Merge pull request #23496 from lynn-stephenson/fix/related-key-issue

Fixes related key issue.

2 files changed, 35 insertions, 7 deletions

diff --git a/lib/private/Security/Crypto.php b/lib/private/Security/Crypto.php
index 154448281b9..35add2dc649 100644
--- a/lib/private/Security/Crypto.php
+++ b/lib/private/Security/Crypto.php
@@ -10,6 +10,7 @@ declare(strict_types=1);
  * @author Lukas Reschke <lukas@statuscode.ch>
  * @author Morris Jobke <hey@morrisjobke.de>
  * @author Roeland Jago Douma <roeland@famdouma.nl>
+ * @author Lynn Stephenson <lynn.stephenson@protonmail.com>
  *
  * @license AGPL-3.0
  *
@@ -90,16 +91,17 @@ class Crypto implements ICrypto {
 		if ($password === '') {
 			$password = $this->config->getSystemValue('secret');
 		}
-		$this->cipher->setPassword($password);
+		$keyMaterial = hash_hkdf('sha512', $password);
+		$this->cipher->setPassword(substr($keyMaterial, 0, 32));
 
 		$iv = \random_bytes($this->ivLength);
 		$this->cipher->setIV($iv);
 
 		$ciphertext = bin2hex($this->cipher->encrypt($plaintext));
 		$iv = bin2hex($iv);
-		$hmac = bin2hex($this->calculateHMAC($ciphertext.$iv, $password));
+		$hmac = bin2hex($this->calculateHMAC($ciphertext.$iv, substr($keyMaterial, 32)));
 
-		return $ciphertext.'|'.$iv.'|'.$hmac.'|2';
+		return $ciphertext.'|'.$iv.'|'.$hmac.'|3';
 	}
 
 	/**
@@ -114,7 +116,7 @@ class Crypto implements ICrypto {
 		if ($password === '') {
 			$password = $this->config->getSystemValue('secret');
 		}
-		$this->cipher->setPassword($password);
+		$hmacKey = $encryptionKey = $password;
 
 		$parts = explode('|', $authenticatedCiphertext);
 		$partCount = \count($parts);
@@ -128,14 +130,20 @@ class Crypto implements ICrypto {
 
 		if ($partCount === 4) {
 			$version = $parts[3];
-			if ($version === '2') {
+			if ($version >= '2') {
 				$iv = hex2bin($iv);
 			}
-		}
 
+			if ($version === '3') {
+				$keyMaterial = hash_hkdf('sha512', $password);
+				$encryptionKey = substr($keyMaterial, 0, 32);
+				$hmacKey = substr($keyMaterial, 32);
+			}
+		}
+		$this->cipher->setPassword($encryptionKey);
 		$this->cipher->setIV($iv);
 
-		if (!hash_equals($this->calculateHMAC($parts[0] . $parts[1], $password), $hmac)) {
+		if (!hash_equals($this->calculateHMAC($parts[0] . $parts[1], $hmacKey), $hmac)) {
 			throw new \Exception('HMAC does not match.');
 		}
 
diff --git a/tests/lib/Security/CryptoTest.php b/tests/lib/Security/CryptoTest.php
index dbdf6f6a195..0c7c1aa1ac7 100644
--- a/tests/lib/Security/CryptoTest.php
+++ b/tests/lib/Security/CryptoTest.php
@@ -75,4 +75,24 @@ class CryptoTest extends \Test\TestCase {
 
 		$this->assertSame('legacy test', $this->crypto->decrypt($cipherText, $password));
 	}
+
+	public function testVersion2CiphertextDecryptsToCorrectPlaintext() {
+		$this->assertSame(
+			'This is a plaintext value that will be encrypted with version 2. Which addresses the reduced permutations on the IV.',
+			$this->crypto->decrypt(
+				'be006387f753e8728717e43cfc5526c37adf7b2c9b4a113ceec03b7b0bccfebee74e0acfa0015c5712b4376dacbd7bce26a8fbca916fdccee46203d8289f6b2e4c19318044d375edfc67c72e6c3ae329d4c276b8d866ac1b281844e81f7681fe83d90bc4b6fffa4f3cbc157d64257a493b67fd2af3c8976cb76df520f5739305|02e78ea7c73a32f3b407c54227a9d2ce|3e7a09628f818b7b1cd7724467f5b1b33135de6d2ec62d8c0361be4f2c5203385f10babdcae017d7b30abe5be2117803e3195fb6d9ef20949fe35dad5e9241ea|2',
+				'insecure-static-password'
+			)
+		);
+	}
+
+	public function testVersion3CiphertextDecryptsToCorrectPlaintext() {
+		$this->assertSame(
+			'Another plaintext value that will be encrypted with version 3. It addresses the related key issue. Old ciphertexts should be decrypted properly, but only use the better version for encryption.',
+			$this->crypto->decrypt(
+				'c99823461db746aa74f819c8640e9e3c367fa3bb9c21dff905b5dd14072c1d1b0da8b7e6b7307bf1561b6ba7aaa932a16c23b1fd5217dc019d55233ef0813c65fccaeabd6ea3a971ce1bbbdfda790ae00fb4442693cbb50072e02875b9f50591df74d00e96fd5b9bd13cb02a5f57b062ec98a4c64fc518ed325d097454883adbfc1687c2af995a392407c5e040a54afee4b2997ab158fe48ef67ccf721a6a7031fcb44d51170892ce7971021a7f3a00d19002eb9b007efe7aecf397ec0dc22064fb5d4a15ad83949f0804feca3c69cdd|8476f53c8d49a7e119798a70086d8911|ae3f7e23d469fbc791714ceb07d854624b1bbd39ac6a4edc05d552e10659adfdcada3a059fae737ffd7d842dd3fcc84bcc364cd298e814dd4967de4ad4a658eb|3',
+				'insecure-static-password'
+			)
+		);
+	}
 }