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psalm/docs/running_psalm/issues/TaintedHeader.md
Lukas Reschke 78f4a0691c
Add dedicated types for 'file', 'header' and 'cookie' (#4630)
* [WIP] Add dedicated sinks for 'file', 'header' and 'cookie'

* Add documentation

* Add mapping for taint flows

* Add tests

* Fix test
2020-11-19 17:47:29 -05:00

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# TaintedHeader
Potential header injection. This rule is emitted when user-controlled input can be passed into a HTTP header.
## Risk
The risk of a header injection depends hugely on your environment.
If your webserver supports something like [`XSendFile`](https://www.nginx.com/resources/wiki/start/topics/examples/xsendfile/) / [`X-Accel`](https://www.nginx.com/resources/wiki/start/topics/examples/x-accel/), an attacker could potentially access arbitrary files on the systems.
If your system does not do that, there may be other concerns, such as:
- Cookie Injection
- Open Redirects
- Proxy Cache Poisoning
## Example
```php
<?php
header($_GET['header']);
```
## Mitigations
Make sure only the value and not the key can be set by an attacker. (e.g. `header('Location: ' . $_GET['target']);`)
Verify the set values are sensible. Consider using an allow list. (e.g. for redirections)
## Further resources
- [Unvalidated Redirects and Forwards Cheat Sheet](https://cheatsheetseries.owasp.org/cheatsheets/Unvalidated_Redirects_and_Forwards_Cheat_Sheet.html)
- [OWASP Wiki for Cache Poisoning](https://owasp.org/www-community/attacks/Cache_Poisoning)
- [CWE-601](https://cwe.mitre.org/data/definitions/601.html)
- [CWE-644](https://cwe.mitre.org/data/definitions/644.html)