Azure storage API: download entire folder / prefix / directory - powershell

Question

I need to be able to download a folder with its contents from a blob storage account using the Azure Storage REST API only.
I have created a function (New-StorageAccountAthorisationHeader) that creates the (authentication) header that I can download a single file, but I cannot find any reference on how I might go about downloading the whole folder.
If I pass the folder as the $blob parameter, I get a BlobNotFound error.
The URL of the said folder is: https://mystorageaccount.blob.core.windows.net/acontainer/somefolder. The contents of "somefolder" looks like:
Folder1
FolderA
FileA.txt
FolderB
FileB.txt
FileC.txt
New-StorageAccountAthorisationHeader:
function New-StorageAccountAuthorizationHeader
{
[cmdletbinding()]
param
(
[string]$StorageAccountName,
[string]$Container,
[string]$Blob,
[string]$accesskey ,
[string]$ResourceUri,
[string]$xmsversion = "2017-04-17"
)
$xmsdate = Get-Date
$xmsdate = $xmsdate.ToUniversalTime()
$xmsdate = $xmsdate.toString('r')
function GetRestApiParameters
{
[cmdletbinding()]
param
(
[Parameter(Mandatory=$true)]
[string]$Uri
)
if($Uri.Contains("?"))
{
Write-Verbose "URI to extract REST parameters: $uri"
return ($Uri.Split("?")[1]).Split("&")
}
}
Write-Verbose "Generating string for signature encryption..."
$partUrl = "/$StorageAccountName/"
if($Container)
{
$partUrl = $partUrl + "$Container/"
}
if($Blob)
{
$parturl = $partUrl + "$Blob"
}
######Don't change the line count or indentation of the here-string#####
$hereString = #"
GET
x-ms-date:$xmsdate
x-ms-version:$xmsversion
$partUrl
"#
$hereString =$hereString -replace "$([char]13)$([char]10)","$([char]10)" #Change `r`n to just `n
$empty = $oSignature = New-Object System.Text.StringBuilder
$empty = $oSignature.Append($hereString)
Write-Verbose "Appending parameters from URI into authorisation string..."
$restParameters = GetRestApiParameters -Uri $ResourceUri -Verbose
if ($restParameters -ne $null)
{
foreach ($param in $restParameters)
{
$empty = $oSignature.Append("$([char]10)$($param.Replace('=',':'))")
}
}
#$oSignature.toString()
Write-Verbose "Encrypting string..."
$hmacsha = New-Object System.Security.Cryptography.HMACSHA256
$hmacsha.key = [Convert]::FromBase64String($accesskey)
$signature = $hmacsha.ComputeHash([Text.Encoding]::UTF8.GetBytes($oSignature.ToString()))
$signature = [Convert]::ToBase64String($signature)
Write-Verbose "Building header..."
$headers = New-Object "System.Collections.Generic.Dictionary[[String],[String]]"
$headers.Add("x-ms-version", $xmsversion)
$headers.Add("x-ms-date", $xmsdate)
$headers.Add("Authorization", "SharedKey " + $StorageAccountName + ":" + $signature)
#$headers.Add("x-ms-blob-type","BlockBlob")
#$headers.Add("Content-Type", "application\xml")
Write-Verbose ("Header: $($headers | Out-String)")
Return $headers
}
And I would call it:
$StorageAccountName = "mystorageaccount"
$container = "acontainer"
$blob = "somefile.txt"
$uriToDownloadBlobs = "https://" + $StorageAccountName + ".blob.core.windows.net/$container/$blob"
$header = $null
$header = New-StorageAccountAuthorizationHeader -StorageAccountName $StorageAccountName -ResourceUri $uriToDownloadBlobs -Verbose -Container $container -Blob $blob
$result = Invoke-WebRequest -Headers $header -Uri $uriToDownloadBlobs -OutFile C:\Temp\$blob -PassThru
$result
So this works, but as I said, I'm after any hints to help with downloading the whole folder.

Answer 1

It looks like this is not possible? Although I'd be interested to see how it's done with the likes of Azure Storage Explorer.
My solution was to zip the files up and then use the above to download the single ZIP file. A few extra lines of code to compress and extract at either end, but it was the quickest way at the time and it works well with VSTS tasks.