(C) Verify JWT Using HS256, HS384, or HS512

Demonstrates how to verify a JWT that was signed using HS256, HS384, or HS512. (HS256 is JWT's acronym for HMAC-SHA256.)

This example verifies the 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 <C_CkJwt.h>
#include <C_CkJsonObject.h>

void ChilkatSample(void)
    {
    HCkJwt jwt;
    const char *token;
    BOOL sigVerified;
    int leeway;
    BOOL bTimeValid;
    const char *payload;
    HCkJsonObject json;
    BOOL success;
    const char *joseHeader;

    // Demonstrates how to verify an HMAC JWT using a shared secret (password).

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

    jwt = CkJwt_Create();

    token = "eyJhbGciOiJIUzI1NiIsInR5cCI6IkpXVCJ9.eyJpc3MiOiJodHRwOi8vZXhhbXBsZS5vcmciLCJzdWIiOiJKb2huIiwiYXVkIjoiaHR0cDovL2V4YW1wbGUuY29tIiwiaWF0IjoxNDYzNDMxODEyLCJuYmYiOjE0NjM0MzE4MTIsImV4cCI6MTQ2MzQzNTQxMn0.SHnMJ11qJH5pbp22YchT_9fL2HIx0koHiUHLG67_foU";

    // First verify the signature.
    // The password used to create this JWT was "secret".
    sigVerified = CkJwt_VerifyJwt(jwt,token,"secret");
    printf("with correct password: %d\n",sigVerified);

    // Now try with a different password:
    sigVerified = CkJwt_VerifyJwt(jwt,token,"secret2");
    printf("with incorrect password %d\n",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);
    printf("time constraints valid: %d\n",bTimeValid);

    // Now let's recover the original claims JSON (the payload).
    payload = CkJwt_getPayload(jwt,token);
    // The payload will likely be in compact form:
    printf("%s\n",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);
    printf("%s\n",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:
    printf("%s\n",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);
    printf("%s\n",CkJsonObject_emit(json));


    CkJwt_Dispose(jwt);
    CkJsonObject_Dispose(json);

    }