Finding cache-control in foreign code

PHP
1

Hello,

I have a foreign php-app and try to find the location where the cache-control is defined.

The header output is

Expires: Thu, 19 Nov 1981 08:52:00 GMT
Cache-Control: no-store, no-cache, must-revalidate, post-check=0, pre-check=0

I scanned the complete site for things like
cache-control
HttpResponse::setCacheControl
session_cache_limiter
but could not find anything.

Where could it be hidden?
Do things like output buffing add headers?

Thanks for suggestions.
Flözen

2

It can be set from php with the function [fphp]header[/fphp] or it may be configured in the webserver or in a proxy/loadbalancer, if there is one.

3

When set with header, I would find

header("cache-control:

… somewhere…

The server does not add it. Othere files are delivered without the cache-control header.

So these both option can be excluded.

Further suggestions?

4

Which files has these headers? There are some modules for Apache that will add headers for certain filetypes.

5

All pages generated by the CMS have these headers, so these files are php files.
But not all PHP files do have such a header.
These headers in the CMS are also produced, when Apache is set to
ExpiresActive Off

6

In that case, I would suggest that you look at all calls to header. It might be a variable that you should be looking for. Eg. something like header($foo)

7

But $foo must be defined somewhere too. So I should at least find words like cache or cache-control…?!

8

I agree. But it could be read from many places. A config file or a database or some such thing. If you already grepped the code (case-insensitively), then I would find all calls to header and work back from there.

9

You said you scanned for session_cache_limiter, but did you check the value? It has a default, and I know I’ve seen that combination of values as a default before. All or part of it can be set via config file. You also might want to strategically sprinkle the code with calls to headers_list(). You might be able to divide and conquer your way to the origin.