CODEWITHSUNDEEP
pythonhtmlregexpython-requestspython-re
S.Jackson
S.Jackson

Reputation: 159

TypeError: cannot use a string pattern on a bytes-like object using re.findall()

I am beginning to solve programming CTFs in Python when I came accross a challenge for automating math calculations to get the flag.

The source code of the welcoming page looks like this:

<html>

<head>

    <meta charset="utf-8">
    <title>FastMath</title>

</head>
<body>

<div id="content" style="text-align: center;">

Can you solve the level 1?<br/><h3><div id='calc'>1 + 1</div></h3><br/>
<form action="play.php" method="post">
 <input type="text" name="res" />
 <input type="submit" value="OK">
</form>
</div>
</body>

I wrote my Python code to automate it in order to get the flag as follows

#!/usr/bin/env python
import requests
import re
encoding = 'utf-8'
url = '0.0.0.0:8091'
session = requests.Session()

response = session.get(url)
content = response.text

while True:
    try:
        #solves = re.findall('Can you solve the level (.*) ?', content)[0]
        number =  re.findall('(?:[0-9 ()]+[*+/-])+[0-9 ()]+', content)[0]

        post_url = url + '/play.php'
        solution = eval(number)
        post_data = { "res" : solution }

        response = session.post(post_url, data = post_data)
        content = response.content

        #debug
        print(content)
        #print('number of solves: ' + solves)
    except:
        flag = re.findall('FLAG{(.*)}', content)[0]
        print(flag)
        break

It manages to make the first calculation as I get Can you solve the level 2? and submits as I can see from the output but then it gives out errors:

b'<html>\n\n<head>\n\n\t<meta charset="utf-8">\n\t<title>FastMath</title>\n\n</head>\n<body>\n\n\t<div id="content" style="text-align: center;">\n\t\tCan you solve the level 2?<br/><h3><div id=\'calc\'>1 - 5</div></h3><br/>\t\t<form action="#" method="post">\n\t\t\t<input type="text" name="res" /></p>\n\t\t\t<p><input type="submit" value="OK"></p>\n\t\t</form>\n\t</div>\n</body>\n\n'
Traceback (most recent call last):
  File "mmm.py", line 14, in <module>
    number =  re.findall('(?:[0-9 ()]+[*+/-])+[0-9 ()]+', content)[0]
  File "/usr/lib/python3.6/re.py", line 222, in findall
    return _compile(pattern, flags).findall(string)
TypeError: cannot use a string pattern on a bytes-like object

During handling of the above exception, another exception occurred:

Traceback (most recent call last):
  File "mmm.py", line 27, in <module>
    flag = re.findall('LMFRCTF{(.*)}', content)[0]
  File "/usr/lib/python3.6/re.py", line 222, in findall
    return _compile(pattern, flags).findall(string)
TypeError: cannot use a string pattern on a bytes-like object

I tried making in the converting it all to string but it didn't work, even using r"something" or b"something" didn't help much!

Upvotes: 0

Views: 632

Answers (1)

Javier
Javier

Reputation: 2776

response.text will give you a str, not bytes but response.content will give you bytes.

Choose the type you want to use and use it consistently.

re will handle bytes if the regular expression is bytes as well.

Upvotes: 2

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