Add Cross Origin Policies headers

Closes #250

h5bp/security/cross-origin-policy.conf

@@ -0,0 +1,46 @@
+# ----------------------------------------------------------------------
+# | Cross Origin Policy                                                |
+# ----------------------------------------------------------------------
+
+# Set strict a Cross Origin Policy to mitigate information leakage.
+#
+# (1) Cross-Origin-Embedder-Policy prevents a document from loading any
+#     cross-origin resources that don’t explicitly grant the document
+#     permission.
+#     https://html.spec.whatwg.org/multipage/origin.html#coep
+#     https://owasp.org/www-project-secure-headers/#cross-origin-embedder-policy
+#     https://developer.mozilla.org/en-US/docs/Web/HTTP/Headers/Cross-Origin-Embedder-Policy
+#
+# (2) Cross-Origin-Opener-Policy allows you to ensure a top-level document does
+#     not share a browsing context group with cross-origin documents.
+#     https://html.spec.whatwg.org/multipage/origin.html#cross-origin-opener-policies
+#     https://owasp.org/www-project-secure-headers/#cross-origin-opener-policy
+#     https://developer.mozilla.org/en-US/docs/Web/HTTP/Headers/Cross-Origin-Opener-Policy
+#
+# (3) Cross-Origin-Resource-Policy allows to define a policy that lets web
+#     sites and applications opt in to protection against certain requests from
+#     other origins, to mitigate speculative side-channel attacks.
+#     https://fetch.spec.whatwg.org/#cross-origin-resource-policy-header
+#     https://owasp.org/www-project-secure-headers/#cross-origin-resource-policy
+#     https://developer.mozilla.org/en-US/docs/Web/HTTP/Headers/Cross-Origin-Resource-Policy
+#     https://resourcepolicy.fyi/
+#
+# To check your Cross Origin Policy, you can use an online service, such as:
+# https://securityheaders.com/
+# https://observatory.mozilla.org/
+#
+# https://web.dev/coop-coep/
+# https://web.dev/why-coop-coep/
+# https://web.dev/cross-origin-isolation-guide/
+# https://scotthelme.co.uk/coop-and-coep/
+
+<IfModule mod_headers.c>
+    # (1)
+    Header always set Cross-Origin-Embedder-Policy "require-corp" "expr=%{CONTENT_TYPE} =~ m#text\/(html|javascript)|application\/pdf|xml#i"
+
+    # (2)
+    Header always set Cross-Origin-Opener-Policy "same-origin" "expr=%{CONTENT_TYPE} =~ m#text\/(html|javascript)|application\/pdf|xml#i"
+
+    # (3)
+    Header always set Cross-Origin-Resource-Policy "same-origin" "expr=%{CONTENT_TYPE} =~ m#text\/(html|javascript)|application\/pdf|xml#i"
+</IfModule>