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[SOLVED] GEt a keyed SHA256 hash from string

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torbente:
Sometime ago, getmem gracefully help me a lot in this topic:
https://forum.lazarus.freepascal.org/index.php/topic,39821.msg274338.html#msg274338

Now, i need the same, but using SHA256, so this is what im doing: (using dcpcrypt2)


--- Code: Pascal  [+][-]window.onload = function(){var x1 = document.getElementById("main_content_section"); if (x1) { var x = document.getElementsByClassName("geshi");for (var i = 0; i < x.length; i++) { x[i].style.maxHeight='none'; x[i].style.height = Math.min(x[i].clientHeight+15,306)+'px'; x[i].style.resize = "vertical";}};} ---function GetSignature(const AText, AKey: String): String;var  SHA256: TDCP_sha256;  AB: array[0..31] of byte;  I: Integer;begin  Result := '';  SHA256 := TDCP_sha256.Create(nil);  try    SHA256.Init;    SHA256.UpdateStr(AText + AKey);    SHA256.Final(AB);    for I := 0 to 31 do      Result := Result + IntToHex(AB[i], 2);  finally    SHA256.Free;  end;end;
But im receiving the "Signature for this request is not valid." message ALWAYS.

I used this page to test my code:
https://www.freeformatter.com/hmac-generator.html

And im getting different hashes. Any idea?

Gammatester:
You are not using a valid HMAC construction: HMAC is not HASH(Text+Key).

Actually it is HMAC(key,text) = hash((const1 xor key) || hash((const2 xor key) || text)) , see http://www.wolfgang-ehrhardt.de/hash_intro.html.

Xor-el:
If you want to calculate hmac, you can use HashLib4Pascal
https://github.com/Xor-el/HashLib4Pascal

Gammatester:
Here is a complete test program for HMAC compiled with http://www.wolfgang-ehrhardt.de/crc_hash_2018-01-01.zip

--- Code: Pascal  [+][-]window.onload = function(){var x1 = document.getElementById("main_content_section"); if (x1) { var x = document.getElementsByClassName("geshi");for (var i = 0; i < x.length; i++) { x[i].style.maxHeight='none'; x[i].style.height = Math.min(x[i].clientHeight+15,306)+'px'; x[i].style.resize = "vertical";}};} ---uses  hash,hmac,hmacsha2,mem_util;const  akey = 'Key';const  atext: ansistring = 'Message';var  ctx: THMAC_Context;  mac: TSHA256Digest;begin  hmac_SHA256_inits(ctx, akey);  hmac_SHA256_updateXL(ctx, @atext[1], length(atext));  hmac_SHA256_final(ctx,mac);  writeln(HexStr(@mac, sizeof(mac)));end.
--- Code: ---D:\Work\CRC_HASH>D:\FPC304\bin\i386-win32\fpc.exe -b THMACSHA.PAS
Free Pascal Compiler version 3.0.4 [2017/10/06] for i386
Copyright (c) 1993-2017 by Florian Klaempfl and others
Target OS: Win32 for i386
Compiling THMACSHA.PAS
Linking THMACSHA.exe
14 lines compiled, 0.1 sec, 30848 bytes code, 1764 bytes data

D:\Work\CRC_HASH>THMACSHA.exe
507285548137b5424eb5572c46496631b7ade8e88ac323c529fa142def26ffa1
--- End code ---

and verified with your online-calculator.

torbente:
I used it and worked


--- Code: Pascal  [+][-]window.onload = function(){var x1 = document.getElementById("main_content_section"); if (x1) { var x = document.getElementsByClassName("geshi");for (var i = 0; i < x.length; i++) { x[i].style.maxHeight='none'; x[i].style.height = Math.min(x[i].clientHeight+15,306)+'px'; x[i].style.resize = "vertical";}};} ---function getsha256signature(StringToSign , mykey:string):string;var  LHMAC: IHMAC;beginLHMAC := THashFactory.THMAC.CreateHMAC(THashFactory.TCrypto.CreateSHA2_256);LHMAC.Key := TConverters.ConvertStringToBytes(MyKey, TEncoding.UTF8);getsha256signature := LHMAC.ComputeString(StringToSign, TEncoding.UTF8).ToString();end;

 but my app start crashing, probably due to this previous function i had:


--- Code: Pascal  [+][-]window.onload = function(){var x1 = document.getElementById("main_content_section"); if (x1) { var x = document.getElementsByClassName("geshi");for (var i = 0; i < x.length; i++) { x[i].style.maxHeight='none'; x[i].style.height = Math.min(x[i].clientHeight+15,306)+'px'; x[i].style.resize = "vertical";}};} ---function GetTimestamp():string;BeginGetTimestamp := inttostr(Trunc((Now - EncodeDate(1970, 1 ,1)) * 24 * 60 * 60));end;
ANy idea if this can be done with dcpcrypt?


--- Quote from: Xor-el on June 01, 2018, 08:59:57 pm ---If you want to calculate hmac, you can use HashLib4Pascal
https://github.com/Xor-el/HashLib4Pascal

--- End quote ---

@Gammatester i will try your code. Thanks!!

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