Perl: Passing a URL in a query string - perl

Question

I'm trying to pass a URL as a query string so it can be read by another website and then used:
www.example.com/domain?return_url=/another/domain
Gets returned as:
www.example.com/domain?return_url=%2Fanother%2Fdomain
Is there a way this URL can be read and parsed by the other application with the escaped characters?
The only way I can think of is to encode it somehow so it comes out like this:
www.example.com/domain?return_url=L2Fub3RoZXIvZG9tYWlu
then the other application can decode and use?
https://www.base64encode.org/

Answer 1

www.example.com/domain?return_url=%2Fanother%2Fdomain
This is called URL encoding. Not because you put a URL in it, but because it encodes characters that have a special meaning in a URL.
The %2F corresponds to a slash /. You've probably also seen the %20 before, which is a space .
Putting a complete URI into a URL parameter of another URI is totally fine.
http://example.org?url=http%3A%2F%2Fexample.org%2Ffoo%3Fbar%3Dbaz
The application behind the URL you are calling needs to be able to understand URL encoding, but that is a trivial thing. Typical web frameworks and interfaces to the web (like CGI.pm or Plack in Perl) will do that. You should not have to care about it a all.
To URL-encode something in Perl, you have several options.
You could use the URI module to create the whole URI including the URL encoded query.
use URI;
my $u = URI->new("http://example.org");
$u->query_form( return_url => "http://example.org/foo/bar?baz=qrr");
print $u;
__END__
http://example.org?return_url=http%3A%2F%2Fexample.org%2Ffoo%2Fbar%3Fbaz%3Dqrr
This seems like the natural thing to do.
You could also use the URI::Encode module, which gives you a uri_encode function. That's useful if you want to encode strings without building a URI object.
use URI::Encode qw(uri_encode uri_decode);
my $encoded = uri_encode($data);
my $decoded = uri_decode($encoded);
All of this is a normal part of how the web works. There is no need to do Base 64 encoding.

Answer 2

The correct way would be to uri-encode the second hop as you do in your first example. The URI and URI::QueryParam modules make this nice and easy:
To encode a URI, you simply create a URI object on your base url. Then add any query parameters that you want. (NOTE: they will be automatically uri-encoded by URI::QueryParam):
use strict;
use warnings;
use feature qw(say);
use URI;
use URI::QueryParam;
my $u = URI->new('http://www.example.com/domain');
$u->query_param_append('return_url', 'http://yahoo.com');
say $u->as_string;
# http://www.example.com/domain?return_url=http%3A%2F%2Fyahoo.com
To receive this url and then redirect to return_url, you simply create a new URI object then pull off the return_url query parameter with URI::QueryParam. (NOTE: again URI::QueryParam automatically uri-decodes the parameter for you):
my $u = URI->new(
'http://www.example.com/domain?return_url=http%3A%2F%2Fyahoo.com'
);
my $return_url = $u->query_param('return_url');
say $return_url;
# http://yahoo.com