The full subject of an EV certificate is a line of street address and registration
numbers and pushed the useful part of the log line off the screen. The CN answers the
question the log has to answer. The full subject is still logged in the one case where it
is the finding itself: a valid signature from a publisher that is not us.
Loader 1.1 -> 1.2; a Pester case pins the short form. Suite on PS 5.1: 45/45.
Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>
Invoke-BootstrapDownload.ps1 and Start-AutopilotMonitor.ps1 had become the same script:
download the current installer, run it, log, always exit 0. The MSI copy additionally
downloaded and executed WITHOUT verifying what it got, which is exactly the gap the loader
was written to close. The MSI is now packaging only -- it installs and runs the same file
that is assigned directly in Intune, and both delivery channels get publisher verification
from one implementation.
Dropped from the MSI path: its own Deployed-marker check. That guard lives in stage 2 and
runs there anyway, so the only cost is one download on a device that is already deployed.
Kept: the log file name. bootstrap-msi.log is what the diagnostics tooling keys on to tell
the MDM-LOB channel apart from the Intune script channel, so the loader takes -LogFileName
(default bootstrap-loader.log) and the custom action passes bootstrap-msi.log. A Pester
test now pins that contract across the two files -- renaming the parameter on either side
would leave the MSI channel logging under the wrong name.
Package version 1.0.2 -> 1.1.0 so Intune LOB update detection sees the new payload, and a
new component GUID because the key path file changed.
Loader 1.0 -> 1.1. Bootstrap suite on Windows PowerShell 5.1: 44/44.
Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>
Start-AutopilotMonitor.ps1 is the new stage 1 -- the file an administrator assigns in
Intune. It carries no enrollment logic: it downloads the published installer, verifies its
Authenticode signature, and runs it in the same process, passing through every remaining
argument. Assigning the installer directly stays supported and unchanged.
The point of the split is that the customer-held artifact stops changing. Today every
bootstrap change forces customers to replace their Intune copy, so the fleet runs a
distribution of script versions we do not control. It is also what makes script signing
worth doing: signing a file that gets swapped by hand each release is a one-off gain,
signing a loader that never changes is permanent.
The loader is deliberately minimal, because it is the one piece that cannot be fixed
remotely -- every guard placed in it would be frozen for years. All guards stay in stage 2.
Verification pins the certificate SUBJECT, never a thumbprint: certificates get renewed and
a deployed loader cannot be, so a thumbprint pin would strand the fleet at the next
renewal. A hash oracle was rejected for a different reason -- it would have to be fetched
from the same host as the script, so it could not survive a compromise of that host, while
the expected publisher travels inside the loader.
Fail-closed on verification, fail-soft on exit: nothing runs without a valid signature from
us (running unverified code as SYSTEM is the risk being removed here), but the loader still
exits 0, because a device without monitoring is acceptable and a failed enrollment step is
not. The accepted cost is that a device which can never fetch or verify stays silent.
Publisher changes:
- every published script is signed (loader, installer, both -Dev renders,
Test-ShouldBootstrapAgent, Grant-AutopilotMonitorAddOn), and signing is the LAST
transformation: it covers exactly the CRLF/UTF-8 bytes Get-PublishBytes produced, so
nothing may normalise or re-encode them afterwards.
- signing is mandatory for a real publish. Only -DryRun may run unsigned, because the PR
gate executes the publisher without any Azure login.
- comparisons against a published copy strip the signature block first. A timestamped
signature differs on every run, so without stripping the version-bump guard and the
drift check would report a change for every unchanged script.
- the bump guard became Assert-VersionBump and now covers the loader as well.
- version.json gains loaderVersion. Additive, no consumer yet: stage 2 is current by
construction, so only stage 1's version says anything about a customer's Intune copy.
- -SignedOutputDir writes the exact uploaded bytes for the CI artifact, in a dry run too --
that is how a signed script gets inspected before it reaches anyone.
publish-scripts.yml logs in with the signing identity first and only to fetch the Key Vault
token (azure/login sets the default az account and the storage login has to be the one that
stays), then publishes and offers the signed scripts as an artifact. build-agent.yml passes
the same parameters on a stable cutover.
Tests: 14 new Pester cases, including that a validly signed script from a FOREIGN publisher
is refused -- that is what an attacker with any code-signing certificate can produce. Full
bootstrap suite on Windows PowerShell 5.1: 43/43.
Not covered: the MSI runner still downloads stage 2 without verifying it, and the customer
docs still describe the direct assignment only.
Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>
Oliver Kieselbach