Lua Requires Chilkat v11.0.0+

Verify a JWT Created by the Amazon Cognito Service

See more JSON Web Token (JWT) Examples

Demonstrates how to verify a JWT created by the Amazon Cognito Service. Lua

local chilkat = require("chilkat")

-- This example requires the Chilkat API to have been previously unlocked.
-- See Global Unlock Sample for sample code.

-- The public keys for this example are at https://cognito-idp.us-east-2.amazonaws.com/us-east-2_******/.well-known/jwks.json
-- Let's get them:

local http = chilkat.Http.new()
local sbJsonKeys = chilkat.StringBuilder.new()
local success = http:quick_get_sb("https://cognito-idp.us-east-2.amazonaws.com/us-east-2_******/.well-known/jwks.json", sbJsonKeys)
if not success then
    print(http.last_error_text)
    return
end

local jsonKeys = chilkat.JsonObject.new()
jsonKeys:load_sb(sbJsonKeys)
jsonKeys.emit_compact = false
print(jsonKeys:emit())

-- Here are the keys:

-- {
--   "keys": [
--     {
--       "alg": "RS256",
--       "e": "AQAB",
--       "kid": "1A/L5Fsb2EsEwxy5E0cmCMS1BnMe6Jl6NXiMig4iNwU=",
--       "kty": "RSA",
--       "n": "y0w7BJrIJYi ... jKG27z2P3OKw",
--       "use": "sig"
--     },
--     {
--       "alg": "RS256",
--       "e": "AQAB",
--       "kid": "mos6VTJnvDwurY3ghJg6IAPUq+dMwl6CL/iThzJOkzg=",
--       "kty": "RSA",
--       "n": "qbIEH-7tg6yrT ... 3Fj94ooTd0w",
--       "use": "sig"
--     }
--   ]
-- }

-- Try the 1st key.
local jsonKey1 = chilkat.JsonObject.new()
jsonKeys:object_of2("keys[0]", jsonKey1)

local pubKey1 = chilkat.PublicKey.new()
success = pubKey1:load_from_string(jsonKey1:emit())
if not success then
    print(pubKey1.last_error_text)
    return
end

print("Success")

local jwt = chilkat.Jwt.new()

-- I did not include the an actual AWS Cognito token here because our test sample used customer-provided data..
local token = "eyJ..asXg"

-- First verify the signature.
local sigVerified = jwt:verify_jwt_pk(token, pubKey1)
print("verified: " .. tostring(sigVerified))

-- Let's see if the time constraints, if any, are valid.
-- The above JWT was created on the afternoon of 16-May-2016, with an expiration of 1 hour.
-- If the current system time is before the "nbf" time, or after the "exp" time,
-- then IsTimeValid will return false/0.
-- Also, we'll allow a leeway of 60 seconds to account for any clock skew.
-- Note: If the token has no "nbf" or "exp" claim fields, then IsTimeValid is always true.
local leeway = 60
local bTimeValid = jwt:is_time_valid(token, leeway)
print("time constraints valid: " .. tostring(bTimeValid))

-- Now let's recover the original claims JSON (the payload).
local payload = jwt:get_payload(token)
-- The payload will likely be in compact form:
print(payload)

-- We can format for human viewing by loading it into Chilkat's JSON object
-- and emit.
local json = chilkat.JsonObject.new()
success = json:load(payload)
json.emit_compact = false
print(json:emit())

-- We can recover the original JOSE header in the same way:
local joseHeader = jwt:get_header(token)
-- The payload will likely be in compact form:
print(joseHeader)

-- We can format for human viewing by loading it into Chilkat's JSON object
-- and emit.
success = json:load(joseHeader)
json.emit_compact = false
print(json:emit())