feat: mTLS client certificates for desktop server links

electron/linked-server.cjs

@@ -34,6 +34,8 @@ function setLinkedServer(config) {
     basicAuth:
       config.basicAuth && config.basicAuth.username ? config.basicAuth : null,
     allowInvalidCertificate: !!config.allowInvalidCertificate,
+    clientCert:
+      config.clientCert && config.clientCert.pfx ? config.clientCert : null,
   };
 }
 
@@ -45,6 +47,16 @@ function isLinkedOrigin(url) {
   return !!linked && getOrigin(url) === linked.origin;
 }
 
+// The PFX of the link's client certificate, for TLS this process makes itself
+// to the linked origin. Null for any other origin.
+function clientCertOptionsFor(url) {
+  if (!isLinkedOrigin(url) || !linked.clientCert) return {};
+  return {
+    pfx: Buffer.from(linked.clientCert.pfx, "base64"),
+    passphrase: linked.clientCert.passphrase || "",
+  };
+}
+
 function basicAuthValue(basicAuth) {
   return `Basic ${Buffer.from(
     `${basicAuth.username}:${basicAuth.password || ""}`,
@@ -99,6 +111,7 @@ module.exports = {
   setLinkedServer,
   getLinkedServer,
   isLinkedOrigin,
+  clientCertOptionsFor,
   applyLinkHeaders,
   linkedRequestHeaders,
   answerLogin,

electron/main.cjs

@@ -459,6 +459,7 @@ function isInvalidCertificateAllowedForUrl(url) {
 function getTlsVerificationOptions(url) {
   return {
     rejectUnauthorized: !isInvalidCertificateAllowedForUrl(url),
+    ...linkedServer.clientCertOptionsFor(url),
   };
 }
 
@@ -690,6 +691,39 @@ ipcMain.handle("allow-invalid-certificate-for-origin", (_event, origin) => {
   }
 });
 
+// Mutual TLS for the linked server: Chromium asks which certificate from the
+// OS store to present. Other origins keep Chromium's default (none).
+const chosenClientCerts = new Map();
+
+app.on(
+  "select-client-certificate",
+  async (event, _webContents, url, list, callback) => {
+    if (!linkedServer.isLinkedOrigin(url) || !list.length) return;
+    event.preventDefault();
+    const origin = new URL(url).origin;
+    const remembered = list.find(
+      (cert) => cert.fingerprint === chosenClientCerts.get(origin),
+    );
+    let chosen = remembered || (list.length === 1 ? list[0] : null);
+    if (!chosen) {
+      const { response } = await dialog.showMessageBox(mainWindow, {
+        type: "question",
+        title: "Client certificate",
+        message: "Choose the certificate for this server",
+        detail: origin,
+        buttons: [
+          ...list.slice(0, 8).map((cert) => cert.subjectName),
+          "Cancel",
+        ],
+        cancelId: Math.min(list.length, 8),
+      });
+      chosen = list[response] || null;
+    }
+    if (chosen) chosenClientCerts.set(origin, chosen.fingerprint);
+    callback(chosen || undefined);
+  },
+);
+
 app.on(
   "certificate-error",
   (event, _webContents, url, error, certificate, callback) => {