Sanity Module

Nils Ohlmeier

iptelorg GmbH

Edited by

Nils Ohlmeier

Table of Contents

1. Admin Guide
1.1. Overview
1.2. Dependencies
1.2.1. Kamailio Modules
1.2.2. External Libraries or Applications
1.3. Exported Parameters
1.3.1. default_checks (integer)
1.3.2. uri_checks (integer)
1.3.3. proxy_require (string)
1.4. Exported Functions
1.4.1. sanity_check([checks, [uri_checks]])

List of Examples

1.1. Set default_checks parameter
1.2. Set proxy_require parameter
1.3. sanity_check usage
1.4. sanity_check usage with parameter
1.5. sanity_check usage with two parameters

Chapter 1. Admin Guide

1.1. Overview

This module aims to implement several sanity checks on incoming requests which are suggested or even required by a RFC.

This checks are not required by Kamailio 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 Kamailio 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 Kamailio.

  • 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 Kamailio 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

1.2.1. Kamailio Modules

The following modules must be loaded before this module:

  • sl - send reply.

1.2.2. External Libraries or Applications

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

  • None.

1.3. Exported 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), content_length (128), expires_value (256), proxy_require (512).

Example 1.1. 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 Kamailio. 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 1.2. Set proxy_require parameter

modparam("sanity", "proxy_require", "foo, bar")

1.4. Exported Functions

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

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 1.3. sanity_check usage

if (sanity_check()) {
	xlog("malformed message from $si:$sp\n");


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 1.4. sanity_check usage with parameter

if (method=="REGISTER" && sanity_check("256")) {
	/* the register contains an invalid expires value and is replied with a 400 */
	xlog("malformed message from $si:$sp\n");


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 1.5. 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 */
	xlog("malformed message from $si:$sp\n");