Add security headers to synapse-admin (on Traefik)

We've had it on `matrix-nginx-proxy` before, but
our initial support for Traefik did not include any of these security
headers.

roles/custom/matrix-synapse-admin/defaults/main.yml

@@ -27,6 +27,11 @@ matrix_synapse_admin_container_network: matrix-synapse-admin
 # Use this to expose this container to a reverse proxy, which runs in a different container network.
 matrix_synapse_admin_container_additional_networks: []
 
+# Controls whether the matrix-synapse-admin container exposes its HTTP port (tcp/80 in the container).
+#
+# Takes an "<ip>:<port>" or "<port>" value (e.g. "127.0.0.1:8766"), or empty string to not expose.
+matrix_synapse_admin_container_http_host_bind_port: ''
+
 # A list of extra arguments to pass to the container
 matrix_synapse_admin_container_extra_arguments: []
 
@@ -44,6 +49,21 @@ matrix_synapse_admin_container_labels_traefik_entrypoints: web-secure
 matrix_synapse_admin_container_labels_traefik_tls: "{{ matrix_synapse_admin_container_labels_traefik_entrypoints != 'web' }}"
 matrix_synapse_admin_container_labels_traefik_tls_certResolver: default  # noqa var-naming
 
+# Controls which additional headers to attach to all HTTP responses.
+# To add your own headers, use `matrix_synapse_admin_container_labels_traefik_additional_response_headers_custom`
+matrix_synapse_admin_container_labels_traefik_additional_response_headers: "{{ matrix_synapse_admin_container_labels_traefik_additional_response_headers_auto | combine(matrix_synapse_admin_container_labels_traefik_additional_response_headers_custom) }}"
+matrix_synapse_admin_container_labels_traefik_additional_response_headers_auto: |
+  {{
+    {}
+    | combine ({'X-XSS-Protection': matrix_synapse_admin_http_header_xss_protection} if matrix_synapse_admin_http_header_xss_protection else {})
+    | combine ({'X-Frame-Options': matrix_synapse_admin_http_header_frame_options} if matrix_synapse_admin_http_header_frame_options else {})
+    | combine ({'X-Content-Type-Options': matrix_synapse_admin_http_header_content_type_options} if matrix_synapse_admin_http_header_content_type_options else {})
+    | combine ({'Content-Security-Policy': matrix_synapse_admin_http_header_content_security_policy} if matrix_synapse_admin_http_header_content_security_policy else {})
+    | combine ({'Permission-Policy': matrix_synapse_admin_http_header_content_permission_policy} if matrix_synapse_admin_http_header_content_permission_policy else {})
+    | combine ({'Strict-Transport-Security': matrix_synapse_admin_http_header_strict_transport_security} if matrix_synapse_admin_http_header_strict_transport_security and matrix_synapse_admin_container_labels_traefik_tls else {})
+  }}
+matrix_synapse_admin_container_labels_traefik_additional_response_headers_custom: {}
+
 # matrix_synapse_admin_container_labels_additional_labels contains a multiline string with additional labels to add to the container label file.
 # See `../templates/labels.j2` for details.
 #
@@ -59,10 +79,56 @@ matrix_synapse_admin_systemd_required_services_list: ['docker.service']
 # List of systemd services that matrix-synapse-admin.service wants
 matrix_synapse_admin_systemd_wanted_services_list: []
 
-# Controls whether the matrix-synapse-admin container exposes its HTTP port (tcp/80 in the container).
+# Specifies the value of the `X-XSS-Protection` header
+# Stops pages from loading when they detect reflected cross-site scripting (XSS) attacks.
 #
-# Takes an "<ip>:<port>" or "<port>" value (e.g. "127.0.0.1:8766"), or empty string to not expose.
+# Learn more about it is here:
-matrix_synapse_admin_container_http_host_bind_port: ''
+# - https://developer.mozilla.org/en-US/docs/Web/HTTP/Headers/X-XSS-Protection
+# - https://portswigger.net/web-security/cross-site-scripting/reflected
+matrix_synapse_admin_http_header_xss_protection: "1; mode=block"
+
+# Specifies the value of the `X-Frame-Options` header which controls whether framing can happen.
+# See: https://developer.mozilla.org/en-US/docs/Web/HTTP/Headers/X-Frame-Options
+matrix_synapse_admin_http_header_frame_options: SAMEORIGIN
+
+# Specifies the value of the `X-Content-Type-Options` header.
+# See: https://developer.mozilla.org/en-US/docs/Web/HTTP/Headers/X-Content-Type-Options
+matrix_synapse_admin_http_header_content_type_options: nosniff
+
+# Specifies the value of the `Content-Security-Policy` header.
+# See: https://developer.mozilla.org/en-US/docs/Web/HTTP/Headers/Content-Security-Policy
+matrix_synapse_admin_http_header_content_security_policy: frame-ancestors 'self'
+
+# Specifies the value of the `Permission-Policy` header.
+# See: https://developer.mozilla.org/en-US/docs/Web/HTTP/Headers/Permission-Policy
+matrix_synapse_admin_http_header_content_permission_policy: "{{ 'interest-cohort=() always' if matrix_synapse_admin_floc_optout_enabled else '' }}"
+
+# Specifies the value of the `Strict-Transport-Security` header.
+# See: https://developer.mozilla.org/en-US/docs/Web/HTTP/Headers/Strict-Transport-Security
+matrix_synapse_admin_http_header_strict_transport_security: "{{ '\"max-age=31536000; includeSubDomains; preload\" always' if matrix_synapse_admin_hsts_preload_enabled else '\"max-age=31536000; includeSubDomains\" always' }}"
+
+# Controls whether to send a "Permissions-Policy interest-cohort=();" header along with all responses
+#
+# Learn more about what it is here:
+# - https://www.eff.org/deeplinks/2021/03/googles-floc-terrible-idea
+# - https://paramdeo.com/blog/opting-your-website-out-of-googles-floc-network
+# - https://amifloced.org/
+#
+# Of course, a better solution is to just stop using browsers (like Chrome), which participate in such tracking practices.
+# See: `matrix_synapse_admin_content_permission_policy`
+matrix_synapse_admin_floc_optout_enabled: true
+
+# Controls if HSTS preloading is enabled
+#
+# In its strongest and recommended form, the [HSTS policy](https://www.chromium.org/hsts) includes all subdomains, and
+# indicates a willingness to be "preloaded" into browsers:
+# `Strict-Transport-Security: max-age=31536000; includeSubDomains; preload`
+# For more information visit:
+# - https://en.wikipedia.org/wiki/HTTP_Strict_Transport_Security
+# - https://developer.mozilla.org/en-US/docs/Web/HTTP/Headers/Strict-Transport-Security
+# - https://hstspreload.org/#opt-in
+# See: `matrix_synapse_admin_http_header_strict_transport_security`
+matrix_synapse_admin_hsts_preload_enabled: false
 
 # The path at which Synapse Admin will be exposed on `matrix.DOMAIN`
 # (only applies when matrix-nginx-proxy is used).

roles/custom/matrix-synapse-admin/templates/labels.j2

@@ -18,6 +18,13 @@ traefik.http.middlewares.matrix-synapse-admin-strip-prefix.stripprefix.prefixes=
 {% set middlewares = middlewares + ['matrix-synapse-admin-strip-prefix'] %}
 {% endif %}
 
+{% if matrix_synapse_admin_container_labels_traefik_additional_response_headers.keys() | length > 0 %}
+{% for name, value in matrix_synapse_admin_container_labels_traefik_additional_response_headers.items() %}
+traefik.http.middlewares.matrix-synapse-admin-add-headers.headers.customresponseheaders.{{ name }}={{ value }}
+{% endfor %}
+{% set middlewares = middlewares + ['matrix-synapse-admin-add-headers'] %}
+{% endif %}
+
 traefik.http.routers.matrix-synapse-admin.rule={{ matrix_synapse_admin_container_labels_traefik_rule }}
 {% if middlewares | length > 0 %}
 traefik.http.routers.matrix-synapse-admin.middlewares={{ middlewares | join(',') }}