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

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

Chilkat C/C++ Library Downloads MS Visual C/C++ Libs

See Also: Using MFC CString in Chilkat

#include <CkHttp.h>
#include <CkStringBuilder.h>
#include <CkJsonObject.h>
#include <CkPublicKey.h>
#include <CkJwt.h>

void ChilkatSample(void)
    {
    CkString strOut;

    // 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:

    CkHttp http;
    CkStringBuilder sbJsonKeys;
    bool success = http.QuickGetSb("https://cognito-idp.us-east-2.amazonaws.com/us-east-2_******/.well-known/jwks.json",sbJsonKeys);
    if (success == false) {
        strOut.append(http.lastErrorText());
        strOut.append("\r\n");
        SetDlgItemText(IDC_EDIT1,strOut.getUnicode());
        return;
    }

    CkJsonObject jsonKeys;
    jsonKeys.LoadSb(sbJsonKeys);
    jsonKeys.put_EmitCompact(false);
    strOut.append(jsonKeys.emit());
    strOut.append("\r\n");

    // 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.
    CkJsonObject *jsonKey1 = jsonKeys.ObjectOf("keys[0]");
    if (jsonKeys.get_LastMethodSuccess() == false) {
        strOut.append("Did not get the 1st JSON public key.");
        strOut.append("\r\n");
        SetDlgItemText(IDC_EDIT1,strOut.getUnicode());
        return;
    }

    CkPublicKey pubKey1;
    success = pubKey1.LoadFromString(jsonKey1->emit());
    if (success == false) {
        strOut.append(pubKey1.lastErrorText());
        strOut.append("\r\n");
        SetDlgItemText(IDC_EDIT1,strOut.getUnicode());
        return;
    }

    delete jsonKey1;

    strOut.append("Success");
    strOut.append("\r\n");

    CkJwt jwt;

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

    // First verify the signature.
    bool sigVerified = jwt.VerifyJwtPk(token,pubKey1);
    strOut.append("verified: ");
    strOut.appendInt(sigVerified);
    strOut.append("\r\n");

    // 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.
    int leeway = 60;
    bool bTimeValid = jwt.IsTimeValid(token,leeway);
    strOut.append("time constraints valid: ");
    strOut.appendInt(bTimeValid);
    strOut.append("\r\n");

    // Now let's recover the original claims JSON (the payload).
    const char *payload = jwt.getPayload(token);
    // The payload will likely be in compact form:
    strOut.append(payload);
    strOut.append("\r\n");

    // We can format for human viewing by loading it into Chilkat's JSON object
    // and emit.
    CkJsonObject json;
    success = json.Load(payload);
    json.put_EmitCompact(false);
    strOut.append(json.emit());
    strOut.append("\r\n");

    // We can recover the original JOSE header in the same way:
    const char *joseHeader = jwt.getHeader(token);
    // The payload will likely be in compact form:
    strOut.append(joseHeader);
    strOut.append("\r\n");

    // We can format for human viewing by loading it into Chilkat's JSON object
    // and emit.
    success = json.Load(joseHeader);
    json.put_EmitCompact(false);
    strOut.append(json.emit());
    strOut.append("\r\n");


    SetDlgItemText(IDC_EDIT1,strOut.getUnicode());

    }