Use Powershell to get blob from Azure Storage without using the Azure PowerShell module

Question

I've tried this answer but it is for Azure Table Storage, how do I retrive a blob from Azure storage with Powershell but without the use of the Azure Powershell Module? In the documentation it says that I should create a string from

StringToSign = VERB + "\n" +  
           Content-MD5 + "\n" +  
           Content-Type + "\n" +  
           Date + "\n" +  
           CanonicalizedHeaders +   
           CanonicalizedResource;

but when I add those to the function previously mentioned, it still doesn't work, what do I do wrong?

Oskar · Accepted Answer · 2019-02-06 13:33:14Z

Turns out there is a little mistake in the docs, you need a newline after CanonicalizedHeaders as well, even if the docs says otherwise. If you read carefully the next code example in the docs they actually have that newline there:

PUT\n\ntext/plain; charset=UTF-8\n\nx-ms-date:Sun, 20 Sep 2009 20:36:40 GMT\nx-ms-meta-m1:v1\nx-ms-meta-m2:v2\n/testaccount1/mycontainer/hello.txt

Anyway, here is a fully functioning script to get a blob from Azure Blob Storage:

function GenerateHeader(
    [string]$accountName,
    [string]$accountKey,
    [string]$verb,
    [string]$resource)
{
    $xmsversion = '2015-02-21'
    $xmsdate = Get-Date
    $xmsdate = $xmsdate.ToUniversalTime()
    $xmsdate = $xmsdate.toString('R')

    $newLine = "`n";

    $contentType = 'application/json'

    $headers = New-Object "System.Collections.Generic.Dictionary[[String],[String]]"
    $headers.Add("Content-Type", $contentType)
    $headers.Add("x-ms-date", $xmsdate)
    $headers.Add("x-ms-version", $xmsversion)

    $canonicalizedHeaders = "x-ms-date:$xmsdate"+$newLine+"x-ms-version:$xmsversion"
    $canonicalizedResource = $resource

    $stringToSign = $verb.ToUpper() + $newLine +`
                $contentMD5 + $newLine +`
                $contentType + $newLine +`
                $dateHeader + $newLine +`
                $canonicalizedHeaders + $newLine +`
                $canonicalizedResource;

    $hmacsha = New-Object System.Security.Cryptography.HMACSHA256
    $hmacsha.key = [Convert]::FromBase64String($accountKey)
    $signature = $hmacsha.ComputeHash([Text.Encoding]::UTF8.GetBytes($stringToSign))
    $signature = [Convert]::ToBase64String($signature)
    $headers.Add("Authorization", "SharedKeyLite " + $accountName + ":" + $signature)

    return $headers
}

$accountName = ''
$accountKey = ''
$container = ''
$fileName = ''

$blobUri = "https://$accountName.blob.core.windows.net/$container/$fileName"
$outputPath = "$PSScriptRoot\$fileName"
$headers = GenerateHeader $accountName $accountKey 'GET' "/$accountName/$container/$fileName"

$webClient = New-Object System.Net.WebClient

foreach ($key in $headers.Keys)
{
    $webClient.Headers.Add($key, $headers[$key])
}

$start_time = Get-Date
$webClient.DownloadFile($blobUri, $outputPath)
Write-Output "Time taken: $((Get-Date).Subtract($start_time).Seconds) second(s)"
Write-Output $stringToSign

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