Powershell Script to call out to AWS APIGateway

Powershell script that enables you to call out to AWS API Gateway on a given node.

$apiGatewayEndpoint = "apiGatewatyId i.e. m123abc2d1"
$region = "us-west-2"

function HmacSHA256($message, $secret)
{
    $hmacsha = New-Object System.Security.Cryptography.HMACSHA256
    $hmacsha.key = $secret
    $signature = $hmacsha.ComputeHash([Text.Encoding]::ASCII.GetBytes($message))

    return $signature
}

function getSignatureKey($key, $dateStamp, $regionName, $serviceName)
{
    $kSecret = [Text.Encoding]::UTF8.GetBytes(("AWS4" + $key).toCharArray())
    $kDate = HmacSHA256 $dateStamp $kSecret;
    $kRegion = HmacSHA256 $regionName $kDate;
    $kService = HmacSHA256 $serviceName $kRegion;
    $kSigning = HmacSHA256 "aws4_request" $kService;

    return $kSigning
}

function hash($request)
{
    $hasher = [System.Security.Cryptography.SHA256]::Create()
    $content = [Text.Encoding]::UTF8.GetBytes($request)
    $bytes = $hasher.ComputeHash($content)

    return ($bytes|ForEach-Object ToString x2) -join ''
}

function GETAPIGatewayResponse($nodeIp, $request) {
    $br = [regex]::Unescape('\u000a')

    #$access_key = aws configure get aws_access_key_id --profile $credName
    #$secret_key = aws configure get aws_secret_access_key --profile $credName
    
    $now = [DateTime]::UtcNow
    $amz_date = $now.ToString('yyyyMMddTHHmmssZ')
    $datestamp = $now.ToString('yyyyMMdd')
    $service = "execute-api"
    $method = "GET"

    $apiGatewayId = $apiGatewayEndpoint

    $host1 = "$($apiGatewayId).execute-api.$($region).amazonaws.com"

    $signed_headers = 'host'
    $credential_scope = $datestamp + '/' + $region + '/' + $service + '/' + 'aws4_request'

    $canonical_querystring = ''
    $canonical_querystring = 'X-Amz-Algorithm=AWS4-HMAC-SHA256'
    $canonical_querystring += '&X-Amz-Credential=' + [uri]::EscapeDataString(($access_key + '/' + $credential_scope))
    $canonical_querystring += '&X-Amz-Date=' + $amz_date
    $canonical_querystring += '&X-Amz-SignedHeaders=' + $signed_headers

    $canonical_headers = 'host:' + $host1 + $br

    $canonical_request = $method + $br
    $canonical_request += "/test/host/" + $nodeIp + "/" + $request + $br
    $canonical_request += $canonical_querystring + $br
    $canonical_request += $canonical_headers + $br
    $canonical_request += $signed_headers + $br
    $canonical_request += hash -request ""

    $algorithm = 'AWS4-HMAC-SHA256'

    $canonical_request_hash = hash -request $canonical_request
    $string_to_sign = $algorithm + $br
    $string_to_sign += $amz_date + $br
    $string_to_sign += $credential_scope + $br
    $string_to_sign += $canonical_request_hash

    $signing_key = getSignatureKey $secret_key $datestamp $region $service
    $signature =  HmacSHA256 -secret $signing_key -message $string_to_sign
    $signature = ($signature|ForEach-Object ToString x2) -join ''

    $canonical_querystring += '&X-Amz-Signature=' + $signature

    $request_url = "https://" + $host1 + "/test/host/" + $nodeIp + "/" + $request + "?" + $canonical_querystring

    Write-Host "Request: $($request), RequestUrl: $($request_url)"

    $StandardHeaders = @{
        "Accept"="application/json"
        "Content-Type"="application/json"
    }
   
    $apiGatwayResponse = Invoke-WebRequest -Method GET -Headers $StandardHeaders -Uri $request_url

    if([int]$apiGatwayResponse.StatusCode -ge 200 -AND [int]$apiGatwayResponse.StatusCode -lt 300) {
        #do something with response
    } else {
        Write-Host "Request to $($request_url) failed"
    }
}

GETAPIGatewayResponse -nodeIp "127.0.0.1" -request "api/endpoint"