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From nik600 <nik...@gmail.com>
Subject strange behaviour using mod_proxy when the r->filename partially overlaps the requested uri
Date Tue, 21 Aug 2012 11:39:27 GMT
Dear all

i've got a strange behaviour in my custom module:

it seems that if the set filename overlaps the requested uri ths final
uri passed to mod_proxy is wrong, or has some added strange
characters.

some information:

* the module is activated only when the requested uri contains the
string "/files/anteprima"
* the module just redirect the request to mod_proxy changing the
request from "/files/anteprima" to "nocachedfiles/anteprima/"
* i know all is hardcoded here but is just to reproduce the problem

My module is configured in a vhost and related to a specific Location:

<Location /data>
    SetHandler kcache
</Location>

if i make a request to this module, for example:

http://kcache.foo.com:19007/data/_www.foo.com/files/anteprima/whatyouwant

Looking at the code it should be redirected to:

proxy:http://www.foooo.com/nocachedfiles/anteprima/12345

but looking at apache logs i see:

[Tue Aug 21 13:27:01 2012] [debug] mod_proxy_http.c(56): proxy: HTTP:
canonicalising URL //www.foooo.com/nocachedfiles/anteprima/12345
dJ\x98\x01\x7f
[Tue Aug 21 13:27:01 2012] [debug] proxy_util.c(1515): [client
127.0.0.1] proxy: *: found forward proxy worker for
http://www.foooo.com/nocachedfiles/anteprima/12345 dJ\x98\x01\x7f
[Tue Aug 21 13:27:01 2012] [debug] mod_proxy_http.c(1973): proxy:
HTTP: serving URL http://www.foooo.com/nocachedfiles/anteprima/12345
dJ\x98\x01\x7f
[Tue Aug 21 13:27:01 2012] [debug] proxy_util.c(2067): proxy:
connecting http://www.foooo.com/nocachedfiles/anteprima/12345
dJ\x98\x01\x7f to www.foooo.com:80

You can see some "garbage" at the end of the string.

I've tried to investigate a lot on in, but i'm not able to figure it
out... notice that if you change the length of the newurl string, or
if you change it from:

"proxy:http://www.foooo.com/nocachedfiles/anteprima/12345";	
to
"proxy:http://www.foooo.com/nocachedfiles2/anteprima/12345";	

The module tries correctly to load
http://www.foooo.com/nocachedfiles2/anteprima/12345 withoud any
garbage at the end.

It seems to be a combination of overlaps of the requested uri, the
destination file and their length... here there is the exact code to
reproduce it:

One last thing :
is not yet clear to me if is correct to put this kind of redirection
in  ap_hook_translate_name or if i have to use another type of hook,
by the way if you use a ap_hook_handler in the same conditions you get
an http contatenated at the end of your filename:

[Tue Aug 21 13:37:02 2012] [debug] proxy_util.c(1515): [client
127.0.0.1] proxy: *: found forward proxy worker for
http://www.foooo.com/nocachedfiles/anteprima/12345http

Any idea?

Thanks to all in advance

/************************************************/
#include <httpd.h>
#include <http_protocol.h>
#include <http_config.h>

static void   register_hooks(apr_pool_t *pool);

module AP_MODULE_DECLARE_DATA kcache_module = {
    STANDARD20_MODULE_STUFF,
    NULL,
    NULL,
    NULL,
    NULL,
    NULL,
    register_hooks
};

static int kcache_handler_translate(request_rec* r)
{
    if (r->method_number != M_GET && r->method_number != M_POST){
        return HTTP_METHOD_NOT_ALLOWED;
    }

	if(
		strstr(r->unparsed_uri, "/files/anteprima")==NULL){
		return DECLINED;
	}  	
  	
  	char *newurl = "proxy:http://www.foooo.com/nocachedfiles/anteprima/12345";	

  	r->filename = apr_pcalloc(r->pool,strlen(newurl));
	strcpy(r->filename,newurl);
    r->proxyreq = PROXYREQ_PROXY;
    r->handler  = "proxy-server";

    return DECLINED;

}

static void register_hooks(apr_pool_t* pool)
{


	static const char *succ[] =
{"mod_proxy.c","mod_alias.c","mod_userdir.c", NULL};
    ap_hook_translate_name(kcache_handler_translate, NULL, succ,
APR_HOOK_MIDDLE);
}

/***********************************************/


-- 
/*************/
nik600
http://www.kumbe.it

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