drop.chapril.org-firefoxsend/server/keychain.js

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const { Crypto } = require('@peculiar/webcrypto');
const crypto = new Crypto();
const encoder = new TextEncoder();
const decoder = new TextDecoder();
module.exports = class Keychain {
constructor(secretKeyB64) {
if (secretKeyB64) {
this.rawSecret = new Uint8Array(Buffer.from(secretKeyB64, 'base64'));
} else {
throw new Error('key is required');
}
this.secretKeyPromise = crypto.subtle.importKey(
'raw',
this.rawSecret,
'HKDF',
false,
['deriveKey']
);
this.metaKeyPromise = this.secretKeyPromise.then(function(secretKey) {
return crypto.subtle.deriveKey(
{
name: 'HKDF',
salt: new Uint8Array(),
info: encoder.encode('metadata'),
hash: 'SHA-256'
},
secretKey,
{
name: 'AES-GCM',
length: 128
},
false,
['decrypt']
);
});
}
async decryptMetadata(ciphertext) {
const metaKey = await this.metaKeyPromise;
const plaintext = await crypto.subtle.decrypt(
{
name: 'AES-GCM',
iv: new Uint8Array(12),
tagLength: 128
},
metaKey,
ciphertext
);
return JSON.parse(decoder.decode(plaintext));
}
};