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.

SER 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 1.1.1, “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”.

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

Main purpose of the function is to prevent referring a SIP UA to "prohibited" IP addresses. One example is user sending a REFER request to PSTN gateway trying to refer it to an expensive phone number.

Function for Refer-To checking is called allow_refer_to and the algorithm is very similar to the algorithm described in Section 1.1.1. The only difference is in the way how pairs are created.

Instead of Request-URI the function uses Refer-To header field because Refer-To header field in REFER messages contains the URI to which the UA is being referred to. The algorithm of matching is same as described in Section 1.1.1.

The module can be also used for catching messages coming from or going to specific network elements, for example gateways or peering partners.

Users can register or forward the calls to the address of a gateway resulting unauthorized access to them. Such calls must be catched and dropped, see ipmatch functions for details.

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 both of the default file parameters are set to "" the module does not try to load them.

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")
...

Maximum number of allow/deny file pairs.

Default value is 64.

Module initialization fails in case of a missing config file if safe_file_load is true.

Default value is 0 (false).

URL of the database to be used.

Disables/enables database cache.

Default value is 0 (cache is disabled)

NOTE: ipmatch functions can operate only in cache mode, set db_mode to 1 if you want to use them.

Name of the table containing ipmatch entries.

Default value is "ipmatch".

Declares name of ip set which can be manipulated via RPC commands and tested using ip_is_trusted. Identifier must start with letter or underscore.

IP mask may follow equal sign to initialize ipset on startup.

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.

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

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:

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

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:

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

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:

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

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:

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

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:

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

The function returns true if all pairs constructed as described in Section 1.1.2 have appropriate permissions according to the configuration files given as parameters.

Meaning of the parameters is as follows:

...
if (method=="REFER") {
    if (allow_register("refer.allow", "refer.deny")) {
       ...
    } else {
        sl_send_reply("403", "Forbidden");
    };
};
...

The function tries to find an IP address and port pair (defined by the first function parameter) in the cached database table. Port is optional, it is compared only if both the function parameter and the database entry contain it.

Meaning of the parameters is as follows:

Note that IPv6 addresses must be enclosed in square brackets in case of port is defined: [1111:2222::3333]:5060

ipmatch() function replacement for onsend_route block.

The function accepts only string parameter, because even AVP reading is unsafe in onsend_route.

Meaning of the parameter:

The function can be used for example to catch unauthorized requests going to gateways: Use a flag to mark the call as PSTN either in request or in failure_route, and do not touch it in onreply_route. See the examples below.

Entries in the database can be marked to group the different kind of network elements. The function sets the filter which is used on the mark while comparing the IP addresses. The mark must be the power of 2 in the database!

Note that ipmatch() and ipmatch_onsend() functions reset the filter!

+-----------------+-------------------+------+------+
| ip              | avp_val           | mark | flag |
+-----------------+-------------------+------+------+
| 1111:2222::1001 | first_gw          |    1 |    1 |
| 10.38.2.10:5060 | second_gw         |    1 |    1 |
| 10.0.0.10       | first_peering     |    2 |    1 |
+-----------------+-------------------+------+------+


route[0] {
  # is this a request from a GW?
  ipmatch_filter("1");
  if (ipmatch("src", "$gw_id")) {
    # yes, it is from a GW
    ...
  } else {
    # is this a request from a peering partner?
    ipmatch_filter("2");
    if (ipmatch("src", "$peering_id")) {
       # yes, it is from a peering partner
       ...
    };
  }
  ...
  # request goes to PSTN
  setflag(PSTN);
}

onsend_route[0] {
  if (method == "INVITE" && (!isflagset(PSTN))) {
     # is this a request to a GW?
     ipmatch_filter("1");
     if (ipmatch_onsend("dst")) {
        # request is not marked with PSTN flag, but it goes to a gateway
        drop;
     }
  }
  ...
}

The function returns true if ip is contained in ip_set. Both IPv4 and IPv6 are supported.

Meaning of the parameters is as follows:

modparam("permissions", "declare_ipset", "my_ipset1");
modparam("permissions", "declare_ipset", "my_ipset2=127.0.0.0/24;10.0.0.0/255.255.255.0");
	
route[TT2] {
	if (ip_is_trusted("$net", "$ip")) {
		xlog("L_E", "'%$ip' - TRUE\n");
	} else {
		xlog("L_E", "'%$ip' - FALSE\n");
	}
}

route[TT1] {
	xlog("L_E", "Testing netmask '%$net'\n");
	
	$ip = "s";   # source address
	route(TT2);
	
	$ip = "127.0.0.1";
	route(TT2);
	
	$ip = "127.0.0.2";
	route(TT2);
	
	$ip = "10.0.0.1";
	route(TT2);
	
	$ip = "11.0.0.1";
	route(TT2);
	
	$ip = "172.1.8.1";
	route(TT2);
	
	$ip = "192.168.1.1";
	route(TT2);
	
	$ip = "192.168.1.255";
	route(TT2);
	
	$ip = "192.168.2.1";
	route(TT2);
	
	$ip = "192.168.3.1";
	route(TT2);
	
	$ip = "192.168.4.97";
	route(TT2);
	
	$ip = "192.168.4.100";
	route(TT2);

	$ip = "[0:2:4:A:B:D:E:F301]";
	route(TT2);
	
	$ip = "[0:2:4:A:B:D:E:F401]";
	route(TT2);
	
	$ip = "[0:0:0:0:0:0:0:0]";
	route(TT2);
}
		
route[TEST] {
	$net = "0.0.0.0 128.2.3.4/1 127.0.128.16 [0:2:4:A:B:D:E:F301]";
	route(TT1);

	$net = "255.255.255.255/0"; # all IPv4 addresses, dentical to 0.0.0.0/0
	route(TT1);
	
	$net = "127.0.0.1/255.255.255.0";
	route(TT1);
	
	$net = "10.0.0.0/8";  # All type A addresses
	route(TT1);	         
	
	$net = "192.168.1.0/24";
	route(TT1);
	
	$net = "192.168.4.96/27";
	route(TT1);
	
	$net = "192.168.1.1/32"; # only one IP matches
	route(TT1);
	
	$net = "192.168.1.0/24,192.168.2.0/24";
	route(TT1);
	
	$net = "192.168.1.0/24,192.168.2.0/24,127.0.0.1/31";
	route(TT1);
	
	$net = "[0:0:0:0:0:0:0:0]/0";  # all IPv6 addresses
	route(TT1);
	
	$net = "[0:2:4:A:B:D:E:f300]/120";
	route(TT1);

	$net = "my_ipset1";
	route(TT1);

}
# the result is:

Testing netmask '0.0.0.0 128.2.3.4/1 127.0.128.16 [0:2:4:A:B:D:E:F301]'
's' - FALSE
'127.0.0.1' - FALSE
'127.0.0.2' - FALSE
'10.0.0.1' - FALSE
'11.0.0.1' - FALSE
'172.1.8.1' - TRUE
'192.168.1.1' - TRUE
'192.168.1.255' - TRUE
'192.168.2.1' - TRUE
'192.168.3.1' - TRUE
'192.168.4.97' - TRUE
'192.168.4.100' - TRUE
'[0:2:4:A:B:D:E:F301]' - TRUE
'[0:2:4:A:B:D:E:F401]' - FALSE
'[0:0:0:0:0:0:0:0]' - FALSE
Testing netmask '255.255.255.255/0'
's' - TRUE
'127.0.0.1' - TRUE
'127.0.0.2' - TRUE
'10.0.0.1' - TRUE
'11.0.0.1' - TRUE
'172.1.8.1' - TRUE
'192.168.1.1' - TRUE
'192.168.1.255' - TRUE
'192.168.2.1' - TRUE
'192.168.3.1' - TRUE
'192.168.4.97' - TRUE
'192.168.4.100' - TRUE
'[0:2:4:A:B:D:E:F301]' - FALSE
'[0:2:4:A:B:D:E:F401]' - FALSE
'[0:0:0:0:0:0:0:0]' - FALSE
Testing netmask '127.0.0.1/24'
's' - FALSE
'127.0.0.1' - TRUE
'127.0.0.2' - TRUE
'10.0.0.1' - FALSE
'11.0.0.1' - FALSE
'172.1.8.1' - FALSE
'192.168.1.1' - FALSE
'192.168.1.255' - FALSE
'192.168.2.1' - FALSE
'192.168.3.1' - FALSE
'192.168.4.97' - FALSE
'192.168.4.100' - FALSE
'[0:2:4:A:B:D:E:F301]' - FALSE
'[0:2:4:A:B:D:E:F401]' - FALSE
'[0:0:0:0:0:0:0:0]' - FALSE
Testing netmask '10.0.0.0/8'
's' - FALSE
'127.0.0.1' - FALSE
'127.0.0.2' - FALSE
'10.0.0.1' - TRUE
'11.0.0.1' - FALSE
'172.1.8.1' - FALSE
'192.168.1.1' - FALSE
'192.168.1.255' - FALSE
'192.168.2.1' - FALSE
'192.168.3.1' - FALSE
'192.168.4.97' - FALSE
'192.168.4.100' - FALSE
'[0:2:4:A:B:D:E:F301]' - FALSE
'[0:2:4:A:B:D:E:F401]' - FALSE
'[0:0:0:0:0:0:0:0]' - FALSE
Testing netmask '192.168.1.0/24'
's' - FALSE
'127.0.0.1' - FALSE
'127.0.0.2' - FALSE
'10.0.0.1' - FALSE
'11.0.0.1' - FALSE
'172.1.8.1' - FALSE
'192.168.1.1' - TRUE
'192.168.1.255' - TRUE
'192.168.2.1' - FALSE
'192.168.3.1' - FALSE
'192.168.4.97' - FALSE
'192.168.4.100' - FALSE
'[0:2:4:A:B:D:E:F301]' - FALSE
'[0:2:4:A:B:D:E:F401]' - FALSE
'[0:0:0:0:0:0:0:0]' - FALSE
Testing netmask '192.168.4.96/27'
's' - FALSE
'127.0.0.1' - FALSE
'127.0.0.2' - FALSE
'10.0.0.1' - FALSE
'11.0.0.1' - FALSE
'172.1.8.1' - FALSE
'192.168.1.1' - FALSE
'192.168.1.255' - FALSE
'192.168.2.1' - FALSE
'192.168.3.1' - FALSE
'192.168.4.97' - TRUE
'192.168.4.100' - TRUE
'[0:2:4:A:B:D:E:F301]' - FALSE
'[0:2:4:A:B:D:E:F401]' - FALSE
'[0:0:0:0:0:0:0:0]' - FALSE
Testing netmask '192.168.1.1/32'
's' - FALSE
'127.0.0.1' - FALSE
'127.0.0.2' - FALSE
'10.0.0.1' - FALSE
'11.0.0.1' - FALSE
'172.1.8.1' - FALSE
'192.168.1.1' - TRUE
'192.168.1.255' - FALSE
'192.168.2.1' - FALSE
'192.168.3.1' - FALSE
'192.168.4.97' - FALSE
'192.168.4.100' - FALSE
'[0:2:4:A:B:D:E:F301]' - FALSE
'[0:2:4:A:B:D:E:F401]' - FALSE
'[0:0:0:0:0:0:0:0]' - FALSE
Testing netmask '192.168.1.0/24,192.168.2.0/24'
's' - FALSE
'127.0.0.1' - FALSE
'127.0.0.2' - FALSE
'10.0.0.1' - FALSE
'11.0.0.1' - FALSE
'172.1.8.1' - FALSE
'192.168.1.1' - TRUE
'192.168.1.255' - TRUE
'192.168.2.1' - TRUE
'192.168.3.1' - FALSE
'192.168.4.97' - FALSE
'192.168.4.100' - FALSE
'[0:2:4:A:B:D:E:F301]' - FALSE
'[0:2:4:A:B:D:E:F401]' - FALSE
'[0:0:0:0:0:0:0:0]' - FALSE
Testing netmask '192.168.1.0/24,192.168.2.0/24,127.0.0.1/31'
's' - FALSE
'127.0.0.1' - TRUE
'127.0.0.2' - FALSE
'10.0.0.1' - FALSE
'11.0.0.1' - FALSE
'172.1.8.1' - FALSE
'192.168.1.1' - TRUE
'192.168.1.255' - TRUE
'192.168.2.1' - TRUE
'192.168.3.1' - FALSE
'192.168.4.97' - FALSE
'192.168.4.100' - FALSE
'[0:2:4:A:B:D:E:F301]' - FALSE
'[0:2:4:A:B:D:E:F401]' - FALSE
'[0:0:0:0:0:0:0:0]' - FALSE
Testing netmask '[0:0:0:0:0:0:0:0]/0'
's' - FALSE
'127.0.0.1' - FALSE
'127.0.0.2' - FALSE
'10.0.0.1' - FALSE
'11.0.0.1' - FALSE
'172.1.8.1' - FALSE
'192.168.1.1' - FALSE
'192.168.1.255' - FALSE
'192.168.2.1' - FALSE
'192.168.3.1' - FALSE
'192.168.4.97' - FALSE
'192.168.4.100' - FALSE
'[0:2:4:A:B:D:E:F301]' - TRUE
'[0:2:4:A:B:D:E:F401]' - TRUE
'[0:0:0:0:0:0:0:0]' - TRUE
Testing netmask '[0:2:4:A:B:D:E:f300]/120'
's' - FALSE
'127.0.0.1' - FALSE
'127.0.0.2' - FALSE
'10.0.0.1' - FALSE
'11.0.0.1' - FALSE
'172.1.8.1' - FALSE
'192.168.1.1' - FALSE
'192.168.1.255' - FALSE
'192.168.2.1' - FALSE
'192.168.3.1' - FALSE
'192.168.4.97' - FALSE
'192.168.4.100' - FALSE
'[0:2:4:A:B:D:E:F301]' - TRUE
'[0:2:4:A:B:D:E:F401]' - FALSE
'[0:0:0:0:0:0:0:0]' - FALSE
}