(C++) Verify JWT Using an RSA Public Key (RS256, RS384, RS512)

Demonstrates how to verify a JWT that was signed using an RSA private key.

This example verifies the RSA signature. It also does the following:

• Checks to see if the time constraints ("nbf" and "exp") are valid.
• Recovers the original JOSE header.
• Recovers the original claims JSON.

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

void ChilkatSample(void)
    {
    // Demonstrates how to verify an JWT using an RSA public key.

    // This example requires the Chilkat API to have been previously unlocked.
    // See Global Unlock Sample for sample code.

    CkPublicKey pubKey;
    bool success = pubKey.LoadFromFile("qa_data/pem/rsa_public.pem");

    CkJwt jwt;

    const char *token = "eyJhbGciOiJSUzI1NiIsInR5cCI6IkpXVCJ9.eyJpc3MiOiJodHRwOi8vZXhhbXBsZS5vcmciLCJzdWIiOiJKb2huIiwiYXVkIjoiaHR0cDovL2V4YW1wbGUuY29tIiwiaWF0IjoxNDYzNDQ1MjM4LCJuYmYiOjE0NjM0NDUyMzgsImV4cCI6MTQ2MzQ0ODgzOH0.XRtqed6nuJ9lrp0wbNdDX3fCkSh_d9cHAniPbNcqm7G-5N3mtI5ntQvZBDP3pHtECVqufuDwW7XgUtzAi0ZXhyiRm1iZ3wMSN5lHWv52OQJmMHPA7VPd8Q1hDG-tx-QswzJKd75OEUHP7wIXq2Mg_YVElfDvJI6TGjGyS1y-RLHlz-ldlGsEwIBkO0PtzIYTVov97x8p9KCsPNhS4lZUIqKOYoTZUV5LpuAWARl-636DfMEB_A5_IEaw_W8leh2suP2ULVZxwE-Tk1kBC9tsSGrBrPTtg7sziaV4Lbb0JRANmh98uTRu5f8ji9CVOnpbMiAzjsJSy56kz_olweXSuA";

    // First verify the signature.
    bool sigVerified = jwt.VerifyJwtPk(token,pubKey);
    std::cout << "verified: " << sigVerified << "\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);
    std::cout << "time constraints valid: " << bTimeValid << "\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:
    std::cout << payload << "\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);
    std::cout << json.emit() << "\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:
    std::cout << joseHeader << "\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);
    std::cout << json.emit() << "\r\n";
    }