HTTP TRACE method¶

Disable HTTP TRACE in 8.0 and later¶

Default setting¶

The HTTP TRACE method is disabled by default in IBM HTTP Server 8.0 and later. No action is required in these releases.

Disable HTTP Trace in 7.0 and earlier¶

Disabling the HTTP TRACE method¶

The HTTP TRACE request method causes the data received by IBM HTTP Server from the client to be sent back to the client, as in the following example:

$ telnet 127.0.0.1 8080
Trying...
Connected to 127.0.0.1.
Escape character is '^]'.
TRACE / HTTP/1.0
Host: foo
A: b
C: d

HTTP/1.1 200 OK
Date: Mon, 04 Oct 2004 14:07:59 GMT
Server: IBM_HTTP_SERVER
Connection: close
Content-Type: message/http

TRACE / HTTP/1.0
A: b
C: d
Host: foo

Connection closed.

The TRACE capability could be used by vulnerable or malicious applications to trick a web browser into issuing a TRACE request against an arbitrary site and then send the response to the TRACE to a third party using web browser features.

Making the required configuration changes¶

In IBM HTTP Server 7.0 and later, the "TraceEnable" directive is provided to disable the TRACE HTTP method. See the Apache HTTP Server documentation here for more info. Unlike the mod_rewrite method described below, this directive only controls TRACE responses generated internally by Apache.

After WebServer Plugin APAR PM22860 (6.1.0.35, 7.0.0.15, 8.0.0.0), the core TraceEnable directive is also honored by requests handled by the WebServer plugin.

IHS can be configured to disable normal TRACE request processing so that the request fails with 403 (forbidden) and any private information sent in the TRACE request does not appear in the response. The way to disable normal TRACE request processing is to add several mod_rewrite directives to the web server configuration file, at main scope as well as in every <VirtualHost > container. If you use the IHS Administration Server, and it listens on a client accessible interface, the directives should be added there as well if the listening port can't be restricted to an internally facing interface.

Here is an example:

...
# disable TRACE in the main scope of httpd.conf
RewriteEngine On 
RewriteCond %{REQUEST_METHOD} ^TRACE 
RewriteRule .* - [F] 
...
<VirtualHost www.example.com>
...
# disable TRACE in the www.example.com virtual host
RewriteEngine On 
RewriteCond %{REQUEST_METHOD} ^TRACE 
RewriteRule .* - [F] 
</VirtualHost>

mod_rewrite must be active for these directives to be accepted. If mod_rewrite is not already active in your configuration:

IBM HTTP Server 1.3 customers: Even if mod_rewrite is already enabled, check the instructions for allowing it to take precedence over the WebSphere plug-in.

How to enable mod_rewrite

Verifying that TRACE is disabled¶

After TRACE has been disabled according to the instructions above, a TRACE request will be responded to with either a HTTP status code of 403 or 405.

IBM HTTP Server 7.0 and later: The server will respond with a "405: Method Not Allowed" HTTP status code
IBM HTTP Server 6.1 and earlier: The server will respond with a "403: Forbidden" HTTP status code

Using telnet to verify the configuration for a non-SSL web server port¶

The telnet command provided with most operating systems can be used to verify that the configuration changes to disable TRACE have been made. Note that telnet can only be used to test non-SSL ports, since it does not have the capability to perform the SSL handshake or to encrypt the data.

$ telnet 127.0.0.1 8080
Trying...
Connected to 127.0.0.1.
Escape character is '^]'.
TRACE / HTTP/1.0
A: b
C: d
Host: foo

HTTP/1.1 403 Forbidden
Date: Mon, 04 Oct 2004 14:23:31 GMT
Server: IBM_HTTP_SERVER
Connection: close
Content-Type: text/html; charset=iso-8859-1

<!DOCTYPE HTML PUBLIC "-//IETF//DTD HTML 2.0//EN">
<HTML><HEAD>
<TITLE>403 Forbidden</TITLE>
</HEAD><BODY>
<H1>Forbidden</H1>
You don't have permission to access /
on this server.<P>
</BODY></HTML>
Connection closed.

The information sent by the client is no longer echoed, and the request fails with HTTP status code 403 or 405..

If the response to the TRACE request continues to result in a response with status code 200, verify that the required directives were added to all <VirtualHost > containers and the main scope of the configuration file, and also verify that the web server has been restarted to activate the updated configuration.

Using the `openssl` command to verify the configuration for an SSL-enabled web server port¶

openssl is a command-line program which is part of the OpenSSL toolkit. It is not distributed with IBM HTTP Server. It is a typical component of a Linux system, and it is available for other platforms. A package for AIX can be obtained from the AIX Toolbox for Linux Applications site (follow the link labeled AIX Toolbox Cryptographic Content) and is already installed on many AIX systems. Refer to http://www.openssl.org for availability on other operating systems.

There may be other tools available for testing the TRACE configuration on an SSL port. openssl is used as an example here because it is freely available.

Unlike telnet, the openssl command can be used to perform the SSL handshake with the web server, at which point the TRACE command can be entered. Here is an example:

$ /usr/linux/bin/openssl s_client -connect 127.0.0.1:8444
CONNECTED(00000003)
depth=0
/C=US/2.5.4.17=27607/ST=NC/L=Raleigh/O=IBM/OU=m0xa/CN=TRAWICK-TP
verify error:num=18:self signed certificate
verify return:1
depth=0
/C=US/2.5.4.17=27607/ST=NC/L=Raleigh/O=IBM/OU=m0xa/CN=TRAWICK-TP
verify return:1
---
Certificate chain
 0 s:/C=US/2.5.4.17=27607/ST=NC/L=Raleigh/O=IBM/OU=m0xa/CN=TRAWICK-TP
   i:/C=US/2.5.4.17=27607/ST=NC/L=Raleigh/O=IBM/OU=m0xa/CN=TRAWICK-TP
---
Server certificate
-----BEGIN CERTIFICATE-----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-----END CERTIFICATE-----
subject=/C=US/2.5.4.17=27607/ST=NC/L=Raleigh/O=IBM/OU=m0xa/CN=TRAWICK-TP
issuer=/C=US/2.5.4.17=27607/ST=NC/L=Raleigh/O=IBM/OU=m0xa/CN=TRAWICK-TP
---
No client certificate CA names sent
---
SSL handshake has read 739 bytes and written 310 bytes
---
New, TLSv1/SSLv3, Cipher is RC4-SHA
Server public key is 1024 bit
SSL-Session:
    Protocol  : TLSv1
    Cipher    : RC4-SHA
    Session-ID:
    0000643E040608CBB4770730058AD640E7D7DBF9585858584270B25900000001
    Session-ID-ctx:
    Master-Key:
    AB897789790FFA0917335A49A6A272A162159B854EA2A9C21C1754607B412126AF09F521B0D4102387F80BC60B42FB5A
    Key-Arg   : None
    Start Time: 1114681945
    Timeout   : 300 (sec)
    Verify return code: 18 (self signed certificate)
---
TRACE / HTTP/1.0         <----------- data to be entered starts here
A: b
C: d
Host: foo

HTTP/1.1 403 Forbidden   <----------- web server response starts here, 6.1 and earlier shown only
Date: Thu, 28 Apr 2005 09:52:29 GMT
Server: IBM_HTTP_Server/2.0.47.1-PK01070 Apache/2.0.47 (Unix)
Content-Length: 306
Connection: close
Content-Type: text/html; charset=iso-8859-1

<!DOCTYPE HTML PUBLIC "-//IETF//DTD HTML 2.0//EN">
<html><head>
<title>403 Forbidden</title>
</head><body>
<h1>Forbidden</h1>
<p>You don't have permission to access /
on this server.</p>
<hr />
<address>IBM_HTTP_Server/2.0.47.1-PK01070 Apache/2.0.47 (Unix) Server
at foo Port 8444</address>
</body></html>
read:errno=0
$

TRACE and OPTIONS¶

The OPTIONS method can be used by a client to determine which methods are allowed. Even when TRACE is disabled using the mod_rewrite method above, the OPTIONS response will report that TRACE is enabled. However, TRACE will be rejected with a 403 error before it is processed, and the potentially harmful behavior of TRACE — echoing input data to the response — won't be allowed.

For more information...¶

More background information on the concerns with TRACE is provided at http://www.apacheweek.com/issues/03-01-24#news.

The HTTP TRACK method¶

The TRACK method is a type of request supported by Microsoft web servers. It is not RFC compliant and is not supported directly by IBM HTTP Server. The method may be utilized as part of a cross-site scripting attack. See Vulnerability Note VU#288308 for more information.

Even though IBM HTTP Server does not support the TRACK method natively, it is possible for plug-in modules to provide support for it. To disable this capability for plug-in modules, in addition to disabling the TRACE method, add these two additional directives after the existing RewriteCond and RewriteRule directives which are used to disable TRACE:

RewriteCond %{REQUEST_METHOD} ^TRACK
RewriteRule .* - [F]

Here is a full example showing the directives to disable both TRACE and TRACK:

...
# disable TRACE and TRACK in the main scope of httpd.conf
RewriteEngine On 
RewriteCond %{REQUEST_METHOD} ^TRACE 
RewriteRule .* - [F] 
RewriteCond %{REQUEST_METHOD} ^TRACK
RewriteRule .* - [F] 
...
<VirtualHost www.example.com>
...
# disable TRACE and TRACK in the www.example.com virtual host
RewriteEngine On 
RewriteCond %{REQUEST_METHOD} ^TRACE 
RewriteRule .* - [F] 
RewriteCond %{REQUEST_METHOD} ^TRACK
RewriteRule .* - [F] 
</VirtualHost>

Note that for IBM HTTP Server 7.0 and later, the only method to disable TRACK is via mod_rewrite. Since IHS doesn't do anything with TRACK, there is no directive to "disable" it.