hmac sha 256 in Salesforce?

raphael.rugova

Hi,

I'm trying to implement the hmac sha256 example from the documentation in Salesforce Apex, but I am not able to reproduce the base64 value.

This is the example HTTP request from the documentation:

POST /v1/cases HTTP/1.1
Host: rms-world-check-one-api.thomsonreuters.com
Date: Tue, 07 Jun 2016 20:51:35 GMT
Content-Type: application/json
Content-Length: 88
{
  "caseId": "my customer ID",
  "name": "John Doe",
  "providerTypes": ["WATCHLIST"]
}

According to the example, the following input should be used for the hmac function:

(request-target): post /v1/cases
host: rms-world-check-one-api.thomsonreuters.com
date: Tue, 07 Jun 2016 20:51:35 GMT
content-type: application/json
content-length: 88
{
  "caseId": "my customer ID",
  "name": "John Doe",
  "providerTypes": ["WATCHLIST"]
}

I implemented the function (as shown below), but keep getting different values. I even tried to alter the spaces and the line endings, but never matched the value, which is shown in the example:

"Given the above signing text, if a secret key of “1234” is used, the computed HMAC-SHA256 value would beDA26D7F5BFF89A100D1A597AA015099FC55DD3130F023E952BFBE3A6949F322A when printed using hex encoding, or2ibX9b/4mhANGll6oBUJn8Vd0xMPAj6VK/vjppSfMio= when printed using base64 encoding."

[...]

String testString = '(request-target): post /v1/cases\n'
+'host: rms-world-check-one-api.thomsonreuters.com\n'
+'date: Tue, 07 Jun 2016 20:51:35 GMT\n'
+'content-type: application/json\n'
+'content-length: 88\n'
+'{\n'
+'"caseId": "my customer ID",\n'
+'"name": "John Doe",\n'
+'"providerTypes": ["WATCHLIST"]\n'
+'}';

String testKey = '1234';
String algorithmName = 'HmacSHA256';
Blob hmacData = Crypto.generateMac(algorithmName, Blob.valueOf(testString), Blob.valueOf(testKey));
return EncodingUtil.base64Encode(hmacData);

[...]

In this case, the base64 value was "V9d9dkg2aS1J0P/7GVPdC34ddLMdrRixtt6mf9xsJ+Q="

Line endings should be fine, according to the Salesforce Apex Language Reference. \n should be a LF Line ending.

Source: https://resources.docs.salesforce.com/sfdc/pdf/salesforce_apex_language_reference.pdf - Page 29

Salesforce docs show, the used method is fine: Crypto.generateMac

Source: https://developer.salesforce.com/docs/atlas.en-us.apexcode.meta/apexcode/apex_classes_restful_crypto.htm

Do you have any idea what is wrong here? Do I have an error in my spacing or something like that? I just want to implement the example in Salesforce Apex Code.

Thanks in advance.

brian.bourgault

Hi @raphael.rugova,

I recreated the example in the Documentation with special attention to detailing exactly how I got my results....

I attached a screen shot of what I did... a couple Notes:

1. The body of the message uses Unix LF and not DOS CR/LF (it's documented but easily overlooked if you cut&paste the example.
2. I use Notepad++ to view the message. This helps by showing there are 2 spaces before some of the lines and the LF, plus the count of bytes to confirm I've correctly copied the message body
3. I use Visual Studio C# to produce my results, using the HMACSHA256 code example from the Microsoft Documentation, see code below.

Hope this helps,

Brian

        // Combine the data signature and the API secret key to get the HMAC
        // This is the Microsoft HMACSHA256 code copied from the documentation
        public static string generateAuthHeader(string dataToSign, string apisecret)
            {
                byte[] secretKey = Encoding.UTF8.GetBytes(apisecret);
                HMACSHA256 hmac = new HMACSHA256(secretKey);
                hmac.Initialize();


                byte[] bytes = Encoding.UTF8.GetBytes(dataToSign);
                byte[] rawHmac = hmac.ComputeHash(bytes);
                Console.WriteLine("---rawHmac---");
                string hex = BitConverter.ToString(rawHmac).Replace("-","");
                Console.WriteLine(hex);
                return(Convert.ToBase64String(rawHmac));
            }

brian.bourgault

Hi @raphael.rugova,

The World-Check One API documentation has a misprint. I will post an update shortly.

Sorry for any inconvenience this may have cause you.

Brian

raphael.rugova

Thank you, that solved my problem completely.

raphael.rugova

Thank you, that solved my problem completely.