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From Ruediger Pluem <rpl...@apache.org>
Subject Re: svn commit: r592446 - in /httpd/httpd/trunk: CHANGES modules/ssl/mod_ssl.c modules/ssl/ssl_engine_io.c modules/ssl/ssl_engine_kernel.c modules/ssl/ssl_private.h
Date Tue, 06 Nov 2007 22:06:22 GMT


On 11/06/2007 10:28 PM, Joe Orton wrote:
> On Tue, Nov 06, 2007 at 09:45:42PM +0100, Ruediger Pluem wrote:
>> On 11/06/2007 04:02 PM, jorton@apache.org wrote:
>>> Author: jorton
>>> Date: Tue Nov  6 07:02:32 2007
>>> New Revision: 592446
>>>
>>> URL: http://svn.apache.org/viewvc?rev=592446&view=rev
>>> Log:
> ...
>>> * modules/ssl/ssl_engine_io.c (ssl_io_filter_Upgrade): Remove
>>> function.
>>> (ssl_io_input_add_filter, ssl_io_filter_init): Take a request_rec
>>> pointer and pass to ap_add_*_filter to ensure the filter chain
>>> is modified correctly; remove it from the filter afterwards.
>> Can you explain this in more detail please? I currently don't understand
>> what is going wrong if you call ap_add_input_filter / ap_add_output_filter
>> with NULL instead of r in the case of an upgrade (where r != NULL). Is it
>> because INSERT_BEFORE delivers the wrong value because f->r == NULL for all
>> connection level filters?
> 
> Thanks for the review.  Sorry, I should really have put a comment about 
> that in there somewhere.
> 
> The issue is a long-standing "feature" of filters: if you add (or 
> remove) a connection-level filter during a request, without reference to 
> that request_rec, the r->{proto_}*_filters go stale: e.g. simplified:
> 
> r->output_filters = r->proto_output_filters = HTTP_IN -> CORE_OUT
> r->connection->output_filters = CORE_OUT
> 
> then insert the SSL filter before CORE_OUT leaves you with:
> 
> r->output_filters = r->proto_output_filters = HTTP_IN -> CORE_OUT
> r->connection->output_filters = SSL -> CORE_OUT
> 
> ...which is of course broken.  Some past discussion of the issue:

Ahh, now I get it. Thanks for explaining. This was somewhat hard to
understand without pointers.

 >> Currently I see the danger that the connection level filter ssl_io_filter
>> is allocated out of the request pool by add_any_filter_handle (because r != NULL)
>> instead of the connection pool. I think that even in the upgrade case the lifetime
of
>> ssl_io_filter is the same as the (remaining) lifetime of the connection and that
>> this lifetime might be longer than that of r->pool.
> 
> Great catch, I missed that this actually changes the lifetime of the 
> filter, and regret not testing this in my apr-pool-debug build!
> 
> I would like to say that is an add_any_filter_handle bug, if only 
> because it makes the mod_ssl issue tractable without major surgery on 
> the core filtering design :) 
> 
> If a filter is being added with connection-lifetime it must be allocated 
> out of the c->pool anyway, regardless of whether r is passed in, surely.  
> So, completely untested:
> 
> Index: server/util_filter.c
> ===================================================================
> --- server/util_filter.c	(revision 592444)
> +++ server/util_filter.c	(working copy)
> @@ -279,7 +279,7 @@
>                                            ap_filter_t **p_filters,
>                                            ap_filter_t **c_filters)
>  {
> -    apr_pool_t* p = r ? r->pool : c->pool;
> +    apr_pool_t *p = frec->ftype < AP_FTYPE_CONNECTION && r ? r->pool
: c->pool;
>      ap_filter_t *f = apr_palloc(p, sizeof(*f));
>      ap_filter_t **outf;

I agree that this should do the trick.

Regards

RĂ¼diger



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