SAML2 verification

verif.lua

local resty_rsa = require "resty.rsa"

local function verify_saml2_signature(payload, signature, public_key)
  local rsa_public_key = "-----BEGIN PUBLIC KEY-----\n" .. public_key .. "\n-----END PUBLIC KEY-----"
  local pub, err = resty_rsa:new({ public_key = rsa_public_key, key_type = resty_rsa.KEY_TYPE.PKCS8, algorithm = "SHA256" })
  if not pub then
    ngx.say('unable to extract public key')
    return nil
  end

  local  decoded_signature, err = ngx.decode_base64(signature)
  if not decoded_signature then
    ngx.say("unable to base64 decode signature")
    return nil
  end

  local verify, err = pub:verify(payload, decoded_signature)
  if not verify then
    ngx.say("unable to verify token")
    return nil
  end
  return verify
end

local payload = "_ce3d2948b4cf20146dee0a0b3dd6f69b6cf86f62d72014-07-17T01:01:18Z2024-01-18T06:21:48Z"
local signature = "blYo5Msn1VjXHJPVusrslqz6Yx67Ik5KbXqYRWg6jU9pRyb2X+/3ogkK7sZ3Ec4HBBeBkQ/14PUImgmGXwnjTIwcP5wDbJQUY+RBZR5XC9IyLZLp2gmeXvNVtX+EgFhc"
local public_key = "MHwwDQYJKoZIhvcNAQEBBQADawAwaAJhAOz0YTcc5qsRSyNYUBPD/6H/vcbFqtTb+IcW45PAZ5lMIMj4DLdNF+/4ZlVSVKU9QfC5lio/X76sZhwG2u+7vwOBi1awuwQ91xVroeR4ozpRqs31DYDl7uCfbMZhbG2m4wIDAQAB"

local verify = verify_saml2_signature(payload, signature, public_key)
ngx.say(verify)