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
   Revision History
   Revision $Revision: 5683 $ $Date: 2008-08-06 13:08:33 +0300
                              (Wed, 06 Aug 2008) $
     __________________________________________________________

   Table of Contents

   1. Admin Guide

        1.1. Overview

              1.1.1. Call Routing
              1.1.2. Registration Permissions
              1.1.3. URI Permissions
              1.1.4. Address Permissions
              1.1.5. Trusted Requests

        1.2. Dependencies

              1.2.1. Kamailio Modules
              1.2.2. External Libraries or Applications

        1.3. Exported Parameters

              1.3.1. default_allow_file (string)
              1.3.2. default_deny_file (string)
              1.3.3. check_all_branches (integer)
              1.3.4. allow_suffix (string)
              1.3.5. deny_suffix (string)
              1.3.6. db_url (string)
              1.3.7. address_table (string)
              1.3.8. grp_col (string)
              1.3.9. ip_addr_col (string)
              1.3.10. mask_col (string)
              1.3.11. port_col (string)
              1.3.12. db_mode (integer)
              1.3.13. trusted_table (string)
              1.3.14. source_col (string)
              1.3.15. proto_col (string)
              1.3.16. from_col (string)
              1.3.17. tag_col (string)
              1.3.18. peer_tag_avp (AVP string)

        1.4. Exported Functions

              1.4.1. allow_routing()
              1.4.2. allow_routing(basename)
              1.4.3. allow_routing(allow_file,deny_file)
              1.4.4. allow_register(basename)
              1.4.5. allow_register(allow_file, deny_file)
              1.4.6. allow_uri(basename, pvar)
              1.4.7. allow_address(group_id, ip_addr_pvar,
                      port_pvar)

              1.4.8. allow_source_address(group_id)
              1.4.9. allow_source_address_group()
              1.4.10. allow_trusted([src_ip_pvar, proto_pvar])

        1.5. Exported MI Functions

              1.5.1. address_reload
              1.5.2. address_dump
              1.5.3. subnet_dump
              1.5.4. trusted_reload
              1.5.5. trusted_dump
              1.5.6. 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. allow_routing usage
   1.20. allow_routing(basename) usage
   1.21. allow_routing(allow_file, deny_file) usage
   1.22. allow_register(basename) usage
   1.23. allow_register(allow_file, deny_file) usage
   1.24. allow_uri(basename, pvar) usage
   1.25. allow_address() usage
   1.26. allow_source_address(group_id) usage
   1.27. allow_source_address_group() usage
   1.28. allow_trusted() usage

Chapter 1. Admin Guide

1.1. Overview

1.1.1. 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.

1.1.2. 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 1.1.1, "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 1.1.1, "Call Routing".

1.1.3. 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.

1.1.4. 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 (unsigned integer). Group identifier is given as
   argument to allow_address and allow_source_address functions.

1.1.5. 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.

1.2. Dependencies

1.2.1. Kamailio Modules

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

1.2.2. External Libraries or Applications

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

1.3. Exported Parameters

1.3.1. 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")
...

1.3.2. 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")
...

1.3.3. 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)
...

1.3.4. 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")
...

1.3.5. 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")
...

1.3.6. 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/d
bname")
...

1.3.7. 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")
...

1.3.8. 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")
...

1.3.9. 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")
...

1.3.10. 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")
...

1.3.11. 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")
...

1.3.12. 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)
...

1.3.13. trusted_table (string)

   Name of database table containing matching rules used by
   allow_register function.

   Default value is "trusted".

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

1.3.14. 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")
...

1.3.15. 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")
...

1.3.16. 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")
...

1.3.17. tag_col (string)

   Name of 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 peer matches.

   Default value is "tag".

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

1.3.18. 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)")
...

1.4. Exported Functions

1.4.1.  allow_routing()

   Returns true if all pairs constructed as described in
   Section 1.1.1, "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 1.19. allow_routing usage
...
if (allow_routing()) {
        t_relay();
};
...

1.4.2.  allow_routing(basename)

   Returns true if all pairs constructed as described in
   Section 1.1.1, "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 1.20. allow_routing(basename) usage
...
if (allow_routing("basename")) {
        t_relay();
};
...

1.4.3.  allow_routing(allow_file,deny_file)

   Returns true if all pairs constructed as described in
   Section 1.1.1, "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 1.21. allow_routing(allow_file, deny_file) usage
...
if (allow_routing("rules.allow", "rules.deny")) {
        t_relay();
};
...

1.4.4.  allow_register(basename)

   The function returns true if all pairs constructed as described
   in Section 1.1.2, "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 1.22. allow_register(basename) usage
...
if (method=="REGISTER") {
        if (allow_register("register")) {
                save("location");
                exit;
        } else {
                sl_send_reply("403", "Forbidden");
        };
};
...

1.4.5.  allow_register(allow_file, deny_file)

   The function returns true if all pairs constructed as described
   in Section 1.1.2, "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 1.23. 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");
        };
};
...

1.4.6.  allow_uri(basename, pvar)

   Returns true if the pair constructed as described in
   Section 1.1.3, "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 1.24. 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();
};
...

1.4.7.  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 1.25. 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");
};
...

1.4.8.  allow_source_address(group_id)

   Equal to allow_address(group_id, "$si", "$sp").

   This function can be used from REQUEST_ROUTE, FAILURE_ROUTE.

   Example 1.26. allow_source_address(group_id) usage
...

// Check source address/port of request
if (!allow_source_address("0")) {
        sl_send_reply("403", "Forbidden");
};
...

1.4.9.  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 1.27. allow_source_address_group() usage
...

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

1.4.10.  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 1.1.5, "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
   "UDP, "TCP", "TLS", and "SCTP".

   This function can be used from REQUEST_ROUTE, FAILURE_ROUTE.

   Example 1.28. allow_trusted() usage
...
if (allow_trusted()) {
        t_relay();
};
...
if (allow_trusted("$si", "$proto")) {
        t_relay();
};
...

1.5. Exported MI Functions

1.5.1.  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

1.5.2.  address_dump

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

   Parameters: none

1.5.3.  subnet_dump

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

   Parameters: none

1.5.4.  trusted_reload

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

   Parameters: none

1.5.5.  trusted_dump

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

   Parameters: none

1.5.6.  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
