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Added decrypt web page source code

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M66B 2022-10-17 09:35:03 +02:00
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commit d4abad6684
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<!doctype html>
<html lang="en">
<head>
<meta charset="utf-8">
<title>Decrypt message</title>
<meta name="theme-color" content="#006db3">
<meta name="viewport" content="width=device-width,minimum-scale=1,initial-scale=1">
<meta name="description" content="Decrypt message">
<meta name="author" content="M66B">
<meta name="robots" content="noindex">
<!-- https://developer.mozilla.org/en-US/docs/Web/HTTP/CSP -->
<meta http-equiv="Content-Security-Policy" content="default-src 'self' 'unsafe-inline'; style-src 'self' 'unsafe-inline';">
<style>
body { padding-left: 10px; padding-right: 10px; font-family: Arial, Helvetica, sans-serif; }
</style>
<style>
.noscript { display: none; }
</style>
<noscript>
<style>
.noscript { display: block; }
</style>
</noscript>
<script>
window.addEventListener('load', load);
function load() {
document.getElementById('getpassword').addEventListener('submit', getpassword);
if (window.location.hash)
if (crypto.subtle &&
typeof Uint8Array === 'function' &&
typeof TextEncoder === 'function') {
document.getElementById('getpassword').style.display = 'block';
document.getElementById('password').focus();
}
else {
document.getElementById('error').textContent = 'Your browser is not suitable for decrypting messages';
document.getElementById('error').style.display = 'block';
document.getElementById('details').innerHTML =
'crypto.subtle: ' + (crypto.subtle ? 'Yes' : 'No') + '<br>' +
'Uint8Array: ' + (Uint8Array ? 'Yes' : 'No') + '<br>' +
'TextEncoder: ' + (TextEncoder ? 'Yes' : 'No') + '<br>';
document.getElementById('details').style.display = 'block';
}
else {
document.getElementById('message').textContent = 'Nothing to see here';
document.getElementById('message').style.display = 'block';
}
document.getElementById('year').textContent = new Date().getFullYear();
}
function getpassword(event) {
event.preventDefault();
decrypt();
}
async function decrypt() {
document.getElementById('fields').disabled = true;
try {
document.getElementById('message').style.display = 'none';
document.getElementById('error').style.display = 'none';
document.getElementById('details').style.display = 'none';
let password = document.getElementById('password').value;
if (password) {
let message = await _decrypt(password);
document.getElementById('getpassword').style.display = 'none';
document.getElementById('message').innerHTML = message;
document.getElementById('message').style.display = 'block';
document.getElementById('copyright').style.display = 'none';
}
else
throw new Error('Password required');
} catch (e) {
console.log("%O", e);
document.getElementById('password').value = '';
document.getElementById('error').textContent = 'Could not decrypt the message. Is the password correct?';
document.getElementById('error').style.display = 'block';
document.getElementById('details').textContent = e.toString();
document.getElementById('details').style.display = 'block';
}
document.getElementById('fields').disabled = false;
}
async function _decrypt(password) {
let msg = atob(window.location.hash.substr(1).replaceAll('-', '+').replaceAll('_', '/'));
const buf = new Uint8Array(msg.length);
for (let i = 0; i < msg.length; i++)
buf[i] = msg.charCodeAt(i);
const version = buf[0];
const salt = buf.slice(1, 1 + 16);
const iv = buf.slice(1 + 16, 1 + 16 + 12);
const e = buf.slice(1 + 16 + 12, buf.length);
// https://developer.mozilla.org/en-US/docs/Web/API/Crypto/subtle
// https://developer.mozilla.org/en-US/docs/Web/API/TextEncoder
const passwordBuffer = new TextEncoder('UTF-8').encode(password);
const importedKey = await crypto.subtle.importKey('raw', passwordBuffer, 'PBKDF2', false, ['deriveBits']);
const derivation = await crypto.subtle.deriveBits({name: 'PBKDF2', hash: 'SHA-512', salt: salt, iterations: 120000}, importedKey, 256);
const importedEncryptionKey = await crypto.subtle.importKey('raw', derivation, {name: 'AES-GCM'}, false, ['decrypt']);
const decrypted = await window.crypto.subtle.decrypt({name: 'AES-GCM', iv: iv, tagLength: 128}, importedEncryptionKey, e);
return new TextDecoder('UTF-8').decode(decrypted);
}
</script>
</head>
<body>
<p class="noscript" style="color: red; font-weight: bold;">Please enable JavaScript</p>
<form id="getpassword" action="#" method="GET" style="display: none;">
<p>
Someone sent you an encrypted message with <a href="https://email.faircode.eu/" target="_blank">FairEmail</a>.
</p>
<fieldset id="fields" style="border:0 none; margin: 0; padding: 0;">
<p>
<label for="password">Password</label><br>
<input id="password" name="password" type="password" required><br>
<span style="font-size: smaller;">Passwords are case-sensitive </span>
</p>
<p>
<input id="submit" type="submit" value="Decrypt">
</p>
</fieldset>
<p style="font-size: smaller;">
Messages are decrypted in the browser and not stored an a server.<br>
Messages are encrypted with AES/GCM with a 256 bits key derived with PBKDF2/SHA-512/120,000 iterations.
</p>
</form>
<p id="message" style="display: none;"></p>
<p id="error" style="color: red; font-weight: bold; display: none;"></p>
<p id="details" style="font-size: x-small; display: none;"></p>
<p id="copyright" style="padding-top: 20px;">
Copyright &copy; 2018&ndash;<span id="year">2022</span> by Marcel Bokhorst (M66B)
<br>
<br>
<span style="font-size: smaller;">This page is <a href="https://github.com/M66B/FairEmail/blob/master/decrypt/index.html" target="_blank">open source</a>.</span>
</p>
</body>
</html>