1 files changed, 50 insertions, 0 deletions
diff --git a/background.js b/background.js
new file mode 100644
index 0000000..f619df2
--- /dev/null
+++ b/background.js
@@ -0,0 +1,50 @@
+// Based on https://github.com/mdn/webextensions-examples/blob/main/root-cert-stats/background.js
+
+// On header receive, inspect cert and update app icon as required
+async function onHeaderReceive(details) {
+    try {
+        await certInspectUpdate(details.requestId);
+    } catch(error) {
+        console.error(error);
+    }
+}
+
+async function certInspectUpdate(requestId) {
+    let securityInfo = await browser.webRequest.getSecurityInfo(
+        requestId,
+        {
+            "certificateChain": true
+        }
+    );
+    
+    if (securityInfo.state !== "secure" || securityInfo.isUntrusted) {
+        setIcon("nope");
+        return;
+    }
+
+    // Flagged as "secure" - check if CA is against any of our flagged CAs
+
+    // root is last in the array cert chain
+    let rootCA = securityInfo.certificates[securityInfo.certificates.length - 1];
+    if (rootCA.subject.includes("CN=GlobalSign Root CA")) {
+        setIcon("nope");
+        return;
+    }
+
+    setIcon("ok");
+}
+
+function setIcon(icon) {
+    browser.browserAction.setIcon({ path: "icons/" + icon + ".png" });
+}
+
+// Listen for all header receive events, which contain the cert details we want
+browser.webRequest.onHeadersReceived.addListener(
+    onHeaderReceive,
+    {
+        urls: ["<all_urls>"]
+    },
+    [
+        "blocking"
+    ]
+);
+\ No newline at end of file