AWS4 Signature key - is this tutorial wrong?

问题

According to this page: Examples of How to Derive a Signing Key for Signature Version 4

The result of this code:

$kSecret = "wJalrXUtnFEMI/K7MDENG+bPxRfiCYEXAMPLEKEY";

$kDate = hash_hmac('sha256', "20120215", "AWS4" . $kSecret);
echo "date: " . $kDate . "<br>";

$kRegion = hash_hmac('sha256', "us-east-1", $kDate);
echo "region: " . $kRegion . "<br>";

$kService = hash_hmac('sha256', "iam", $kRegion);
echo "service: " . $kService . "<br>";

$kSigning = hash_hmac('sha256', "aws4_request", $kService);
echo "signing: " . $kSigning . "<br>";

should print:

kDate    = '969fbb94feb542b71ede6f87fe4d5fa29c789342b0f407474670f0c2489e0a0d'

kRegion  = '69daa0209cd9c5ff5c8ced464a696fd4252e981430b10e3d3fd8e2f197d7a70c'

kService = 'f72cfd46f26bc4643f06a11eabb6c0ba18780c19a8da0c31ace671265e3c87fa'

kSigning = 'f4780e2d9f65fa895f9c67b32ce1baf0b0d8a43505a000a1a9e090d414db404d'

So, kDate I get is correct. kRegion is not correct as I get the value:

a59e30f9d899c47b3dd68ea1c0ab3bb529e03a8f4ed2f54cb64af547330a22a0

I have tried using this website to calculate the HMAC (hmac generator) and I get the same result.

I really wonder if the page is wrong. Can anyone explain if it's my fault or AWS fault?

Thank you

回答1:

You should understand the values are binary and printed in hexadecimal form
You are passing date in hexadecimal. You should convert it to binary and pass it before calling hash_hmac. Or store it in binary and print the same in hexadecimal
You never mentioned the language you are using. I had to google to find out what language you are using. In PHP, you can pass: $raw_output = true to get the binary string
Store the strings n binary and convert them to hex before printing.

Since I am not familiar with PHP, I tried the same in Python and the output matched the expected output. See how I convert it to hex and print.

import hmac
import hashlib
from base64 import b16encode as b16

def sign(key, msg):
    return hmac.new(key, msg.encode("utf-8"), hashlib.sha256).digest()

def getSignatureKey(key, dateStamp, regionName, serviceName):
    kDate = sign(("AWS4" + key).encode("utf-8"), dateStamp)
    print b16(kDate)
    kRegion = sign(kDate, regionName)
    print b16(kRegion)
    kService = sign(kRegion, serviceName)
    print b16(kService)
    kSigning = sign(kService, "aws4_request")
    print b16(kSigning)
    return kSigning

key = 'wJalrXUtnFEMI/K7MDENG+bPxRfiCYEXAMPLEKEY'
dateStamp = '20120215'
regionName = 'us-east-1'
serviceName = 'iam'

getSignatureKey(key, dateStamp, regionName, serviceName)

Output

969FBB94FEB542B71EDE6F87FE4D5FA29C789342B0F407474670F0C2489E0A0D
69DAA0209CD9C5FF5C8CED464A696FD4252E981430B10E3D3FD8E2F197D7A70C
F72CFD46F26BC4643F06A11EABB6C0BA18780C19A8DA0C31ACE671265E3C87FA
F4780E2D9F65FA895F9C67B32CE1BAF0B0D8A43505A000A1A9E090D414DB404D

PHP

string hash_hmac ( string $algo , string $data , string $key [, bool $raw_output = false ] )

来源：https://stackoverflow.com/questions/40746016/aws4-signature-key-is-this-tutorial-wrong

标签

php

amazon-web-services

hmac

aws-api-gateway