to the transport
       protocol of request or the transport protocol given in pvar, and
     * regular expression is either empty (NULL in database) or matches
       the From URI of request.

   Otherwise the request is rejected.

   As a side effect of accepting the request, the peer's non-NULL tag (see
   tag_col module parameter) is added as value to peer_tag AVP if the
   peer_tag_avp module parameter has been defined.

   Rules are stored in a database table specified by the module
   parameters. There is a module parameter called db_mode that determines
   if the rules are cached into memory for faster matching or if the
   database is consulted for each invocation of the allow_trusted()
   function call.

2. Dependencies

   2.1. Kamailio Modules
   2.2. External Libraries or Applications

2.1. Kamailio Modules

   The following modules must be loaded before this module:
     * No dependencies on other Kamailio modules.

2.2. External Libraries or Applications

   The following libraries or applications must be installed before
   running Kamailio with this module loaded:
     * None.

3. Parameters

   3.1. default_allow_file (string)
   3.2. default_deny_file (string)
   3.3. check_all_branches (integer)
   3.4. allow_suffix (string)
   3.5. deny_suffix (string)
   3.6. db_url (string)
   3.7. address_table (string)
   3.8. grp_col (string)
   3.9. ip_addr_col (string)
   3.10. mask_col (string)
   3.11. port_col (string)
   3.12. db_mode (integer)
   3.13. trusted_table (string)
   3.14. source_col (string)
   3.15. proto_col (string)
   3.16. from_col (string)
   3.17. tag_col (string)
   3.18. peer_tag_avp (AVP string)
   3.19. peer_tag_mode (integer)

3.1. default_allow_file (string)

   Default allow file used by the functions with no parameters. If you
   don't specify a full pathname then the directory in which is the main
   config file is located will be used.

   Default value is "permissions.allow".

   Example 1.1. Set default_allow_file parameter
...
modparam("permissions", "default_allow_file", "/etc/permissions.allow")
...

3.2. default_deny_file (string)

   Default file containing deny rules. The file is used by functions with
   no parameters. If you don't specify a full pathname then the directory
   in which the main config file is located will be used.

   Default value is "permissions.deny".

   Example 1.2. Set default_deny_file parameter
...
modparam("permissions", "default_deny_file", "/etc/permissions.deny")
...

3.3. check_all_branches (integer)

   If set then allow_routing functions will check Request-URI of all
   branches (default). If disabled then only Request-URI of the first
   branch will be checked.

Warning

   Do not disable this parameter unless you really know what you are
   doing.

   Default value is 1.

   Example 1.3. Set check_all_branches parameter
...
modparam("permissions", "check_all_branches", 0)
...

3.4. allow_suffix (string)

   Suffix to be appended to basename to create filename of the allow file
   when version with one parameter of either allow_routing or
   allow_register is used.

Note

   Including leading dot.

   Default value is ".allow".

   Example 1.4. Set allow_suffix parameter
...
modparam("permissions", "allow_suffix", ".allow")
...

3.5. deny_suffix (string)

   Suffix to be appended to basename to create filename of the deny file
   when version with one parameter of either allow_routing or
   allow_register is used.

Note

   Including leading dot.

   Default value is ".deny".

   Example 1.5. Set deny_suffix parameter
...
modparam("permissions", "deny_suffix", ".deny")
...

3.6. db_url (string)

   This is URL of the database to be used to store rules used by
   allow_trusted function.

   Default value is "NULL".

   Example 1.6. Set db_url parameter
...
modparam("permissions", "db_url", "dbdriver://username:password@dbhost/dbname")
...

3.7. address_table (string)

   The name of the database table containing IP subnets and DNS domain
   names used by allow_address and allow_source_address functions.

   Default value is "address".

   Example 1.7. Set address_table parameter
...
modparam("permissions", "address_table", "addr")
...

3.8. grp_col (string)

   Name of address table column containing the group identifier of the
   address.

   Default value is "grp".

   Example 1.8. Set grp_col parameter
...
modparam("permissions", "grp_col", "group_id")
...

3.9. ip_addr_col (string)

   Name of address table column containing the IP address part of the
   address.

   Default value is "ip_addr".

   Example 1.9. Set ip_addr_col parameter
...
modparam("permissions", "ip_addr_col", "ip_address")
...

3.10. mask_col (string)

   Name of address table column containing the network mask of the
   address. Possible values are 0-32 for IPv4 and 0-128 for IPv6
   addresses.

   Default value is "mask".

   Example 1.10. Set mask_col parameter
...
modparam("permissions", "mask_col", "subnet_length")
...

3.11. port_col (string)

   Name of address table column containing the port part of the address.

   Default value is "port".

   Example 1.11. Set port_col parameter
...
modparam("permissions", "port_col", "prt")
...

3.12. db_mode (integer)

   Database mode. 0 means non-caching, 1 means caching. Valid only for the
   allow_trusted function.

   Default value is 0 (non-caching).

   Example 1.12. Set db_mode parameter
...
modparam("permissions", "db_mode", 1)
...

3.13. trusted_table (string)

   Name of database table containing the matching rules used by the
   allow_trusted function.

   Default value is "trusted".

   Example 1.13. Set trusted_table parameter
...
modparam("permissions", "trusted_table", "pbx")
...

3.14. source_col (string)

   Name of column in the "trusted" table containing the source IP address
   that is matched against source IP address of received request.

   Default value is "src_ip".

   Example 1.14. Set source_col parameter
...
modparam("permissions", "source_col", "source_ip_address")
...

3.15. proto_col (string)

   Name of column in the "trusted" table containing the transport protocol
   that is matched against transport protocol of the received request.
   Possible values that can be stored in proto_col are "any", "udp",
   "tcp", "tls", "sctp", "ws", "wss", and "none". Value "any" matches
   always and value "none" never.

   Default value is "proto".

   Example 1.15. Set proto_col parameter
...
modparam("permissions", "proto_col", "transport")
...

3.16. from_col (string)

   Name of the column trusted table containing a regular expression that
   is matched against the From URI.

   Default value is "from_pattern".

   Example 1.16. Set from_col parameter
...
modparam("permissions", "from_col", "regexp")
...

3.17. tag_col (string)

   Name of the column in the "address" or "trusted" table containing a
   string that is added as value to peer_tag AVP if peer_tag AVP has been
   defined and if the address or peer matches.

   Default value is "tag".

   Example 1.17. Set tag_col parameter
...
modparam("permissions", "tag_col", "peer_tag")
...

3.18. peer_tag_avp (AVP string)

   If defined, the AVP will be set as a side effect of allow_trusted call
   to not NULL tag column value of the matching peer.

   Default value is "undefined".

   Example 1.18. Set peer_tag_avp parameter
...
modparam("permissions", "peer_tag_avp", "$avp(i:707)")
...

3.19. peer_tag_mode (integer)

   Tag mode for allow_trusted. "0" sets only the tag of the first match.
   "1" adds the tags of all matches to the avp. In addition the return
   value of allow_trusted is the number of matches. This parameter is not
   used for address table matching functions.

   Default value is "0".

   Example 1.19. Set peer_tag_mode parameter
...
modparam("permissions", "peer_tag_mode", 1)
...

4. Functions

   4.1. allow_routing()
   4.2. allow_routing(basename)
   4.3. allow_routing(allow_file,deny_file)
   4.4. allow_register(basename)
   4.5. allow_register(allow_file, deny_file)
   4.6. allow_uri(basename, pvar)
   4.7. allow_address(group_id, ip_addr_pvar, port_pvar)
   4.8. allow_source_address([group_id])
   4.9. allow_source_address_group()
   4.10. allow_address_group(addr, port)
   4.11. allow_trusted([src_ip_pvar, proto_pvar])

4.1. allow_routing()

   Returns true if all pairs constructed as described in Section 1.1,
   "Call Routing" have appropriate permissions according to the
   configuration files. This function uses default configuration files
   specified in default_allow_file and default_deny_file.

   This function can be used from REQUEST_ROUTE, FAILURE_ROUTE.

   Example 1.20. allow_routing usage
...
if (allow_routing()) {
        t_relay();
};
...

4.2. allow_routing(basename)

   Returns true if all pairs constructed as described in Section 1.1,
   "Call Routing" have appropriate permissions according to the
   configuration files given as parameters.

   Meaning of the parameters is as follows:
     * basename - Basename from which allow and deny filenames will be
       created by appending contents of allow_suffix and deny_suffix
       parameters.
       If the parameter doesn't contain full pathname then the function
       expects the file to be located in the same directory as the main
       configuration file of the server.

   This function can be used from REQUEST_ROUTE, FAILURE_ROUTE.

   Example 1.21. allow_routing(basename) usage
...
if (allow_routing("basename")) {
        t_relay();
};
...

4.3. allow_routing(allow_file,deny_file)

   Returns true if all pairs constructed as described in Section 1.1,
   "Call Routing" have appropriate permissions according to the
   configuration files given as parameters.

   Meaning of the parameters is as follows:
     * allow_file - File containing allow rules.
       If the parameter doesn't contain full pathname then the function
       expects the file to be located in the same directory as the main
       configuration file of the server.
     * deny_file - File containing deny rules.
       If the parameter doesn't contain full pathname then the function
       expects the file to be located in the same directory as the main
       configuration file of the server.

   This function can be used from REQUEST_ROUTE, FAILURE_ROUTE.

   Example 1.22. allow_routing(allow_file, deny_file) usage
...
if (allow_routing("rules.allow", "rules.deny")) {
        t_relay();
};
...

4.4. allow_register(basename)

   The function returns true if all pairs constructed as described in
   Section 1.2, "Registration Permissions" have appropriate permissions
   according to the configuration files given as parameters.

   Meaning of the parameters is as follows:
     * basename - Basename from which allow and deny filenames will be
       created by appending contents of allow_suffix and deny_suffix
       parameters.
       If the parameter doesn't contain full pathname then the function
       expects the file to be located in the same directory as the main
       configuration file of the server.

   This function can be used from REQUEST_ROUTE, FAILURE_ROUTE.

   Example 1.23. allow_register(basename) usage
...
if (method=="REGISTER") {
        if (allow_register("register")) {
                save("location");
                exit;
        } else {
                sl_send_reply("403", "Forbidden");
        };
};
...

4.5. allow_register(allow_file, deny_file)

   The function returns true if all pairs constructed as described in
   Section 1.2, "Registration Permissions" have appropriate permissions
   according to the configuration files given as parameters.

   Meaning of the parameters is as follows:
     * allow_file - File containing allow rules.
       If the parameter doesn't contain full pathname then the function
       expects the file to be located in the same directory as the main
       configuration file of the server.
     * deny_file - File containing deny rules.
       If the parameter doesn't contain full pathname then the function
       expects the file to be located in the same directory as the main
       configuration file of the server.

   This function can be used from REQUEST_ROUTE, FAILURE_ROUTE.

   Example 1.24. allow_register(allow_file, deny_file) usage
...
if (method=="REGISTER") {
        if (allow_register("register.allow", "register.deny")) {
                save("location");
                exit;
        } else {
                sl_send_reply("403", "Forbidden");
        };
};
...

4.6. allow_uri(basename, pvar)

   Returns true if the pair constructed as described in Section 1.3, "URI
   Permissions" have appropriate permissions according to the
   configuration files specified by the parameter.

   Meaning of the parameter is as follows:
     * basename - Basename from which allow and deny filenames will be
       created by appending contents of allow_suffix and deny_suffix
       parameters.
       If the parameter doesn't contain full pathname then the function
       expects the file to be located in the same directory as the main
       configuration file of the server.
     * pvar - Any pseudo-variable defined in Kamailio.

   This function can be used from REQUEST_ROUTE, FAILURE_ROUTE.

   Example 1.25. allow_uri(basename, pvar) usage
...
if (allow_uri("basename", "$rt")) {  // Check Refer-To URI
        t_relay();
};
if (allow_uri("basename", "$avp(i:705)") {  // Check URI stored in $avp(i:705)
        t_relay();
};
...

4.7. allow_address(group_id, ip_addr_pvar, port_pvar)

   Returns true if the address and port given as values of pvar arguments
   belonging to a group given as group_id argument matches an IP subnet or
   a DNS domain name found in cached address table.

   When matching is done if the argument is an IP address, it is matched
   with the records from that group that are of type exact IP or subnet.
   If the argument is not an IP it is tried to be matched with the records
   that are DNS domain names. No DNS lookup is performed, only strict
   matching. Cached address table entry containing port value "0" matches
   any port. The "group_id" argument can be an integer string or a pseudo
   variable.

   This function can be used from REQUEST_ROUTE, FAILURE_ROUTE.

   Example 1.26. allow_address() usage
...

// Check if source address/port is in group 1
if (!allow_address("1", "$si", "$sp")) {
        sl_send_reply("403", "Forbidden");
};
// Check address/port stored in AVPs src_adr/src_port is in group 2
$avp(dst_adr) = "sipdomain.com";
$avp(dst_port) = "0";
if (!allow_address("2", "$avp(dst_adr)", "$avp(dst_port)") {
        sl_send_reply("403", "Forbidden");
};
...

4.8. allow_source_address([group_id])

   Equal to "allow_address(group_id, "$si", "$sp")". If 'group_id' is
   missing, the function is equal to allow_address("1", "$si", "$sp").

   This function can be used from REQUEST_ROUTE, FAILURE_ROUTE.

   Example 1.27. allow_source_address(group_id) usage
...

// Check source address/port of request
if (!allow_source_address("1")) {
        sl_send_reply("403", "Forbidden");
};
...

4.9. allow_source_address_group()

   Checks if source address/port is found in cached address or subnet
   table in any group. If yes, returns that group. If not returns -1. Port
   value 0 in cached address and group table matches any port.

   This function can be used from REQUEST_ROUTE, FAILURE_ROUTE.

   Example 1.28. allow_source_address_group() usage
...

$var(group) = allow_source_address_group();
if ($var(group) != -1) {
   # do something with $var(group)
};
...

4.10. allow_address_group(addr, port)

   Checks if address/port is found in cached address or subnet table in
   any group. If yes, returns that group. If not returns -1. Port value 0
   in cached address and group table matches any port. The parameters can
   be pseudo-variables.

   This function can be used from ANY_ROUTE.

   Example 1.29. allow_source_address_group() usage
...

$var(group) = allow_address_group("1.2.3.4", "5060");
if ($var(group) != -1) {
   # do something with $var(group)
};
...

4.11. allow_trusted([src_ip_pvar, proto_pvar])

   Checks based either on request's source address and transport protocol
   or source address and transport protocol given in pvar arguments, and
   From URI of request if request can be trusted without authentication.
   Returns "1" if a match is found as described in Section 1.5, "Trusted
   Requests" and "-1" otherwise. If a match is found and peer_tag_avp has
   been defined, adds a non-NULL tag column value of the matching peer to
   AVP peer_tag_avp.

   Source address and transport protocol given in pvar arguments must be
   in string format. Valid transport protocol values are (ignoring case)
   "any", "udp, "tcp", "tls", "ws", "wss" and "sctp".

   This function can be used from REQUEST_ROUTE, FAILURE_ROUTE.

   Example 1.30. allow_trusted() usage
...
if (allow_trusted()) {
        t_relay();
};
...
if (allow_trusted("$si", "$proto")) {
        t_relay();
};
...

5. MI Commands

   5.1. address_reload
   5.2. address_dump
   5.3. subnet_dump
   5.4. trusted_reload
   5.5. trusted_dump
   5.6. allow_uri

5.1. address_reload

   Causes the permissions module to re-read the contents of address
   database table into cache memory. The in-cache memory entries are for
   performance reasons stored in two different tables: address table and
   subnet table depending on the value of the mask field (32 or smaller).

   Parameters: none

5.2. address_dump

   Causes permissions module to dump contents of cache memory address
   table.

   Parameters: none

5.3. subnet_dump

   Causes permissions module to dump contents of cache memory subnet
   table.

   Parameters: none

5.4. trusted_reload

   Causes the permissions module to re-read the contents of trusted table
   into cache memory.

   Parameters: none

5.5. trusted_dump

   Causes the permissions module to dump the contents of trusted table
   from cache memory.

   Parameters: none

5.6. allow_uri

   Tests if (URI, Contact) pair is allowed according to the allow/deny
   files. The files must already have been loaded by Kamailio.

   Parameters:
     * basename - Basename from which allow and deny filenames will be
       created by appending contents of allow_suffix and deny_suffix
       parameters.
     * URI - URI to be tested
     * Contact - Contact to be tested

6. RPC Commands

   6.1. addressReload
   6.2. addressDump
   6.3. subnetDump
   6.4. testUri basename uri contact
   6.5. trustedReload
   6.6. trustedDump

6.1. addressReload

   Causes the permissions module to re-read the contents of address
   database table into cache memory. In cache memory the entries are for
   performance reasons stored in two different tables: address table and
   subnet table depending on the value of the mask field (32 or smaller).

   Parameters: none

6.2. addressDump

   Causes the permissions module to dump the contents of cache memory
   address table. (Not the subnet table).

   Parameters: none

6.3. subnetDump

   Causes permissions module to dump contents of cache memory subnet
   table.

   Parameters: none

6.4. testUri basename uri contact

   Tests if the (URI, Contact) pair is allowed according to allow/deny
   files. The files must already have been loaded by Kamailio.

   Parameters:
     * basename - Basename from which allow and deny filenames will be
       created by appending contents of the allow_suffix and deny_suffix
       parameters.
     * URI - URI to be tested
     * Contact - Contact to be tested

6.5. trustedReload

   Causes the permissions module to re-read the contents of the trusted
   database table into cache memory.

   Parameters: none

6.6. trustedDump

   Causes the permissions module to dump contents of the trusted database
   table from cache memory.

   Parameters: none
