verify-jar.js

const {AppConstants} = ChromeUtils.import("resource://gre/modules/AppConstants.jsm");
const {FileUtils} = ChromeUtils.import("resource://gre/modules/FileUtils.jsm");
const {Services} = ChromeUtils.import("resource://gre/modules/Services.jsm");
const {XPCOMUtils} = ChromeUtils.import("resource://gre/modules/XPCOMUtils.jsm");

XPCOMUtils.defineLazyServiceGetters(this, {
  gCertDB: ["@mozilla.org/security/x509certdb;1", "nsIX509CertDB"],
});

function verifyJar(file) {
    let root = Ci.nsIX509CertDB.AddonsPublicRoot;
    let expectedOrganizationalUnit = "Mozilla Components";

    return new Promise(resolve => {
        gCertDB.openSignedAppFileAsync(root, file, (rv, _zipReader, cert) => {
            console.log("OU", cert.organizationalUnit);
            resolve(Components.isSuccessCode(rv) && cert.organizationalUnit === expectedOrganizationalUnit);
        });
    });
}

let f = FileUtils.File("/Users/rhelmer/Downloads/hotfix-bug-1548973@mozilla.org.xpi");
verifyJar(f);