(Lianja) Verify a JWT Created by the Amazon Cognito Service

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

Chilkat Lianja Extension Download Chilkat Lianja Extension

// 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:

loHttp = createobject("CkHttp")
loSbJsonKeys = createobject("CkStringBuilder")
llSuccess = loHttp.QuickGetSb("https://cognito-idp.us-east-2.amazonaws.com/us-east-2_******/.well-known/jwks.json",loSbJsonKeys)
if (llSuccess = .F.) then
    ? loHttp.LastErrorText
    release loHttp
    release loSbJsonKeys
    return
endif

loJsonKeys = createobject("CkJsonObject")
loJsonKeys.LoadSb(loSbJsonKeys)
loJsonKeys.EmitCompact = .F.
? loJsonKeys.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.
loJsonKey1 = loJsonKeys.ObjectOf("keys[0]")
if (loJsonKeys.LastMethodSuccess = .F.) then
    ? "Did not get the 1st JSON public key."
    release loHttp
    release loSbJsonKeys
    release loJsonKeys
    return
endif

loPubKey1 = createobject("CkPublicKey")
llSuccess = loPubKey1.LoadFromString(loJsonKey1.Emit())
if (llSuccess = .F.) then
    ? loPubKey1.LastErrorText
    release loHttp
    release loSbJsonKeys
    release loJsonKeys
    release loPubKey1
    return
endif

release loJsonKey1

? "Success"

loJwt = createobject("CkJwt")

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

// First verify the signature.
llSigVerified = loJwt.VerifyJwtPk(lcToken,loPubKey1)
? "verified: " + str(llSigVerified)

// 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.
lnLeeway = 60
llBTimeValid = loJwt.IsTimeValid(lcToken,lnLeeway)
? "time constraints valid: " + str(llBTimeValid)

// Now let's recover the original claims JSON (the payload).
lcPayload = loJwt.GetPayload(lcToken)
// The payload will likely be in compact form:
? lcPayload

// We can format for human viewing by loading it into Chilkat's JSON object
// and emit.
loJson = createobject("CkJsonObject")
llSuccess = loJson.Load(lcPayload)
loJson.EmitCompact = .F.
? loJson.Emit()

// We can recover the original JOSE header in the same way:
lcJoseHeader = loJwt.GetHeader(lcToken)
// The payload will likely be in compact form:
? lcJoseHeader

// We can format for human viewing by loading it into Chilkat's JSON object
// and emit.
llSuccess = loJson.Load(lcJoseHeader)
loJson.EmitCompact = .F.
? loJson.Emit()


release loHttp
release loSbJsonKeys
release loJsonKeys
release loPubKey1
release loJwt
release loJson