$Revision: 1.3.2.1 $
$Date: 2005/06/22 23:12:07 $
User's Guide
Overview
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.
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:
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.
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 . 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 .
Dependencies
&ser; Modules
The following modules must be loaded before this module:
No dependencies on other &ser; modules.
External Libraries or Applications
The following libraries or applications must be installed before running
&ser; with this module loaded:
None.
Exported Parameters
<varname>default_allow_file</varname> (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
.
Set <varname>default_allow_file</varname> parameter
...
modparam("permissions", "default_allow_file", "/etc/permissions.allow")
...
<varname>default_deny_file</varname> (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
.
Set <varname>default_deny_file</varname> parameter
...
modparam("permissions", "default_deny_file", "/etc/permissions.deny")
...
<varname>check_all_branches</varname> (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.
Do not disable this parameter unless you really know what you are doing.
Default value is 1.
Set <varname>check_all_branches</varname> parameter
...
modparam("permissions", "check_all_branches", 0)
...
<varname>allow_suffix</varname> (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.
Including leading dot.
Default value is .allow
.
Set <varname>allow_suffix</varname> parameter
...
modparam("permissions", "allow_suffix", ".allow")
...
<varname>deny_suffix</varname> (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.
Including leading dot.
Default value is .deny
.
Set <varname>deny_suffix</varname> parameter
...
modparam("permissions", "deny_suffix", ".deny")
...
<varname>db_url</varname> (string)
The URL of database to be used to obtain the list of trusted hosts.
Default value is "mysql://ser:heslo@localhost/ser".
<varname>db_mode</varname> (integer)
This parameter controls the cache that speeds up lookups of
trusted hosts. The value 1 enables cache, 0 disables it (each
query would result in a database lookup).
Default value is 0 (disable cache).
<varname>trusted_table</varname> (string)
The name of the table in database containing the list of
trusted hosts.
Default value is "trusted".
<varname>source_col</varname> (string)
The name of the column in trusted table which contains source
IP address.
Default value is "src_ip".
<varname>proto_col</varname> (string)
The name of the column in trusted table which contains the
protocol identifier (UDP, TCP, TLS).
Default value is "proto".
<varname>from_col</varname> (string)
The name of the column in trusted table which contains regular
expressions that will be matched agains From header field.
Default value is "from_pattern".
Exported Functions
<function moreinfo="none">allow_routing()</function>
Returns true if all pairs constructed as described in have appropriate permissions according to the
configuration files. This function uses default configuration files specified in
default_allow_file and default_deny_file.
<function>allow_routing</function> usage
...
if (allow_routing()) {
t_relay();
};
...
<function moreinfo="none">allow_routing(basename)</function>
Returns true if all pairs constructed as described in 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.
<function>allow_routing(basename)</function> usage
...
if (allow_routing("basename")) {
t_relay();
};
...
<function moreinfo="none">allow_routing(allow_file, deny_file)</function>
Returns true if all pairs constructed as described in 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.
<function>allow_routing(allow_file, deny_file)</function> usage
...
if (allow_routing("rules.allow", "rules.deny")) {
t_relay();
};
...
<function moreinfo="none">allow_register(basename)</function>
The function returns true if all pairs constructed as described in 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.
<function>allow_register(basename)</function> usage
...
if (method=="REGISTER") {
if (allow_register("register")) {
save("location");
break;
} else {
sl_send_reply("403", "Forbidden");
};
};
...
<function moreinfo="none">allow_register(allow_file, deny_file)</function>
The function returns true if all pairs constructed as described in 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.
<function>allow_register(allow_file, deny_file)</function> usage
...
if (method=="REGISTER") {
if (allow_register("register.allow", "register.deny")) {
save("location");
break;
} else {
sl_send_reply("403", "Forbidden");
};
};
...
<function moreinfo="none">allow_trusted()</function>
The function check the source IP, protocol, and the contents of
From header field against entries in trusted table and returns
true if there is a match. This means that the end-device is trusted.