# PHP SSRF

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### SSRF PHP functions

Some function such as **file_get_contents(), fopen(), file(), md5_file()** accept URLs as input that they will follow making **possible SSRF vulnerabilities** if the use can control the data:

```php
file_get_contents("http://127.0.0.1:8081");
fopen("http://127.0.0.1:8081", "r");
file("http://127.0.0.1:8081");
md5_file("http://127.0.0.1:8081");
```

### Wordpress SSRF via DNS Rebinding

As [**explained in this blog post**](https://patchstack.com/articles/exploring-the-unpatched-wordpress-ssrf), even the Wordpress function **`wp_safe_remote_get`** is vulnerable to DNS rebinding, making it potentially vulnerable to SSRF attacks. The main validation it calls is **wp_http_validate_ur**l, which checks that the protocol is `http://` or `https://` and that the port is one of **80**, **443**, and **8080**, but it's **vulnerable to DNS rebinding**.

Other vulnerable functions according to the post are:

- `wp_safe_remote_request()`
- `wp_safe_remote_post()`
- `wp_safe_remote_head()`
- `WP_REST_URL_Details_Controller::get_remote_url()`
- `download_url()`
- `wp_remote_fopen()`
- `WP_oEmbed::discover()`

### CRLF

Moreover, in some cases it might be even possible to send arbitrary headers via CRLF "vulnerabilities" in the previous functions:

```php
# The following will create a header called from with value Hi and
# an extra header "Injected: I HAVE IT"
ini_set("from", "Hi\r\nInjected: I HAVE IT");
file_get_contents("http://127.0.0.1:8081");

GET / HTTP/1.1
From: Hi
Injected: I HAVE IT
Host: 127.0.0.1:8081
Connection: close

# Any of the previously mentioned functions will send those headers
```

> [!WARNING]
> For more info about that CRLF vuln, check this bug [https://bugs.php.net/bug.php?id=81680\&edit=1](https://bugs.php.net/bug.php?id=81680&edit=1)

Note that these function might have other methods to set arbitrary headers in requests, like:

```php
$url = "";

$options = array(
  'http'=>array(
    'method'=>"GET",
    'header'=>"Accept-language: en\r\n" .
              "Cookie: foo=bar\r\n" .  // check function.stream-context-create on php.net
              "User-Agent: Mozilla/5.0 (iPad; U; CPU OS 3_2 like Mac OS X; en-us) AppleWebKit/531.21.10 (KHTML, like Gecko) Version/4.0.4 Mobile/7B334b Safari/531.21.102011-10-16 20:23:10\r\n" // i.e. An iPad
  )
);

$context = stream_context_create($options);
$file = file_get_contents($url, false, $context);
```

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