Authorized Keys on a Windows Network Drive

Tectia Server supports storing domain users' authorized keys (and authorization files) on a network drive.

Because the user's network drives are restored only after the user has been fully authenticated, the path to the authorized keys directory must be specified in UNC format, for example:

\\server.my-company.com\dfs\authorized_keys

Tectia Server is accessing the network drive from a thread impersonating the user who is logging on. The impersonation token is obtained via Microsoft Kerberos extension Service for User to Self (S4U2self)^[1]. Therefore, the computer domain account is acting on behalf of the user.

To enable access to network resources this way, the following requirements must be met:

The computer must be configured on a domain controller to be trusted for delegation of CIFS services for the particular network drive. For instructions on how to configure this, see Virtual Folders Defined on Windows Network Shared Folders Are Not Available on Tectia Server on Windows.
The individual users must have read access to their files granted in the access control list of the folder itself, as well as in the network drive.

Example configuration:

<authentication-methods login-grace-time="600">
  <authentication name="Default-Authentication" action="allow" password-cache="no">
    <auth-publickey 
      authorized-keys-directory="\\server.my-company.com\dfs\authorized_keys\%U" 
      require-dns-match="no" />
    <auth-password failure-delay="2" max-tries="3" />
    <auth-gssapi allow-ticket-forwarding="no" />
    <auth-keyboard-interactive failure-delay="2" max-tries="3">
      <submethod-password />
    </auth-keyboard-interactive>
  </authentication>
</authentication-methods>

^[1]S4U2self is an extension that allows a service to obtain a Kerberos service ticket to itself. The service ticket contains the user's groups and can therefore be used in authorization decisions.