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_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

   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_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_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

1. Overview

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

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.

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

   Thus, 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 same as described in Section 1.1, “Call
   Routing”.

1.3. URI Permissions

   The module can be used to determine if request is allowed to the
   destination specified by 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 allow_uri function is called, it tries to find a rule that matches
   selected fields of the message. The matching algorithm is as follows,
   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.
     * Otherwise 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.

   From URI and 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)
   matches any of the IP subnets stored in cached openser database table.
   Port 0 in cached database table matches any port. IP 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 cached 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). Group identifier is given as
   argument to allow_address and allow_source_address functions.

   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 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 source address of request or source
       address given in pvar,
     * transport protocol is either "ANY" or equal to transport protocol
       of request or transport protocol given in pvar, and
     * regular expression is either empty (NULL in database) or matches
       From URI of request.

   Otherwise the request is rejected.

   As a side effect of accepting the request, peer's 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.

   Rules are stored in a database table specified by module parameters.
   There also exists a module parameter dm_mode that determines if rules
   are cached into memory for faster matching or if database is consulted
   for each invocation of 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 functions without parameters. If you don't
   specify 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
   without parameters. If you don't specify 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)

   Name of database table containing IP subnet information 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 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 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 network mask of the address.
   Possible values are 0-32.

   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 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
   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 matching rules used by 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 trusted table column containing 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 trusted table column containing transport protocol that is
   matched against transport protocol of received request. Possible values
   that can be stored in proto_col are “any”, “udp”, “tcp”, “tls”, “sctp”,
   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 trusted table column containing regular expression that is
   matched against 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 address or trusted table column 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 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.

   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_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 IP address and port given as values of pvar arguments
   belonging to a group given as group_id argument matches an IP subnet
   found in cached address table. Cached address table entry containing
   port value 0 matches any port. 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 IP address/port stored in AVPs i:704/i:705 is in group 2
if (!allow_address("2", "$avp(i:704)", "$avp(i:705)") {
        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_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)
   "udp, "tcp", "tls", and "sctp".

   This function can be used from REQUEST_ROUTE, FAILURE_ROUTE.

   Example 1.29. 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 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

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

   Parameters: none

5.5.  trusted_dump

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

   Parameters: none

5.6.  allow_uri

   Tests if (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 allow_suffix and deny_suffix
       parameters.
     * URI - URI to be tested
     * Contact - Contact to be tested
