CSP: block WebRTC

Merged to the webappsec-csp repo in April:
w3c/webappsec-csp#457

Author: Seirdy

nginx/nginx.conf

@@ -376,7 +376,7 @@ http {
 
         location = /install/web {
             include snippets/security-headers-base.conf;
-            add_header Content-Security-Policy "default-src 'none'; child-src 'self'; connect-src 'self' https://releases.grapheneos.org/; font-src 'self'; img-src 'self'; manifest-src 'self'; script-src 'self'; style-src 'self'; form-action 'none'; frame-ancestors 'none'; block-all-mixed-content; base-uri 'none'" always;
+            add_header Content-Security-Policy "default-src 'none'; child-src 'self'; connect-src 'self' https://releases.grapheneos.org/; font-src 'self'; img-src 'self'; manifest-src 'self'; script-src 'self'; style-src 'self'; form-action 'none'; frame-ancestors 'none'; block-all-mixed-content; base-uri 'none'; webrtc 'block'" always;
             add_header Permissions-Policy "accelerometer=(), ambient-light-sensor=(), autoplay=(), battery=(), camera=(), clipboard-read=(), clipboard-write=(), display-capture=(), document-domain=(), encrypted-media=(), fullscreen=(), geolocation=(), gyroscope=(), hid=(), idle-detection=(), interest-cohort=(), magnetometer=(), microphone=(), midi=(), payment=(), picture-in-picture=(), publickey-credentials-get=(), screen-wake-lock=(), serial=(), sync-xhr=(), xr-spatial-tracking=()" always;
             add_header Cross-Origin-Resource-Policy "same-origin" always;
             add_header Cache-Control "public, no-cache";

nginx/snippets/security-headers.conf

@@ -1,5 +1,5 @@
 include snippets/security-headers-base.conf;
 
-add_header Content-Security-Policy "default-src 'none'; connect-src 'self' https://releases.grapheneos.org/; font-src 'self'; img-src 'self'; manifest-src 'self'; script-src 'self'; style-src 'self'; form-action 'none'; frame-ancestors 'none'; block-all-mixed-content; base-uri 'none'; require-trusted-types-for 'script'; trusted-types 'none'" always;
+add_header Content-Security-Policy "default-src 'none'; connect-src 'self' https://releases.grapheneos.org/; font-src 'self'; img-src 'self'; manifest-src 'self'; script-src 'self'; style-src 'self'; form-action 'none'; frame-ancestors 'none'; block-all-mixed-content; base-uri 'none'; require-trusted-types-for 'script'; trusted-types 'none'; webrtc 'block'" always;
 
 add_header Permissions-Policy "accelerometer=(), ambient-light-sensor=(), autoplay=(), battery=(), camera=(), clipboard-read=(), clipboard-write=(), display-capture=(), document-domain=(), encrypted-media=(), fullscreen=(), gamepad=(), geolocation=(), gyroscope=(), hid=(), idle-detection=(), interest-cohort=(), magnetometer=(), microphone=(), midi=(), payment=(), picture-in-picture=(), publickey-credentials-get=(), screen-wake-lock=(), serial=(), speaker-selection=(), sync-xhr=(), usb=(), xr-spatial-tracking=()" always;