permissions Module

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:

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.

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”.

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:

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.

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.

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

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.

The following modules must be loaded before this module:

The following libraries or applications must be installed before running Kamailio with this module loaded:

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”.

...
modparam("permissions", "default_allow_file", "/etc/permissions.allow")
...

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”.

...
modparam("permissions", "default_deny_file", "/etc/permissions.deny")
...

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.

Default value is 1.

...
modparam("permissions", "check_all_branches", 0)
...

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.

Default value is “.allow”.

...
modparam("permissions", "allow_suffix", ".allow")
...

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.

Default value is “.deny”.

...
modparam("permissions", "deny_suffix", ".deny")
...

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

Default value is “NULL”.

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

Name of database table containing IP subnet information used by allow_address and allow_source_address functions.

Default value is “address”.

...
modparam("permissions", "address_table", "addr")
...

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

Default value is “grp”.

...
modparam("permissions", "grp_col", "group_id")
...

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

Default value is “ip_addr”.

...
modparam("permissions", "ip_addr_col", "ip_address")
...

Name of address table column containing network mask of the address. Possible values are 0-32.

Default value is “mask”.

...
modparam("permissions", "mask_col", "subnet_length")
...

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

Default value is “port”.

...
modparam("permissions", "port_col", "prt")
...

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

Default value is 0 (non-caching).

...
modparam("permissions", "db_mode", 1)
...

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

Default value is “trusted”.

...
modparam("permissions", "trusted_table", "pbx")
...

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

Default value is “src_ip”.

...
modparam("permissions", "source_col", "source_ip_address")
...

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”.

...
modparam("permissions", "proto_col", "transport")
...

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

Default value is “from_pattern”.

...
modparam("permissions", "from_col", "regexp")
...

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”.

...
modparam("permissions", "tag_col", "peer_tag")
...

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”.

...
modparam("permissions", "peer_tag_avp", "$avp(i:707)")
...

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”.

...
modparam("permissions", "peer_tag_mode", "1")
...

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.

...
if (allow_routing()) {
	t_relay();
};
...

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:

This function can be used from REQUEST_ROUTE, FAILURE_ROUTE.

...
if (allow_routing("basename")) {
	t_relay();
};
...

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:

This function can be used from REQUEST_ROUTE, FAILURE_ROUTE.

...
if (allow_routing("rules.allow", "rules.deny")) {
	t_relay();
};
...

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:

This function can be used from REQUEST_ROUTE, FAILURE_ROUTE.

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

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:

This function can be used from REQUEST_ROUTE, FAILURE_ROUTE.

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

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:

This function can be used from REQUEST_ROUTE, FAILURE_ROUTE.

...
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();
};
...

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.

...

// 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");
};
...

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.

...

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

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.

...

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

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", and "sctp".

This function can be used from REQUEST_ROUTE, FAILURE_ROUTE.

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

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

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

Parameters: none

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

Parameters: none

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

Parameters: none

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

Parameters: none

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

Parameters: