class/Class.ps1

class ApiClient {
  [System.Net.Http.HttpClientHandler]$Handler
  [System.Net.Http.HttpClient]$Client
  [System.Collections.Hashtable]$Collector
  [string]$UserAgent
  ApiClient() {
    $this.Collector = $null
    $this.Handler = [System.Net.Http.HttpClientHandler]::New()
    $this.Client = [System.Net.Http.HttpClient]::New($this.Handler)
    $this.Client.Timeout = [System.TimeSpan]::New(0,1,0)
    $this.UserAgent = 'crowdstrike-psfalcon/2.2.7'
  }
  [string] Path([string]$Path) {
    $Output = if (![IO.Path]::IsPathRooted($Path)) {
      # Convert partial file path to a full file path
      $FullPath = Join-Path -Path (Get-Location).Path -ChildPath $Path
      $FullPath = Join-Path -Path $FullPath -ChildPath '.'
      [IO.Path]::GetFullPath($FullPath)
    } else {
      $Path
    }
    return $Output
  }
  [System.Object] Invoke([System.Object]$Param) {
    # Send API endpoint and headers to verbose stream
    $this.Verbose('ApiClient.Invoke',($Param.Method.ToUpper(),$Param.Path -join ' '))
    if ($Param.Headers) {
      [string]$Verbose = $Param.Headers.GetEnumerator().foreach{ "$($_.Key)=$($_.Value)" } -join ', '
      if ($Verbose) { $this.Verbose('ApiClient.Invoke',$Verbose) }
    }
    $Output = try {
      # Create basic HTTP request message and add headers
      $Message = [System.Net.Http.HttpRequestMessage]::New($Param.Method.ToUpper(),$Param.Path)
      $Param.Headers.GetEnumerator().foreach{ $Message.Headers.Add($_.Key,$_.Value) }
      if ($Param.Formdata) {
        # Create Formdata message
        $Message.Content = [System.Net.Http.MultipartFormDataContent]::New()
        $Param.Formdata.GetEnumerator().foreach{
          $Verbose = if ($_.Key -match '^((data_)?file|upfile)$') {
            # With 'file' or 'upfile', create StreamContent from key/value pair
            $FileStream = [System.IO.FileStream]::New($this.Path($_.Value),[System.IO.FileMode]::Open)
            $Filename = [System.IO.Path]::GetFileName($this.Path($_.Value))
            $StreamContent = [System.Net.Http.StreamContent]::New($FileStream)
            $FileType = $this.StreamType($Filename)
            if ($FileType) { $StreamContent.Headers.ContentType = $FileType }
            $Message.Content.Add($StreamContent,$_.Key,$Filename)
            @($_.Key,'<StreamContent>') -join '='
          } else {
            # Add StringContent for other Formdata key/value pairs
            $Message.Content.Add([System.Net.Http.StringContent]::New($_.Value),$_.Key)
            @($_.Key,$_.Value) -join '='
          }
          $this.Verbose('ApiClient.Invoke',($Verbose -join ', '))
        }
      } elseif ($Param.Body) {
        $Message.Content = if ($Param.Body -is [string] -and $Param.Headers.ContentType) {
          # Add 'Body' as StringContent
          [System.Net.Http.StringContent]::New($Param.Body,[System.Text.Encoding]::UTF8,$Param.Headers.ContentType)
          if ($Param.Path -notmatch '/oauth2/token$') { $this.Verbose('ApiClient.Invoke',$Param.Body) }
        } else {
          $Param.Body
        }
      }
      # Log request when enabled
      if ($this.Collector.Enable -contains 'requests') { $this.Log($Message) }
      $Request = if ($Param.Outfile) {
        # Download file
        @($Param.Headers.Keys).foreach{ $this.Client.DefaultRequestHeaders.Add($_,$Param.Headers.$_) }
        $this.Verbose('ApiClient.Invoke','Receiving ByteArray content...')
        $this.Client.GetByteArrayAsync($Param.Path)
      } else {
        # Send request
        $this.Client.SendAsync($Message,[System.Net.Http.HttpCompletionOption]::ResponseHeadersRead)
      }
      if ($Request -and $Param.Outfile) {
        try {
          # Download file to provided 'OutFile' path and display file information when successful
          $LocalPath = $this.Path($Param.Outfile)
          $this.Verbose('ApiClient.Invoke',"Creating '$LocalPath'.")
          [System.IO.File]::WriteAllBytes($LocalPath,$Request.Result)
          if (Test-Path $LocalPath) { Get-ChildItem $LocalPath | Select-Object FullName,Length,LastWriteTime }
        } catch {
          throw $_
        } finally {
          @($Param.Headers.Keys).foreach{
            if ($this.Client.DefaultRequestHeaders.$_) { [void]($this.Client.DefaultRequestHeaders.Remove($_)) }
          }
        }
      } elseif ($Request) {
        # Output HTTP response code to verbose stream
        $HashCode = if ($Request.Result.StatusCode) { $Request.Result.StatusCode.GetHashCode() }
        if ($HashCode) { $this.Verbose('ApiClient.Invoke',($HashCode,$Request.Result.StatusCode -join ': ')) }
        if ($Request.Result.Headers) {
          # Output response headers to verbose stream and warn when 'X-Api-Deprecation' appears
          $this.Verbose('ApiClient.Invoke',"$($Request.Result.Headers.GetEnumerator().foreach{
            @($_.Key,(@($_.Value) -join ', ')) -join '=' } -join ', ')"
)
          @($Request.Result.Headers.GetEnumerator().Where({$_.Key -match '^X-Api-Deprecation'})).foreach{
            Write-Warning ([string]$_.Key,[string]$_.Value -join ': ')
          }
        }
        if ($Request.Result.Content -and $this.Collector.Enable -contains 'responses') {
          # Log response when enabled
          $this.Log($Request.Result)
        }
        $RetryAfter = if ($HashCode -eq 429 -and $Param.Path -notmatch '/oauth2/token$') {
          # Capture 'X-Ratelimit-Retryafter' when present
          $Request.Result.Headers.GetEnumerator().Where({$_.Key -eq 'X-Ratelimit-Retryafter'}).Value
        }
        if ($RetryAfter) {
          # Subtract current time from 'X-Ratelimit-Retryafter', warn, and retry when rate limited
          [int32]$Wait = (([System.DateTimeOffset]::FromUnixTimeSeconds($RetryAfter)).LocalDateTime -
            (Get-Date)).Seconds
          $Limit = $Request.Result.Headers.GetEnumerator().Where({$_.Key -eq 'X-Ratelimit-Limit'}).Value
          $Remaining = $Request.Result.Headers.GetEnumerator().Where({$_.Key -eq 'X-Ratelimit-Remaining'}).Value
          Write-Warning ('Rate limited for {0} second(s). [{1}, {2}]' -f $Wait,('Limit',$Limit -join '='),
            ('Remaining',$Remaining -join '='))
          Start-Sleep -Seconds $Wait
          $this.Invoke($Param)
        } elseif ($Request.Result.Content -and $Param.Path -notmatch '/oauth2/token$') {
          # Convert from Json or output string content
          if ($Request.Result.Content.Headers.ContentType -eq 'application/json' -or
          $Request.Result.Content.Headers.ContentType.MediaType -eq 'application/json') {
            ConvertFrom-Json ($Request.Result.Content).ReadAsStringAsync().Result
          } else {
            ($Request.Result.Content).ReadAsStringAsync().Result
          }
        } else {
          # Output entire response
          $Request
        }
      }
    } catch {
      throw $_
    } finally {
      if ($Request) { $Request.Dispose() }
    }
    return $Output
  }
  [void] Log([System.Object]$Object) {
    # Create Falcon LogScale/NGSIEM message payload from 'HttpRequestMessage' or 'HttpResponseMessage'
    $Timestamp = if ($this.Collector.Token -match '^[a-fA-F0-9]{32}$') {
      [DateTimeOffset]::UtcNow.ToUnixTimeMilliseconds()
    } else {
      Get-Date -Format o
    }
    if ($this.Collector.Token -match '^[a-fA-F0-9]{32}$') {
      $Item = @{
        event = @{
          '@timestamp' = $Timestamp
          '@sourcetype' = $this.UserAgent
          '#ecs.version' = '8.11.0'
          '#Cps.version' = '1.0.0'
          'Parser.version' = '1.0.0'
        }
      }
      if ($Object -is [System.Net.Http.HttpRequestMessage]) {
        # Add request URI, method and headers (without 'authorization')
        $Item.event['url.full'] = $Object.RequestUri.ToString()
        $Item.event['http.request.method'] = $Object.Method.ToString()
        $Item.event['http.request.headers'] = @{}
        $Object.Headers.GetEnumerator().Where({$_.Key -ne 'Authorization'}).foreach{
          $Item.event.'http.request.headers'[$_.Key] = $_.Value
        }
        if ($Object.Content) {
          # Redact 'client_secret' from request
          $Item.event['http.request.body.content'] =
            $Object.Content.ReadAsStringAsync().Result -replace 'client_secret=\w+&?','client_secret=redacted'
        }
      } elseif ($Object -is [System.Net.Http.HttpResponseMessage]) {
        $Item.event['http.response.headers'] = @{}
        $Object.Headers.GetEnumerator().foreach{ $Item.event.'http.response.headers'[$_.Key] = $_.Value }
        if ($Object.Content -and ($Object.Content.Headers.ContentType -eq 'application/json' -or
        $Object.Content.Headers.ContentType.MediaType -eq 'application/json')) {
          # Add response content (excluding 'access_token')
          $Content = @{}
          @(($Object.Content.ReadAsStringAsync().Result | ConvertFrom-Json).PSObject.Properties).Where({
          $_.Name -ne 'access_token'}).foreach{ $Content[$_.Name] = $_.Value }
          $Item.event['http.response.body.content'] = $Content
        } elseif ($Object.Content) {
          # Add content as a string when unable to determine if 'HttpRequestMessage' or 'HttpResponseMessage'
          $Item.event['http.response.body.content'] = $Object.Content.ReadAsStringAsync().Result
        }
      }
    } else {
      $Item = @{ timestamp = $Timestamp; attributes = @{ Headers = @{} }}
      if ($Object -is [System.Net.Http.HttpRequestMessage]) {
        @('RequestUri','Method').foreach{ $Item.attributes[$_] = $Object.$_.ToString() }
        $Object.Headers.GetEnumerator().Where({$_.Key -ne 'Authorization'}).foreach{
          $Item.attributes.Headers[$_.Key] = $_.Value
        }
        if ($Object.Content) {
          # Redact 'client_secret' from request
          $Item.attributes['Content'] = $Object.Content.ReadAsStringAsync().Result -replace 'client_secret=\w+&?',
            'client_secret=redacted'
        }
      } elseif ($Object -is [System.Net.Http.HttpResponseMessage]) {
        $Object.Headers.GetEnumerator().foreach{ $Item.attributes.Headers[$_.Key] = $_.Value }
        if ($Object.Content -and ($Object.Content.Headers.ContentType -eq 'application/json' -or
        $Object.Content.Headers.ContentType.MediaType -eq 'application/json')) {
          @(($Object.Content.ReadAsStringAsync().Result | ConvertFrom-Json).PSObject.Properties).Where({
          $_.Name -ne 'access_token'}).foreach{
            # Add content, but exclude 'access_token'
            $Item.attributes[$_.Name] = $_.Value
          }
        } elseif ($Object.Content) {
          # Add content as a string when unable to determine if 'HttpRequestMessage' or 'HttpResponseMessage'
          $Item.attributes['Content'] = $Object.Content.ReadAsStringAsync().Result
        }
      }
    }
    # Use Invoke-RestMethod to send to Falcon LogScale/NGSIEM within a background job
    $Job = @{
      Name = 'ApiClient_Log',$Timestamp -join '.'
      ScriptBlock = { $Param = $args[0]; Invoke-RestMethod @Param }
      ArgumentList = @{
        Uri = $this.Collector.Uri
        Method = 'post'
        Headers = @{ Authorization = 'Bearer',$this.Collector.Token -join ' '; ContentType = 'application/json' }
        Body = if ($this.Collector.Token -match '^[a-fA-F0-9]{32}') {
          ConvertTo-Json $Item -Depth 32 -Compress
        } else {
          ConvertTo-Json @(
            @{
              tags = @{
                host = [System.Net.Dns]::GetHostName()
                source = $this.UserAgent
              }
              events = @(,$Item)
            }
          ) -Depth 32 -Compress
        }
      }
    }
    [void](Start-Job @Job)
    $this.Verbose('ApiClient.Log',"Submitted job '$($Job.Name)'.")
    @(Get-Job | Where-Object { $_.Name -match '^ApiClient_Log' -and $_.State -eq 'Completed' }).foreach{
      # Remove completed background jobs
      $this.Verbose('ApiClient.Log',"Removed job '$($_.Name)'.")
      Remove-Job -Id $_.Id
    }
  }
  [string] StreamType([string]$String) {
    [string]$Extension = [System.IO.Path]::GetExtension($String) -replace '^\.',$null
    $Output = switch -Regex ($Extension) {
      # Output string based on file extension
      '^(bmp|gif|jp(e?)g|png)$' { "image/$_" }
      '^(pdf|zip)$' { "application/$_" }
      '^7z$' { 'application/x-7z-compressed' }
      '^(yaml|yml)$' { 'application/yaml' }
      '^(csv|txt)$' { if ($_ -eq 'txt') { 'text/plain' } else { "text/$_" }}
      '^doc(x?)$' {
        if ($_ -match 'x$') {
          'application/vnd.openxmlformats-officedocument.wordprocessingml.document'
        } else {
          'application/msword'
        }
      }
      '^ppt(x?)$' {
        if ($_ -match 'x$') {
          'application/vnd.openxmlformats-officedocument.presentationml.presentation'
        } else {
          'application/vnd.ms-powerpoint'
        }
      }
      '^xls(x?)$' {
        if ($_ -match 'x$') {
          'application/vnd.openxmlformats-officedocument.spreadsheetml.sheet'
        } else {
          'application/vnd.ms-excel'
        }
      }
    }
    return $Output
  }
  [void] Verbose([string]$Function,[string]$String) {
    Write-Verbose ((Get-Date -Format 'HH:mm:ss'),"[$Function]",$String -join ' ')
  }
}