How can I download a file from S3 via Powershell without installing AWS SDK?

问题

I want to download a file from my AWS S3 bucket using Windows Powershell. I cannot install any AWS software and need to create an API to be able to access a file in AWS S3. I used Postman for testing that the file is accessible and it was successful.

Given this success I tried following AWS' guide which says that I need to create the following:

Create a canonical request.
Use the canonical request and additional metadata to create a string for signing.
Derive a signing key from your AWS secret access key. Then use the signing key, and the string from the previous step, to create a signature.
Add the resulting signature to the HTTP request in a header or as a query string parameter.

The closest I've seen is this example from https://forums.aws.amazon.com/thread.jspa?threadID=251722 by Abhaya however it is also unresolved. (The payload hash in this example is the payload hash for blank). I have gone through several AWS guides but these are very confusing when trying to apply them to powershell. https://docs.aws.amazon.com/general/latest/gr/sigv4-create-canonical-request.html

The url the code below generates a url that looks correct:http://SAMPLEBUCKETNAME HERE.s3-ap-southeast-1.amazonaws.com/test.xlsx?&X-Amz-Algorithm=AWS4-HMAC-SHA256&X-Amz-Credential=%2F20190907%2Fap-southeast-1%2Fs3%2Faws4_request&X-Amz-Date=20190907T1644136560000Z&X-Amz-E0&X-Amz-SignedHeaders=host&X-Amz-Signature=HASH HERE

$method = 'GET'
$service = 's3'
$host1 = 'SAMPLES3BUCKETNAME.s3-ap-southeast-1.amazonaws.com'
$region = 'ap-southeast-1'
$endpoint = 'http://SAMPLES3BUCKETNAME.s3-ap-southeast-1.amazonaws.com/test.xlsx'

function HmacSHA256($message, $secret){
   <#$hmacsha = New-Object System.Security.Cryptography.HMACSHA256
    $hmacsha.key = [Text.Encoding]::UTF8.GetBytes($secret)
    #$hmacsha.key = $secret
    $signature = $hmacsha.ComputeHash([Text.Encoding]::UTF8.GetBytes($message))
    $signature = [Convert]::ToBase64String($signature)
   #>
    $hmacsha = New-Object System.Security.Cryptography.HMACSHA256

    $hmacsha.Key = @($secret -split '(?<=\G..)(?=.)'|ForEach-Object {[byte]::Parse($_,'HexNumber')})

    $sign = [BitConverter]::ToString($hmacsha.ComputeHash([Text.Encoding]::UTF8.GetBytes($message))).Replace('-','').ToLower()

    return $sign
}

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;
}


$access_key = 'SAMPLEACCESSKEY'
$secret_key = 'SAMPLESECRETKEY'

$amz_date = [DateTime]::UtcNow.ToString('yyyyMMddTHHmmssfffffffZ')
$datestamp = [DateTime]::UtcNow.ToString('yyyyMMdd')

$canonical_uri = '/'
$canonical_headers = 'host:' + $host1 + "`n"
$signed_headers = 'host'

$algorithm = 'AWS4-HMAC-SHA256'
$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-Expires=86400'
$canonical_querystring += '&X-Amz-SignedHeaders=' + $signed_headers


$payload_hash = 'e3b0c44298fc1c149afbf4c8996fb92427ae41e4649b934ca495991b7852b855'

$canonical_request1 = $method + "`n" +$canonical_uri + "`n" + $canonical_querystring + "`n" + $canonical_headers + "`n" + $signed_headers + "`n" + $payload_hash
Write-Host $canonical_request1

function hash($request) {

$hasher = [System.Security.Cryptography.SHA256]::Create()
$content = [Text.Encoding]::UTF8.GetBytes($request)
$hash = [System.Convert]::ToBase64String($hasher.ComputeHash($content))
return $hash

}

$canonical_request = hash -request $canonical_request1
$string_to_sign = $algorithm + "`n" +  $amz_date + "`n" +  $credential_scope + "`n" +  $canonical_request


$signing_key = getSignatureKey $secret_key $datestamp $region $service
$signature =  HmacSHA256 -secret $signing_key -message $string_to_sign

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

$request_url = $endpoint + "?" + $canonical_querystring
$request_url

I get the following error when I try accessing the url.

回答1:

There were a few errors, notably how you were computing the signature, building the timestamp, and the error that you were seeing is because the parameters weren't properly being passed along.

Here's a version that corrects those issues:

$method = 'GET'
$service = 's3'
$bucket = "SAMPLES3BUCKETNAME"
$key = 'test.xlsx'
$region = 'ap-southeast-1'
$host1 = $bucket + '.s3-' + $region + '.amazonaws.com'
$access_key = 'SAMPLEACCESSKEY'
$secret_key = 'SAMPLESECRETKEY'

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 ''
}

$now = [DateTime]::UtcNow
$amz_date = $now.ToString('yyyyMMddTHHmmssZ')
$datestamp = $now.ToString('yyyyMMdd')

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

$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-Expires=86400'
$canonical_querystring += '&X-Amz-SignedHeaders=' + $signed_headers

$canonical_headers = 'host:' + $host1 + "`n"

$canonical_request = $method + "`n"
$canonical_request += "/" + $key + "`n"
$canonical_request += $canonical_querystring + "`n"
$canonical_request += $canonical_headers + "`n"
$canonical_request += $signed_headers + "`n"
$canonical_request += "UNSIGNED-PAYLOAD"

$algorithm = 'AWS4-HMAC-SHA256'

$canonical_request_hash = hash -request $canonical_request
$string_to_sign = $algorithm + "`n"
$string_to_sign += $amz_date + "`n"
$string_to_sign += $credential_scope + "`n"
$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 = "http://" + $host1 + "/" + $key + "?" + $canonical_querystring

Write-Host $request_url

来源：https://stackoverflow.com/questions/57835886/how-can-i-download-a-file-from-s3-via-powershell-without-installing-aws-sdk

标签

amazon-web-services

powershell

amazon-s3