First 2 challenges from 247ctf

.gitignore

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+*.zip
+*.tar.gz
+*.tar
+*.bin
+*.exe
+*.jpg
+*.enc
+*.png
+*.gif

247ctf/beginner_tutorial/tips_and_tricks/addition.py

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+#!/usr/bin/python
+import pwn
+import re
+import time
+
+r = pwn.remote('0c2450d17014ac4e.247ctf.com', 50319)
+
+while not r.can_recv(0):
+    time.sleep(0.5)
+
+# can be substituted by True to speed up the process (:
+while r.can_recv(0):
+    answ = r.recvline().decode('utf-8')
+    ns = re.findall("\d{1,4}", answ)
+    if len(ns) == 2:
+        sum = int(ns[0]) + int(ns[1])
+        ans = bytes(str(sum) + '\r\n', 'utf-8')
+        r.send(ans)
+        time.sleep(0.05)
+    else:
+        print(answ)

247ctf/cryptography/my_magic_bytes/xor.py

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+#!/bin/python
+# JPEG (JFIF) has the following header: FF D8 FF E0 00 10 4A 46 49 46 00 01
+correct_header = [0xff, 0xd8, 0xff, 0xe0, 0x00, 0x10, 0x4a, 0x46, 0x49, 0x46, 0x00, 0x01]
+# The file we got has this header: (Inspected using xxd / emacs hexl-mode)
+# false_header = [0xb9, 0x14, 0x06, 0x45, 0x71, 0xe0, 0xb5, 0xf7, 0x37, 0x07, 0xcb, 0x85]
+
+# A: Correct header, B: Wrong header, X: de/encryption key
+# Get the XOR key to decrypt the file (A ^ X = B => X = A ^ B)
+xor = []
+with open("my_magic_bytes.jpg.enc", "rb") as f:
+    for i in range(len(correct_header)):
+        xor.append(correct_header[i] ^ int(f.read(1).hex(), 16))
+
+# read binary data from file, write xored binary data to file
+i = 0
+with open("my_magic_bytes.jpg.enc", "rb") as f, open("mep.jpg", "wb") as o:
+    while (cb := f.read(1)):
+        xored = int(cb.hex(), 16) ^ xor[i]
+        o.write(bytes([xored]))
+        i = (i + 1) % len(xor)
+
+# FLAG: 247CTF{ca4e3b7f913ca7ca8f33fb0504f2947f}