Solution to Sunshine CTF 2019's Entry Exam challenge.

entryExam.py

from PIL import Image, ImageDraw
from io import BytesIO
from math import floor
import requests as rq
import time

filepath = "/home/george/"
questionUrl = "http://archive.sunshinectf.org:19005/exam"

x1 = 337
y1 = 435
yOffset = 90.5
xOffset = 68
xJump = 490
size = 50

session = rq.Session()

def fillForm(question, answer):
    answer = list("ABCDE").index(answer)
    question = question - 1
    if question <= 9:
        drawScantron.ellipse((x1+(answer*xOffset), y1+(question*yOffset), x1+size+(answer*xOffset), y1+size+(question*yOffset)), fill=0, outline=0)
    else:
        question -= 10
        drawScantron.ellipse((x1+(answer*xOffset)+xJump, y1+(question*yOffset), x1+size+(answer*xOffset)+xJump, y1+size+(question*yOffset)), fill=0, outline=0)


while True:
    scantron = Image.open(filepath+"scantron.png")
    drawScantron = ImageDraw.Draw(scantron)
    start = time.time() #Start timer
    questions = session.get(questionUrl).text.split("\n")[1:] #Get questions from page
    for i in range(20):
        question = questions[i*7][4:-5] #Get question from HTML
        answerNumber = floor(eval(question)) #Eval question to get answer
        answerChoices = [z[4:-5] for z in questions[i*7+2:i*7+2+4]] #Get possible answers
        answerPosition = answerChoices.index(str(answerNumber)) #Get position of our answer in given answers
        answerLetter = list("ABCDE")[answerPosition] #Translate position to number
        fillForm(i+1, answerLetter) #Draw to scantron

    imgByteArr = BytesIO()
    scantron.save(imgByteArr, format='PNG')
    imgByteArr = imgByteArr.getvalue()
    files = {'file': imgByteArr}
    resp = session.post(questionUrl, files=files)
    end = time.time()
    scantron.close()

    print(resp.text)
    if "sun" in resp.text.lower:
        break
    print(f"{len(resp.text)} : {end - start}")