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Dynamics 365 Community / Forums / Small and medium business | Business Central, N... / Unable to create the c...
Small and medium business | Business Central, N...
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Unable to create the correct HMACSHA256 Hash in AL

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Posted on by C_J_S 5

Hello!

I have the following code i C-sharp below that generates a hashed signature:

HMACSHA256 hmac = new HMACSHA256(Encoding.UTF8.GetBytes(key));
        var signature = Convert.ToBase64String(hmac.ComputeHash(Encoding.UTF8.GetBytes(stringToSign)));

This works fine.

But when I try to replicate this in AL I'm unable to generate the same hash:

Crypto: Codeunit "Cryptography Management";
HashAlgo: Option HMACMD5,HMACSHA1,HMACSHA256,HMACSHA384,HMACSHA512;

Crypto.GenerateBase64KeyedHashAsBase64String(stringToSign, key, HashAlgo::HMACSHA256);

I would be very grateful if someone could explain to me what I'm doing wrong.

  • PravinDangar Profile Picture
    PravinDangar 30 on at
    RE: Unable to create the correct HMACSHA256 Hash in AL

    C_J_S  Can you please share that blog Or sample code How you resolve it ? Thanks in dvance

  • C_J_S Profile Picture
    C_J_S 5 on at
    RE: Unable to create the correct HMACSHA256 Hash in AL

    I was able to solve the problem by following the example in this blogpost:

    futuriot.com/.../

  • C_J_S Profile Picture
    C_J_S 5 on at
    RE: Unable to create the correct HMACSHA256 Hash in AL

    I'm sorry for not including the whole code example. But I'm already assigning the rusult to a text variable:

    signature := Crypto.GenerateBase64KeyedHashAsBase64String(stringToSign, keyText, HashAlgo::HMACSHA256);

       procedure GetSignature(Uri: Text; keyName: Text; keyText: Text; ttl: Duration): Text

       var

           Crypto: Codeunit "Cryptography Management";

           TypeHelper: Codeunit "Type Helper";

           expiry: Text;

           stringToSign: Text;

           signature: Text;

           HashAlgo: Option HMACMD5,HMACSHA1,HMACSHA256,HMACSHA384,HMACSHA512;

       begin

           expiry := GetExpiry(ttl);

           stringToSign := TypeHelper.UrlEncode(Uri) + '\' + 'n' + expiry;

           signature := Crypto.GenerateBase64KeyedHashAsBase64String(stringToSign, keyText, HashAlgo::HMACSHA256);

           exit(signature );

       end;

  • Suggested answer
    Inge M. Bruvik Profile Picture
    Inge M. Bruvik 999 Moderator on at
    RE: Unable to create the correct HMACSHA256 Hash in AL

    You have to put the result into a text variable

    MyText:=Crypto.GenerateBase64KeyHasedBase64String......

    It looks to me that you do not fetch the result of the hash process.

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