[RFC PATCH 24/24] gitweb: Add beginnings of cache administration page (proof of concept)

[Jakub Narebski <jnareb@gmail.com>]

Currently cache administration page ('cache' action) shows estimated
size of cache, and provides link to clearing cache.

Cache administration page is visible only on local computer; the same
is true with respect to ability to clear cache.  Those are bare
beginnings of autorization framework.

If you can use cache administration page, you will see 'admin' link at
the botom of the page to it.

Signed-off-by: Jakub Narebski <jnareb@gmail.com>
---
This is "frontend" (interface) patch for gitweb cache management.

This is very much work in progress, sent to git mailing list as a
proof of concept.  Would something like that (perhaps with more
advanced authorization for admin) be useful?

The 'cache' page looks like this:

  Cache location      Size	 
  ------------------+---------+--------------
  cache/gitweb        14 KiB	[Clear cache]
  ------------------+---------+--------------

where '[Clear cache]' is a submit button.


Compared to previous series there is now 'admin' link that leads to
cache administration page, which is present only if you have
permissions to access said page.

Also for empty cache we show '-'.  

Code was made slightly safer, though still I wouldn't use it in
production, as there might be a chance that remote attacker could
possibly clear cache (meaning I didn't prove that it couldn't happen).


In the final version this patch should probably be split into a few
smaller commits, for example:
* adding support for $opts{'-title'} to git_header_html
* action_is_cacheable subroutine
* human_readable_size (which could also be used in 'tree' view at request)
* xxx_admin_auth_ok, i.e. authorization and authentication for admin and
  write actions in gitweb
* 'cache' (i.e. cache admin) and 'clear_cache' (worker) methods

 gitweb/gitweb.perl |  138 ++++++++++++++++++++++++++++++++++++++++++++++++++--
 1 files changed, 134 insertions(+), 4 deletions(-)

diff --git a/gitweb/gitweb.perl b/gitweb/gitweb.perl
index 1521bf2..66e240f 100755
--- a/gitweb/gitweb.perl
+++ b/gitweb/gitweb.perl
@@ -25,6 +25,8 @@ use Encode;
 use Fcntl qw(:mode :flock);
 use File::Find qw();
 use File::Basename qw(basename);
+use POSIX; # for POSIX::ceil($x)
+
 binmode STDOUT, ':utf8';
 
 our $t0;
@@ -888,6 +890,10 @@ sub evaluate_actions_info {
 	map { $actions_info{$_}{'output_format'} = undef }
 		qw(blob_plain object);
 	$actions_info{'snapshot'}{'output_format'} = 'binary';
+
+	# specify uncacheable actions
+	map { $actions_info{$_}{'uncacheable'} = 1 }
+		qw(cache clear_cache);
 }
 
 sub action_outputs_html {
@@ -895,6 +901,11 @@ sub action_outputs_html {
 	return $actions_info{$action}{'output_format'} eq 'html';
 }
 
+sub action_is_cacheable {
+	my $action = shift;
+	return !$actions_info{$action}{'uncacheable'};
+}
+
 sub browser_is_robot {
 	return 1 if !exists $ENV{'HTTP_USER_AGENT'}; # gitweb run as script
 	if (eval { require HTTP::BrowserDetect; }) {
@@ -1245,12 +1256,13 @@ sub dispatch {
 	if (!defined($actions{$action})) {
 		die_error(400, "Unknown action");
 	}
-	if ($action !~ m/^(?:opml|project_list|project_index)$/ &&
+	if ($action !~ m/^(?:opml|project_list|project_index|cache|clear_cache)$/ &&
 	    !$project) {
 		die_error(400, "Project needed");
 	}
 
-	if ($caching_enabled) {
+	if ($caching_enabled &&
+	    action_is_cacheable($action)) {
 		# human readable key identifying gitweb output
 		my $output_key = href(-replay => 1, -full => 1, -path_info => 0);
 
@@ -1397,6 +1409,10 @@ sub configure_caching {
 		require GitwebCache::Capture::Simple;
 		$capture = GitwebCache::Capture::Simple->new();
 	}
+
+	# some actions are available only if cache is turned on
+	$actions{'cache'} = \&git_cache_admin;
+	$actions{'clear_cache'} = \&git_cache_clear;
 }
 
 run();
@@ -3760,7 +3776,7 @@ sub git_header_html {
 	my $expires = shift;
 	my %opts = @_;
 
-	my $title = get_page_title();
+	my $title = $opts{'-title'} || get_page_title();
 	my $content_type;
 	# require explicit support from the UA if we are to send the page as
 	# 'application/xhtml+xml', otherwise send it as plain old 'text/html'.
@@ -3936,10 +3952,18 @@ sub git_footer_html {
 
 	} else {
 		print $cgi->a({-href => href(project=>undef, action=>"opml"),
-		              -class => $feed_class}, "OPML") . " ";
+		              -class => $feed_class}, "OPML") . "\n";
 		print $cgi->a({-href => href(project=>undef, action=>"project_index"),
 		              -class => $feed_class}, "TXT") . "\n";
+
 	}
+
+	if ($actions{'cache'} &&
+	    cache_admin_auth_ok()) {
+		print $cgi->a({-href => href(project=>undef, action=>"cache"),
+		              -class => $feed_class}, "<i>admin</i>") . "\n";
+	}
+
 	print "</div>\n"; # class="page_footer"
 
 	# timing info doesn't make much sense with output (response) caching,
@@ -7412,3 +7436,109 @@ XML
 </opml>
 XML
 }
+
+# see Number::Bytes::Human
+sub human_readable_size {
+	my $bytes = shift || return;
+
+	my @units = ('', 'KiB', 'MiB', 'GiB', 'TiB');
+	my $block = 1024;
+
+	my $x = $bytes;
+	my $unit;
+	foreach (@units) {
+		$unit = $_, last if POSIX::ceil($x) < $block;
+		$x /= $block;
+	}
+
+	my $num;
+	if ($x < 10.0) {
+		$num = sprintf("%.1f", POSIX::ceil($x*10)/10); 
+	} else {
+		$num = sprintf("%d", POSIX::ceil($x));
+	}
+
+	return "$num $unit";
+}
+
+sub cache_admin_auth_ok {
+	if (defined $ENV{'REMOTE_ADDR'}) {
+		if (defined $ENV{'SERVER_ADDR'}) {
+			# SERVER_ADDR is not in RFC 3875
+			return $ENV{'SERVER_ADDR'} eq $ENV{'REMOTE_ADDR'};
+		} elsif ($ENV{'REMOTE_ADDR'} =~ m!^(?:127\.0\.0\.1|::1/128)$!) {
+			# localhost in IPv4 or IPv6
+			return 1;
+		}
+	} else {
+		# REMOTE_ADDR not defined, probably calling gitweb as script
+		return 1;
+	}
+
+	# restrict all but specified cases
+	return 0;
+}
+
+sub git_cache_admin {
+	$caching_enabled
+		or die_error(403, "Caching disabled");
+	cache_admin_auth_ok()
+		or die_error(403, "Cache administration not allowed");
+	$cache && ref($cache)
+		or die_error(500, "Cache is not present");
+
+	git_header_html(undef, undef,
+		-title => to_utf8($site_name) . " - Gitweb cache");
+
+	print <<'EOF_HTML';
+<table class="cache_admin">
+<tr><th>Cache location</th><th>Size</th><th>&nbsp;</th></tr>
+EOF_HTML
+	print '<tr class="light">' .
+	      '<td class="path">' . esc_path($cache->path_to_namespace()) . '</td>' .
+	      '<td>';
+	my $size;
+	if ($cache->can('size')) {
+		$size = $cache->size();
+	} elsif ($cache->can('get_size')) {
+		$size = $cache->get_size();
+	}
+	if (defined $size) {
+		print human_readable_size($size);
+	} else {
+		print '-';
+	}
+	print '</td><td>';
+	if ($cache->can('clear')) {
+		print $cgi->start_form({-method => "POST",
+		                        -action => $my_uri,
+		                        -enctype => CGI::URL_ENCODED}) .
+		      $cgi->input({-name=>"a", -value=>"clear_cache", -type=>"hidden"}) .
+		      $cgi->submit({-label => 'Clear cache'}) .
+		      $cgi->end_form();
+	}
+	print <<'EOF_HTML';
+</td></tr>
+</table>
+EOF_HTML
+
+	git_footer_html();
+}
+
+sub git_cache_clear {
+	$caching_enabled
+		or die_error(403, "Caching disabled");
+	cache_admin_auth_ok()
+		or die_error(403, "Clearing cache not allowed");
+	$cache && ref($cache)
+		or die_error(500, "Cache is not present");
+
+	if ($cgi->request_method() eq 'POST') {
+
+		$cache->clear();
+	}
+
+	#print "cleared";
+	print $cgi->redirect(-uri => href(action=>'cache', -full=>1),
+	                     -status => '303 See Other');
+}
-- 
1.7.3