Upstream kup provided this patch, that was apparently written by the Gitolite
author.

--- standard/kup-server	2017-03-28 13:01:24.000000000 -0400
+++ gitolite/kup-server	2018-03-26 15:01:20.000000000 -0400
@@ -1,4 +1,4 @@
-#!/usr/bin/perl -T
+#!/usr/bin/perl
 ## -----------------------------------------------------------------------
 ##
 ##   Copyright 2011 Intel Corporation; author: H. Peter Anvin
@@ -68,12 +68,20 @@
 
 use Digest::SHA;
 
-my $VERSION = '0.3.6';
-
-# Scrub the environment completely
-%ENV = ('PATH' => '/bin:/usr/bin',
-		'LANG' => 'C',
-		'SHELL' => '/bin/false'); # Nothing in this program should shell out
+use lib $ENV{GL_LIBDIR};
+use Gitolite::Easy;
+use Gitolite::Conf::Load;
+
+my $VERSION = '0.3.6 (gitolite integrated)';
+
+# Scrub the environment completely, except gitolite variables and HOME
+{
+	my %env = %ENV;
+	%ENV = ('PATH' => '/bin:/usr/bin',
+			'LANG' => 'C',
+			'SHELL' => '/bin/false'); # Nothing in this program should shell out
+	$ENV{$_} = $env{$_} for ('HOME', grep(/^GL_/, keys %env));
+}
 
 # The standard function to call on bail
 sub fatal($) {
@@ -88,16 +96,7 @@
 }
 
 sub my_username() {
-	my $whoami = getuid();
-	my ($name,$passwd,$uid,$gid,$quota,$comment,$gcos,$dir,$shell,$expire) = getpwuid($whoami);
-
-	if (!defined($name) || $whoami != $uid) {
-		# We haven't called openlog() yet so we need to do it here
-		openlog("kup-server($whoami)", 'ndelay,pid', LOG_LOCAL5);
-		fatal("You don't exist, go away!");
-	}
-
-	return (defined($name) && $whoami == $uid) ? $name : $whoami;
+	return $ENV{GL_USER};
 }
 
 my $user_name = my_username();
@@ -106,7 +105,7 @@
 
 
 # Get config values from kup-server.cfg
-my $cfg_file = '/etc/kup/kup-server.cfg';
+my $cfg_file = '/var/lib/gitolite3/.gitolite/local-code/configs/kup-server.cfg';
 
 my $cfg = new Config::Simple($cfg_file);
 
@@ -371,6 +370,51 @@
 	return 1;
 }
 
+# kup-server may "read" files from the kup data_path, or repos.  If a repo is
+# supplied, we assume it's a gitolite repo and check access accordingly (while
+# remembering that kup seems to add a leading slash).  If a repo is *not*
+# supplied, we assume we're talking about the kup data_path, which means we
+# make gitolite access rules from the "fake" repo called "@kup-server"
+sub read_allowed
+{
+	Gitolite::Common::trace( 1, 'read_allowed', @_ );
+	my $repo = shift || '@kup-server';
+
+	# gitolite expects a "normalised" repo name; no leading slash, no trailing ".git"
+	$repo =~ s(^/)(); $repo =~ s/\.git$//;
+
+	return can_read($repo);
+}
+
+# kup-server does not write to normal repos, it only writes to files in the
+# kup data_path.  So we don't have to worry about any repo other than
+# "@kup-server", which is therefore hardcoded in here.
+sub write_allowed
+{
+	Gitolite::Common::trace( 1, 'write_allowed', @_ );
+	my($path, $perm) = @_;
+
+	# other values for perm are + (rm) and C (mkdir), analogous to gitolite's
+	# "+ means delete or rewind branch, C means create branch"
+	$perm ||= 'W';
+
+	my $repo = '@kup-server';
+
+	# the paths that gitolite expects start with "refs/heads/", since we are
+	# simply re-using the existing ACL for this.  (But remember $path, in
+	# kup-land, already starts with a "/".)
+	$path = "refs/heads" . $path;
+
+	return can_write($repo, $perm, $path) ||
+		   can_write($repo, $perm, "$path/");
+	# the second check is because, when specifying a permission on a directory
+	# in gitolite, you end with a "/", say "RW+C foo/ = user".  To exercise
+	# that right, the user runs "kup mkdir foo" or "kup rm foo".  This fails,
+	# because the regex "foo/" won't match.  (In a *git* repo it doesn't
+	# matter, because git doesn't allow empty directories, so it never
+	# happens).
+}
+
 # Return a percentage, valid even if the denominator is zero
 sub percentage($$)
 {
@@ -526,6 +570,10 @@
 		fatal("Invalid pathname in TAR command");
 	}
 
+	if (!read_allowed($tree)) {
+		fatal("Read access denied");
+	}
+
 	if (!is_clean_string($prefix)) {
 		fatal("Invalid prefix string");
 	}
@@ -569,6 +617,10 @@
 		fatal("Invalid pathname in DIFF command");
 	}
 
+	if (!read_allowed($tree)) {
+		fatal("Read access denied");
+	}
+
 	if ($tree !~ /\.git$/ || ! -d $git_path.$tree ||
 		! -d $git_path.$tree.'/objects') {
 		fatal("No such git tree");
@@ -788,8 +840,13 @@
 		or fatal("dup error");
 	close($devnull);
 
+	my $gpgvbin = '/opt/gnupg22/bin/gpgv';
+	if ( ! -x $gpgvbin) {
+		$gpgvbin = '/usr/bin/gpgv';
+	}
+
 	my $status =
-		system('/usr/bin/gpgv',
+		system($gpgvbin,
 			   '--quiet',
 			   '--homedir', $tmpdir,
 			   '--keyring', $pgp_path."/${user_name}.gpg",
@@ -839,6 +896,10 @@
 		fatal("Invalid filename in PUT command");
 	}
 
+	if (!write_allowed($file)) {
+		fatal("Write access denied");
+	}
+
 	my @install_ext;
 	my @conflic_ext;
 	my $stem;
@@ -917,6 +978,10 @@
 		fatal("Invalid filename in MKDIR command");
 	}
 
+	if (!write_allowed($file, 'C')) {
+		fatal("MKDIR access denied");
+	}
+
 	my @badext = ('.sign', keys(%zformats));
 
 	foreach my $e (@badext) {
@@ -991,6 +1056,16 @@
 		fatal("Invalid filename in $cmd command");
 	}
 
+	if ($cmd eq 'MOVE') {
+		if (!write_allowed($from, '+')) {
+			fatal("Delete (as part of MOVE) access denied");
+		}
+	}
+
+	if (!write_allowed($to)) {
+		fatal("Write access denied");
+	}
+
 	if ($from =~ /\.gz$/) {
 		if ($to !~ /\.gz$/) {
 			fatal("$cmd of .gz file must itself end in .gz");
@@ -1093,6 +1168,10 @@
 		fatal("Invalid pathname in DELETE command");
 	}
 
+	if (!write_allowed($file, "+")) {
+		fatal("Delete access denied");
+	}
+
 	if ($file !~ /\.gz$/ &&
 		has_extension($file, '.sign', keys(%zformats))) {
 		fatal("DELETE of auxiliary files not supported");
@@ -1222,6 +1301,10 @@
 
 	my($dir) = @args;
 
+	if (!read_allowed()) {
+		fatal("Read access denied");
+	}
+
 	# DIR / is permitted unlike any other command
 	$dir =~ s:/$::g;
 	if ($dir ne '' && !is_valid_filename($dir)) {
@@ -1261,7 +1344,25 @@
 
 sub do_info()
 {
-	print "kup-server $VERSION\n";
+	print "kup-server $VERSION\n\n";
+
+	my %xlat = (
+		R       =>	'ls',
+		RW      =>	'put',
+		'RW+'   =>	'put/rm/mv',
+		'RWC'   =>	'put/mkdir',
+		'RW+C'  =>	'put/rm/mv/mkdir',
+		'-'     =>	'(denied)',
+	);
+	Gitolite::Conf::Load::load('@kup-server');
+	my @rules = Gitolite::Conf::Load::rules('@kup-server', $ENV{GL_USER});
+	for my $r (@rules) {
+		my ($dummy, $perm, $ref) = @$r;
+		$ref =~ s(^refs/heads/)();
+		$ref =~ s(/USER/)(/$ENV{GL_USER}/);
+		$ref = ($ref eq 'refs/.*') ? '/*' : '/' . $ref . '*';
+		printf "%-24s %s\n", ($xlat{$perm} || $perm), $ref;
+	}
 }
 
 sub get_command()