Akamai EdgeGrid Signature for use as an Octopus build step template

edge.ps1

$RestMethod = "#{RestMethod}"
$AkamaiSecret = "#{AkamaiSecret}"
$AkamaiUri = "#{AkamaiUri}"
$AkamaiObjects = "#{AkamaiObjects}"
$AkamaiClientToken = "#{AkamaiClientToken}"
$AkamaiClientAccessToken = "#{AkamaiClientAccessToken}"

[System.Net.ServicePointManager]::Expect100Continue = $false

function sha256asb64str
{
	param($data)

	$hasher = [System.Security.Cryptography.HashAlgorithm]::Create('sha256')
	$hash = $hasher.ComputeHash([System.Text.Encoding]::UTF8.GetBytes($data))
	[Convert]::ToBase64String($hash)
}


function hmacsha256
{
	param($key,$data)
	$hmac = New-Object System.Security.Cryptography.HMACSHA256
	$hmac.key = [System.Text.Encoding]::UTF8.GetBytes($key)
	$hash = $hmac.ComputeHash([System.Text.Encoding]::UTF8.GetBytes($data))
	return [Convert]::ToBase64String($hash)
}

function MakeAuthHeader
{
	param(
		[uri]$uri,
		[string]$method,
		$headers,
		[string]$clientToken,
		[string]$accessToken,
		[string]$clientSecret,
		[string]$data
	)

	$guid = [Guid]::NewGuid().ToString()
	$timestamp = [datetime]::UtcNow.tostring("yyyyMMddTHH:mm:ss+0000")

	$reqsig = "EG1-HMAC-SHA256 client_token=$($clientToken);access_token=$($accessToken);timestamp=$($timestamp);nonce=$($guid);"

	if( $headers -ne $null )
	{
		$canonHeaders = ($headers.GetEnumerator() | %{ "$($_.name.trim().toLowerInvariant()):$($_.value.trim())" }) -join "`t"
	}
	else
	{
		$canonHeaders = ""
	}
	if( $method -eq "POST" )
	{
		$contentHash = sha256asb64str $data
	}
	else
	{
		$contentHash = ""
	}

	$requestdatafields = @(
		$method.ToUpperInvariant(),
		$uri.Scheme,
		$uri.Host,
		$uri.PathAndQuery,
		$canonHeaders,
		$contentHash,
		$reqsig
	);

	$signingkey = hmacsha256 -key $clientSecret -data $timestamp
	$stringtosign = $requestdatafields -join "`t"
	$signature = hmacsha256 -key $signingKey -data $stringtosign
	$signedheader= "$($reqsig)signature=$($signature)"

	return $signedheader
}

$objectlist = $AkamaiObjects -split ","
$data = @{ "objects" = @($objectlist); } | ConvertTo-Json -depth 99 -Compress
$headers = @{
	"Content-Type"="application/json";
}
$method = $RestMethod
$auth = MakeAuthHeader -uri $AkamaiUri -method $method -headers @{} -clientToken $AkamaiClientToken -accessToken $AkamaiClientAccessToken -clientSecret $AkamaiSecret -data $data
$headers.Add("Authorization",$auth)
$data |  Invoke-Webrequest -UseBasicParsing -Method POST -Uri $AkamaiUri -Headers $headers -UserAgent $null