[Benoît Cortier (CBenoit)]

The installer writes the agent's data under %ProgramData%\Devolutions\Agent as SYSTEM, but it accepted those folders whatever their owner, applied only the DACL from its SDDL so the folders kept the owner they had, and the uninstall deleted the Agent Identity state with a path-based recursive delete.
An account that owned or could replace one of those folders could therefore keep control of what the installer and the agent write there.

The installer now:

• refuses an install, upgrade, repair or feature change, before it changes anything, with a localized error naming the folder and the account, when Devolutions or Agent is a link, a file, can't be read, or is owned by anyone but SYSTEM, Administrators, TrustedInstaller or a member of Administrators, or when the DACL of Devolutions lets any other account replace it or an entry of it, matching what the agent refuses; a full uninstall is never refused;
• creates a missing Agent with its final security descriptor, or resets the owner and DACL of an existing one on the handle it checked, and sets both on Agent and Agent\pedm without following any link on the path and without propagating to existing children; a failed reset now fails the run;
• deletes Agent\identity at uninstall without following any link, holding each directory open without delete sharing while the entries below it are resolved.

Issue: DGW-478
Security: yes

🤖 Generated with Claude Code

[Benoît Cortier (CBenoit)]

Validation

Head b244bff73.

• Lines changed: production code +1159 −26 (Actions/*.cs), tests +845 −64, localization resources and intent +104 −0.
• dotnet test package/AgentWindowsManaged.Tests: 160 passed, 0 failed (non-elevated run; the owner assertions only discriminate when elevated).
• ci/check-oracle-markers.ps1 -Base a66a019d0: passes.
• Update-InstallerLocalization.ps1 -Product agent run twice: second run leaves the tree unchanged.
• MSI built locally with placeholder binaries; InstallExecuteSequence: InstallInitialize 1500, CA.checkProgramDataDirectory 1503, RemoveExistingProducts 1504, CreateFolders 3700, CA.createProgramDataDirectory 3702, CA.createProgramDataPedmDirectories 3704, then the two permission resets, InstallFiles 4000.
• Held directory handles request FILE_TRAVERSE so that their share mode applies; tests assert a held directory can't be renamed.
• Two independent review rounds on the whole delta; the second found nothing blocking.
• The DACL rule for Devolutions follows the agent's ancestor rule in refactor(agent): keep private files with private-fs #2154 (head 9b8b60380f6c); a later change there needs the installer to follow.

Intent

The Data folder section of package/AgentWindowsManaged/INTENT.md and the uninstall sentence under Agent Identity were approved verbatim by the maintainer before the code; the tests cite them.

Known limits

• A Devolutions folder created by a non-elevated process carries a full-control entry for that user, so the installer refuses it, as the agent does; the fix is to give the folder to SYSTEM or Administrators and remove the entry.
• The reset of an existing Agent doesn't propagate to the entries it already holds.
• A Devolutions the installer created stays after a refusal.
• The Gateway installer (package/WindowsManaged) isn't changed here.

UNTESTED

• SecureDirectory.DeleteTree: each directory handle stays open until the entries below it are done.
• DataFolders.Create: the Devolutions handle stays open until Agent is created, or checked and reset.
• DataFolders.Create: setting the owner of an existing Agent to SYSTEM succeeds only for a caller allowed to set another owner (the installer's SYSTEM process).
• DataFolders.Check/Create: an existing Agent that is a link or has an untrusted owner is refused (needs a passing Devolutions, whose owner a non-elevated test can't set).
• SecureDirectory.IsTrustedOwner: a member of Administrators is trusted through Authz, or the local member list when Authz fails.
• CustomActions.Refuse: a refusal is sent as InstallMessage.Error, which a silent install logs and an interactive one shows.
• CustomActions.SetProgramDataPedmDirectoryPermissions: a missing pedm folder doesn't fail the run.

---

🤖 Generated with Claude Code