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Convert AWS IAM credentials to AWS SMTP credentials

Convert AWS IAM credentials to AWS SMTP credentials

If you do, or want to, use AWS to deploy your apps, you will end up using AWS SES via SMTP when you're launching an app that sends out emails of any kind (user registrations, email notifications, etc). For example, I have used this configuration on various Ruby on Rails apps, however, it is just basic SMTP configurations and crosses over to any framework that supports SMTP sendmail.

There are two ways to go about this:

Luckily, you found this MD file and the NOT SO EASY WAY is suddenly copy-pasta... sudo yum....

Assuming you've already set up your SES Policy on your IAM User:

    {
      "Version": "2012-10-17",
      "Statement": [
        {
          "Effect":"Allow",
          "Action":["ses:SendEmail", "ses:SendRawEmail"],
          "Resource":"*"
        }
      ]
    }

Go ahead and drop this into an bash session, or somewhere in your app, and pass in your IAM user's secret key to generate your SMTP password :)

Ruby

Thanks @talreg and @cristim and @jschroed91

require 'openssl'
require 'base64'

def aws_iam_smtp_password_generator(key, region)
      # The values of the following variables should always stay the same.
      date = "11111111"
      service = "ses"
      terminal = "aws4_request"
      message = "SendRawEmail"
      version_in_bytes = "\x04"

      k_date = OpenSSL::HMAC.digest('sha256', "AWS4" + key, date)
      k_region = OpenSSL::HMAC.digest('sha256', k_date, region)
      k_service = OpenSSL::HMAC.digest('sha256', k_region, service)
      k_terminal = OpenSSL::HMAC.digest('sha256', k_service, terminal)
      k_message = OpenSSL::HMAC.digest('sha256', k_terminal, message)
      signature_and_version = version_in_bytes + k_message
      smtp_password = Base64.encode64(signature_and_version)

      smtp_password.to_s.strip
end

# print aws_iam_smtp_password_generator(ENV['AWS_SECRET_ACCESS_KEY'], "us-east-1")

PHP

    <?php

      function aws_iam_smtp_password_generator($secret) {
        $message = "SendRawEmail";
        $versionInBytes = chr(2);
        $signatureInBytes = hash_hmac('sha256', $message, $secret, true);
        $signatureAndVer = $versionInBytes.$signatureInBytes;
        $smtpPassword = base64_encode($signatureAndVer);

        return $smtpPassword;
      }

    ?>

Python

Thanks to @avdhoot and @techsolx

# v2
import base64
import hmac
import hashlib
import sys

def hash_smtp_pass_from_secret_key(key):
    message = "SendRawEmail"
    version = '\x02'
    h = hmac.new(key, message, digestmod=hashlib.sha256)
    return base64.b64encode("{0}{1}".format(version, h.digest()))

if __name__ == "__main__":
    print hash_smtp_pass_from_secret_key(sys.argv[1])


#####################


# v3
import argparse
import base64
import hashlib
import hmac


def hash_iam_secret(sakey, version):
    key_bytes = str.encode(sakey)
    message_bytes = str.encode('SendRawEmail')
    version_bytes = str.encode(version)
    dig = hmac.new(key_bytes, message_bytes, digestmod=hashlib.sha256)
    return base64.b64encode(version_bytes+dig.digest()).decode()


def main():
    parser = argparse.ArgumentParser()
    parser.add_argument('iam_secret_access_key',
                        type=str,
                        help='The AWS IAM secret access key')
    parser.add_argument('version',
                        type=str,
                        nargs='?',
                        default='\0x2',
                        help='Optional version number, default is 2')
    args = parser.parse_args()

    if len(args.iam_secret_access_key) != 40:
        print('AWS secret access keys should be 40 characters.')
    else:
        dig = hash_iam_secret(args.iam_secret_access_key,
                              args.version)

    print(dig)


if __name__ == '__main__':
    main()

Go

Thanks @talreg and @anieri

import (
	"crypto/hmac"
	"crypto/sha256"
	"encoding/base64"
)

const (
	awsDate     string = "11111111"
	awsService  string = "ses"
	awsMessage  string = "SendRawEmail"
	awsTerminal string = "aws4_request"
	awsVersion  byte   = 0x04
)

func DeriveSMTPCredential(region, secretKey string) string {
	signature := sign([]byte("AWS4"+secretKey), []byte(awsDate))
	signature = sign(signature, []byte(region))
	signature = sign(signature, []byte(awsService))
	signature = sign(signature, []byte(awsTerminal))
	signature = sign(signature, []byte(awsMessage))

	infoWithSignature := make([]byte, 1+len(signature))
	infoWithSignature[0] = awsVersion
	copy(infoWithSignature[1:], signature)

	return base64.StdEncoding.EncodeToString(infoWithSignature)
}

func sign(key, msg []byte) []byte {
	h := hmac.New(sha256.New, key)
	h.Write(msg)

	return h.Sum(nil)
}

PowerShell

https://gist.github.com/jacqueskang/96c444ee01e6a4b37300aa49e8097513

$key = "${SecretAccessKey}";
$region = "${AWS::Region}";

$date = "11111111";
$service = "ses";
$terminal = "aws4_request";
$message = "SendRawEmail";
$versionInBytes = 0x04;

function HmacSha256($text, $key2) {
    $hmacsha = New-Object System.Security.Cryptography.HMACSHA256
    $hmacsha.key = $key2;
    $hmacsha.ComputeHash([Text.Encoding]::UTF8.GetBytes($text));
}

$signature = [Text.Encoding]::UTF8.GetBytes("AWS4" + $key)
$signature = HmacSha256 "$date" $signature;
$signature = HmacSha256 "$region" $signature;
$signature = HmacSha256 "$service" $signature;
$signature = HmacSha256 "$terminal" $signature;
$signature = HmacSha256 "$message" $signature;
$signatureAndVersion = [System.Byte[]]::CreateInstance([System.Byte], $signature.Length + 1);
$signatureAndVersion[0] = $versionInBytes;
$signature.CopyTo($signatureAndVersion, 1);
$smtpPassword = [Convert]::ToBase64String($signatureAndVersion);

Write-Host $smtpPassword;

Erlang

#!/usr/bin/env escript
%% -*- erlang -*-
-define(DATE    , <<"11111111">>    ).
-define(SERVICE , <<"ses">>         ).
-define(MESSAGE , <<"SendRawEmail">>).
-define(TERMINAL, <<"aws4_request">>).
-define(VERSION , 4                ).

main([Key,Region]) ->
    KeyBinary           = list_to_binary(Key),
    RegionBinary        = list_to_binary(Region),
    Sig1                = sign(<<"AWS4", KeyBinary/binary>>,?DATE),
    Sig2                = sign(Sig1,RegionBinary),
    Sig3                = sign(Sig2, ?SERVICE),
    Sig4                = sign(Sig3, ?TERMINAL),
    Sig5                = sign(Sig4, ?MESSAGE),
    SignatureAndVersion = << ?VERSION,Sig5/binary>>,
    HB                  = base64:encode(SignatureAndVersion),
    io:format("~s\n",[HB]);

main(_) ->
    usage().

sign(Key,Msg) ->
  crypto:mac(hmac,sha256,Key,Msg).

usage() ->
    io:format("usage: ~p secret_access_key region\n",[escript:script_name()]),
    halt(1).

Java

I'm not a Java programmer, yet, but AWS's documentation [http://docs.aws.amazon.com/ses/latest/DeveloperGuide/smtp-credentials.html#smtp-credentials-convert] has a snippet you can use

I spent way too much time figuring this stuff out. I hope this helps!!!

HAPPY SES-ing!

@samuelsons
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samuelsons commented May 12, 2024

Thank you for the great assitance.

I was trying to test my SES-dashboard generated SMTP-credentials via powershell command line using the template below, but I keep getting this error, any ideas ?

I am using a production ready account, verified domain & from-email address,

Error
Exception calling "Send" with "4" argument(s): "The SMTP server requires a secure connection or the client was not authenticated. The server response was: Authentication required"
At line:13 char:1
$SMTPClient.Send($EmailFrom, $EmailTo, $Subject, $Body)

    + CategoryInfo          : NotSpecified: (:) [], MethodInvocationException
    + FullyQualifiedErrorId : SmtpException`
    
**Powershell Script below:**
>> <# Source:
>>    https://docs.aws.amazon.com/ses/latest/DeveloperGuide/send-email-smtp-client-command-line.html
>> #>
>> $EmailFrom = "contact@r***********.com"
>> $EmailTo = "***********"
>> $Subject = "Hello from Amazon SES SMTP Test for Windows"
>> $Body = "This message was sent using the Amazon SES SMTP interface. There is no more content in this test email."
>> $SMTPServer = "email-smtp.eu-west-1.amazonaws.com"
>> $SMTPClient = New-Object Net.Mail.SmtpClient($SmtpServer, 587)
>> $SMTPClient.EnableSsl = $true
>> $SMTPClient.Credentials = New-Object System.Net.NetworkCredential("AKIA4************", "**********************************************");
>> $SMTPClient.Send($EmailFrom, $EmailTo, $Subject, $Body)
>> Remove-Variable -Name SMTPClient

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