From 532f7adfdba3c852487216b0241b25d3de57acc6 Mon Sep 17 00:00:00 2001
From: Simon McVittie <smcv@debian.org>
Date: Sun, 5 Oct 2014 15:56:19 +0100
Subject: [PATCH] Use protocol-relative URIs if cgiurl and url differ only by
 authority (hostname)

---
 IkiWiki.pm                                        | 11 +++++++++--
 ...ocol_relative_urls_for_stylesheet_linking.mdwn |  8 ++++++++
 t/relativity.t                                    |  3 ---
 t/urlto.t                                         | 15 ++++++++++++---
 4 files changed, 29 insertions(+), 8 deletions(-)

diff --git a/IkiWiki.pm b/IkiWiki.pm
index d5d11ee85..c1518a2ae 100644
--- a/IkiWiki.pm
+++ b/IkiWiki.pm
@@ -613,12 +613,19 @@ sub checkconfig () {
 
 			$local_cgiurl = $cgiurl->path;
 
-			if ($cgiurl->scheme ne $baseurl->scheme or
-				$cgiurl->authority ne $baseurl->authority) {
+			if ($cgiurl->scheme ne $baseurl->scheme) {
 				# too far apart, fall back to absolute URLs
 				$local_url = "$config{url}/";
 				$local_cgiurl = $config{cgiurl};
 			}
+			elsif ($cgiurl->authority ne $baseurl->authority) {
+				# slightly too far apart, fall back to
+				# protocol-relative URLs
+				$local_url = "$config{url}/";
+				$local_url =~ s{^https?://}{//};
+				$local_cgiurl = $config{cgiurl};
+				$local_cgiurl =~ s{^https?://}{//};
+			}
 		}
 
 		$local_url =~ s{//$}{/};
diff --git a/doc/todo/Protocol_relative_urls_for_stylesheet_linking.mdwn b/doc/todo/Protocol_relative_urls_for_stylesheet_linking.mdwn
index ccbaf4e73..0ab4814e6 100644
--- a/doc/todo/Protocol_relative_urls_for_stylesheet_linking.mdwn
+++ b/doc/todo/Protocol_relative_urls_for_stylesheet_linking.mdwn
@@ -26,6 +26,14 @@ but this breaks all sorts of things, like the 404 plugin and wiki rebuilds will
 > protocol-relative URLs in this situation, but it isn't clear to me how
 > widely-supported those are.
 >
+>> HTML5 says protocol-relative URLs work, and they seem to be widely
+>> supported in practice, so I've changed the rule to: if the url and cgiurl
+>> share a scheme (protocol) but differ only by hostname, use `//foo/bar`
+>> protocol-relative URLs. This partially addresses this todo.
+>> I'm still thinking about what the right thing is for more complicated
+>> situations: see [[todo/design for cross-linking between content and CGI]].
+>> --[[smcv]]
+>
 > If you set both the `$config{url}` and `$config{cgiurl}` to https, but make
 > the resulting HTML available over HTTP as well as HTTPS, that should work
 > fine - accesses will be over http until the user either explicitly
diff --git a/t/relativity.t b/t/relativity.t
index eb6cc448a..6c4d1107e 100755
--- a/t/relativity.t
+++ b/t/relativity.t
@@ -227,13 +227,10 @@ run(["./t/tmp/ikiwiki.cgi"], \undef, \$content, init => sub {
 	$ENV{HTTPS} = 'on';
 });
 %bits = parse_cgi_content($content);
-TODO: {
-local $TODO = "avoid mixed content";
 like($bits{basehref}, qr{^https://static.example.com/$});
 like($bits{stylehref}, qr{^(?:(?:https:)?//static.example.com)?/style.css$});
 like($bits{tophref}, qr{^(?:https:)?//static.example.com/$});
 like($bits{cgihref}, qr{^(?:(?:https:)?//cgi.example.com)?/ikiwiki.cgi$});
-}
 
 # when accessed via a different hostname, links to the CGI (only) should
 # stay on that host?
diff --git a/t/urlto.t b/t/urlto.t
index 338632e94..025409b7f 100755
--- a/t/urlto.t
+++ b/t/urlto.t
@@ -1,7 +1,7 @@
 #!/usr/bin/perl
 use warnings;
 use strict;
-use Test::More tests => 26;
+use Test::More tests => 31;
 
 BEGIN { use_ok("IkiWiki"); }
 
@@ -41,11 +41,20 @@ is(IkiWiki::urlto('', 'penguin/herring'), "../../");
 is(IkiWiki::cgiurl(cgiurl => 'https://foo/ikiwiki'), "https://foo/ikiwiki");
 is(IkiWiki::cgiurl(do => 'badger', cgiurl => 'https://foo/ikiwiki'), "https://foo/ikiwiki?do=badger");
 
-# with url and cgiurl on different sites, "local" degrades to absolute
+# with url and cgiurl on different sites, "local" degrades to protocol-relative
 $IkiWiki::config{url} = "http://example.co.uk/~smcv";
 $IkiWiki::config{cgiurl} = "http://dynamic.example.co.uk/~smcv/ikiwiki.cgi";
 is(IkiWiki::checkconfig(), 1);
-is(IkiWiki::cgiurl(), "http://dynamic.example.co.uk/~smcv/ikiwiki.cgi");
+is(IkiWiki::cgiurl(), "//dynamic.example.co.uk/~smcv/ikiwiki.cgi");
+is(IkiWiki::baseurl(undef), "//example.co.uk/~smcv/");
+is(IkiWiki::urlto('stoats', undef), "//example.co.uk/~smcv/stoats/");
+is(IkiWiki::urlto('', undef), "//example.co.uk/~smcv/");
+
+# with url and cgiurl on different schemes, "local" degrades to absolute
+$IkiWiki::config{url} = "http://example.co.uk/~smcv";
+$IkiWiki::config{cgiurl} = "https://dynamic.example.co.uk/~smcv/ikiwiki.cgi";
+is(IkiWiki::checkconfig(), 1);
+is(IkiWiki::cgiurl(), "https://dynamic.example.co.uk/~smcv/ikiwiki.cgi");
 is(IkiWiki::baseurl(undef), "http://example.co.uk/~smcv/");
 is(IkiWiki::urlto('stoats', undef), "http://example.co.uk/~smcv/stoats/");
 is(IkiWiki::urlto('', undef), "http://example.co.uk/~smcv/");