ruby-jwt encode, decode with RS256 algorithm - ruby-on-rails

Question

It seems like we have always initialize and use the same private key when encoding and decoding a token in RSA256 algorithm:
payload = {:data => 'test'}
rsa_private = OpenSSL::PKey::RSA.generate 2048
rsa_public = rsa_private.public_key
token = JWT.encode payload, rsa_private, 'RS256'
# eyJ0eXAiOiJKV1QiLCJhbGciOiJSUzI1NiJ9.eyJ0ZXN0IjoiZGF0YSJ9.c2FynXNyi6_PeKxrDGxfS3OLwQ8lTDbWBWdq7oMviCy2ZfFpzvW2E_odCWJrbLof-eplHCsKzW7MGAntHMALXgclm_Cs9i2Exi6BZHzpr9suYkrhIjwqV1tCgMBCQpdeMwIq6SyKVjgH3L51ivIt0-GDDPDH1Rcut3jRQzp3Q35bg3tcI2iVg7t3Msvl9QrxXAdYNFiS5KXH22aJZ8X_O2HgqVYBXfSB1ygTYUmKTIIyLbntPQ7R22rFko1knGWOgQCoYXwbtpuKRZVFrxX958L2gUWgb4jEQNf3fhOtkBm1mJpj-7BGst00o8g_3P2zHy-3aKgpPo1XlKQGjRrrxA
puts token
decoded_token = JWT.decode token, rsa_public, true, { :algorithm => 'RS256' }
# Array
# [
# {"data"=>"test"}, # payload
# {"alg"=>"RS256"} # header
# ]
puts decoded_token
But what is the best way t do that in a Rails 5.1 app ?

Answer 1

I figured out how to fix that.
So I have a class JsonWebTokenwith 2 class methods: encodeand decodedefined as follows:
class JsonWebToken
ALGO = 'RS256'
class << self
def encode(payload, exp = 2.hours.from_now)
# set expiry to 2 hours from creation time
payload[:exp] = exp.to_i
JWT.encode(payload, private_key, ALGO)
end
def decode(token)
body = JWT.decode(token, private_key.public_key, true, algorithm: ALGO)[0]
HashWithIndifferentAccess.new body
# rescue from expiry exception
rescue JWT::ExpiredSignature, JWT::VerificationError => e
# raise custom error to be handled by custom handler
raise ExceptionHandler::ExpiredSignature, e.message
end
private
def private_key
#rsa_private ||= OpenSSL::PKey::RSA.generate 2048
end
end
end
I just use another private static method to generate an rsa private key if needed.