[Koha-devel] Serving Intranet from a subpath

[Thomas Klausner]

Hi!

(I'm sending this to koha-devel because I guess it's too technical for 
the general list?)

We are running running the "Intranet" inside an actual intranet (i.e. 
inside a VPN). But this Koha instance is also hosting a related Library 
whose staff cannot access the VPN. For various reasons it is not 
possible to mount Koha at it's own domain, so we must make it available 
at a sub-path (something like "https://www.example.com/foo/koha")

For the OPAC, I already implemented a hacky Plack Middleware that does 
some rather ugly rewriting or URLs and HTML (ughh..). While we could do 
the same for Intranet, I first wanted to check if it is maybe already 
possible to mount it under a subpath, i.e. have an Apache use something 
like 

ProxyPass /foo/koha/index.html   ...
ProxyPass /foo/koha/cgi-bin/koha ...

Now, while this actually works, the pages returned do not, as all the 
links they contain point to /cgi-bin/koha (i.e., they loose the mount 
point and generate bad links).

The usual way to solve this is via something like
https://metacpan.org/pod/Plack::Middleware::ReverseProxyPath

But for this work, two things (one small, one not) have to be changed:

* the plack app (i.e. Koha) needs to honor some HTTP Header ENV vars
  (X_FORWARDED_SCRIPT_NAME, X_TRAVERSAL_PATH)
* and all links generated by the app need to also honor those vars.

The usual way for the latter is to *not* generate links by concatenating 
path fragments or hardcoded them in templates (which seems to be what 
Koha is doing), but to use a function/method to generate all links (to 
html pages, static assets and endpoints)

So for example in a template like prog/en/modules/cataloguing/addbooks.tt
we find:
            <a href="/cgi-bin/koha/mainpage.pl">Home</a>

This would need to be changed to 

            <a href=uri_for("/cgi-bin/koha/mainpage.pl")>Home</a>

and uri_for needs to take a look at the ENV and fix the link 
accordingly.

(The ugly workaround I am using in an OPAC is to use a Middleware to 
change the HTML after it's generated by Koha but before it is send to 
the client. shudder...)

So on the one hand this seems to be a small change, but to work it needs 
to touch ALL templates. (and it will be hard to automatically identify 
all link-ish text in the templates (href, src, maybe sometimes the url 
is generated in a template, ...)

Another approach would be to set the mount-point into <base 
href="/foo/koha">
https://developer.mozilla.org/en-US/docs/Web/HTML/Element/base
But we would still need to change all the links to relative links, as 
`base` will ignore absolute links, which is what Koha is using now.
though maybe the regex to replace the code is a bit easier 
(s{/cgi-bin}{cgi-bin}) as it does have to fiddle with quotes etc.


Our customer is willing to do the work to implement this (probably also 
in OPAC), but only if the change will be accepted upstream and be usable 
by the end of this year (i.e. 22.11).

Shall we try to tackle this? Or will this massive change never be 
accepted? If there is interest, I guess the next step is to open a 
bug...


Greetings,
domm



-- 
#!/usr/bin/perl                             https://domm.plix.at
for(ref bless{},just'another'perl'hacker){s-:+-$"-g&&print$_.$/}