dotfiles: point git at the Windows SSH client, split out the non-elevated half

[dotfiles] / setup-windows-no-uac.ps1

<#
  setup-windows-no-uac.ps1
  Non-elevated portion of the Windows provisioning. Invoked by setup-windows.bat
  after its winget installs, or run directly from an ordinary (NOT elevated)
  prompt:

      powershell -NoProfile -ExecutionPolicy Bypass -File .\setup-windows-no-uac.ps1

  Run it non-elevated on purpose. Every step here writes per-user state - the
  HKCU PATH and the global .gitconfig under $env:USERPROFILE - so running it
  elevated would configure the *administrator's* profile instead of yours.

  What this installs / configures:
    - WinMerge on the user PATH
    - BinSkim (binary hardening analyzer) in %LOCALAPPDATA%\Programs\BinSkim,
      on the user PATH
    - Global git identity, and core.sshCommand pointed at the Windows OpenSSH
      client so git shares the Windows ssh-agent

  FILL IN $GitUserName / $GitUserEmail below before the first run.

  Steps are independent: one failing warns and the rest still run. The exit code
  is 1 if any step failed, 0 otherwise.
#>

[CmdletBinding()]
param(
    # Skip individual steps. Note that `powershell -File` cannot pass more than
    # one value to an array parameter (neither comma- nor space-separated), so
    # for several, dot-call the script or use -Command:
    #     .\setup-windows-no-uac.ps1 -Skip BinSkim,GitConfig
    #     powershell -File .\setup-windows-no-uac.ps1 -Skip BinSkim
    [ValidateSet('WinMerge', 'BinSkim', 'GitConfig')]
    [string[]] $Skip = @()
)

$ErrorActionPreference = 'Stop'

# --- Global git identity: FILL THESE IN BEFORE RUNNING ---
# Left empty, Set-GlobalGitConfig skips the identity and says so, rather than
# stamping a placeholder onto your commits. Leaving them empty is a legitimate
# choice - it keeps your identity per-repository. core.sshCommand is set either
# way, so the ssh side works regardless.
$GitUserName  = ''   # e.g. 'Ada Lovelace'
$GitUserEmail = ''   # e.g. 'ada@example.com'

# BinSkim's win-x64 build, from the NuGet flat container.
$BinSkimPackage = 'microsoft.codeanalysis.binskim'
$BinSkimDir     = Join-Path $env:LOCALAPPDATA 'Programs\BinSkim'

function Write-Step([string]$Msg) {
    Write-Host "`n==> $Msg" -ForegroundColor Cyan
}

function Add-ToUserPath([string]$Dir) {
    # HKCU PATH, not the process PATH: this must outlive the script. Idempotent,
    # and re-applied on every run so an entry lost to an unrelated PATH edit is
    # repaired without re-doing the install that put it there.
    $user = [Environment]::GetEnvironmentVariable('Path', 'User')
    if (-not $user) { $user = '' }
    if (($user -split ';') -contains $Dir) {
        Write-Host "    $Dir already in user PATH."
        return
    }
    $new = if ($user.Trim()) { $user.TrimEnd(';') + ';' + $Dir } else { $Dir }
    [Environment]::SetEnvironmentVariable('Path', $new, 'User')
    Write-Host "    Added $Dir to user PATH (restart your shell to pick it up)."
}

function Add-WinMergeToUserPath {
    Write-Step 'WinMerge on the user PATH'
    $candidates = @(
        (Join-Path $env:ProgramFiles 'WinMerge'),
        (Join-Path ${env:ProgramFiles(x86)} 'WinMerge'),
        (Join-Path $env:LOCALAPPDATA 'Programs\WinMerge')
    )
    $dir = $candidates |
           Where-Object { Test-Path (Join-Path $_ 'WinMergeU.exe') } |
           Select-Object -First 1
    if (-not $dir) {
        Write-Warning 'WinMerge not found; user PATH unchanged.'
        return
    }
    Add-ToUserPath $dir
}

function Install-BinSkim {
    # BinSkim checks the exact mitigations the native project enables in
    # CMakeLists.txt (CFG/XFG, CET, ASLR/HighEntropyVA, DEP, /GS, stack cookies,
    # DEPENDENTLOADFLAG, ...). The NuGet package ships a self-contained win-x64
    # build, so this needs no .NET SDK/runtime: the .nupkg is a zip - extract the
    # win-x64 tool folder and put it on the PATH. After restarting the shell:
    #     binskim analyze path\to\your.exe
    #
    # VERSION CHECK FIRST. The .nupkg is a large download (well over 100 MB), so
    # ask NuGet what the newest stable version is BEFORE fetching anything, and
    # skip the download entirely when the installed copy already matches.
    # Re-provisioning an up-to-date box should not pay for it.
    #
    # The installed version is recorded in nupkg-version.txt next to the tool.
    # For a copy installed before that marker existed, fall back to BinSkim.exe's
    # own ProductVersion; either way the marker is (re)written once we know the
    # version, so the fallback runs at most once per install. The
    # flat-container URL pins the exact version we checked,
    # unlike the v2 /package/<id> endpoint, which just redirects to whatever is
    # newest at the moment of the request.
    Write-Step 'BinSkim'
    [Net.ServicePointManager]::SecurityProtocol = [Net.SecurityProtocolType]::Tls12

    $exe    = Join-Path $BinSkimDir 'BinSkim.exe'
    $marker = Join-Path $BinSkimDir 'nupkg-version.txt'

    $have = $null
    if (Test-Path $exe) {
        if (Test-Path $marker) {
            $have = (Get-Content $marker -Raw).Trim()
        } else {
            $pv = (Get-Item $exe).VersionInfo.ProductVersion
            # NuGet versions carry no build metadata; ProductVersion may ("1.2.3+sha").
            if ($pv) { $have = $pv.Split('+')[0].Trim() }
        }
    }

    $latest = $null
    try {
        $index = Invoke-RestMethod -UseBasicParsing `
            -Uri "https://api.nuget.org/v3-flatcontainer/$BinSkimPackage/index.json"
        # Versions come back oldest-first; '-' marks a prerelease.
        $latest = $index.versions | Where-Object { $_ -notmatch '-' } | Select-Object -Last 1
    } catch {
        Write-Warning "BinSkim version check failed: $($_.Exception.Message)"
    }

    if (-not $latest) {
        if (-not $have) {
            Write-Warning 'BinSkim not installed and NuGet unreachable; skipping.'
            return
        }
        Write-Host "    BinSkim $have kept (could not reach NuGet to check for a newer one)."
    } elseif ($have -and ($have -eq $latest -or $have -eq "$latest.0")) {
        Write-Host "    BinSkim $have is already the newest stable release; skipping download."
        # Records what the ProductVersion fallback just worked out, so the next
        # run reads the marker instead of re-deriving it.
        Set-Content -Path $marker -Value $latest -Encoding ascii
    } else {
        if ($have) {
            Write-Host "    BinSkim $have -> $latest; downloading."
        } else {
            Write-Host "    BinSkim $latest; downloading."
        }
        $tmp = Join-Path $env:TEMP ('binskim_' + [guid]::NewGuid().ToString('N'))
        New-Item -ItemType Directory -Force -Path $tmp | Out-Null
        try {
            $zip = Join-Path $tmp 'binskim.zip'
            Invoke-WebRequest -UseBasicParsing -OutFile $zip `
                -Uri "https://api.nuget.org/v3-flatcontainer/$BinSkimPackage/$latest/$BinSkimPackage.$latest.nupkg"
            Expand-Archive -Path $zip -DestinationPath $tmp -Force

            $src = Get-ChildItem -Path $tmp -Recurse -Filter 'BinSkim.exe' |
                   Where-Object { $_.FullName -match 'win-x64' } |
                   Sort-Object FullName | Select-Object -Last 1
            if (-not $src) { throw 'BinSkim.exe (win-x64) not found in package.' }

            # Replace wholesale rather than merging over the old tree, so files
            # dropped between releases don't linger.
            if (Test-Path $BinSkimDir) { Remove-Item -Recurse -Force $BinSkimDir }
            New-Item -ItemType Directory -Force -Path $BinSkimDir | Out-Null
            Copy-Item -Path (Join-Path $src.Directory.FullName '*') `
                      -Destination $BinSkimDir -Recurse -Force
            # Written last: the marker must only claim a version that fully landed.
            Set-Content -Path $marker -Value $latest -Encoding ascii
            Write-Host "    BinSkim $latest installed to $BinSkimDir"
        } finally {
            Remove-Item -Recurse -Force $tmp -ErrorAction SilentlyContinue
        }
    }

    Add-ToUserPath $BinSkimDir
}

function Get-GitPath {
    # winget installed Git moments ago, but this process inherited its PATH
    # before that happened, so Get-Command can miss it on a first run. Prefer a
    # git already on PATH, then the usual install roots.
    $onPath = Get-Command git.exe -ErrorAction SilentlyContinue
    if ($onPath) { return $onPath.Source }
    $roots = @(
        (Join-Path $env:ProgramFiles 'Git\cmd\git.exe'),
        (Join-Path ${env:ProgramFiles(x86)} 'Git\cmd\git.exe'),
        (Join-Path $env:LOCALAPPDATA 'Programs\Git\cmd\git.exe')
    )
    return $roots | Where-Object { Test-Path $_ } | Select-Object -First 1
}

function Set-GlobalGitConfig {
    Write-Step 'Global git config'
    $git = Get-GitPath
    if (-not $git) {
        Write-Warning 'git.exe not found; skipping global git config.'
        return
    }
    Write-Host "    using $git"

    if (-not $GitUserName -or -not $GitUserEmail) {
        Write-Host '    Identity not configured; leaving user.name / user.email alone.' -ForegroundColor Yellow
        Write-Host '    Fill in $GitUserName / $GitUserEmail at the top of this script, or set' -ForegroundColor Yellow
        Write-Host '    your identity per-repository.' -ForegroundColor Yellow
    } else {
        & $git config --global user.name  $GitUserName
        & $git config --global user.email $GitUserEmail
        Write-Host "    identity: $GitUserName <$GitUserEmail>"
    }

    # --- Make git use the Windows OpenSSH client ---
    # Git for Windows ships its own MSYS2 ssh.exe and prefers it, and that client
    # cannot reach the Windows ssh-agent service that the elevated half enables:
    # Win32-OpenSSH publishes the agent on a named pipe the MSYS2 build does not
    # speak. So keys added with `ssh-add` from PowerShell stay invisible to git,
    # and a push falls back to hunting for a key file and prompting for its
    # passphrase. Pointing core.sshCommand at the in-box ssh.exe gives git the
    # same client, the same agent, and the same %USERPROFILE%\.ssh\config as
    # `ssh` from an ordinary shell.
    $winSsh = Join-Path $env:WINDIR 'System32\OpenSSH\ssh.exe'
    if (-not (Test-Path $winSsh)) {
        Write-Warning "No Windows OpenSSH client at $winSsh. Add the 'OpenSSH Client' optional feature and re-run; until then git uses its own bundled ssh.exe, which cannot see keys held by the Windows ssh-agent service."
        return
    }
    # Forward slashes on purpose: git parses core.sshCommand with shell quoting
    # rules, in which a backslash is an escape character.
    $value = $winSsh -replace '\\', '/'
    & $git config --global core.sshCommand $value
    Write-Host "    core.sshCommand: $value"
}

# ---------------------------------------------------------------------------
# Main
# ---------------------------------------------------------------------------
if (([Security.Principal.WindowsPrincipal][Security.Principal.WindowsIdentity]::GetCurrent()).IsInRole(
        [Security.Principal.WindowsBuiltInRole]::Administrator)) {
    Write-Warning 'Running elevated. The user PATH and .gitconfig changes below will apply to the administrator profile, not yours.'
}

$steps = [ordered]@{
    WinMerge  = { Add-WinMergeToUserPath }
    BinSkim   = { Install-BinSkim }
    GitConfig = { Set-GlobalGitConfig }
}

$failed = @()
foreach ($name in $steps.Keys) {
    if ($Skip -contains $name) {
        Write-Host "`n==> $name (skipped)" -ForegroundColor DarkGray
        continue
    }
    try {
        & $steps[$name]
    } catch {
        # One broken step must not cost the others. Collect and report at the end.
        Write-Warning "$name failed: $($_.Exception.Message)"
        $failed += $name
    }
}

if ($failed) {
    Write-Host "`n[setup-windows-no-uac] FAILED: $($failed -join ', ')" -ForegroundColor Red
    exit 1
}
Write-Host "`n[setup-windows-no-uac] All steps completed." -ForegroundColor Green
exit 0