bug #34738 [SecurityBundle] Passwords are not encoded when algorithm …

…set to "true" (nieuwenhuisen)

This PR was merged into the 3.4 branch.

Discussion
----------

[SecurityBundle] Passwords are not encoded when algorithm set to "true"

| Q             | A
| ------------- | ---
| Branch?       | 3.4
| Bug fix?      | yes
| New feature?  | no
| Deprecations? | no
| Tickets       | Fix #34725
| License       | MIT
| Doc PR        | -

If the algorithm is set to `true`, password will be encode as plain password.

```
security:
    encoders:
        App\User\User:
            algorithm: true
```

The reason for this is the not strict comparison of php switches.

```
switch ($config['algorithm']) {
            case 'plaintext':
}
```

`true == 'plaintext'` is `true`, so the first case is hit. My first solution was to cast the algorithm to a string, to prevent this. After some feedback I have catch this problem earlier and does not allow true as valid value to the algorithm option.

Ps. This is my first PR for Symfony, any feedback is welcome :-)!

Commits
-------

83a5517 [SecurityBundle] Passwords are not encoded when algorithm set to \"true\"

src/Symfony/Bundle/SecurityBundle/DependencyInjection/MainConfiguration.php

@@ -421,7 +421,13 @@ private function addEncodersSection(ArrayNodeDefinition $rootNode)
                         ->performNoDeepMerging()
                         ->beforeNormalization()->ifString()->then(function ($v) { return ['algorithm' => $v]; })->end()
                         ->children()
-                            ->scalarNode('algorithm')->cannotBeEmpty()->end()
+                            ->scalarNode('algorithm')
+                                ->cannotBeEmpty()
+                                ->validate()
+                                    ->ifTrue(function ($v) { return !\is_string($v); })
+                                    ->thenInvalid('You must provide a string value.')
+                                ->end()
+                            ->end()
                             ->scalarNode('hash_algorithm')->info('Name of hashing algorithm for PBKDF2 (i.e. sha256, sha512, etc..) See hash_algos() for a list of supported algorithms.')->defaultValue('sha512')->end()
                             ->scalarNode('key_length')->defaultValue(40)->end()
                             ->booleanNode('ignore_case')->defaultFalse()->end()