ALL the CTFS of Crypto2025 finally

crypto-simmetric/forge-a-cookie/attack.py

@@ -0,0 +1,58 @@
+#!/usr/bin/env python3
+from Cryptodome.Cipher import ChaCha20
+from Cryptodome.Random import get_random_bytes
+import json
+import base64
+def foo(name,nonce):
+
+    #token = json.dumps({
+    #    "username" : name
+    #})
+    token = json.dumps({
+        "admin" : True
+    })
+    if json.loads(token).get("admin",False) == True:
+        print("ADMIN achieved")
+    else:
+        print("erorr")
+    #ENCRYPTED token.encode()
+    tc = token.encode()
+    etc = base64.b64encode(tc).decode()
+    dec_token = base64.b64decode(etc)
+    user = json.loads(dec_token)
+    print(user)
+    print(user.get("admin",False))
+    print(f"Token encoded: {tc}")
+    print(f"Token:{token}")
+foo("admin",1)
+name = input("Give me name!\n").strip()
+token = json.dumps({
+    "username" : name
+})
+print(token.encode())
+
+def attack():
+    enc_token = input("Give me the token:")
+    nonce, token = enc_token.split(".")
+    print(f"{nonce}, {token}")
+    payload = json.dumps({
+        "username" : "aaaa"
+    }).encode()
+    adminPayload = json.dumps({
+        "admin" : True
+    }).encode()
+    adminTok = b''
+    tok = base64.b64decode(token)
+    keystream = b''
+    print(f"Len payload:{len(payload)} Len tok:{len(tok)}")
+    keystream = bytes([p ^ t for p, t in zip(payload, tok)])
+    print(len(keystream))
+    adminTok = bytes([aP ^ k for aP, k in zip(adminPayload, keystream)])
+    print(f"admin Token:{adminTok} len admin Payload:{len(adminPayload)} lenTok:{len(adminTok)}")
+    print(f"{nonce}.{base64.b64encode(adminTok).decode()}")
+    #for i,j in zip(tok,payload):
+
+    #    print(bytes(i^j))
+    #print(keystream)
+#attack("j5l1MgGWqU06x2GvgXGEnXkoFPs=")
+attack()