add headers to embed nextcloud in frame on external site

This introduces new env variables to configure nextloud to be embedded via
iframe on an external site.
Setting X_FRAME_OPTIONS_ENABLED=1 will configure nginx and nextcloud to
set X-Frame-Options and CSP headers to allow the domain configured in
X_FRAME_OPTIONS_ALLOW_FROM.

.env.sample

@@ -16,3 +16,6 @@ SECRET_DB_PASSWORD_VERSION=v1
 SECRET_ADMIN_PASSWORD_VERSION=v1
 
 EXTRA_VOLUME=/dev/null:/tmp/.dummy
+
+# X_FRAME_OPTIONS_ENABLED=1
+# X_FRAME_OPTIONS_ALLOW_FROM=embedding-site.example.org

abra.sh

@@ -1,6 +1,7 @@
 export FPM_TUNE_VERSION=v4
-export NGINX_CONF_VERSION=v2
+export NGINX_CONF_VERSION=v3
 export MY_CNF_VERSION=v4
+export ENTRYPOINT_VERSION=v1
 
 NC_APP_DIR="app:/var/www/html"
 

compose.yml

@@ -6,6 +6,8 @@ services:
       - source: nginx_conf
         target: /etc/nginx/nginx.conf
     environment:
+      - X_FRAME_OPTIONS_ALLOW_FROM
+      - X_FRAME_OPTIONS_ENABLED
       - DOMAIN
       - STACK_NAME
     volumes:
@@ -39,10 +41,16 @@ services:
     configs:
       - source: fpm_tune
         target: /usr/local/etc/php-fpm.d/fpm-tune.conf
+      - source: entrypoint
+        target: /custom-entrypoint.sh
+        mode: 555
+    entrypoint: /custom-entrypoint.sh
     secrets:
       - db_password
       - admin_password
     environment:
+      - X_FRAME_OPTIONS_ALLOW_FROM
+      - X_FRAME_OPTIONS_ENABLED
       - DOMAIN
       - STACK_NAME
       - NEXTCLOUD_ADMIN_USER=${ADMIN_USER}
@@ -73,7 +81,6 @@ services:
         - "backupbot.backup=true"
         - "backupbot.backup.path=/var/www/html/config/,/var/www/html/data/,/var/www/html/custom_apps/"
 
-
   cron:
     image: nextcloud:24.0.3-fpm
     volumes:
@@ -111,6 +118,7 @@ volumes:
   nextconfig:
   redis:
 
+
 configs:
   nginx_conf:
     name: ${STACK_NAME}_nginx_${NGINX_CONF_VERSION}
@@ -119,6 +127,10 @@ configs:
   fpm_tune:
     name: ${STACK_NAME}_fpm_tune_${FPM_TUNE_VERSION}
     file: fpm-tune.ini
+  entrypoint:
+    name: ${STACK_NAME}_entrypoint_${ENTRYPOINT_VERSION}
+    file: entrypoint.sh.tmpl
+    template_driver: golang
 
 networks:
   proxy:

entrypoint.sh.tmpl

@@ -0,0 +1,9 @@
+#!/bin/bash
+
+{{ if eq (env "X_FRAME_OPTIONS_ENABLED") "1" }}
+if ! [[ $(grep {{ env "X_FRAME_OPTIONS_ALLOW_FROM" }} lib/public/AppFramework/Http/ContentSecurityPolicy.php) ]]; then
+    sed -i "91 a\\\t\t'{{ env "X_FRAME_OPTIONS_ALLOW_FROM" }}', " lib/public/AppFramework/Http/ContentSecurityPolicy.php
+fi
+{{ end }}
+
+/entrypoint.sh php-fpm

nginx.conf.tmpl

@@ -41,6 +41,7 @@ http {
         # could take several months.
         #add_header Strict-Transport-Security "max-age=15768000; includeSubDomains; preload;" always;
 
+
         # set max upload size
         client_max_body_size 512M;
         fastcgi_buffers 64 4K;
@@ -61,11 +62,18 @@ http {
         add_header Referrer-Policy                      "no-referrer"   always;
         add_header X-Content-Type-Options               "nosniff"       always;
         add_header X-Download-Options                   "noopen"        always;
-        add_header X-Frame-Options                      "SAMEORIGIN"    always;
         add_header X-Permitted-Cross-Domain-Policies    "none"          always;
         add_header X-Robots-Tag                         "none"          always;
         add_header X-XSS-Protection                     "1; mode=block" always;
 
+        {{ if eq (env "X_FRAME_OPTIONS_ENABLED") "1" }}
+        add_header X-Frame-Options                      "{{ env "X_FRAME_OPTIONS_ALLOW_FROM" }}"    always;
+        add_header Content-Security-Policy              "frame-ancestors {{ env "X_FRAME_OPTIONS_ALLOW_FROM" }}";
+        {{ else }}
+        add_header X-Frame-Options                      "SAMEORIGIN"    always;
+        {{ end }}
+
+
         # Remove X-Powered-By, which is an information leak
         fastcgi_hide_header X-Powered-By;