1 files changed, 81 insertions, 0 deletions
diff --git a/background.js b/background.js
new file mode 100644
index 0000000..835ee51
--- /dev/null
+++ b/background.js
@@ -0,0 +1,81 @@
+// 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) {
+    if (details.tabId < 0) // tabId < 0 means non-user tab
+        return;
+
+    try {
+        await certInspectUpdate(details.requestId, details.tabId);
+    } catch(error) {
+        console.error(error);
+    }
+}
+
+function daysBetween(a, b) {
+    return Math.ceil((b - a) / (24 * 60 * 60 * 1000));
+}
+
+async function certInspectUpdate(requestId, tabId) {
+    let securityInfo = await browser.webRequest.getSecurityInfo(requestId, {});
+
+    // Not HTTPS
+    if (securityInfo.state !== "secure")
+        return;
+
+    // Grab cert itself
+    let cert = securityInfo.certificates[0];
+
+    // Check expiry against 30 days
+    let in30d = new Date();
+    in30d.setDate(in30d.getDate() + 30);
+    let expiry = new Date(cert.validity.end);
+
+    // HACK: Schedule for this to run after a little later for 'blocking' element
+    //       This is so that main_frame doesn't clear tabId-specific things again
+    setTimeout(() => {
+        let bad = expiry <= in30d;
+        setIcon(bad ? "nope" : "ok", tabId);
+
+        let days = daysBetween(new Date(), expiry);
+        let daysShort = days + "d";
+        if (days > 90)
+            daysShort = "3m+";
+        else if (days > 180)
+            daysShort = "6m+";
+        else if (days > 365)
+            daysShort = "1y+";
+
+        // Set expiry days as text
+        browser.browserAction.setBadgeText({
+            text: daysShort,
+            tabId: tabId
+        });
+        browser.browserAction.setTitle({
+            title: "certose - " + cert.issuer + " - " + days + "d to validity end",
+            tabId: tabId
+        });
+        if (!bad)
+            browser.browserAction.setBadgeBackgroundColor({ color: "blue" });
+    }, 100);
+}
+
+function setIcon(icon, tabId) {
+    browser.browserAction.setIcon({
+        path: "icons/" + icon + ".png",
+        tabId: tabId
+    });
+}
+
+// Listen for all header receive events, which contain the cert details we want
+// Firefox only supports onHeadersReceived at the moment, hence the hack above
+browser.webRequest.onHeadersReceived.addListener(
+    onHeaderReceive,
+    {
+        urls: ["<all_urls>"],
+        types: ["main_frame"] // Only for the top level website
+    },
+    [
+        "blocking"
+    ]
+);