[wp-hackers] When HTTP_HOST does not point to the blog

Kimmo Suominen kimmo at global-wire.fi
Tue Jun 24 19:42:58 GMT 2008

Isn't $_SERVER['HTTP_HOST'] basically data supplied by the browser?
Shouldn't WordPress use $_SERVER['SERVER_NAME'] instead, which is
data provided by the web server?

Since I run my site on a dedicated IP (for https) I sometimes get
requested without $_SERVER['HTTP_HOST'] set at all.  I always thought
that was because there simply was no "Host:" header in the request.

Best regards,
+ Kimmo
<A HREF="http://kimmo.suominen.com/">Kimmo Suominen</A>

On Tue, Jun 24, 2008 at 08:29:57PM +0200, Oliver Hohlfeld wrote:
> Hi,
> I'm using WordPress on an Apache Vhost which -- for some reason I didn't
> figure out so far - does not set the correct HTTP_HOST as specified in the
> ServerName setting. Thus, requests to $_SERVER['HTTP_HOST'] will not be
> directed to the requested blog.
> I noticed this issue when updating WordPress to version 2.3 which caused
> an infinite redirection loop due to canonical URLs. When examining the
> problem I noticed that some other users experienced the same problem and
> this is the main motivation for my post. I'm not sure whether this is an
> issue that should be really considered, as this is probably caused by a
> misconfiguration of my Apache HTTP server. But maybe it is worth a pointer.
> The initial problem with the redirect loop was caused by an HTTP_HOST
> environmental setting that does not correspond to the true host name of the
> blog. Further analysis showed that also some other parts are affected by
> this; the cron functionality can not be accessed and the self link in ATOM
> feeds points to a wrong host. I ignored some places where HTTP_HOST is used
> in the admin interface so far.
> To fix these issues, I mostly changed the host to the one specified in the
> configuration:
>   $site_url = get_option( ?siteurl? );
>   if (strlen($site_url) > 0) {
>     $parts = parse_url( $site_url );
>     $requested_url .= $parts['host'];
>   } else {
>     $requested_url .= $_SERVER['HTTP_HOST'];
>   }
> I briefly described these changes in my blog post, in hope of some other
> people experiencing the same problem might find that useful:
> http://blog.ohohlfeld.com/2008/06/infinite-301-redirect-loop-in-wordpress-due-to-canonical-urls-fixed/
> Regarding the cron, requests are directed to the correct host, as specified
> in the configuration ( $argyle = @ fsockopen( $parts['host'], .... ), but
> by supplying a wrong HTTP Host attribute. When using name based virtual
> hosts, several servers will listen on a single IPs. Requests are distinguished
> by the "Host: " attribute supplied in the HTTP header. As
> $_SERVER['HTTP_HOST'] != $parts['host'] in my case, requests will be directed
> to a wrong virtual host causing a 404 - file not found (wp-cron.php does not
> exist on this particular vhost).
> In general, I'm not sure whether it makes sense to establish a connection to
> $parts['host'] but then issue an request for HTTP_HOST.
> However, these changes fixed the host related issues for me, but I'm not
> sure whether this is useful in general...
> Would it be useful to add a getBlogHost() procedure whose code might look like
> the above mentioned block?
> --Oliver
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