filter HTTP request headers to remove Hachette cookies in case they slip through

1 files changed, 45 insertions, 0 deletions

diff --git a/background/cookie_filter.js b/background/cookie_filter.js
new file mode 100644
index 0000000..fea2d23
--- /dev/null
+++ b/background/cookie_filter.js
@@ -0,0 +1,45 @@
+/**
+ * part of Hachette
+ * Filtering request headers to remove hachette cookies that might have slipped
+ * through.
+ *
+ * Copyright (C) 2021 Wojtek Kosior
+ * Redistribution terms are gathered in the `copyright' file.
+ */
+
+/*
+ * IMPORTS_START
+ * IMPORT extract_signed
+ * IMPORTS_END
+ */
+
+function is_valid_hachette_cookie(cookie)
+{
+    const match = /^hachette-(\w*)=(.*)$/.exec(cookie);
+    if (!match)
+	return false;
+
+    return !extract_signed(match.slice(1, 3)).fail;
+}
+
+function remove_hachette_cookies(header)
+{
+    if (header.name !== "Cookie")
+	return header;
+
+    const cookies = header.value.split("; ");
+    const value = cookies.filter(c => !is_valid_hachette_cookie(c)).join("; ");
+
+    return value ? {name: "Cookie", value} : null;
+}
+
+function filter_cookie_headers(headers)
+{
+    return headers.map(remove_hachette_cookies).filter(h => h);
+}
+
+/*
+ * EXPORTS_START
+ * EXPORT filter_cookie_headers
+ * EXPORTS_END
+ */