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Saving Web Crypto Keys using indexedDB

This is a working example on how to store CryptoKeys locally in your browser. We are able to save the objects, without serializing them. This means we can keep them not exportable (which might be more secure?? not sure what attack vectors this prevents).

To try out this example, first make sure you are in a browser that has support for async...await and indexedDB (latest chrome canary with chrome://flags "Enable Experimental Javascript" works). Load some page and copy and paste this code into the console. Then call encryptDataSaveKey(). This will create a private/public key pair and encrypted some random data with the private key. Then save both of them. Now reload the page, copy in the code, and run loadKeyDecryptData(). It will load the keys and encrypted data and decrypt it. You should see the same data logged both times.

async function encryptDataSaveKey() {
var data = await makeData();
console.log("generated data", data);
var keys = await makeKeys()
var encrypted = await encrypt(data, keys);
callOnStore(function (store) {
store.put({id: 1, keys: keys, encrypted: encrypted});
})
}
function loadKeyDecryptData() {
callOnStore(function (store) {
var getData = store.get(1);
getData.onsuccess = async function() {
var keys = getData.result.keys;
var encrypted = getData.result.encrypted;
var data = await decrypt(encrypted, keys);
console.log("decrypted data", data);
};
})
}
function callOnStore(fn_) {
// This works on all devices/browsers, and uses IndexedDBShim as a final fallback
var indexedDB = window.indexedDB || window.mozIndexedDB || window.webkitIndexedDB || window.msIndexedDB || window.shimIndexedDB;
// Open (or create) the database
var open = indexedDB.open("MyDatabase", 1);
// Create the schema
open.onupgradeneeded = function() {
var db = open.result;
var store = db.createObjectStore("MyObjectStore", {keyPath: "id"});
};
open.onsuccess = function() {
// Start a new transaction
var db = open.result;
var tx = db.transaction("MyObjectStore", "readwrite");
var store = tx.objectStore("MyObjectStore");
fn_(store)
// Close the db when the transaction is done
tx.oncomplete = function() {
db.close();
};
}
}
async function encryptDecrypt() {
var data = await makeData();
console.log("generated data", data);
var keys = await makeKeys()
var encrypted = await encrypt(data, keys);
console.log("encrypted", encrypted);
var finalData = await decrypt(encrypted, keys);
console.log("decrypted data", data);
}
function makeData() {
return window.crypto.getRandomValues(new Uint8Array(16))
}
function makeKeys() {
return window.crypto.subtle.generateKey(
{
name: "RSA-OAEP",
modulusLength: 2048, //can be 1024, 2048, or 4096
publicExponent: new Uint8Array([0x01, 0x00, 0x01]),
hash: {name: "SHA-256"}, //can be "SHA-1", "SHA-256", "SHA-384", or "SHA-512"
},
false, //whether the key is extractable (i.e. can be used in exportKey)
["encrypt", "decrypt"] //must be ["encrypt", "decrypt"] or ["wrapKey", "unwrapKey"]
)
}
function encrypt(data, keys) {
return window.crypto.subtle.encrypt(
{
name: "RSA-OAEP",
//label: Uint8Array([...]) //optional
},
keys.publicKey, //from generateKey or importKey above
data //ArrayBuffer of data you want to encrypt
)
}
async function decrypt(data, keys) {
return new Uint8Array(await window.crypto.subtle.decrypt(
{
name: "RSA-OAEP",
//label: Uint8Array([...]) //optional
},
keys.privateKey, //from generateKey or importKey above
data //ArrayBuffer of the data
));
}
@dscaravaggi
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dscaravaggi commented Jan 10, 2022

I'm interested in this thread and I tried to understand if chromium has already included TPM2 by heart, I found some git commit about it but I'm not able to understand is is rolled up in officials builds.
on the other hand should I trust webcrytpt in android >10 webview ?

@Vishwas1
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Vishwas1 commented Apr 15, 2022

Is there any paper on security of cryptoKey storage?

@tcortega
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tcortega commented Apr 15, 2022

@Vishwas1 The way I was successfull in extracting non-extractable keys was simply via http request interception and modifying the js that generated the key in the first place. This should be possible in literally any application. Although it may not be as easy as it was for me.

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