Skip to content

perf(crypto): reuse the key for consecutive operations #65401

New issue

Have a question about this project? Sign up for a free GitHub account to open an issue and contact its maintainers and the community.

Sign up for GitHub

By clicking “Sign up for GitHub”, you agree to our terms of service and privacy statement. We’ll occasionally send you account related emails.

Already on GitHub? Sign in to your account

Draft
RobinDev wants to merge 1 commit into
base: master
Choose a base branch
from
Draft

perf(crypto): reuse the key for consecutive operations #65401

Show file tree
Hide file tree
Changes from all commits
Commits
Show all changes
1 commit
Select commit
File filter

Filter by extension

Filter by extension
Conversations
Failed to load comments.
Loading
Jump to
Jump to file
Failed to load files.
Loading
Diff view
Diff view
26 changes: 18 additions & 8 deletions lib/private/Security/Crypto.php
View file
Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -28,6 +28,7 @@
*/
class Crypto implements ICrypto {
private AES $cipher;
private ?string $cipherPasswordHash = null;
private int $ivLength = 16;

public function __construct(
Expand Down Expand Up @@ -77,11 +78,7 @@ public function encrypt(
$password = $this->config->getSystemValueString('secret');
}
$keyMaterial = hash_hkdf('sha512', $password);
// Pin the PBKDF2 parameters to phpseclib v2 defaults ('sha1' hash, 'phpseclib' salt).
// phpseclib v3 changed the default salt to 'phpseclib/salt', which would derive a
// different AES key and break decryption of previously stored ciphertexts.
// TODO: We should put our own salt into the HKDF derivation to avoid this dependency on phpseclib's defaults!
$this->cipher->setPassword(substr($keyMaterial, 0, 32), 'pbkdf2', 'sha1', 'phpseclib');
$this->setCipherPassword(substr($keyMaterial, 0, 32));

$iv = \random_bytes($this->ivLength);
$this->cipher->setIV($iv);
Expand Down Expand Up @@ -176,9 +173,7 @@ private function decryptWithoutSecret(string $authenticatedCiphertext, string $p
$hmacKey = substr($keyMaterial, 32);
}
}
// Match the v2-compatible PBKDF2 parameters used in encrypt(), see the note there.
// TODO: We should put our own salt into the HKDF derivation to avoid this dependency on phpseclib's defaults!
$this->cipher->setPassword($encryptionKey, 'pbkdf2', 'sha1', 'phpseclib');
$this->setCipherPassword($encryptionKey);
$this->cipher->setIV($iv);

if ($isOwnCloudV2Migration) {
Expand All @@ -200,6 +195,21 @@ private function decryptWithoutSecret(string $authenticatedCiphertext, string $p
return $result;
}

private function setCipherPassword(#[SensitiveParameter] string $password): void {
// Keep only one fingerprint; the derived key remains in the cipher.
$passwordHash = hash('sha256', $password, true);
if ($this->cipherPasswordHash !== null && hash_equals($this->cipherPasswordHash, $passwordHash)) {
return;
}

// Pin the PBKDF2 parameters to phpseclib v2 defaults ('sha1' hash, 'phpseclib' salt).
// phpseclib v3 changed the default salt to 'phpseclib/salt', which would derive a
// different AES key and break decryption of previously stored ciphertexts.
// TODO: We should put our own salt into the HKDF derivation to avoid this dependency on phpseclib's defaults!
$this->cipher->setPassword($password, 'pbkdf2', 'sha1', 'phpseclib');
$this->cipherPasswordHash = $passwordHash;
}

private function hex2bin(string $hex): string {
if (!ctype_xdigit($hex)) {
throw new \RuntimeException('String contains non hex chars: ' . $hex);
Expand Down
123 changes: 123 additions & 0 deletions tests/lib/Security/CryptoTest.php
View file
Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -13,6 +13,7 @@
use OC\Security\Crypto;
use OCP\IConfig;
use OCP\Server;
use phpseclib3\Crypt\AES;

class CryptoTest extends \Test\TestCase {
public static function defaultEncryptionProvider(): array {
Expand Down Expand Up @@ -129,4 +130,126 @@ public function testVersion3CiphertextDecryptsToCorrectPlaintext(): void {
)
);
}

public static function consecutivePasswordProvider(): array {
return [[''], ['explicit-password']];
}

#[\PHPUnit\Framework\Attributes\DataProvider('consecutivePasswordProvider')]
public function testDecryptConsecutiveFieldsDerivesKeyOnce(string $password): void {
$writer = $this->createCryptoWithDerivationCount(1);
$ciphertexts = [];
for ($field = 0; $field < 6; $field++) {
$ciphertexts[] = $writer->encrypt('field ' . $field, $password);
}

$reader = $this->createCryptoWithDerivationCount(1);
foreach ($ciphertexts as $field => $ciphertext) {
$this->assertSame('field ' . $field, $reader->decrypt($ciphertext, $password));
}
}

public function testAlternatingPasswordsDeriveAgain(): void {
$first = $this->crypto->encrypt('first', 'password-A');
$second = $this->crypto->encrypt('second', 'password-B');
$reader = $this->createCryptoWithDerivationCount(3);

$this->assertSame('first', $reader->decrypt($first, 'password-A'));
$this->assertSame('second', $reader->decrypt($second, 'password-B'));
$this->assertSame('first', $reader->decrypt($first, 'password-A'));
}

public function testAlternatingEncryptDecryptKeepsCurrentKeyAndRefreshesIv(): void {
$crypto = $this->createCryptoWithDerivationCount(1);
$ivs = [];
for ($field = 0; $field < 6; $field++) {
$ciphertext = $crypto->encrypt('same plaintext', 'same-password');
$ivs[] = explode('|', $ciphertext)[1];
$this->assertSame('same plaintext', $crypto->decrypt($ciphertext, 'same-password'));
}
$this->assertCount(6, array_unique($ivs));
}

public function testLegacyAndVersion3DeriveDifferentKeys(): void {
$legacy = 'e16599188e3d212f5c7f17fdc2abca46|M1WfLAxbcAmITeD6|509457885d6ca5e6c3bfd3741852687a7f2bffce197f8d5ae97b65818b15a1b7f616b68326ff312371540f4ca8ac55f8e2de4aa13aab3474bd3431e51214e3ee';
$current = $this->crypto->encrypt('current', 'mypass');
$reader = $this->createCryptoWithDerivationCount(3);

$this->assertSame('current', $reader->decrypt($current, 'mypass'));
$this->assertSame('legacy test', $reader->decrypt($legacy, 'mypass'));
$this->assertSame('current', $reader->decrypt($current, 'mypass'));
}

public function testReusedKeyStillRejectsTamperedCiphertextIvAndHmac(): void {
$ciphertext = $this->crypto->encrypt('plaintext', 'password');
$reader = $this->createCryptoWithDerivationCount(1);
$this->assertSame('plaintext', $reader->decrypt($ciphertext, 'password'));

foreach ([0, 1, 2] as $part) {
$parts = explode('|', $ciphertext);
$parts[$part][0] = $parts[$part][0] === '0' ? '1' : '0';
try {
$reader->decrypt(implode('|', $parts), 'password');
$this->fail('Tampered ciphertext was accepted');
} catch (\RuntimeException $e) {
$this->assertSame('HMAC does not match.', $e->getMessage());
}
$this->assertSame('plaintext', $reader->decrypt($ciphertext, 'password'));
}
}

public function testWrongPasswordDoesNotPoisonKeyReuse(): void {
$ciphertext = $this->crypto->encrypt('plaintext', 'password');
$reader = $this->createCryptoWithDerivationCount(3);
$this->assertSame('plaintext', $reader->decrypt($ciphertext, 'password'));
try {
$reader->decrypt($ciphertext, 'wrong-password');
$this->fail('Wrong password was accepted');
} catch (\RuntimeException $e) {
$this->assertSame('HMAC does not match.', $e->getMessage());
}
$this->assertSame('plaintext', $reader->decrypt($ciphertext, 'password'));
}

public function testChangedDefaultSecretDerivesAgain(): void {
$first = $this->crypto->encrypt('first', 'secret-A');
$second = $this->crypto->encrypt('second', 'secret-B');
$config = $this->createMock(IConfig::class);
$config->method('getSystemValue')->with('secret')->willReturnOnConsecutiveCalls('secret-A', 'secret-B');
$reader = $this->createCryptoWithDerivationCount(2, $config);

$this->assertSame('first', $reader->decrypt($first));
$this->assertSame('second', $reader->decrypt($second));
}

public function testLegacyEmptySecretFallbackCanReplaceTheCurrentKey(): void {
$reader = $this->createCryptoWithDerivationCount(2);
$cipher = new AES('cbc');
$cipher->setPassword('', 'pbkdf2', 'sha1', 'phpseclib');
$iv = str_repeat("\0", 16);
$cipher->setIV($iv);
$ciphertext = bin2hex($cipher->encrypt('empty-key fixture'));
$iv = bin2hex($iv);
$hmac = bin2hex($reader->calculateHMAC($ciphertext . $iv, 'configured-secret'));

$this->assertSame('empty-key fixture', $reader->decrypt($ciphertext . '|' . $iv . '|' . $hmac . '|2'));
}

private function createCryptoWithDerivationCount(int $count, ?IConfig $config = null): Crypto {
if ($config === null) {
$config = $this->createMock(IConfig::class);
$config->method('getSystemValue')->with('secret')->willReturn('configured-secret');
$config->method('getSystemValueString')->with('secret')->willReturn('configured-secret');
}
$crypto = new Crypto($config);
$cipher = $this->getMockBuilder(AES::class)
->setConstructorArgs(['cbc'])
->onlyMethods(['setPassword'])
->getMock();
$cipher->expects($this->exactly($count))
->method('setPassword')
->willReturnCallback(fn (...$parameters) => (new \ReflectionMethod(AES::class, 'setPassword'))->invokeArgs($cipher, $parameters));
$this->invokePrivate($crypto, 'cipher', [$cipher]);
return $crypto;
}
}