Question Re: ABAP string to SHA256 different to SAPUI5/Javascript in Technology Q&A

ABAP string to SHA256 different to SAPUI5/Javascript

former_member595185 — Tue, 16 Jul 2019 11:02:28 GMT

Hi all,

Currently on my SAPUI5 project, I am creating a HMAC encoded string with this line of code;

var secretKey = CryptoJS.enc.Hex.parse('SECRETKEY'); //USING THE CRYPTOJS LIBRARY!
var hash = CryptoJS.HmacSHA256('abc', secretKey);
hashInBase64 = CryptoJS.enc.Base64.stringify(hash);

I am using the CryptoJS library to execute this code in UI5.

However the problem is that I am receiving the wrong HMAC encoded string when I want to do the same in ABAP. After testing a few times, it seems like the encoding (in abap) is wrong before the HMAC is calculated.

Is there a function module that does 'CryptoJS.enc.Hex.parse()' - after googling what it does it interprets the parameter as encoded and converts it into a word array.

DATA:
      lv_sign_key_x                TYPE xstring,
      lv_hmac_result               TYPE string.

DATA(lv_binary_secret) = cl_abap_hmac=>string_to_xstring('SECRETKEY').

    cl_abap_hmac=>calculate_hmac_for_char(
      EXPORTING
        if_algorithm           = 'SHA256'           "Hash Algorithm
        if_key                 = lv_binary_secret   "HMAC Key
        if_data                = 'abc'   "Data
      IMPORTING
        ef_hmacb64string       = lv_hmac_result  "HMAC value as base64-encoded string
    ).

Thank you in advance.

Re: ABAP string to SHA256 different to SAPUI5/Javascript

rudramani — Tue, 16 Jul 2019 11:38:49 GMT

You can write your javascript code too within ABAP. Have you tried that?

Re: ABAP string to SHA256 different to SAPUI5/Javascript

UweFetzer_se38 — Tue, 16 Jul 2019 12:18:13 GMT

The use of Javascript in ABAP is depreciated since many releases now (see also https://help.sap.com/viewer/fe1d31bb6c551014b75bc66f0328fefe/7.02.19/en-US/808676416e805958e10000000a1550b0.html )

Re: ABAP string to SHA256 different to SAPUI5/Javascript

Former Member — Tue, 16 Jul 2019 13:01:19 GMT

Hi, Sunil,

If string is already hex-encoded, you can do a direct conversion:

DATA lv_binary_secret TYPE xstring.
DATA lv_input TYPE string VALUE 'EFBBBF'.
 
"only uppercase, translate to upper case if needed
lv_binary_secret = lv_input.

Re: ABAP string to SHA256 different to SAPUI5/Javascript

former_member595185 — Tue, 16 Jul 2019 13:17:10 GMT

Hi Victor, The problem is that it needs to be hex encoded the same as the javascript version which is why they are bringing back two different output values.

Using 'SECRETKEY' as the key and 'abc' as the data...

Javascript is giving me 'eZdbNMwgWKOANEiozokNG2FGfzI7Yy/B8IQKXr3+krY=' whilst the ABAP code is giving me '9dyEZn5G+uiRwsNqgY5S6k9/gmCheFNF4vFa5qBKK1w='

Re: ABAP string to SHA256 different to SAPUI5/Javascript

former_member595185 — Tue, 16 Jul 2019 13:25:31 GMT

I just need to know how to do the hex-encode. - Thanks.

Re: ABAP string to SHA256 different to SAPUI5/Javascript

Former Member — Tue, 16 Jul 2019 13:41:55 GMT

In this case are you sure about this line in your JS code?

var secretKey = CryptoJS.enc.Hex.parse('SECRETKEY');//USING THE CRYPTOJS LIBRARY!

Method CryptoJS.enc.Hex.parse parses the already Hex-encoded string and converts it into string.

So if you want string from Hex, you use it and if you want hex-encoding from string then you use Hex.stringify.

var words = CryptoJS.enc.Hex.parse("48656c6c6f2c20576f726c6421");
var hex = CryptoJS.enc.Hex.stringify(words);

So I am a bit confused here.

What is a value returned by this code? I assume null.

var secretKey = CryptoJS.enc.Hex.parse('SECRETKEY');//USING THE CRYPTOJS LIBRARY!

Check CryptoJS docs:

https://cryptojs.gitbook.io/docs/

Viktor

Re: ABAP string to SHA256 different to SAPUI5/Javascript

former_member595185 — Tue, 16 Jul 2019 14:07:19 GMT

Sorry if it may seem confusing to you. not sure if 'SECRETKEY' is confusing you, I only used that word as I don't want to share the actual key I'll use '48656c6c6f2c20576f726c6421' as the key I am parsing for now.. The code in Javascript is perfectly correct and I need the ABAP to perform the same way/same results.

In Javascript I am parsing the hex which comes back with a word array using this line of code

var words = CryptoJS.enc.Hex.parse("48656c6c6f2c20576f726c6421");

words: Array(4)
1. 0: 1214606444
2. 1: 1865162839
3. 2: 1869769828
4. 3: 553648128

I then use the word array to be placed in var hash = CryptoJS.HmacSHA256('abc', wordArray); and then converted into Base64

This is all correct and the documentation is in this page - https://docs.adyen.com/classic-integration/hosted-payment-pages/hmac-signature-calculation/ which is what I have done in Javascript and have tested that it works. The javascript is completely fine. I just need a solution in ABAP.

However, I want to do the same thing in ABAP... The ABAP is returning a completely different encode

DATA(lv_binary_secret)= cl_abap_hmac=>string_to_xstring('48656c6c6f2c20576f726c6421').

Relating to the link I have provided above on step 4, Do you know how to hex encode my key in ABAP?

Re: ABAP string to SHA256 different to SAPUI5/Javascript

Former Member — Tue, 16 Jul 2019 14:27:10 GMT

In this case the following should work:

    data lv_binary_secret type xstring.
    data lv_string type string value '48656c6c6f2c20576f726c6421'.
    translate lv_string to upper case.
    lv_binary_secret = lv_string.


    cl_abap_hmac=>calculate_hmac_for_char(
      EXPORTING
        if_algorithm           = 'SHA256'           "Hash Algorithm
        if_key                 = lv_binary_secret   "HMAC Key
        if_data                = 'abc'   "Data
      IMPORTING
        ef_hmacb64string       = data(lv_hmac_result)  "HMAC value as base64-encoded string
    ).

Re: ABAP string to SHA256 different to SAPUI5/Javascript

former_member595185 — Tue, 16 Jul 2019 14:34:23 GMT

Working as intended. Thanks a lot Viktor.