1 files changed, 54 insertions, 0 deletions
diff --git a/common/misc.js b/common/misc.js
index 7158d32..3c7dc46 100644
--- a/common/misc.js
+++ b/common/misc.js
@@ -155,6 +155,59 @@ function sign_policy(policy, now, hours_offset) {
     return gen_unique(time + policy);
 }
 
+/* Parse a CSP header */
+function parse_csp(csp) {
+    let directive, directive_array;
+    let directives = {};
+    for (directive of csp.split(';')) {
+	directive = directive.trim();
+	if (directive === '')
+	    continue;
+
+	directive_array = directive.split(/\s+/);
+	directive = directive_array.shift();
+	/* The "true" case should never occur; nevertheless... */
+	directives[directive] = directive in directives ?
+	    directives[directive].concat(directive_array) :
+	    directive_array;
+    }
+    return directives;
+}
+
+/* Make CSP headers do our bidding, not interfere */
+function sanitize_csp_header(header, rule, block)
+{
+    const csp = parse_csp(header.value);
+
+    if (block) {
+	/* No snitching */
+	delete csp['report-to'];
+	delete csp['report-uri'];
+
+	delete csp['script-src'];
+	delete csp['script-src-elem'];
+
+	csp['script-src-attr'] = ["'none'"];
+	csp['prefetch-src'] = ["'none'"];
+    }
+
+    if ('script-src' in csp)
+	csp['script-src'].push(rule);
+    else
+	csp['script-src'] = [rule];
+
+    if ('script-src-elem' in csp)
+	csp['script-src-elem'].push(rule);
+    else
+	csp['script-src-elem'] = [rule];
+
+    const new_policy = Object.entries(csp).map(
+	i => `${i[0]} ${i[1].join(' ')};`
+    );
+
+    return {name: header.name, value: new_policy.join('')};
+}
+
 /* Regexes and objest to use as/in schemas for parse_json_with_schema(). */
 const nonempty_string_matcher = /.+/;
 
@@ -178,6 +231,7 @@ const matchers = {
  * EXPORT nice_name
  * EXPORT open_in_settings
  * EXPORT is_privileged_url
+ * EXPORT sanitize_csp_header
  * EXPORT matchers
  * EXPORTS_END
  */