View headers of HTML requests to apache

Question

Is there a good way of viewing a detailed version of incoming requests to apache? At the minimum I'd like to check for the existence of a specific header and check its value. Requests are not coming from a browser, so it's tricky to view them going out. I'm not sure my custom HTTP header is actually being added by the client, so debugging my rewritecond directive is difficult.

Answer 1

You can create a custom LogFormat containing headers:

%{Foobar}i : The contents of Foobar: header line(s) in the request sent to the server. Changes made by other modules (e.g. mod_headers) affect this. If you're interested in what the request header was prior to when most modules would have modified it, use mod_setenvif to copy the header into an internal environment variable and log that value with the %{VARNAME}e described above.

Then reuse this LogFormat on your AccessLog directive

LogFormat "%v %h %l %u %t \"%r\" %>s %b %{MySpecialHeader}i " my_special_format
CustomLog logs/access_log_with_details my_special_format

Or even in one line only:

CustomLog logs/access_log_with_details "%v %h %l %u %t \"%r\" %>s %b %{MySpecialHeader}i"

UPDATE:

A note about the SetEnvIf:

This part is made to store the value of the Header on the start of any internal rewrite, and then then, instead of using the %{FOO}i syntax to extract the header at the end of the process you would use the %{MyEnvVar}e to log the value backuped at the beginning, this is the syntax to log an environment variable.

So ending with something like that:

SetEnvIf MySpecialHeader "(.*)" BACKUPHEADER=$1
(... stuff and things ...)
CustomLog logs/access_log_with_details "init: %{BACKUPHEADER}e final: %{MySpecialHeader}i "

Answer 2

You can also do it with mod_security:

http://static.askapache.com/httpd/mod_security/doc/modsecurity-manual.html#N107EE

LogFormat "%h %l %u %t \"%r\" %>s %{mod_security-body}n