Backup & restore of E2E session data

e2e-backup.js

// backup (tested in Chrome console...). N.B. this does *NOT ENCRYPT THE SESSION KEYS!*

Object.keys(window.localStorage).forEach(k=>{
    if (k.match(/^session\.e2e\.sessions\/|^session\.e2e\.inboundgroupsessions\//)) localStorageCopy[k] = window.localStorage[k];
});

blob = new Blob([JSON.stringify(localStorageCopy, null, '\t')], { type: "text/plain;charset=utf-8" });

fetch('https://raw.githubusercontent.com/eligrey/FileSaver.js/master/FileSaver.js')
    .then(response => response.text())
    .then(text => { eval(text); saveAs(blob, "e2e-backup.json") });