1. Sanity Module

Nils Ohlmeier

   iptelorg GmbH

   Copyright © 2006 iptelorg GmbH
     __________________________________________________________________

   1.1. Overview
   1.2. Dependencies
   1.3. Parameters

        1.3.1. default_checks (integer)
        1.3.2. uri_checks (integer)
        1.3.3. proxy_require (string)
        1.3.4. autodrop (integer)

   1.4. Functions

        1.4.1. sanity_check([msg_checks [, uri_checks]])

1.1. Overview

   This module aims to implement several sanity checks on incoming
   requests which are suggested or even required by a RFC, but are not
   available yet in the core of SIP-router.

   This checks are not required by SIP-router itself for its
   functionality. But on the other side it makes not much sence if a
   broken request traverses through a SIP network if it is rejected sooner
   or later by a SIP device any way. As every sanity cost extra
   performance because of additional parsing and evaluation it is now with
   this module up to the SIP-router adminstrator which checks should be
   done on which request.

   The following checks are available:
     * ruri sip version - (1) - checks if the SIP version in the request
       URI is supported, currently only 2.0.
     * ruri scheme - (2) - checks if the URI scheme of the request URI is
       supported (sip[s]|tel[s]) by SIP-router.
     * required headers - (4) -checks if the minimum set of required
       headers to, from, cseq, callid and via is present in the request.
     * via sip version - (8) - not working because parser fails already
       when another version then 2.0 is present.
     * via protocol - (16) - not working because parser fails already if
       an unsupported transport is present.
     * cseq method - (32) - checks if the method from the cseq header is
       equal to the request method.
     * cseq value - (64) - checks if the number in the cseq header is a
       valid unsigend integer.
     * content length - (128) - checks if the size of the body matches
       with the value from the content length header.
     * expires value - (256) - checks if the value of the expires header
       is a valid unsigned integer.
     * proxy require - (512) - checks if all items of the proxy require
       header are present in the list of the extensions from the module
       parameter proxy_require.
     * parse uri's - (1024) - checks if the specified URIs are present and
       parseable by the SIP-router parsers
     * digest credentials (2048) Check all instances of digest credentials
       in a message. The test checks whether there are all required digest
       parameters and have meaningful values.

1.2. Dependencies

   The following modules must be loaded before this module:
     * sl - Stateless replies.

1.3. Parameters

1.3.1. default_checks (integer)

   This parameter determines which of the checks from the sanity module
   are executed if no parameter was given to the sanity_check function
   call. By default all implemented checks are included in the execution
   of the sanity_check function. The integer value is the sum of the check
   numbers which should be executed by default.

   Default value is 999. This resolves to the following list of checks:
   ruri_sip_version (1), ruri_scheme (2), required_headers (4),
   cseq_method (32), cseq_value (64), cotent_length (128), expires_value
   (256), proxy_require (512).

   Example 1. Set default_checks parameter
...
modparam("sanity", "default_checks", 1)
...

1.3.2. uri_checks (integer)

   This parameter determines which URIs are going to be checked if the
   'parse uri' will be executed.

   Default value is 7. This resolves to the following list of parsed URIs:
   Request RUI (1), From URI (2) and To URI (4).

   Example 2. Set uri_checks parameter
...
modparam("sanity", "uri_checks", 3)
...

1.3.3. proxy_require (string)

   This parameter set the list of supported extensions for this
   SIP-router. The value is expected as comma separated list of the
   extensions. This list is separated into single tokens. Each token from
   a proxy require header will be compare to the tokens from this list.

   Example 3. Set proxy_require parameter
...
modparam("sanity", "proxy_require", "foo, bar")
...

1.3.4. autodrop (integer)

   This parameter controls whether the module drops automatically or not
   the SIP message if the sanity checks fail. Default value is 1 (auto
   drop). If set to 0, sanity_check() function will return -1 (false) to
   configuration file, allowing to write log messages for example - be
   sure you exit execution of config without sending a SIP reply because
   it is sent by module itself.

   Example 4. Set autodrop parameter
...
modparam("sanity", "autodrop", 1)
...

1.4. Functions

1.4.1. sanity_check([msg_checks [, uri_checks]])

   This function makes a row of sanity checks over the given SIP request.
   The behavior of the function is also controled by 'autodrop' parameter.
   If autodrop=0, the function returns false (-1) if one of the checks
   failed. When autodrop=1, the function stops the execution of
   configuration file. In both cases, ff one of the checks fails the
   module sends a precise error reply via SL send_reply(). Thus there is
   no need to reply with a generic error message.

   Example 5. sanity_check usage
...
if (!sanity_check()) {
        exit;
}
...

   Optionally the function takes an integer argument which overwrites the
   global module parameter default_checks. This allows to make certain
   test from script regions. The integer value is again the sum of the
   checks (like for the module parameter) which should be executed at this
   function call.

   Example 6. sanity_check usage with parameter
...
if (method=="REGISTER" && !sanity_check("256")) {
        /* the register contains an invalid expires value and is replied with a
400 */
        exit;
}
...

   Optionally the function takes a second integer argument which
   overwrites the global module parameter uri_checks and thus determines
   which URIs will be checked if the parse uri test will be executed.

   Example 7. sanity_check usage with two parameters
...
if (method=="INVITE" && !sanity_check("1024", "6")) {
        /* the INVITE contains an invalid From or To header and is replied with
a 400 */
        exit;
}
...
