Update challenges for simple challenge image

hello/apple/apple

@@ -1,4 +1,4 @@
-#!/opt/pwn.college/python
+#!/usr/bin/exec-suid -- /usr/local/bin/python -I
 
 with open("/flag") as f:
     print(f.read())

hello/banana/banana

@@ -1,4 +1,4 @@
-#!/opt/pwn.college/python
+#!/usr/bin/exec-suid -- /usr/local/bin/python -I
 
 import pathlib
 

world/earth/.init

@@ -1,4 +1,4 @@
-#!/opt/pwn.college/python
+#!/usr/local/bin/python
 
 import pathlib
 

world/earth/earth

@@ -1,4 +1,4 @@
-#!/opt/pwn.college/python
+#!/usr/bin/exec-suid -- /usr/local/bin/python -I
 
 with open("/flag") as f:
     print(f.read())

world/mars/orbit

@@ -1,4 +1,4 @@
-#!/opt/pwn.college/python
+#!/usr/bin/exec-suid -- /usr/local/bin/python -I
 
 import pathlib
 import random

world/venus/.init

@@ -1,22 +1,21 @@
-#!/opt/pwn.college/python
+#!/usr/local/bin/python
 
 import pathlib
 import random
-
-import jinja2
+import string
 
 with open("/flag") as f:
     random.seed(f.read())
 
 init_path = pathlib.Path(__file__)
 planets_path = (pathlib.Path(__file__).parent / "planets.txt")
 launch_path = (pathlib.Path(__file__).parent / "launch")
-launch_template_path = (pathlib.Path(__file__).parent / "launch.j2")
+launch_template_path = (pathlib.Path(__file__).parent / "launch.template")
 
 planet = random.choice(planets_path.read_text().strip().splitlines())
 
-template = jinja2.Template(launch_template_path)
-launch_path.write_text(template.render(planet=planet))
+template = string.Template(launch_template_path.read_text())
+launch_path.write_text(template.safe_substitute(planet=planet))
 
 launch_template_path.unlink()
 planets_path.unlink()

world/venus/README.md

@@ -9,9 +9,9 @@ When users start this challenge, their environment will have:
 - `/challenge/launch`
 
 In this challenge, `takeoff` is a statically instanced file.
-There is also files `.init`, `planets.txt`, and `launch.j2` which students will never see.
-At run time, `.init` reads in `planets.txt` to construct `launch` from the templated file `launch.j2`.
+There is also files `.init`, `planets.txt`, and `launch.template` which students will never see.
+At run time, `.init` reads in `planets.txt` to construct `launch` from the templated file `launch.template`.
 This gives the challenge static instancing dependent upon the flag.
 In general, it is best to define a pool of static instanced files prior, so that this setup does not need to be performed at runtime every challenge start.
 However, for simple cases, this may be acceptable.
-It is important to note, however, that the results of these static instances are still dependent upon the flag, which means running the challenge with a different flag (e.g. with a practice flag), will fundamentally change the instance.
+It is important to note, however, that the results of these static instances are still dependent upon the flag, which means running the challenge with a different flag (e.g. with a practice flag), will change the behavior of the instance.

world/venus/launch.template

@@ -0,0 +1,8 @@
+#!/usr/bin/exec-suid -- /usr/local/bin/python -I
+
+import subprocess
+
+subprocess.run(["/challenge/takeoff", "${planet}"])
+
+with open("/flag") as f:
+    print(f.read())