utilize Pattern Tree to decide the policy to use and modify HTTP response headers according to that policy

This commit also enhances the build script so that preprocessor conditionals can now use operators '&&' and '||'.
The features being developed are not yet included in the actual Haketilo build.
Some of the new source files contain similar functionality to other ones already existing in the source tree. At some point the latter will be removed.

1 files changed, 11 insertions, 1 deletions

diff --git a/background/policy_injector.js b/background/policy_injector.js
index 2544e8e..b1fc733 100644
--- a/background/policy_injector.js
+++ b/background/policy_injector.js
@@ -43,13 +43,23 @@
  * proprietary program, I am not going to enforce this in court.
  */
 
-#FROM common/misc.js IMPORT make_csp_rule, csp_header_regex
+#FROM common/misc.js IMPORT csp_header_regex
 
 /* Re-enable the import below once nonce stuff here is ready */
 #IF NEVER
 #FROM common/misc.js IMPORT gen_nonce
 #ENDIF
 
+/* CSP rule that blocks scripts according to policy's needs. */
+function make_csp_rule(policy)
+{
+    let rule = "prefetch-src 'none'; script-src-attr 'none';";
+    const script_src = policy.nonce !== undefined ?
+         `'nonce-${policy.nonce}'` : "'none'";
+    rule += ` script-src ${script_src}; script-src-elem ${script_src};`;
+    return rule;
+}
+
 function inject_csp_headers(headers, policy)
 {
     let csp_headers;