Add win-add-temp-user

[Marcus Ferreira (mvaferreira)]

What this adds

win-add-temp-user: one scenario script and its own map.json entry. Windows creates the
requested local administrator during a nested boot using SYSTEM\Setup\CmdLine; the script
does not edit SAM structures or depend on Group Policy startup scripts.

Success requires a complete guest result for the requested account confirming creation,
administrator membership and enablement, with no contradictory readable SAM observation.
SAM presence alone is never proof that this run created the account. If account creation
fails, the payload does not promote or enable an existing account.

Recovery and safety

• Cryptographic password generation, percent-safe batch transport and disabled delayed
  expansion. Printable ASCII passwords are supported except double quotes; unsupported
  characters are rejected rather than silently changed by ASCII encoding.
• Records recovery metadata atomically before arming the hook. A pending operation,
  unreadable manifest or pre-existing nonzero SetupType blocks a new operation.
• Restores and verifies both recorded Setup values. Incomplete restoration or cleanup returns
  an error and preserves recovery information instead of reporting success.
• Pins the original disk and Windows drive during rediscovery. Never cleans up through a stale
  drive path after failed rediscovery; recovery instructions require stopping a managed guest.
• Releases temporary drive letters and flushes helper diagnostics before the final status.

Generated passwords are delivered in run output, not the scenario's desktop log. Azure Run
Command and the CLI can retain that output; handle it as sensitive. A supplied password is
not echoed by the scenario.

Parameters

Parameter	Effect
username	Account to create; defaults to azrepairadmin. An existing account is not modified.
password	Optional compliant password. When omitted, a cryptographic password is generated and printed.
detectOnly	Inspect readiness without creating an account or applying a hook. Discovery can stop an unmanaged repair guest, prepare attached disks and assign temporary letters; writable hive reads may perform recovery. This is not a zero-write disk-forensics mode.
revert	Restore the recorded Setup hook and remove residual payload/result files. Does not delete an account already created by Windows. Cannot be combined with detectOnly.
windowsDrive	Explicit offline Windows drive when automatic selection is inappropriate.
bootTimeoutSeconds	Nested heartbeat timeout; defaults to 600 seconds.

Use a repair VM created with az vm repair create --enable-nested, then invoke with
az vm repair run --run-on-repair --run-id win-add-temp-user.

Validation

The remediation was exercised using the real product workflow against deliberately broken
disposable VMs, not just static checks. Windows Server 2016 and 2025 were randomly selected
from the available 2016/2019/2025 choices; both selected images are Gen1.

Check	Server 2016, build 14393	Server 2025, build 26100
Native batch transport, actual-main failure paths and manifest/restore regressions	53/53	53/53
Actual create --enable-nested and pinned run --preview detection	Passed	Passed
Deliberately incomplete Setup hook, preview revert, independent on-disk checks	5/5	5/5
Actual nested account creation and restore to the original VM	Passed	Passed
Original guest boot, enabled administrator/group membership and cleanup	Passed	Passed

Preview candidate: 804cd4ae80110bc919e62d9966aadf674d6691b8.
Script SHA256: 19789E8023484613D1B337EC31AA491E96C8EE507A259E40A030195C435DC30B.

Server 2016 required a forced nested power-off after graceful shutdown timed out. The
script re-read the result and SAM and verified Setup restoration rather than trusting
an unflushed guest state; original-VM verification is recorded separately above.
Server 2025 shut down cleanly. These runs do not establish fresh password/RDP authentication,
Gen2, BitLocker or domain-joined coverage.
The final 2016 guest checks were collected after an additional Azure VM restart and correcting
the verifier's transport. No further scenario changes were made. On both original guests,
the new account was enabled and belonged to Administrators/Remote Desktop Users, the original
fixture account remained disabled, and Setup values and all three temporary artifacts were clear.

The September 2 sign-in test and September 10 helper lifecycle tests remain historical
evidence for their then-current code, not additional fresh coverage for this revision.

Review disposition and scope

The maintainer-supplied agent's report on b2814df9f55c0e915423c260e1cd43949f69dea7
identified 3 Critical, 7 Warning and 4 Info items. Confirmed defects were implemented and
exercised; descriptive findings were clarified. The empty SAM Names-key distinction was
not changed: a normal SAM contains built-in accounts, and the conservative unreadable
classification cannot satisfy the new success gate by itself.

First wave of four independent scenario PRs. Helpers from #143, #146 and #147 are already
merged. This PR changes only the new scenario and its catalog entry, not shared helpers or
other scenarios. Private break/verify/regression tooling is not included in the contribution.

[Marcus Ferreira (mvaferreira)]

Automated review using the supplied PR Review Agent

Reviewed head: b2814df9f55c0e915423c260e1cd43949f69dea7
Agent recommendation: request changes
Finding-table counts: 3 Critical / 7 Warning / 4 Info

This is the supplied agent's static analysis, not a maintainer decision or a fresh repair/boot test. Findings have not been independently reproduced. No source or Azure resources were changed during review. The original report is retained locally; only leading process narration and local prompt-path provenance were normalized for posting. Finding text is unchanged.

Full automated review report

PR Review: #152 — Add win-add-temp-user

Generated: 2026-09-10
Target: Azure/repair-script-library → main

PR	#152
Head reviewed	b2814df9f55c0e915423c260e1cd43949f69dea7
Base / merge-base	3cdb744e1592c1aa0e6c5840bea43e5b8a1911ad
Head repository	https://github.com/mvaferreira/repair-script-library
Changed files	map.json, src/windows/win-add-temp-user.ps1 (new, 1031 lines)
Review prompt SHA256	5451BA5C325F61E34FE63B9AF99322A17D70E55210CAF23F5CE27E0F839D8F70

Reviewed against the pinned head snapshot only. Helper contracts consulted: src/windows/common/setup/init.ps1, common/helpers/Logger.ps1, common/helpers/README.md, Get-OfflineWindowsDisk.ps1, Use-OfflineRegistryHive.ps1, Use-NestedRepairVm.ps1, doc/adding_new_scripts.md, and the comparable upstream script src/windows/win-create-troubleshooting-user.ps1.

Standards baseline passes. The script sources init.ps1 (line 116), returns $STATUS_SUCCESS/$STATUS_ERROR on every path, uses only Logger functions (no Write-Host), declares a Param() block with defaults, wraps the body in try/catch, and pairs every hive mount through Invoke-WithHive. Its use of Invoke-WithHive, Get-OfflineWindowsDisk, Start-NestedRepairVm, Wait-NestedRepairVmBoot and Stop-NestedRepairVmGraceful matches those helpers' documented parameter names and returned properties. The scope-capture comments at 331-332 and 437-438 are correct: Invoke-WithHive calls & $ScriptBlock with no arguments (Use-OfflineRegistryHive.ps1), the helpers are dot-sourced rather than module-scoped, and Invoke-WithHive declares no local named $command, $setupType, $targetSetupType or $targetCmdLine, so the blocks resolve those from the caller's scope as claimed. The findings below are defects within that otherwise conforming structure.

Findings

Critical

File	Line/Context	Issue	Recommendation
src/windows/win-add-temp-user.ps1	169, 519, 1014	A generated password containing % is silently corrupted, and the run still reports success. $special = '!@#$%^&*()-_=+' (169) includes %. Line 519 emits net user "<user>" "<password>" /add /y into an ASCII .cmd. cmd.exe percent-expansion runs before quote processing, so double quotes do not protect %: a lone % is stripped, and a %…% pair is consumed as a variable reference. net.exe therefore receives a different string than the one printed to the engineer at 1014. net user still returns 0, so add=0, the offline SAM shows the account, and line 1004 reports SUCCESS. The engineer cannot sign in — the exact failure this script exists to fix — after a full nested boot cycle. The generator produces 16 characters (1 seeded special from a 14-character set, 12 drawn from a 71-character set): P(contains %) = 1 − (13/14)(70/71)¹² ≈ 21.7%, roughly one run in five. This is introduced by this PR: the comparator's generator (win-create-troubleshooting-user.ps1, "@zurE" + 8 alphanumerics) cannot emit %. " is the same hazard for an operator-supplied -password; the ValidateScript at 100-108 accepts it via \W.	Remove %, ", ^, &, <, >, `
src/windows/win-add-temp-user.ps1	941-942, 968-973, 1004	The success gate accepts offline-SAM presence alone, which cannot distinguish an account this run created from one that already existed. Line 968 requires only one of the two signals, and 1004 explicitly renders the SAM-only case as "confirmed by the offline SAM". But $samSaysCreated (942) is presence, not creation. It is authoritative only when detect proved the account absent (775-782). When detect could not read SAM, the script warns and continues (784-787) — and 786 promises the collision "will surface as a failed payload", which 968 then contradicts: a pre-existing account yields add != 0 → $payloadSaysCreated = $false, yet SAM presence alone passes the gate, so SUCCESS is printed with a password that was never applied. Precondition chain: SAM unreadable at detect (785) and readable at verify — reachable because a hive too dirty to reg load at detect is reconciled by the guest's boot and clean shutdown. Reliance on the weaker signal is not exotic: $payloadResult.Complete (941) is false whenever the result file is missing or truncated, which the tolerated non-graceful stop at 923-925 makes a normal outcome.	Require $payloadSaysCreated for success; accept $samSaysCreated as confirming only when $userState.Known -and -not $userState.Exists at detect. Fail closed when SAM was unreadable at detect rather than proceeding on a signal that cannot answer the question.
src/windows/win-add-temp-user.ps1	519-525, 774-787, 699-762	The payload promotes and enables a pre-existing account unconditionally, with no rollback. Lines 521, 523 and 525 run net localgroup Administrators … /add, net localgroup "Remote Desktop Users" … /add and net user … /active:yes without testing %RC_ADD% from 520. When the requested name already exists on the disk — the case detect cannot rule out when SAM is unreadable (784-787) — the run adds that pre-existing account to local Administrators and Remote Desktop Users and enables it, including a deliberately disabled account. This is a privilege grant to an account the operator never intended to touch (Phase 4, Privilege Escalation), and it occurs even on runs that later report FAILED at 969. -revert cannot undo it: the revert path restores the hook, deletes payload/result and only reports the surviving account (743-748).	Gate 521-525 on if "%RC_ADD%"=="0" so the payload only modifies an account it created. Record group membership in the revert manifest, or make an unreadable detect-time SAM a blocking finding rather than a warning.

Warning

File	Line/Context	Issue	Recommendation
src/windows/win-add-temp-user.ps1	670-1030 (no finally), 676, 928	The documented helper caller contract is not met. common/helpers/README.md ("Required caller contract") mandates releasing temporary drive letters and flushing helper logs in finally, "including when discovery fails partway through", and Get-OfflineWindowsDisk's own .OUTPUTS states: "AssignedDriveLetters holds the letters this run assigned; pass each to Remove-OfflineDriveLetter, or call Clear-OfflineDriveLetter, in the caller's finally." The script has no finally and never calls either. Discovery runs twice (676, 928), and each pass assigns letters to EFI System/Recovery partitions via Add-PartitionDriveLetter; none are released on any of the ten return paths or the catch at 1026. The catch also does not call Write-OfflineRepairLog, so helper-buffered diagnostics from the failing call are discarded and only the exception text survives (1027-1028).	Adopt the README skeleton: set $status and return it after a finally that calls Clear-OfflineDriveLetter and Write-OfflineRepairLog, each guarded by Get-Command.
src/windows/win-add-temp-user.ps1	928-936, 1026-1029	The highest-consequence failure window is the only one with no remediation guidance. The guard at 931 implies Get-OfflineWindowsDisk can return $null or an object without WindowsPath; it cannot. Every failure inside it throws (Get-OfflineWindowsDisk.ps1: "Could not determine the rescue VM's own system disk number…", "No attached broken OS disk was found…", "No offline Windows installation was found on the attached disk(s)."). So 931-936 is dead code and a failed rediscovery lands in the bare catch at 1026. At that point the Setup hook is armed and, if the payload never ran, Windows\Temp\win-add-temp-user.cmd — containing the plaintext password — is still on the disk, because the cleanup at 959-965 sits after the throwing call. Every other failure path emits recovery text (889, 970, 989); this one emits only an exception and a stack trace.	Wrap 928 in its own try/catch that logs the same "-revert true" guidance and states that the payload may remain on the disk. Remove the unreachable guard at 931.
src/windows/win-add-temp-user.ps1	676, 699, 919-921	The documented -revert recovery can itself be blocked by this script's own failure. -revert is handled at 699, after discovery at 676, so revert requires Get-OfflineWindowsDisk to succeed. Start-NestedRepairVm marks the guest with a persistent repair-script-library:nested-repair:v1 Notes line via Set-NestedRepairVmManaged, and per common/helpers/README.md discovery "refuses to proceed while it is active". If Stop-NestedRepairVmGraceful returns Stopped = $false, line 921 returns $STATUS_ERROR with the guest still running and marked — so re-running with -revert true, the remedy offered at 889 and 970, fails at 676. The message at 920 does not tell the operator to stop the guest first.	Add to the 920 message that ProblemVM must be stopped (Hyper-V Manager or Stop-VM) before -revert can run; or move the -revert branch ahead of discovery, or let it pass -NestedVmId.
src/windows/win-add-temp-user.ps1; map.json	50, 828-831; map.json:95	detectOnly is described as changing nothing, but it changes rescue-VM and disk state before it reports. Line 50 says "Report what is on the disk and change nothing" and map.json:95 says "Pass detectOnly=true to report only", yet detect runs the full discovery at 676 first. Get-OfflineWindowsDisk unconditionally calls Stop-NestedRepairVm -VmId $NestedVmId before disk preparation — so detectOnly=true powers off a running unmanaged ProblemVM — then Set-OfflineDisksOnline runs diskpart online disk / attributes disk clear readonly, and Add-PartitionDriveLetter may assign letters. Detect also reads through Invoke-WithHive (774, 763), which mounts SYSTEM and SAM writably via reg load; the library exposes a read-only offreg reader for exactly this (common/helpers/README.md, "Read-only hive access"). The source does not establish a zero-write detect. The PR's "Detect-only made no writes" is a recorded historical observation, not something this review can confirm — the packet's validation was static and executed nothing.	Reword line 50 and the map.json description to "makes no changes to the Windows installation" and state the guest-stop and disk-online side effects, or route the detect-only reads through the read-only reader.
src/windows/win-add-temp-user.ps1	172-175, 180, 183	An administrator password is generated with Get-Random. Get-Random is backed by System.Random, a non-cryptographic PRNG, and Sort-Object { Get-Random } (183) is a biased shuffle. The supplied Phase 3 checklist classifies "user-created passwords use secure generation" as Critical. Rated Warning here because it matches the comparable upstream script, which also uses Get-Random — so it is not a regression — but this is new code being added, and the "not predictable" claim in the function's own help (164) overstates what Get-Random provides.	Draw from [System.Security.Cryptography.RandomNumberGenerator] with rejection sampling, and shuffle with the same source.
src/windows/win-add-temp-user.ps1	443, 457	Restore-OfflineSetupHook verifies only half of what it wrote. Set-OfflineSetupHook reads back and compares both CmdLine (401) and SetupType (406). Restore-OfflineSetupHook compares only SetupType (457) and never inspects $readBack.CmdLine, while the removal at 443 uses -ErrorAction SilentlyContinue. A CmdLine that could not be removed or rewritten is therefore reported as Restored = $true, leaving a stale value pointing at a deleted payload on both the revert path (720) and the finalize path (984). Impact is bounded — SetupType is proven 0, so the stale command does not execute — but the disk is returned in a state the script asserts it cleaned.	Mirror 401-404: compare $readBack.CmdLine against the intended value (empty when removed) and fail the restore when it does not match.
src/windows/win-add-temp-user.ps1	981-989	Finalize can restore a non-zero SetupType and then give circular advice. The SetupHookInUse guard at 791-793 blocks only when SetupType != 0 and CmdLine is non-empty, so a disk arriving with a non-zero SetupType and no CmdLine proceeds. Finalize then deliberately restores $hook.PreviousSetupType (984), leaving it non-zero, so 987 is true and 989 warns "SetupType is still N … Re-run with -revert true before restoring the disk" — but -revert writes back the same recorded previous value (720), so the advice cannot resolve it. Line 988 additionally interpolates $restore.Reason, which is $null on this path, producing "The Setup hook could not be cleared: " with an empty reason.	Distinguish "restore failed" from "the recorded previous state was itself non-zero", suppress 988 when $restore.Restored, and surface a non-zero pre-existing SetupType as a detect finding at 791.

Info

File	Line/Context	Suggestion
src/windows/win-add-temp-user.ps1	928	Rediscovery passes -DiskNumber $offline.DiskNumber but -WindowsDrive $windowsDrive — the caller's parameter, normally empty — rather than $offline.WindowsDrive. Get-OfflineWindowsDisk re-scores candidates and subtracts 20 for SetupInProgress, a flag this script itself sets at 981's precondition. On a disk carrying more than one Windows installation the second pass could therefore select a different install and verify the wrong SAM. Not demonstrated, and single-installation disks are unaffected. Passing -WindowsDrive $offline.WindowsDrive would pin it.
src/windows/win-add-temp-user.ps1	1010, 1014-1015	The comment "Printed, never logged" and the message at 1015 are accurate only for the rescue-VM desktop log. Logger.ps1 implements every Log-* function with Write-Output, and doc/adding_new_scripts.md states the logs "are written to stdout which are redirected to file when used with the CLI vm-repair extension", so the password still transits the Run Command output stream and the CLI's local output. This is inherent to the delivery model and strictly better than the comparator, which additionally writes the password to $env:PUBLIC\Desktop. Worth wording so the guarantee is not read as broader than it is.
src/windows/win-add-temp-user.ps1	235-238	& $ScriptBlock unrolls an empty array to $null, so a Names key that exists with zero subkeys is indistinguishable from a missing key and is reported as "the account name key was not present" (256). Harmless in practice — a real SAM always carries Administrator and Guest — but the two cases carry different meanings elsewhere in this script.
map.json	95	The description asserts "The file carrying the password deletes itself, and the setup hook is cleared, so nothing is left on the disk." Both guarantees have failure windows the script itself handles and reports (959-961, 987-989), and one it does not (Warning 2). Softening to "removes the password file and clears the setup hook, and reports when it could not" would match the implementation.

Operational Risk Assessment

Factor	Rating	Notes
Scope	Low	One new scenario script plus one appended map.json entry. No helper file is added or modified and no existing scenario is touched, so nothing outside this run-id can regress. Blast radius is confined to operators who invoke win-add-temp-user.
Destructive ops	High	Writes SYSTEM\Setup\SetupType/CmdLine on a customer OS disk (338-341), writes and deletes files under the customer Windows\Temp (536, 961, 965, 1000), boots the customer disk in a nested guest, and creates — or, per Critical 3, silently promotes and enables — a local administrator. Discovery additionally powers off a running ProblemVM and runs diskpart against attached disks, including under detectOnly.
Rollback possible	Partial	-revert restores the recorded hook and removes payload/result (699-762), and the manifest merge at 596-625 preserves earlier undo data. But it deliberately does not delete a created account, cannot undo the group membership and enablement of Critical 3, is blocked when the guest is left running and marked (Warning 3), reports success without verifying CmdLine (Warning 6), and cannot resolve a restored non-zero SetupType (Warning 7).
Testing documented	Yes, but not reproduced here	The PR records a 2 Sept product-path acceptance run via az vm repair run --run-on-repair and a separate revert exercise, and a 10 Sept shared nested-lifecycle suite (87/87 on PS5.1 and PS7, plus 93 native Hyper-V assertions). The PR is candid that the 10 Sept guests were firmware-only. No repair-script-library test harness exists (tests/ is a placeholder), and doc/adding_new_scripts.md notes local --custom-script-file testing cannot pass parameters, so detectOnly/revert/username/password cannot be exercised that way. This review executed nothing — no repair script, no boot, no Azure operation, no hive mount. The packet's validation was likewise static. Critical 1 in particular is a ~1-in-5 probabilistic path that a small number of manual runs would very plausibly miss.
Gen compatibility	Unknown	The script itself is generation-agnostic: it delegates Gen1/Gen2 handling to Get-OfflineWindowsDisk (partition-style → generation) and Connect-NestedRepairVmDisk (Gen2 boot-order promotion), and only reports $vmState.Generation at 805. It never branches on generation. But the PR explicitly declines to claim a fresh Gen1/Gen2 account-creation matrix, and the SYSTEM\Setup\CmdLine hook is untested here on both firmware types. BitLocker-protected volumes are not detected or reported by this script.

Overall Risk: High 🔴 — driven by Critical 1 (a ~22%-per-run silent wrong-password outcome reported as success), Critical 3 (an unrollbackable privilege grant to an account the operator did not target), and the destructive-operation profile on a customer OS disk.

Validation

Deterministic checks below were performed by the launcher and recorded in the review packet; the source assessment is this review's own.

• map.json valid: pass (MapJsonValid: true, MapJsonError: null)
• map.json paths exist and are in-tree: pass (MissingOrUnsafeMapPaths: []) — map.json:94 src/windows/win-add-temp-user.ps1 is present in the head snapshot
• Duplicate IDs: none (DuplicateIds: [])
• PowerShell parse errors: none (PowerShellParseErrors: [])
• New entry placement and JSON shape: pass — map.json:92-96, appended after win-create-troubleshooting-user, correct comma placement, every upstream entry preserved; the diff is purely additive (@@ -89,6 +89,11 @@)
• id naming convention: pass — win-add-temp-user matches win-* and equals the file stem
• Init sourcing: pass — . .\src\windows\common\setup\init.ps1 at line 116
• Status return: pass — every exit returns $STATUS_SUCCESS or $STATUS_ERROR; no bare throw escapes the catch at 1026
• Logger usage: pass — no Write-Host or bare Write-Output; all output via Log-Output/Log-Warning/Log-Error
• Helper signature binding: pass — parameter names and consumed properties match Get-OfflineWindowsDisk, Invoke-WithHive, Get-NestedRepairVm, Start-NestedRepairVm, Wait-NestedRepairVmBoot and Stop-NestedRepairVmGraceful
• Helper caller contract (finally, Clear-OfflineDriveLetter, log flush): fail — see Warning 1
• Repair scripts executed: no (RepairScriptsExecuted: false). Azure operations performed: no (AzureOperationsPerformed: false). No file was modified and nothing was posted to GitHub during this review.

Recommendation

request changes

The design is a genuine advance on win-create-troubleshooting-user: the SYSTEM\Setup\CmdLine hook is the right mechanism for a domain-joined VM, letting the guest create the account avoids hand-editing SAM, the payload is single-use and self-deleting rather than left on the disk with the password in it, and the script verifies its own outcome instead of asserting success after Start-VM. Those are real improvements and the helper integration is largely correct.

The three Critical findings should be resolved before merge. Critical 1 is the priority: it is unconditional, quantified at roughly one run in five, introduced by this PR relative to the comparator's generator, and silent — both of the script's verification signals still report success. Criticals 2 and 3 share a precondition (the detect-time SAM read failing, which the script treats as a warning at 784-787) and are best fixed together, by gating the payload's group/enable commands on %RC_ADD% and by refusing to treat SAM presence as proof of creation when detect could not establish absence. Warnings 1-3 concern recovery behaviour after a failed run and are cheap to address alongside.

Because Critical 1 is probabilistic, the fixes should be validated by a targeted test — assert the exact password string round-trips through the generated .cmd, with %, ", ^ and & forced into the input — rather than by further end-to-end runs, which can pass repeatedly while the defect remains.

This is an automated review produced by the rsl-pr-review agent from the pinned head snapshot. It is not a human maintainer approval, and no repair, boot or Azure testing was performed as part of it.

[Marcus Ferreira (mvaferreira)]

Review findings implemented and exercised

Publication head: ea46b96325dbaea9400131840b03d13c94f7cbe5

The earlier automated report remains a static review of
b2814df9f55c0e915423c260e1cd43949f69dea7. This follow-up records implementation and actual
execution evidence; it is not a relabelled or newly generated agent review.

Finding	Disposition
C1: corrupted batch arguments	Fixed percent expansion and delayed expansion; verifies payload bytes and rejects lossy/non-ASCII or double-quote input. Valid quoted metacharacters are retained rather than banned unnecessarily.
C2: SAM-only false success	Requires a complete matching guest result with successful creation, administrator membership and enablement. Readable SAM must not contradict it. Unreadable SAM is not a blanket blocker when the fresh guest result is authoritative.
C3: promotion after failed creation	Group additions and enablement run only after successful account creation. A collision does not modify the existing account.
W1: missing caller cleanup	Finally releases temporary letters and flushes diagnostics before the single final status.
W2/W3: incomplete recovery guidance	Preserves recovery state, avoids stale drive paths and explicitly requires a stopped managed guest before revert.
W4: detect-only side effects	Documents the distinction between no account/hook changes and discovery/disk/hive-read side effects.
W5: password randomness	Uses cryptographic random bytes, rejection sampling and Fisher-Yates shuffle.
W6: incomplete hook verification	Verifies both CmdLine and SetupType on restore and reports incomplete cleanup as failure.
W7: nonzero initial SetupType	Blocks new work on a nonzero initial state; preserves legacy recorded state without circular revert advice.
I1: rediscovery selection	Pins both the original disk number and Windows drive.
I2/I4: retention/cleanup claims	Documents service-retained output and retained recovery artifacts instead of unconditional cleanup guarantees.
I3: empty SAM Names key	Not changed: normal SAMs contain built-in accounts; conservative unreadable handling cannot produce SAM-only success.

Additional confirmed recovery gaps were fixed alongside these findings: strict existing
manifest validation, staged/read-back atomic publication, manifest-before-hook ordering,
pending-operation protection, and rejection of conflicting detect/revert flags.

Actual product testing: randomly selected Windows Server 2016/build 14393 and
2025/build 26100, both Gen1. On each version, 53 targeted checks passed. Real
az vm repair create --enable-nested, pinned run --preview, deliberate partial-hook
revert with 5/5 independent checks, nested administrator creation and restore completed.
Original-guest verification passed on both versions: the new account is enabled, belongs to
Administrators and Remote Desktop Users, and the original fixture account remains disabled.
SetupType is zero, CmdLine is empty, and payload/result/manifest files are absent.

The tested script is byte-identical to candidate
804cd4ae80110bc919e62d9966aadf674d6691b8
(SHA256 19789E8023484613D1B337EC31AA491E96C8EE507A259E40A030195C435DC30B).
Server 2016's graceful nested shutdown timed out and the helper used forced power-off;
result/SAM and Setup cleanup were subsequently rechecked. Server 2025 stopped cleanly.
This is not a fresh Gen2, domain-joined, BitLocker or password/RDP authentication matrix.
The final 2016 guest checks followed an additional Azure VM restart and correction of the
verifier's transport, with no further scenario changes.
Generated-password lines were redacted on the repair hosts before full driver logs were collected.

Original review provenance

• Supplied prompt SHA256: 5451BA5C325F61E34FE63B9AF99322A17D70E55210CAF23F5CE27E0F839D8F70.
• Original finding-table counts: 3 Critical / 7 Warning / 4 Info.
• Preserved original report.
• Its request changes recommendation belongs to the old reviewed head; no maintainer approval is implied.

[Edwin Bernal Microsoft (EdwinBernal1)]

Reviewed the current head after the earlier credential and recovery findings were addressed. Password generation is cryptographic, supplied input is constrained for the batch transport, generated credentials are kept out of the desktop log, and a failed account creation cannot promote an existing account. Success requires a complete guest result, while hook restoration and payload cleanup are verified with recovery metadata retained on failure. The catalog entry is consistent. I found no new blocking issue.

Residual validation gap: only the CLA check is reported by GitHub. This was a static review; I did not independently rerun the nested Hyper-V account-creation and recovery scenarios.

[Gabriela Limoli (glimoli)]

Tip

✅ APPROVE — Overall Score 90/100 (Grade A)

WS2022-Gen2 end-to-end validation is clean, and closes the exact coverage gap flagged in the PR body ("These runs do not establish fresh password/RDP authentication, Gen2, BitLocker or domain-joined coverage"). All security invariants held on a real live repair; the generated password authenticates via LogonUser and the pre-existing disabled admin stays disabled.

VMRepair Script Test Report: win-add-temp-user.ps1

Script under test: src/windows/win-add-temp-user.ps1
PR head: ea46b96325dbaea9400131840b03d13c94f7cbe5
Script SHA256 at head: 19789E8023484613D1B337EC31AA491E96C8EE507A259E40A030195C435DC30B (matches PR-body-declared preview candidate 804cd4ae…, byte-identical)
Test date: 2026-09-16

Summary

Overall Score: 90/100 (Grade: A) — APPROVE

Ready to merge after the PR author's own maintainer review.

• Static analysis — PSScriptAnalyzer clean (0 errors, 3 low-impact warnings, all PSUseShouldProcessForStateChangingFunctions, two of them false positives). Follows every VMRepair convention: $STATUS_SUCCESS/$STATUS_ERROR (8 uses), Log-Info/Log-Error/Log-Output/Log-Warning (75 uses, 0 raw Write-Host/Write-Output), full try/catch/finally at both function and top-level scopes, dot-sources the standard init.ps1/OfflineRepairCommon.ps1/Get-OfflineWindowsDisk.ps1/Use-OfflineRegistryHive.ps1/Use-NestedRepairVm.ps1 helpers.
• Real end-to-end run on WS2022-Gen2 (the exact coverage gap the PR author flagged in the PR body):
  • Source VM: srcvm-ws22-g2, Standard_D2s_v5, MicrosoftWindowsServer:WindowsServer:2022-Datacenter-Azure-Edition:latest, Gen2, westus2
  • Break: net user labowner /active:no — disabled the initial admin
  • Rescue: az vm repair create --enable-nested --size Standard_D4s_v5 — 760 s
  • Script: az vm repair run --run-on-repair --run-id win-add-temp-user --preview <PR head map.json> — 189 s, nested-boot heartbeat 70 s, payload settle 30 s, graceful shutdown 5 s
  • Restore: az vm repair restore — 139 s
  • Post-restore verification: azrepairadmin present, enabled, in Administrators and Remote Desktop Users; LogonUser P/Invoke succeeded with the generated password; labowner still returns ERROR_ACCOUNT_DISABLED (1331) even with the correct password — proving the "does not promote or enable an existing account" invariant held under a real disabled-admin scenario; Setup values restored (SetupType=0, CmdLine=""); all three temp artifacts (.cmd, .result, -revert.json) cleaned up.
• Coverage gaps that remain (see Opportunities for Improvement below): WS2019 (any gen), WS2022 Gen1, WS2025 Gen2, BitLocker OS disk, domain-joined VM, and the detectOnly/revert/custom-parameter/invalid-parameter branches were statically analysed but not exercised on live infrastructure by this run. The PR author's own PR-body evidence still covers WS2016 Gen1 and WS2025 Gen1 for the happy-path plus detectOnly + revert unit branches.

Category	Score	Notes
Functional Correctness	20/20	Real WS2022-Gen2 cycle — break → repair → restore → verify — is a clean PASS. Both the success and the "does not promote existing account" invariants demonstrated with LogonUser P/Invoke evidence.
Code Quality	19/20	PSScriptAnalyzer clean apart from 3 low-impact PSUseShouldProcess warnings; VMRepair conventions perfectly followed. −1 point for optional [CmdletBinding(SupportsShouldProcess)] on Set-OfflineSetupHook / Restore-OfflineSetupHook if the reviewer wants CI to be quiet.
Safety & Rollback	20/20	Atomic manifest with cross-run UserName collision refusal, batch payload sanitized to a small charset, self-deleting payload, read-back on every hive write, graceful-shutdown gate before disk reclaim, revert deliberately refuses to touch the SAM.
Telemetry Coverage	17/20	75 Log-* calls, every catch block emits a typed error, structured logs at every state transition. −3 for the ecosystem-wide fact that repair-script-library scripts do not directly emit AppInsights events (they flow through the run-command wrapper). Not a script-specific gap.
Test Coverage	14/20	1 live cell exercised (WS2022-Gen2). PR-body author covered WS2016 Gen1 and WS2025 Gen1. Remaining matrix cells (WS2019 any gen, WS2022 Gen1, WS2025 Gen2, BitLocker, domain-joined) unverified on live infrastructure.

Fault Injection Results

Phase	WS2022 Gen2 (Standard_D2s_v5, westus2)	Status
Pre-injection (baseline)	labowner present, enabled, in Administrators; azrepairadmin NOT present	Baseline
Post-injection (breaker)	labowner present, disabled (Get-LocalUser labowner | Select Enabled → false); LogonUser(labowner, correct password) → ERROR_ACCOUNT_DISABLED (1331)	CORRUPTED
Post-repair (script on rescue VM)	Offline hive: SetupType=2, CmdLine="cmd.exe /d /c "C:\Windows\Temp\win-add-temp-user.cmd""; offline SAM contains azrepairadmin; guest reported add=0,admin=0,rdp=0,active=0,done=1,user=azrepairadmin; Setup values offline-restored to SetupType=0, CmdLine=""	FIXED
Post-restore + boot	Live VM: azrepairadmin present, enabled, member of Administrators and Remote Desktop Users; LogonUser(azrepairadmin) → true; labowner still present, still disabled, LogonUser(labowner, correct password) → ERROR_ACCOUNT_DISABLED (1331); SetupType=0, CmdLine=""; payload/result/manifest files all cleared	VERIFIED

Testing Performed

Strategy: breaker-integrated, real live cycle with az vm repair create --enable-nested
Fault Injection: ✅ Inline breaker: net user labowner /active:no (documented as follow-up to author a persistent break-win-add-temp-user.ps1 — see Opportunities for Improvement)
Region: westus2 (eastus and eastus2 rejected Standard_D2s_v5 with SkuNotAvailable on the day of this run — subscription-level flake, not a script issue)
Date: 2026-09-16
PR head SHA: ea46b96325dbaea9400131840b03d13c94f7cbe5 (script SHA256 19789E8023484613D1B337EC31AA491E96C8EE507A259E40A030195C435DC30B — identical to PR-body-declared preview candidate 804cd4ae…)

Dimension	Configuration	Result
WS2022 Gen2	Source: Standard_D2s_v5 / WS2022 DC Azure Edition build 20348 / westus2	✅ PASS — full cycle 25 min wall-clock
Rescue VM	Standard_D4s_v5 / WS2022 Datacenter smalldisk-g2 / --enable-nested	✅ PASS — nested Hyper-V extension installed and rerun after reboot; 760 s
Nested boot	Heartbeat OkApplicationsUnknown after 70 s; graceful shutdown after 5 s	✅ PASS
Success gate	Complete payload result matching -username + non-contradictory SAM	✅ PASS — both signals present and agree
Setup restore	Offline hive SetupType=2/… → SetupType=0/"" from rescue VM before disk reclaim	✅ PASS
Cleanup	.cmd + .result + -revert.json all removed	✅ PASS
Live authentication	LogonUser("azrepairadmin", …, generated password, LOGON32_LOGON_INTERACTIVE)	✅ PASS — succeeds (proves RDP-eligible credential is real)
Invariant: does not promote existing account	LogonUser("labowner", …, real initial password, LOGON32_LOGON_INTERACTIVE)	✅ PASS — returns ERROR_ACCOUNT_DISABLED (1331) (proves disabled admin was not re-enabled or touched)

Execution Timeline

UTC	Step	Duration
00:04	az vm create --size Standard_D2s_v5 (source VM)	~5 min
00:10	az vm run-command invoke net user labowner /active:no (break)	~30 s
00:01:12	az vm repair create --repair-username labrescue --size Standard_D4s_v5 --enable-nested	760 s
00:14:37	az vm repair run --run-id win-add-temp-user --run-on-repair --preview <PR head map.json>	189 s
00:15:24	Setup hook applied on offline disk
00:15:24	Nested guest ProblemVM started
00:16:36	Nested guest reported heartbeat OkApplicationsUnknown	70 s wait
00:17:06	Rescue asked nested guest to shut down
00:17:11	Nested guest shut down cleanly	5 s wait
00:17:16	Disk rediscovered as Gen2 / WS2022 DC Azure Edition build 20348
00:17:18	[STATUS]::SUCCESS — Setup values offline-restored
00:18:18	az vm repair restore	139 s
00:20:37	az vm start source VM + wait 60 s + Get-LocalUser/Get-LocalGroupMember/Get-ItemProperty	~90 s
00:22:00	LogonUser P/Invoke as azrepairadmin and as labowner with real password	~60 s

Convention Audit

PSScriptAnalyzer

Severity	Count	Rule	Verdict
Error	0	—	✅
Warning	3	PSUseShouldProcessForStateChangingFunctions (New-Finding L144, New-TempUserPassword L160, Set-OfflineSetupHook L359)	⚠ Low impact
Information	0	—	✅

• New-Finding and New-TempUserPassword are pure helpers (build a PSCustomObject or generate a string); the rule is a false positive.
• Set-OfflineSetupHook genuinely mutates the offline hive; a [CmdletBinding(SupportsShouldProcess)] decoration would silence the warning but the function is only invoked from a controlled top-level path that already gates on the failure findings — not a blocker.

VMRepair Conventions

Convention	Status	Evidence
$STATUS_SUCCESS / $STATUS_ERROR return values	✅	8 uses, all correct terminal-status assignments
Log-Info / Log-Error / Log-Warning / Log-Output	✅	75 calls, always Tee-Object -FilePath $logFile -Append
Zero Write-Host / Write-Output misuse	✅	0 raw uses
top-level try { … } catch { … } finally { … }	✅	16/14/3 blocks total; main entry has a full triple
Dot-sourced standard helpers	✅	init.ps1, OfflineRepairCommon.ps1, Get-OfflineWindowsDisk.ps1, Use-OfflineRegistryHive.ps1, Use-NestedRepairVm.ps1
Fail-fast parameter validation	✅	ValidateScript on $password runs full Windows-complexity check + reserved-word denylist BEFORE any offline work
Log file on $env:PUBLIC\Desktop	✅	Standard SME pattern
Suppress-message annotations for known false-positive rules	✅	PSAvoidUsingPlainTextForPassword + PSAvoidUsingUsernameAndPasswordParams on Write-TempUserPayload with rationale

Security Invariants

Invariant	Location	Verdict
Batch payload arguments are strictly sanitised (reject ", \x00-\x1F, \x7F-\uFFFF; escape % as %%)	ConvertTo-TempUserBatchArgument L494-506	✅
An existing account with the requested name is not promoted or enabled if creation fails	Write-TempUserPayload batch: if not "%RC_ADD%"=="0" goto write_result skips localgroup Administrators, localgroup "Remote Desktop Users", /active:yes	✅ — matches the map.json claim byte-for-byte
Payload is single-use — deletes itself	del /f /q "%~f0" last line of the batch	✅
Payload written with explicit ASCII + CRLF and read back byte-for-byte before use	L603-616 of Write-TempUserPayload	✅ — silent-encoding-conversion attacks blocked
Recovery manifest is atomically written (temp file + move/replace) with readback and cannot silently merge across different UserNames	Write-RevertManifest L676-724, throws on existing.UserName -ine Entry.UserName	✅
Unreadable manifest fails fast rather than corrupting the disk further	Read-RevertManifest L726-…, throws on missing PreviousSetupType/PreviousCmdLine/UserName or invalid ints	✅
Pre-existing nonzero SYSTEM\Setup\SetupType blocks a new operation	Main L946-947 emits SetupHookInUse finding, Repairable = $false	✅
Hive writes are read back on every write	Set-OfflineSetupHook L406-431, Restore-OfflineSetupHook L472-491 both compare after write	✅
The disk is not taken back while the nested guest may still be writing	Stop-NestedRepairVmGraceful gate L1067 — hard-abort if $graceful.Stopped -eq $false	✅
SAM presence alone cannot satisfy success	Main L1077-1085 requires complete payload result matching the requested username; SAM used only as a contradiction signal	✅
revert does not delete an already-created account	Main L847-853 explicitly warns instead of deleting	✅ — deleting a local user offline is a SAM-hive rewrite, correctly refused
detectOnly + revert are mutually exclusive	Main L797-799 hard-errors before any offline work	✅

Opportunities for Improvement

10 points recoverable (current 90 → potential 100). None are blocking for PR #152.

• [P2 — testing framework] Author a persistent breaker script. Skills/.breaker-scripts/ has no break-win-add-temp-user.ps1. This run used an ad-hoc net user labowner /active:no inline. A dedicated breaker with the tag registry would let nightly regression runs pick this scenario up automatically. Suggested payload: (a) disable all enabled Administrators members that are not built-in DefaultAccount/Guest/Administrator, (b) mark the source VM with BreakerStatus=SUCCESS, (c) verify with LogonUser returning ERROR_ACCOUNT_DISABLED.
• [P2 — testing framework] Nightly matrix — the still-unverified cells. Add to the nightly pairwise matrix for win-add-temp-user: WS2019 Gen1 + Gen2 (neither PR author nor this run touched), WS2022 Gen1 (source-VM Gen1 branch on this exact script), WS2025 Gen2 (neither PR author nor this run touched), BitLocker-protected OS disk + TPM protector, and domain-joined VM (the whole reason the script exists over win-create-troubleshooting-user). Reference values from this run for the pairwise generator: rescue-VM size must support nested Hyper-V (Standard_D4s_v5 worked; Standard_D2s_v5 may or may not — docs list v3+ as nested-capable); westus2 has capacity while eastus and eastus2 hit SkuNotAvailable for D2s_v5 on the day of this run (subscription-level flake, not a script bug).
• [P3 — cosmetic] Silence PSScriptAnalyzer false positives. For New-Finding and New-TempUserPassword, add either

  [Diagnostics.CodeAnalysis.SuppressMessageAttribute('PSUseShouldProcessForStateChangingFunctions', '',
      Justification = 'Pure helper; does not change system state.')]

  or rename to a non-state-verb (Get-Finding / Get-TempUserPassword). For Set-OfflineSetupHook, adding [CmdletBinding(SupportsShouldProcess)] with an if ($PSCmdlet.ShouldProcess(...)) guard around the actual hive write would silence the warning while adding a small operational nicety (allows -WhatIf from a wrapper). All three are cosmetic.
• [P4 — DX] One-line operator-log distinguishability. revert=true returns [STATUS]::SUCCESS just like the happy path. Log-Output "REVERT COMPLETE" already exists at L864 so revert runs are distinguishable; this is fine as-is. No change needed.
• [P3 — cross-repo follow-up, not a script defect] Azure/repair-vm-extension DX signals. Two DX signals from this run against the extension, not against the script:
  1. az vm repair restore unconditionally deletes the rescue RG. If a future validation run wants to inspect the emitted win-add-temp-user.log or SAM hive on the rescue VM, that data is gone before the restore returns. A --keep-rescue-vm opt-in flag would fix this (same recommendation as PR153 §Improvements_02 — separate WI already drafted there).
  2. az vm repair create --enable-nested requires a nested-capable size (v3/v4/v5 D/Ds/E family). The current CLI does not clearly warn if a caller passes a non-nested-capable --size; a preflight warning in the returned JSON would help.

How to Reach 100/100

Action	Category Impact	New Score
Add persistent break-win-add-temp-user.ps1 under Skills/.breaker-scripts/	Enables nightly regression	Test Coverage +2
Add nightly cells for WS2019, WS2022-Gen1, WS2025-Gen2, BitLocker, domain-joined	Broadest impact	Test Coverage +4, → 20/20
[SuppressMessageAttribute] (or verb rename) for New-Finding + New-TempUserPassword	Cosmetic	Code Quality +1, → 20/20
[CmdletBinding(SupportsShouldProcess)] on Set-OfflineSetupHook (optional)	Cosmetic	included above
AppInsights emit shim in the repair-vm-extension run-command wrapper	Ecosystem change, not this PR	Telemetry +3, → 20/20

Validation Evidence

Before (broken — labowner disabled by breaker):

LABOWNER_LOGIN_REFUSED_WITH_CORRECT_PASSWORD: LastError=1331
  1331 = ERROR_ACCOUNT_DISABLED (proves account is disabled)

After (repaired — azrepairadmin created, labowner still disabled):

{
  "azrepairadmin_present": true,
  "azrepairadmin_enabled": true,
  "azrepairadmin_in_admins": true,
  "azrepairadmin_in_rdu": true,
  "admin_group_members": [
    "srcvm-ws22-g2\\azrepairadmin",
    "srcvm-ws22-g2\\labowner"
  ],
  "rdu_group_members": [
    "srcvm-ws22-g2\\azrepairadmin"
  ],
  "labowner_present": true,
  "labowner_enabled": false,
  "setup_type": 0,
  "setup_cmdline": "",
  "file_payload_present": false,
  "file_result_present": false,
  "file_manifest_present": false
}

Guest-reported payload result (from az vm repair run output):

add=0     (net user … /add — succeeded)
admin=0   (net localgroup Administrators … /add — succeeded)
rdp=0     (net localgroup "Remote Desktop Users" … /add — succeeded)
active=0  (net user … /active:yes — succeeded)
done=1    (payload reached its terminal line)
user=azrepairadmin

Script self-reported completion (from az vm repair run stdout):

The payload reported: add=0, admin=0, rdp=0, active=0.
The offline SAM contains an account named 'azrepairadmin'.
FINALIZE: restoring and verifying both recorded Setup values from the rescue VM.
SUCCESS: 'azrepairadmin' was created, added to Administrators and enabled, confirmed by the payload result and the offline SAM. The recorded Setup state was restored.
[STATUS]::SUCCESS

Authentication proofs (LogonUser P/Invoke, LOGON32_LOGON_INTERACTIVE):

• LogonUser("azrepairadmin", <machine>, "<generated>", LOGON32_LOGON_INTERACTIVE) — returned true. The generated password is a real, working, RDP-eligible credential.
• LogonUser("labowner", <machine>, "<real-initial-password>", LOGON32_LOGON_INTERACTIVE) — returned false, GetLastWin32Error() == 1331 = ERROR_ACCOUNT_DISABLED. The pre-existing disabled admin was not re-enabled, promoted, or otherwise mutated by the script.

Condensed stdout:

AUTH_SUCCESS: azrepairadmin credentials are valid

Review Checklist

• Fault injection verified (labowner disabled before repair, disabled after repair with ERROR_ACCOUNT_DISABLED on both attempts)
• Code quality clean (PSScriptAnalyzer: 0 errors, 3 low-impact warnings — 2 false positives, 1 optional cosmetic)
• Telemetry coverage reviewed (75 Log-* calls, 0 uninstrumented catch blocks in this script)
• Safety features verified (atomic manifest, batch sanitization, payload self-delete, hive-write readback, graceful-shutdown gate, revert refuses SAM edit)
• Multi-generation tested (WS2022 Gen2 by this run + WS2016 Gen1 & WS2025 Gen1 from PR-body author evidence)

Test Artifacts

Artifact	Path	Purpose
HTML report	Output/TestReports/PR152-win-add-temp-user/2026-09-16/TestReport_01.html	Human-readable single-file report
Improvements report	Output/TestReports/PR152-win-add-temp-user/2026-09-16/Improvements_01.md	Full findings + follow-up items
Execution manifest	Output/TestReports/PR152-win-add-temp-user/2026-09-16/test_execution_manifest_01.json	Machine-readable full manifest
PR comment draft	Output/TestReports/PR152-win-add-temp-user/2026-09-16/PR152_comment.md	This comment body (USER-GATED)
PSScriptAnalyzer output	evidence/scr2-psscriptanalyzer.json	Raw PSSA JSON
Break-step evidence	evidence/scr1-break-disable-admin.json	Confirms labowner was disabled before repair
Post-restore state	evidence/scr3-post-restore-verify-v2.json	Full post-restore state on the source VM
Authentication proof	evidence/scr4-auth-test.json, evidence/scr4b-labowner-still-disabled.json	LogonUser P/Invoke results for azrepairadmin and labowner
az vm repair create log	logs/az-vm-repair-create.log	760 s nested-VM provisioning
az vm repair run log	logs/az-vm-repair-run.log	189 s script run with all guest telemetry
az vm repair restore log	logs/az-vm-repair-restore.log	139 s disk swap

No credentials retained in any artifact. Output/TestReports/PR152-win-add-temp-user/2026-09-16/evidence/.creds-repair and .creds-tempuser were purged before this report was written; the az vm repair run log had the one-time generated password redacted to [REDACTED-GENERATED-PASSWORD].

No SME work item is tracked for this PR — all findings above are inlined; raw artifacts live in this workspace at the paths listed.

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Generated by VMRepairMint Script Testing sub-agent | Head SHA validated: ea46b96325dbaea9400131840b03d13c94f7cbe5 (script content byte-identical to PR-body-declared preview candidate 804cd4ae…)