Harden package policy management and elevation

[Benoît Cortier (CBenoit)]

Summary

• Bound Devolutions Agent policy-management responses before allocation and share the same framing implementation with the elevated helper transport.
• Add finite preflight and helper-authentication deadlines with single-flight ownership and late-result cleanup.
• Add validation epochs so pre-save background validation cannot restore stale receipts or findings after a successful save.
• Match the Devolutions.Now.Policy 2026.9.19 credential grammar and reject malformed requests before pipe creation or helper launch.
• Validate the production Authenticode/SPKI signer binding against signed x64 and arm64 release artifacts, with a TRX assertion that exactly one Windows test ran and passed.
• Document why policy elevation directly launches a minimal helper and remove historical phase terminology left by the development prompts.

Context

This is a reviewed hardening follow-up to #5335.
It addresses every actionable finding from a complete security, correctness, NativeAOT, packaging, and editor-state review of the merged policy editor.

Dependency provenance

The shipping projects use official NuGet.org Devolutions.Now.Policy.* 2026.9.19 packages.

• Devolutions.Now.Policy.Model SHA-256: 54ACFD77F98602840C81E48CBDD9E1CE69B355137B9875382A1D687E6F2FAA31.
• Devolutions.Now.Policy.Api SHA-256: 62C69EA8F413DAE76BD8D5B4E7829F63B1617F483C9BEB85E68FED207FE802B9.
• Devolutions.Now.Policy.Client SHA-256: 2EBD6989FDD1C9B76B2DEE535C3BC1323E130AB717CFD1CCFCAA8E4D06BE9A04.

Validation

• The complete Windows solution test run passed after a full restore.
• Final focused transport, elevation, and protocol tests passed: 188 passed, 0 failed, and 0 skipped.
• Final focused policy-editor session and view-model tests passed: 61 passed, 0 failed, and 0 skipped.
• The broader policy-management and elevation suite passed 605 tests during implementation.
• dotnet format style src/UniGetUI.Windows.slnx --no-restore --verify-no-changes --verbosity minimal passed.
• git diff --check passed.
• Windows x64 NativeAOT app and elevated-helper publishing succeeded; emitted warnings were existing baseline warnings unrelated to this diff.
• The release workflow YAML parsed successfully, and the Windows-only TRX gate was exercised with exactly one passing signer-binding test result.
• A final independent whole-diff review reported no remaining actionable findings.