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util/EncFile: wallet file format gains a trailing HMAC checksum 

Standard security practice of encrypt-then-MAC.
This commit is contained in:
Jeff Garzik 2013-08-14 20:47:25 -04:00
parent 45f201c4da
commit 5fdd7ded14
1 changed files with 25 additions and 3 deletions
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28
util/EncFile.js
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@ -4,10 +4,26 @@ var crypto = require('crypto');
exports.readFileSync = function(enc_method, enc_passphrase, filename)
{
var crypted = fs.readFileSync(filename, 'binary');
// read entire file into memory
var fileData = fs.readFileSync(filename, 'binary');
if (fileData.length < 32)
throw new Error("Crypted file " + filename + " truncated");
// separate into data, hmac parts
var fileCrypted = fileData.slice(0, -32);
var fileHmac = fileData.slice(-32);
// generate and verify HMAC
var hmac = crypto.createHmac('sha256', enc_passphrase);
hmac.update(fileCrypted);
var digest = hmac.digest('binary');
if (digest.toString() != fileHmac.toString())
throw new Error("Crypted file " + filename + " failed HMAC checksum verification");
// decrypt to plaintext
var decipher = crypto.createDecipher(enc_method, enc_passphrase);
var dec = decipher.update(crypted, 'binary', 'binary');
var dec = decipher.update(fileCrypted, 'binary', 'binary');
dec += decipher.final('binary');
return dec;
};
@ -20,11 +36,17 @@ exports.readJFileSync = function(enc_method, enc_passphrase, filename)
exports.writeFileSync = function(enc_method, enc_passphrase, filename, data)
{
// encrypt to ciphertext
var cipher = crypto.createCipher(enc_method, enc_passphrase);
var crypted = cipher.update(data, 'binary', 'binary');
crypted += cipher.final('binary');
fs.writeFileSync(filename, crypted, 'binary');
// compute HMAC
var hmac = crypto.createHmac('sha256', enc_passphrase);
hmac.update(crypted);
var digest = hmac.digest('binary');
fs.writeFileSync(filename, crypted + digest, 'binary');
return true;
};