Xbase++ Requires Chilkat v11.0.0+
Verify a JWT Created by the Amazon Cognito Service

Demonstrates how to verify a JWT created by the Amazon Cognito Service.
Chilkat Xbase++ Downloads

Xbase++
LOCAL nSuccess
LOCAL oHttp
LOCAL oSbJsonKeys
LOCAL oJsonKeys
LOCAL oJsonKey1
LOCAL oPubKey1
LOCAL oJwt
LOCAL cToken
LOCAL nSigVerified
LOCAL nLeeway
LOCAL nBTimeValid
LOCAL cPayload
LOCAL oJson
LOCAL cJoseHeader

nSuccess := 0

//  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:

oHttp := CreateObject("Chilkat.Http")
oSbJsonKeys := CreateObject("Chilkat.StringBuilder")
nSuccess := oHttp:QuickGetSb("https://cognito-idp.us-east-2.amazonaws.com/us-east-2_******/.well-known/jwks.json", oSbJsonKeys)
IF (nSuccess == 0)
    ? oHttp:LastErrorText
    oHttp:destroy()
    oSbJsonKeys:destroy()
    RETURN
ENDIF

oJsonKeys := CreateObject("Chilkat.JsonObject")
oJsonKeys:LoadSb(oSbJsonKeys)
oJsonKeys:EmitCompact := 0
? oJsonKeys: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.
oJsonKey1 := CreateObject("Chilkat.JsonObject")
oJsonKeys:ObjectOf2("keys[0]", oJsonKey1)

oPubKey1 := CreateObject("Chilkat.PublicKey")
nSuccess := oPubKey1:LoadFromString(oJsonKey1:Emit())
IF (nSuccess == 0)
    ? oPubKey1:LastErrorText
    oHttp:destroy()
    oSbJsonKeys:destroy()
    oJsonKeys:destroy()
    oJsonKey1:destroy()
    oPubKey1:destroy()
    RETURN
ENDIF

? "Success"

oJwt := CreateObject("Chilkat.Jwt")

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

//  First verify the signature.
nSigVerified := oJwt:VerifyJwtPk(cToken, oPubKey1)
? "verified: " + Str(nSigVerified)

//  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.
nLeeway := 60
nBTimeValid := oJwt:IsTimeValid(cToken, nLeeway)
? "time constraints valid: " + Str(nBTimeValid)

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

//  We can format for human viewing by loading it into Chilkat's JSON object
//  and emit.
oJson := CreateObject("Chilkat.JsonObject")
nSuccess := oJson:Load(cPayload)
oJson:EmitCompact := 0
? oJson:Emit()

//  We can recover the original JOSE header in the same way:
cJoseHeader := oJwt:GetHeader(cToken)
//  The payload will likely be in compact form:
? cJoseHeader

//  We can format for human viewing by loading it into Chilkat's JSON object
//  and emit.
nSuccess := oJson:Load(cJoseHeader)
oJson:EmitCompact := 0
? oJson:Emit()

oHttp:destroy()
oSbJsonKeys:destroy()
oJsonKeys:destroy()
oJsonKey1:destroy()
oPubKey1:destroy()
oJwt:destroy()
oJson:destroy()