library: staff signed in to Koha open Add books without a second login

Quick Add asks Koha (C4::Auth::check_cookie_auth via a secret-guarded svc script) whether the
browser's session may edit the catalogue; falls back to its own login otherwise. Cookie-authenticated
writes need an X-Quickadd header; the direct port never accepts cookies.

Co-Authored-By: Claude Sonnet 5.5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_013wi3ZSot4XbUViwRFgLpRf

library/koha/Dockerfile

@@ -39,6 +39,10 @@ RUN for c in koha-create koha-plack koha-zebra koha-rebuild-zebra koha-upgrade-s
       command -v "$c" >/dev/null || { echo "BUILD ERROR: $c is missing from the image" >&2; exit 1; }; \
     done
 
+# The endpoint Quick Add uses to recognise a signed-in staff user (see the file header).
+COPY quickadd-session.pl /usr/share/koha/intranet/cgi-bin/svc/quickadd-session
+RUN chmod 0755 /usr/share/koha/intranet/cgi-bin/svc/quickadd-session
+
 COPY bootstrap.pl ensure.pl entrypoint.sh /opt/koha-init/
 COPY seed/ /opt/koha-init/seed/
 RUN chmod 0755 /opt/koha-init/entrypoint.sh && chmod -R a+rX /opt/koha-init

library/koha/entrypoint.sh

@@ -60,22 +60,36 @@ if [ ! -d "/etc/koha/sites/$INST" ]; then
     # (The staff and public catalogue sites cannot share one address: Koha gives both the
     # same URL shapes. The staff site is the natural home for a home library.)
     if [ -n "${KOHA_QUICKADD_URL:-}" ]; then
+        # Single sign-on for staff: when KOHA_SSO_SECRET is set, this web server tells Quick Add (via a
+        # secret header nobody outside can forge: it is overwritten here on every request) that the
+        # request came through the staff site, and Quick Add then asks Koha whether the browser's login
+        # cookie belongs to a staff user who may edit the catalogue. Without the secret, or if anything
+        # about that fails, Quick Add just asks for its own login as before.
+        SSO_BLOCK=""
+        if [ -n "${KOHA_SSO_SECRET:-}" ]; then
+            install -m 0640 -o root -g "$INST-koha" /dev/null /etc/koha/quickadd-sso.secret
+            printf '%s' "$KOHA_SSO_SECRET" > /etc/koha/quickadd-sso.secret
+            SSO_BLOCK="    <IfModule mod_headers.c>
+        <Location /add/>
+            RequestHeader set X-Quickadd-Proxy \"$KOHA_SSO_SECRET\"
+        </Location>
+    </IfModule>"
+        fi
         cat > /etc/koha/apache-quickadd.conf << APACHE
 <IfModule mod_proxy_http.c>
     RedirectMatch ^/add\$ /add/
     ProxyPass /add/ ${KOHA_QUICKADD_URL%/}/
     ProxyPassReverse /add/ ${KOHA_QUICKADD_URL%/}/
+${SSO_BLOCK}
 </IfModule>
 APACHE
         sed -i 's|^\(\s*\)Include /etc/koha/apache-shared-intranet.conf|&\n\1Include /etc/koha/apache-quickadd.conf|' "/etc/apache2/sites-available/$INST.conf"
     fi
 
-    # Run Apache itself as the instance user instead of mpm_itk's per-vhost
-    # uid switching (which needs extra capabilities and is pointless here:
-    # Plack does the real work as that user already).
     # koha-create insists on mpm_itk being enabled, but inside a container it can
     # not switch users (initgroups: Operation not permitted -> HTTP 500 on every
-    # page). Now that the instance exists, swap to plain prefork.
+    # page). Now that the instance exists, swap to plain prefork; Apache runs as the
+    # instance user (Plack does the real work as that user already).
     rm -f /etc/apache2/mods-enabled/mpm_itk.*
     a2enmod mpm_prefork >/dev/null 2>&1 || true
     sed -i '/AssignUserID/d' "$SITE"

library/koha/quickadd-session.pl

@@ -0,0 +1,44 @@
+#!/usr/bin/perl
+# Installed as .../intranet/cgi-bin/svc/quickadd-session (URL /cgi-bin/koha/svc/quickadd-session).
+#
+# Lets the Add books page (Quick Add) ask: "is this browser signed in to the staff site as
+# someone allowed to edit the catalogue?" so staff do not have to log in a second time.
+#
+# It wraps Koha's own C4::Auth::check_cookie_auth (documented for exactly this: services that
+# are invoked by pages authenticated in the usual way) and only answers callers that present a
+# shared secret, so it cannot be used to probe sessions from outside. The browser's address is
+# passed in explicitly, so Koha's "session is tied to the IP that logged in" rule keeps working.
+use Modern::Perl;
+use CGI qw( -utf8 );
+use JSON qw( encode_json );
+use Digest::SHA qw( sha256_hex );
+use C4::Auth qw( check_cookie_auth );
+
+my $q = CGI->new;
+
+# Takes the CGI object as an argument: under Plack this file runs wrapped in a sub, where a named
+# sub would otherwise see a stale copy of a file-level variable.
+sub reply {
+    my ( $q, $status, $data ) = @_;
+    print $q->header( -type => 'application/json', -status => $status, -charset => 'utf-8', -cache_control => 'no-store' ),
+        encode_json($data);
+    exit;
+}
+
+# 1. The caller must know the shared secret (a file only the Koha user and root can read).
+my $secret = '';
+if ( open my $fh, '<', '/etc/koha/quickadd-sso.secret' ) { $secret = <$fh> // ''; $secret =~ s/\s+$//; close $fh }
+my $given = $ENV{HTTP_X_QUICKADD_SECRET} // '';
+reply( $q, '403 Forbidden', { status => 'forbidden' } )
+    unless length($secret) >= 16 && sha256_hex($given) eq sha256_hex($secret);
+
+# 2. Plausible-looking inputs only.
+my $sid = $q->param('sid') // '';
+my $ip  = $q->param('ip')  // '';
+reply( $q, '200 OK', { status => 'failed' } )
+    unless $sid =~ /\A[A-Za-z0-9]{16,64}\z/ && $ip =~ /\A[0-9A-Fa-f:.]{3,45}\z/;
+
+# 3. Ask Koha. Staff who may edit the catalogue (superlibrarians always may) are let in.
+my ( $status, $session ) = check_cookie_auth( $sid, { editcatalogue => 'edit_catalogue' }, { remote_addr => $ip } );
+reply( $q, '200 OK', { status => 'ok', user => scalar $session->param('id') } ) if $status eq 'ok' && $session;
+reply( $q, '200 OK', { status => $status || 'failed' } );