Delphi DLL 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. Delphi DLL

var
success: Boolean;
http: HCkHttp;
sbJsonKeys: HCkStringBuilder;
jsonKeys: HCkJsonObject;
jsonKey1: HCkJsonObject;
pubKey1: HCkPublicKey;
jwt: HCkJwt;
token: PWideChar;
sigVerified: Boolean;
leeway: Integer;
bTimeValid: Boolean;
payload: PWideChar;
json: HCkJsonObject;
joseHeader: PWideChar;

begin
success := False;

//  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:

http := CkHttp_Create();
sbJsonKeys := CkStringBuilder_Create();
success := CkHttp_QuickGetSb(http,'https://cognito-idp.us-east-2.amazonaws.com/us-east-2_******/.well-known/jwks.json',sbJsonKeys);
if (success = False) then
  begin
    Memo1.Lines.Add(CkHttp__lastErrorText(http));
    Exit;
  end;

jsonKeys := CkJsonObject_Create();
CkJsonObject_LoadSb(jsonKeys,sbJsonKeys);
CkJsonObject_putEmitCompact(jsonKeys,False);
Memo1.Lines.Add(CkJsonObject__emit(jsonKeys));

//  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.
jsonKey1 := CkJsonObject_Create();
CkJsonObject_ObjectOf2(jsonKeys,'keys[0]',jsonKey1);

pubKey1 := CkPublicKey_Create();
success := CkPublicKey_LoadFromString(pubKey1,CkJsonObject__emit(jsonKey1));
if (success = False) then
  begin
    Memo1.Lines.Add(CkPublicKey__lastErrorText(pubKey1));
    Exit;
  end;

Memo1.Lines.Add('Success');

jwt := CkJwt_Create();

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

//  First verify the signature.
sigVerified := CkJwt_VerifyJwtPk(jwt,token,pubKey1);
Memo1.Lines.Add('verified: ' + IntToStr(Ord(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.
leeway := 60;
bTimeValid := CkJwt_IsTimeValid(jwt,token,leeway);
Memo1.Lines.Add('time constraints valid: ' + IntToStr(Ord(bTimeValid)));

//  Now let's recover the original claims JSON (the payload).
payload := CkJwt__getPayload(jwt,token);
//  The payload will likely be in compact form:
Memo1.Lines.Add(payload);

//  We can format for human viewing by loading it into Chilkat's JSON object
//  and emit.
json := CkJsonObject_Create();
success := CkJsonObject_Load(json,payload);
CkJsonObject_putEmitCompact(json,False);
Memo1.Lines.Add(CkJsonObject__emit(json));

//  We can recover the original JOSE header in the same way:
joseHeader := CkJwt__getHeader(jwt,token);
//  The payload will likely be in compact form:
Memo1.Lines.Add(joseHeader);

//  We can format for human viewing by loading it into Chilkat's JSON object
//  and emit.
success := CkJsonObject_Load(json,joseHeader);
CkJsonObject_putEmitCompact(json,False);
Memo1.Lines.Add(CkJsonObject__emit(json));

CkHttp_Dispose(http);
CkStringBuilder_Dispose(sbJsonKeys);
CkJsonObject_Dispose(jsonKeys);
CkJsonObject_Dispose(jsonKey1);
CkPublicKey_Dispose(pubKey1);
CkJwt_Dispose(jwt);
CkJsonObject_Dispose(json);