cipd.ps1

# Copyright (c) 2016 The Chromium Authors. All rights reserved.
# Use of this source code is governed by a BSD-style license that can be
# found in the LICENSE file.

Param(
  # Path to download the CIPD binary to.
  [parameter(Mandatory=$true)][string]$CipdBinary,
  # E.g. "https://chrome-infra-packages.appspot.com".
  [parameter(Mandatory=$true)][string]$BackendURL,
  # Path to the cipd_client_version file with the client version.
  [parameter(Mandatory=$true)][string]$VersionFile
)

$DepotToolsPath = Split-Path $MyInvocation.MyCommand.Path -Parent

if ([System.IntPtr]::Size -eq 8)  {
  $Platform = "windows-amd64"
} else {
  $Platform = "windows-386"
}

# Put depot_tool's git revision into the user agent string.
try {
  $DepotToolsVersion = &git -C $DepotToolsPath rev-parse HEAD 2>&1
  if ($LastExitCode -eq 0) {
    $UserAgent = "depot_tools/$DepotToolsVersion"
  } else {
    $UserAgent = "depot_tools/???"
  }
} catch [System.Management.Automation.CommandNotFoundException] {
  $UserAgent = "depot_tools/no_git/???"
}
$Env:CIPD_HTTP_USER_AGENT_PREFIX = $UserAgent


# Tries to delete the file, ignoring errors. Used for best-effort cleanups.
function Delete-If-Possible($path) {
  try {
    [System.IO.File]::Delete($path)
  } catch {
    $err = $_.Exception.Message
    echo "Warning: error when deleting $path - $err. Ignoring."
  }
}


# Returns the expected SHA256 hex digest for the given platform reading it from
# *.digests file.
function Get-Expected-SHA256($platform) {
  $digestsFile = $VersionFile+".digests"
  foreach ($line in Get-Content $digestsFile) {
    if ($line -match "^([0-9a-z\-]+)\s+sha256\s+([0-9a-f]+)$") {
      if ($Matches[1] -eq $platform) {
        return $Matches[2]
      }
    }
  }
  throw "No SHA256 digests for $platform in $digestsFile"
}


# Returns SHA256 hex digest of a binary file at the given path.
function Get-Actual-SHA256($path) {
  # Note: we don't use Get-FileHash to be compatible with PowerShell v3.0
  $file = [System.IO.File]::Open($path, [System.IO.FileMode]::Open)
  try {
    $algo = New-Object System.Security.Cryptography.SHA256Managed
    $hash = $algo.ComputeHash($file)
  } finally {
    $file.Close()
  }
  $hex = ""
  foreach ($byte in $hash) {
    $hex += $byte.ToString("x2")
  }
  return $hex
}


$ExpectedSHA256 = Get-Expected-SHA256 $Platform
$Version = (Get-Content $VersionFile).Trim()
$URL = "$BackendURL/client?platform=$Platform&version=$Version"


# Use a lock file to prevent simultaneous processes from stepping on each other.
$CipdLockPath = Join-Path $DepotToolsPath -ChildPath ".cipd_client.lock"
$TmpPath = $CipdBinary + ".tmp"
while ($true) {
  $CipdLockFile = $null
  try {
    $CipdLockFile = [System.IO.File]::OpenWrite($CipdLockPath)

    echo "Downloading CIPD client for $Platform from $URL..."
    $wc = (New-Object System.Net.WebClient)
    $wc.Headers.Add("User-Agent", $UserAgent)
    $wc.DownloadFile($URL, $TmpPath)

    $ActualSHA256 = Get-Actual-SHA256 $TmpPath
    if ($ActualSHA256 -ne $ExpectedSHA256) {
      throw "Invalid SHA256 digest: $ActualSHA256 != $ExpectedSHA256"
    }

    Move-Item -LiteralPath $TmpPath -Destination $CipdBinary -Force
    break

  } catch [System.IO.IOException] {
    echo "CIPD bootstrap lock is held, trying again after delay..."
    Start-Sleep -s 1
  } catch {
    throw  # for some reason this is needed to exit while(...) loop on errors
  } finally {
    Delete-If-Possible $TmpPath
    if ($CipdLockFile) {
      $CipdLockFile.Close()
      Delete-If-Possible $CipdLockPath
    }
  }
}