From 9687febed7fba22ef749e9530d531101bb64e07f Mon Sep 17 00:00:00 2001
From: Roeland Jago Douma <roeland@famdouma.nl>
Date: Wed, 29 Jan 2020 21:39:58 +0100
Subject: [PATCH] Allow selecting the hashing algorithm

Signed-off-by: Roeland Jago Douma <roeland@famdouma.nl>
---
 config/config.sample.php          | 10 +++++
 lib/private/Security/Hasher.php   | 38 ++++++++++++------
 tests/lib/Security/HasherTest.php | 65 ++++++++++++++++++++++++++++++-
 3 files changed, 100 insertions(+), 13 deletions(-)

diff --git a/config/config.sample.php b/config/config.sample.php
index e2d0b2b54a6..4e83563b09e 100644
--- a/config/config.sample.php
+++ b/config/config.sample.php
@@ -1435,6 +1435,16 @@ $CONFIG = array(
 
 /**
  * Hashing
+ */
+
+/**
+ * By default Nextcloud will use the Argon2 password hashing if available.
+ * However if for whatever reason you want to stick with the PASSWORD_DEFAULT
+ * of your php version. Then set the setting to true.
+ */
+'hashing_default_password' => false,
+
+/**
  *
  * Nextcloud uses the Argon2 algorithm (with PHP >= 7.2) to create hashes by its
  * own and exposes its configuration options as following. More information can
diff --git a/lib/private/Security/Hasher.php b/lib/private/Security/Hasher.php
index 5f8529c7828..882f80ea2bf 100644
--- a/lib/private/Security/Hasher.php
+++ b/lib/private/Security/Hasher.php
@@ -92,11 +92,13 @@ class Hasher implements IHasher {
 	 * @return string Hash of the message with appended version parameter
 	 */
 	public function hash(string $message): string {
-		if (\defined('PASSWORD_ARGON2I')) {
+		$alg = $this->getPrefferedAlgorithm();
+
+		if (\defined('PASSWORD_ARGON2I') && $alg === PASSWORD_ARGON2I) {
 			return 2 . '|' . password_hash($message, PASSWORD_ARGON2I, $this->options);
-		} else {
-			return 1 . '|' . password_hash($message, PASSWORD_BCRYPT, $this->options);
 		}
+
+		return 1 . '|' . password_hash($message, PASSWORD_BCRYPT, $this->options);
 	}
 
 	/**
@@ -147,12 +149,7 @@ class Hasher implements IHasher {
 	 */
 	protected function verifyHashV1(string $message, string $hash, &$newHash = null): bool {
 		if(password_verify($message, $hash)) {
-			$algo = PASSWORD_BCRYPT;
-			if (\defined('PASSWORD_ARGON2I')) {
-				$algo = PASSWORD_ARGON2I;
-			}
-
-			if(password_needs_rehash($hash, $algo, $this->options)) {
+			if ($this->needsRehash($hash)) {
 				$newHash = $this->hash($message);
 			}
 			return true;
@@ -170,7 +167,7 @@ class Hasher implements IHasher {
 	 */
 	protected function verifyHashV2(string $message, string $hash, &$newHash = null) : bool {
 		if(password_verify($message, $hash)) {
-			if(password_needs_rehash($hash, PASSWORD_ARGON2I, $this->options)) {
+			if($this->needsRehash($hash)) {
 				$newHash = $this->hash($message);
 			}
 			return true;
@@ -199,8 +196,27 @@ class Hasher implements IHasher {
 			return $this->legacyHashVerify($message, $hash, $newHash);
 		}
 
-
 		return false;
 	}
 
+	private function needsRehash(string $hash): bool {
+		$algorithm = $this->getPrefferedAlgorithm();
+
+		return password_needs_rehash($hash, $algorithm, $this->options);
+	}
+
+	private function getPrefferedAlgorithm() {
+		$default = PASSWORD_BCRYPT;
+		if (\defined('PASSWORD_ARGON2I')) {
+			$default = PASSWORD_ARGON2I;
+		}
+
+		// Check if we should use PASSWORD_DEFAULT
+		if ($this->config->getSystemValue('hashing_default_password', false) === true) {
+			$default = PASSWORD_DEFAULT;
+		}
+
+		return $default;
+	}
+
 }
diff --git a/tests/lib/Security/HasherTest.php b/tests/lib/Security/HasherTest.php
index 3222b5d0984..e680efb19b6 100644
--- a/tests/lib/Security/HasherTest.php
+++ b/tests/lib/Security/HasherTest.php
@@ -126,8 +126,12 @@ class HasherTest extends \Test\TestCase {
 		$this->config
 			->expects($this->any())
 			->method('getSystemValue')
-			->with('passwordsalt', null)
-			->will($this->returnValue('6Wow67q1wZQZpUUeI6G2LsWUu4XKx'));
+			->willReturnCallback(function ($key, $default) {
+				if($key === 'passwordsalt') {
+					return '6Wow67q1wZQZpUUeI6G2LsWUu4XKx';
+				}
+				return $default;
+			});
 
 		$result = $this->hasher->verify($password, $hash);
 		$this->assertSame($expected, $result);
@@ -162,4 +166,61 @@ class HasherTest extends \Test\TestCase {
 
 		$this->assertFalse(password_needs_rehash($relativePath['hash'], PASSWORD_ARGON2I, []));
 	}
+
+	public function testUsePasswordDefaultArgon2iVerify() {
+		if (!\defined('PASSWORD_ARGON2I')) {
+			$this->markTestSkipped('Need ARGON2 support to test ARGON2 hashes');
+		}
+
+		$this->config->method('getSystemValue')
+			->with('hashing_default_password')
+			->willReturn(true);
+
+		$message = 'mysecret';
+
+		$argon2i  = 2 . '|' . password_hash($message, PASSWORD_ARGON2I, []);
+
+		$newHash = null;
+		$this->assertTrue($this->hasher->verify($message, $argon2i, $newHash));
+		$this->assertNotNull($newHash);
+	}
+
+	public function testDoNotUserPasswordDefaultArgon2iVerify() {
+		if (!\defined('PASSWORD_ARGON2I')) {
+			$this->markTestSkipped('Need ARGON2 support to test ARGON2 hashes');
+		}
+
+		$this->config->method('getSystemValue')
+			->with('hashing_default_password')
+			->willReturn(false);
+
+		$message = 'mysecret';
+
+		$argon2i  = 2 . '|' . password_hash($message, PASSWORD_ARGON2I, []);
+
+		$newHash = null;
+		$this->assertTrue($this->hasher->verify($message, $argon2i, $newHash));
+		$this->assertNull($newHash);
+	}
+
+	public function testHashUsePasswordDefault() {
+		if (!\defined('PASSWORD_ARGON2I')) {
+			$this->markTestSkipped('Need ARGON2 support to test ARGON2 hashes');
+		}
+
+		$this->config->method('getSystemValue')
+			->with('hashing_default_password')
+			->willReturn(true);
+
+		$message = 'mysecret';
+
+		$hash = $this->hasher->hash($message);
+		$relativePath = self::invokePrivate($this->hasher, 'splitHash', [$hash]);
+
+		$this->assertSame(1, $relativePath['version']);
+
+		$info = password_get_info($relativePath['hash']);
+		$this->assertEquals(PASSWORD_BCRYPT, $info['algo']);
+
+	}
 }
-- 
2.39.5