OneDrive Client for Linux Application Security

This document details the following information:

• Why is this application an 'unverified publisher'?
• Application Security and Permission Scopes
• How to change Permission Scopes
• How to review your existing application access consent

Why is this application an 'unverified publisher'?

Publisher Verification, as per the Microsoft process has actually been configured, and, actually has been verified!

Verified Publisher Configuration Evidence

As per the image below, the Azure portal shows that the 'Publisher Domain' has actually been verified:

• The 'Publisher Domain' is: https://abraunegg.github.io/
• The required 'Microsoft Identity Association' is: https://abraunegg.github.io/.well-known/microsoft-identity-association.json

Application Security and Permission Scopes

There are 2 main components regarding security for this application:

• Azure Application Permissions
• User Authentication Permissions

Keeping this in mind, security options should follow the security principal of 'least privilege':

The principle that a security architecture should be designed so that each entity is granted the minimum system resources and authorizations that the entity needs to perform its function.

Reference: https://csrc.nist.gov/glossary/term/least_privilege

As such, the following API permissions are used by default:

Default Azure Application Permissions

API / Permissions name	Type	Description	Admin consent required
Files.Read	Delegated	Have read-only access to user files	No
Files.Read.All	Delegated	Have read-only access to all files user can access	No
Sites.Read.All	Delegated	Have read-only access to all items in all site collections	No
offline_access	Delegated	Maintain access to data you have given it access to	No

Default User Authentication Permissions

When a user authenticates with Microsoft OneDrive, additional account permissions are provided by service to give the user specific access to their data. These are delegated permissions provided by the platform:

API / Permissions name	Type	Description	Admin consent required
Files.ReadWrite	Delegated	Have full access to user files	No
Files.ReadWrite.All	Delegated	Have full access to all files user can access	No
Sites.ReadWrite.All	Delegated	Have full access to all items in all site collections	No
offline_access	Delegated	Maintain access to data you have given it access to	No

When these delegated API permissions are combined, these provide the effective authentication scope for the OneDrive Client for Linux to access your data. The resulting effective 'default' permissions will be:

API / Permissions name	Type	Description	Admin consent required
Files.ReadWrite	Delegated	Have full access to user files	No
Files.ReadWrite.All	Delegated	Have full access to all files user can access	No
Sites.ReadWrite.All	Delegated	Have full access to all items in all site collections	No
offline_access	Delegated	Maintain access to data you have given it access to	No

These 'default' permissions will allow the OneDrive Client for Linux to read, write and delete data associated with your OneDrive Account.

How are the Authentication Scopes used?

When using the OneDrive Client for Linux, the above authentication scopes will be presented to the Microsoft Authentication Service (login.microsoftonline.com), where the service will validate the request and provide an applicable token to access Microsoft OneDrive with. This can be illustrated as the following:

This is similar to the Microsoft Windows OneDrive Client:

In a business setting, IT staff who need to authorise the use of the OneDrive Client for Linux in their environment can be assured of its safety. The primary concern for IT staff should be securing the device running the OneDrive Client for Linux. Unlike in a corporate environment where Windows devices are secured through Active Directory and Group Policy Objects (GPOs) to protect corporate data on the device, it is beyond the responsibility of this client to manage security on Linux devices.

Configuring read-only access to your OneDrive data

In some situations, it may be desirable to configure the OneDrive Client for Linux totally in read-only operation.

To change the application to 'read-only' access, add the following to your configuration file:

read_only_auth_scope = "true"

This will change the user authentication scope request to use read-only access.

When using read-only authentication scopes, the uploading of any data or local change to OneDrive will fail with the following error:

2022-Aug-06 13:16:45.3349625    ERROR: Microsoft OneDrive API returned an error with the following message:
2022-Aug-06 13:16:45.3351661      Error Message:    HTTP request returned status code 403 (Forbidden)
2022-Aug-06 13:16:45.3352467      Error Reason:     Access denied
2022-Aug-06 13:16:45.3352838      Error Timestamp:  2022-06-12T13:16:45
2022-Aug-06 13:16:45.3353171      API Request ID:   <redacted>

As such, it is also advisable for you to add the following to your configuration file so that 'uploads' are prevented:

download_only = "true"

Reviewing your existing application access consent

To review your existing application access consent, you need to access the following URL: https://account.live.com/consent/Manage

From here, you are able to review what applications have been given what access to your data, and remove application access as required.