1. Sanity Module

Nils Ohlmeier

   iptelorg GmbH

   Copyright © 2006 iptelorg GmbH
   Revision History
   Revision $Revision: 1.1.2.1 $ $Date: 2008/06/11 13:14:47 $
     __________________________________________________________________

   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)

   1.4. Functions

        1.4.1. sanity_check()

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 SER.

   This checks are not required by SER 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 SER
   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 SER.
     * 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 SER 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

   Revision History
   Revision $Revision: 1.1.2.1 $ $Date: 2008/06/11 13:14:47 $

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).

1.3.3. proxy_require (string)

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

   Example 2. Set proxy_require parameter
...
modparam("sanity", "proxy_require", "foo, bar")
...

1.4. Functions

   Revision History
   Revision $Revision: 1.1.2.1 $ $Date: 2008/06/11 13:14:47 $

1.4.1.  sanity_check()

   This function makes a row of sanity checks on the given request. The
   function returns true if one of the checks failed. If one of the checks
   fails the module sends a precise error reply via sl_send_reply. Thus
   their is no need to reply with a generic error message.

   Example 3. sanity_check usage
...
if (sanity_check()) {
        break;
}
...

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

   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 5. 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 */
        break;
}
...
