Fix division by zero

tvlooy · tvlooy · commit dfcea361da66 · 2022-05-10T16:20:30.000+02:00
diff --git a/src/Symfony/Component/Security/Csrf/CsrfTokenManager.php b/src/Symfony/Component/Security/Csrf/CsrfTokenManager.php
@@ -136,6 +136,10 @@ private function derandomize(string $value): string
         $key = base64_decode(strtr($parts[1], '-_', '+/'));
         $value = base64_decode(strtr($parts[2], '-_', '+/'));
 
+        if (!$key || !$value) {
+            return '';
+        }
+
         return $this->xor($value, $key);
     }
 
diff --git a/src/Symfony/Component/Security/Csrf/Tests/CsrfTokenManagerTest.php b/src/Symfony/Component/Security/Csrf/Tests/CsrfTokenManagerTest.php
@@ -193,6 +193,26 @@ public function testNonExistingTokenIsNotValid($namespace, $manager, $storage)
         $this->assertFalse($manager->isTokenValid(new CsrfToken('token_id', 'FOOBAR')));
     }
 
+    public function testTokenShouldNotTriggerDivisionByZero()
+    {
+        [$generator, $storage] = $this->getGeneratorAndStorage();
+        $manager = new CsrfTokenManager($generator, $storage);
+
+        // Scenario: the token that was returned is abc.def.ghi, and gets modified in the browser to abc..ghi
+
+        $storage->expects($this->once())
+            ->method('hasToken')
+            ->with('https-token_id')
+            ->willReturn(true);
+
+        $storage->expects($this->once())
+            ->method('getToken')
+            ->with('https-token_id')
+            ->willReturn('def');
+
+        $this->assertFalse($manager->isTokenValid(new CsrfToken('token_id', 'abc..ghi')));
+    }
+
     /**
      * @dataProvider getManagerGeneratorAndStorage
      */

Original file line number	Diff line number	Diff line change
`@@ -136,6 +136,10 @@ private function derandomize(string $value): string`
`136`	`136`	`$key = base64_decode(strtr($parts[1], '-_', '+/'));`
`137`	`137`	`$value = base64_decode(strtr($parts[2], '-_', '+/'));`
`138`	`138`
	`139`	`+ if (!$key \|\| !$value) {`
	`140`	`+ return '';`
	`141`	`+ }`
	`142`	`+`
`139`	`143`	`return $this->xor($value, $key);`
`140`	`144`	`}`
`141`	`145`