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psalm/docs/running_psalm/issues/TaintedSSRF.md
2020-11-18 00:52:48 -05:00

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# TaintedSSRF
Potential Server-Side Request Forgery vulnerability. This rule is emitted when user-controlled input can be passed into a network request.
## Risk
Passing untrusted user input to network requests could be dangerous.
If an attacker can fully control a HTTP request they could connect to internal services. Depending on the nature of these, this can pose a security risk. (e.g. backend services, admin interfaces, AWS metadata, ...)
## Example
```php
<?php
$ch = curl_init();
curl_setopt($ch, CURLOPT_URL, $_GET['url']);
curl_exec($ch);
curl_close($ch);
```
## Mitigations
Mitigating SSRF vulnerabilities can be tricky. Disallowing IPs would likely not work as an attacker could create a malicious domain that points to an internal DNS name.
Consider:
1. Having an allow list of domains that can be connected to.
2. Pointing cURL to a proxy that has no access to internal resources.
## Further resources
- [OWASP Wiki for Server Side Request Forgery](https://owasp.org/www-community/attacks/Server_Side_Request_Forgery)
- [CWE-918](https://cwe.mitre.org/data/definitions/918)