Here is a patch [[!tag patch]] to add a *forward*ing functionality
to the [[`meta`_plugin|plugins/meta]].

> [[done]], with some changes --[[Joey]]

Find the most recent version at
<http://www.schwinge.homeip.net/~thomas/tmp/meta_forward.patch>.

I can't use `scrub(...)`, as that will strip out the forwarding HTML command.
How to deal with that?

I can also submit a Git patch, if desired.


# Syntax

**URL** = http://some.nice/place/ (*etc.*)

**WHITHER** = \[\[**[[ikiwiki/wikilink]]**]] | **URL**

**D** = natural number (*meaning seconds*)

**OPT_DELAY** = delay=**D** | empty (*immediatelly*)

\[[!meta forward="**WHITHER**" **OPT_DELAY**]]


# Extensions and Ideas

It might be doable to add references to pages that refer to the page containg
the forwarding statement also to the referred-to page.

--[[tschwinge]]


# Discussion

> The html scrubber cannot scrub meta headers. So if you emit one
> containing user-supplied data, it's up to you to scrub it to avoid all
> possible XSS attacks. Two attacks I'd worry about are cyclic meta refresh
> loops, which some, but not all web browsers detect and break, and any way
> to insert javascript via the user-supplied parameters. (Ie, putting
> something in the delay value that closes the tag can probably insert
> javascript ATM; and are there ways to embed javascript in the url?)
> --[[Joey]]

>> OK.  I can add code to make sure that `$delay` **D** indeed is a natural number
>> and that the passed target address **WHITHER** is nothing but a valid target address.
>> (How to qualify a valid target address?)
>> What is a *cyclic meta refresh loop*?  Two pages in turn forwarding to each other?
>> I think it would be possible to implement such a guard when only in-wiki links
>> ([[ikiwiki/wikilink]]s) are being used, but how to do so for external links?  --[[tschwinge]]

>>> This seems a lot more securely to do for in-wiki links, since we know
>>> that a link generated by a wikilink is safe, and can avoid cycles.
>>> Obviously there's no way to avoid cycles when using external links.
>>> 
>>> An example of code that doesn't detect such cycles is LWP::UserAgent,
>>> which will happily follow cycles forever. There's a LWPx::ParanoidAgent
>>> that can deal with cycles. I suppose this could be considered a client
>>> side issue, except that if I were going to turn this redirect feature
>>> on in my wikis, I'd really prefer to not have to worry about my wiki
>>> causing such problems for clients. I feel it makes sense to make
>>> external redirects or other potentially unsafe things an option,
>>> and have the default behavior be only things that are known to be
>>> secure.
>>>
>>> I haven't checked if there's a way to embed javascript in meta refresh
>>> links or not. Given all the other places I've seen it be embedded, I'll
>>> assume it is possible until it's shown not to be though.. --[[Joey]]
