Mailing List Archive: ModPerl: ModPerl

Internal redirect inside an input filter

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djdesm at wm

Oct 9, 2008, 5:30 AM

Post #1 of 5 (673 views)
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Internal redirect inside an input filter

I'm attempting to write an input filter that performs an internal redirect
based on the contents of the cookies sent in the request headers. The
problem I'm encountering is that the browser is receiving both the content
for the original request, as well as the content generated by the internal
redirect. Ideally, the browser would receive only the content generated
from the internal redirect. Here is a sample filter I wrote while trying to
solve this problem:

package Test::Redirect;

# a bunch of use statements

sub handler : FilterRequestHandler {

my $f = shift;
# this is just any old uri
$f->r->internal_redirect('/reverse');
return Apache2::Const::OK;
}

I've tried setting the filter's context to allow it to run only once, but if
I do that, it never completes the request. Any ideas?

Thanks,
Dan

torsten.foertsch at gmx

Oct 9, 2008, 5:50 AM

Post #2 of 5 (635 views)
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Re: Internal redirect inside an input filter [In reply to]

On Thu 09 Oct 2008, Dan DeSmet wrote:
> I'm attempting to write an input filter that performs an internal
> redirect based on the contents of the cookies sent in the request
> headers.

Why an input filter? What you want is better done in a PerlTransHandler
or a PerlFixupHandler.

Torsten

--
Need professional mod_perl support?
Just hire me: torsten.foertsch [at] gmx

djdesm at wm

Oct 9, 2008, 6:33 AM

Post #3 of 5 (633 views)
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Re: Internal redirect inside an input filter [In reply to]

I took your advice and tried switching it over to a TransHandler. Now, the
beginning of the handler where I manipulate the cookies looks like this:

sub handler {
my $r = shift;
my $cookieString = $r->headers_in->get('Cookie');
...
}

I then do a check to see if the cookies exist; that tells me whether it's a
client's first request, or a subsequent one. I then need to read a bunch of
information out of the cookies and then rewrite one of them. Unfortunately,
the above code always yields me an empty string. I can check my browser
cookies and see that they've been set correctly. Can the TransHandler
manipulate the request headers apart from the URI? Or am I just missing
something?

Thanks,
Dan

On Thu, Oct 9, 2008 at 8:50 AM, Torsten Foertsch
<torsten.foertsch [at] gmx>wrote:

> On Thu 09 Oct 2008, Dan DeSmet wrote:
> > I'm attempting to write an input filter that performs an internal
> > redirect based on the contents of the cookies sent in the request
> > headers.
>
> Why an input filter? What you want is better done in a PerlTransHandler
> or a PerlFixupHandler.
>
> Torsten
>
> --
> Need professional mod_perl support?
> Just hire me: torsten.foertsch [at] gmx
>

torsten.foertsch at gmx

Oct 9, 2008, 7:07 AM

Post #4 of 5 (635 views)
Permalink

Re: Internal redirect inside an input filter [In reply to]

On Thu 09 Oct 2008, Dan DeSmet wrote:
> I took your advice and tried switching it over to a TransHandler.
> Now, the beginning of the handler where I manipulate the cookies
> looks like this:
>
> sub handler {
> my $r = shift;
> my $cookieString = $r->headers_in->get('Cookie');
> ...
> }
>
> I then do a check to see if the cookies exist; that tells me whether
> it's a client's first request, or a subsequent one. I then need to
> read a bunch of information out of the cookies and then rewrite one
> of them. Unfortunately, the above code always yields me an empty
> string. I can check my browser cookies and see that they've been set
> correctly. Can the TransHandler manipulate the request headers apart
> from the URI? Or am I just missing something?

I have just checked it using the following TransHandler (directly
implemented in the httpd.conf):

PerlTransHandler "sub { \
my ($r)=@_; \
warn qq{Got Cookie: }.$r->headers_in->{Cookie}; \
return Apache2::Const::DECLINED; \
}"

Now, I call:

curl -v http://localhost
* About to connect() to localhost port 80 (#0)
* Trying 127.0.0.1... connected
* Connected to localhost (127.0.0.1) port 80 (#0)
> GET / HTTP/1.1
> User-Agent: curl/7.18.1 (x86_64-suse-linux-gnu) libcurl/7.18.1
OpenSSL/0.9.8g zlib/1.2.3 libidn/1.8
> Host: localhost
> Accept: */*
...

No cookie is transmitted and in the error_log appears the line:

Got Cookie: at (eval 91) line 1.

But if I call this:

curl -v -b 'klaus=otto' http://localhost
* About to connect() to localhost port 80 (#0)
* Trying 127.0.0.1... connected
* Connected to localhost (127.0.0.1) port 80 (#0)
> GET / HTTP/1.1
> User-Agent: curl/7.18.1 (x86_64-suse-linux-gnu) libcurl/7.18.1
OpenSSL/0.9.8g zlib/1.2.3 libidn/1.8
> Host: localhost
> Accept: */*
> Cookie: klaus=otto
...

You see the cookie-header? In the error_log I see:

Got Cookie: klaus=otto at (eval 91) line 1.

So, yes, you can manipulate request headers in the translation phase. In
fact, they are already accessible even in a PerlPostReadRequestHandler
which comes before the PerlTransHandler and is the very first occasion
when a Perl module can interfere. The main difference between
postreadrequest and translation is that the former is skipped for
subrequests and internal redirects. You can try my little handler as
PerlPostReadRequestHandler and will see the same result.

Torsten

--
Need professional mod_perl support?
Just hire me: torsten.foertsch [at] gmx

djdesm at wm

Oct 9, 2008, 7:54 AM

Post #5 of 5 (626 views)
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Re: Internal redirect inside an input filter [In reply to]

Thanks for your help. Your confirmation led me to track down the real
problem, which is that I marked the cookies secure, and forgot to do https
rather than http in my browser URL. If not for your help, there's no
telling how long I would've spent trying to fix a problem in my code that
didn't exist.

Thanks.

On Thu, Oct 9, 2008 at 10:07 AM, Torsten Foertsch
<torsten.foertsch [at] gmx>wrote:

> On Thu 09 Oct 2008, Dan DeSmet wrote:
> > I took your advice and tried switching it over to a TransHandler.
> > Now, the beginning of the handler where I manipulate the cookies
> > looks like this:
> >
> > sub handler {
> > my $r = shift;
> > my $cookieString = $r->headers_in->get('Cookie');
> > ...
> > }
> >
> > I then do a check to see if the cookies exist; that tells me whether
> > it's a client's first request, or a subsequent one. I then need to
> > read a bunch of information out of the cookies and then rewrite one
> > of them. Unfortunately, the above code always yields me an empty
> > string. I can check my browser cookies and see that they've been set
> > correctly. Can the TransHandler manipulate the request headers apart
> > from the URI? Or am I just missing something?
>
> I have just checked it using the following TransHandler (directly
> implemented in the httpd.conf):
>
> PerlTransHandler "sub { \
> my ($r)=@_; \
> warn qq{Got Cookie: }.$r->headers_in->{Cookie}; \
> return Apache2::Const::DECLINED; \
> }"
>
> Now, I call:
>
> curl -v http://localhost
> * About to connect() to localhost port 80 (#0)
> * Trying 127.0.0.1... connected
> * Connected to localhost (127.0.0.1) port 80 (#0)
> > GET / HTTP/1.1
> > User-Agent: curl/7.18.1 (x86_64-suse-linux-gnu) libcurl/7.18.1
> OpenSSL/0.9.8g zlib/1.2.3 libidn/1.8
> > Host: localhost
> > Accept: */*
> ...
>
> No cookie is transmitted and in the error_log appears the line:
>
> Got Cookie: at (eval 91) line 1.
>
> But if I call this:
>
> curl -v -b 'klaus=otto' http://localhost
> * About to connect() to localhost port 80 (#0)
> * Trying 127.0.0.1... connected
> * Connected to localhost (127.0.0.1) port 80 (#0)
> > GET / HTTP/1.1
> > User-Agent: curl/7.18.1 (x86_64-suse-linux-gnu) libcurl/7.18.1
> OpenSSL/0.9.8g zlib/1.2.3 libidn/1.8
> > Host: localhost
> > Accept: */*
> > Cookie: klaus=otto
> ...
>
> You see the cookie-header? In the error_log I see:
>
> Got Cookie: klaus=otto at (eval 91) line 1.
>
> So, yes, you can manipulate request headers in the translation phase. In
> fact, they are already accessible even in a PerlPostReadRequestHandler
> which comes before the PerlTransHandler and is the very first occasion
> when a Perl module can interfere. The main difference between
> postreadrequest and translation is that the former is skipped for
> subrequests and internal redirects. You can try my little handler as
> PerlPostReadRequestHandler and will see the same result.
>
> Torsten
>
> --
> Need professional mod_perl support?
> Just hire me: torsten.foertsch [at] gmx
>

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