Using HMAC SHA256 in Ruby

Question

I'm trying to apply HMAC-SHA256 for generate a key for an Rest API.

I'm doing something like this:

def generateTransactionHash(stringToHash)
  key = '123'
  data = 'stringToHash'
  digest = OpenSSL::Digest.new('sha256')

  hmac = OpenSSL::HMAC.digest(digest, key, data)
  puts hmac
end

The output of this is always this: (if I put '12345' as parameter or 'HUSYED815X', I do get the same)

ۯw/{o���p�T����:��a�h��E|q

The API is not working because of this... Can some one help me with that?

Solution 1

According to the documentation OpenSSL::HMAC.digest

Returns the authentication code an instance represents as a binary string.

If you have a problem using that maybe you need a hex encoded form provided by OpenSSL::HMAC.hexdigest

Example

key = 'key'
data = 'The quick brown fox jumps over the lazy dog'
digest = OpenSSL::Digest.new('sha256')

OpenSSL::HMAC.digest(digest, key, data)
#=> "\xF7\xBC\x83\xF40S\x84$\xB12\x98\xE6\xAAo\xB1C\xEFMY\xA1IF\x17Y\x97G\x9D\xBC-\x1A<\xD8"

OpenSSL::HMAC.hexdigest(digest, key, data)
#=> "f7bc83f430538424b13298e6aa6fb143ef4d59a14946175997479dbc2d1a3cd8"

Solution 2

Try This:

hmac = OpenSSL::HMAC.hexdigest(OpenSSL::Digest.new('sha256'), key, data)

Comments

[Mike Szyndel]

According to the documentation digest: Returns the authentication code an instance represents as a binary string.

[Mike Szyndel]

Maybe you should use hexdigest instead, it has the same signature as digest but returns hex-encoded string (from the docs it looks like it's the same string but human readable)

[Eduardo Pedroso]

Worked just fine with hexdigest! Thank You

[Mike Szyndel]

Since I fixed your problem it would be nice if you let me answer instead of doing it yourself.

[Eduardo Pedroso]

Sorry @MichalSzyndel, already delete the answer

[cmunozgar]

In this case to make it HMAC SHA256 you need to put digest = OpenSSL::Digest.new('sha256') in the lower comment: stackoverflow.com/a/42832500/4706812

[Mike Szyndel]

Updated the answer @cmunozgar, not sure why I put sha1 in there in the first place

[Dat Le Tien]

No need to create a digest instance, just put a string represents the algorithm and it works like a charm OpenSSL::HMAC.hexdigest('sha256', key, data) since ruby 2.5 ruby-doc.org/stdlib-2.5.1/libdoc/openssl/rdoc/OpenSSL/…