(Swift 2) Verify a JWT Created by the Amazon Cognito Service

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

Chilkat Downloads for the Swift Programming Language MAC OS X (Cocoa) Objective-C/Swift Libs iOS Objective-C/Swift Libs

func chilkatTest() {
    // 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:

    let http = CkoHttp()
    let sbJsonKeys = CkoStringBuilder()
    var success: Bool = http.QuickGetSb("https://cognito-idp.us-east-2.amazonaws.com/us-east-2_******/.well-known/jwks.json", sbContent: sbJsonKeys)
    if success == false {
        print("\(http.LastErrorText)")
        return
    }

    let jsonKeys = CkoJsonObject()
    jsonKeys.LoadSb(sbJsonKeys)
    jsonKeys.EmitCompact = 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.
    var jsonKey1: CkoJsonObject? = jsonKeys.ObjectOf("keys[0]")
    if jsonKeys.LastMethodSuccess == false {
        print("Did not get the 1st JSON public key.")
        return
    }

    let pubKey1 = CkoPublicKey()
    success = pubKey1.LoadFromString(jsonKey1!.Emit())
    if success == false {
        print("\(pubKey1.LastErrorText)")
        return
    }

    jsonKey1 = nil

    print("Success")

    let jwt = CkoJwt()

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

    // First verify the signature.
    var sigVerified: Bool = jwt.VerifyJwtPk(token, key: pubKey1)
    print("verified: \(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.
    var leeway: Int = 60
    var bTimeValid: Bool = jwt.IsTimeValid(token, leeway: leeway)
    print("time constraints valid: \(bTimeValid)")

    // Now let's recover the original claims JSON (the payload).
    var payload: String? = jwt.GetPayload(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.
    let json = CkoJsonObject()
    success = json.Load(payload)
    json.EmitCompact = false
    print("\(json.Emit())")

    // We can recover the original JOSE header in the same way:
    var joseHeader: String? = jwt.GetHeader(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.EmitCompact = false
    print("\(json.Emit())")

}