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# Basic Ruby Server-Side Template Injection
Basic Ruby Server-Side Template Injection notes for PortSwigger Web Security Academy labs, including exploitation workflow, payload testing, Burp Suite validation, and remediation context.
### Basic Server-side Template Injection
The application uses ERB templates unsecured, making it vulnerable to a **Server-Side Template Injection (SSTI)**./ The objective is to execute arbitrary code for **delete file** `morale.txt` located in Carlos' home:/ `/home/carlos/morale.txt`.
#### 1. Identification of the Vulnerable Parameter
We find a `message` parameter in the application that **reflects our input** directly in the page. / This field will be used to inject ERB code.
#### 2. Check Code Execution (test with 7/\*7)
A simple Ruby expression is injected to confirm the SSTI:
```ruby
<%= 7*7 %>
```
If vulnerability is present, the output will display:
This proves that Ruby expression is evaluated in the server-side template.
#### 3. Read a Sensitive File: `/etc/passwd`
Once the execution is confirmed, try to read a system file to validate access to the file system:
```ruby
<%= File.open('/etc/passwd').read %>
```
The content of `/etc/passwd` is then returned in the answer, confirming that you can read files on the server.
#### 4. Delete Carlos `morale.txt` File
To finalize the lab, run a system command to delete the requested file:
```ruby
<%= system('rm /home/carlos/morale.txt') %>
```
This injection starts the `rm` server-side command and removes the `morale.txt` file in the `/home/carlos/` directory.
---
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