(MFC) 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.

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

See Also: Using MFC CString in Chilkat

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

void ChilkatSample(void)
    {
    CkString strOut;

    // 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.

    CkJwt jwt;

    const char *token = "eyJhbGciOiJIUzI1NiIsInR5cCI6IkpXVCJ9.eyJpc3MiOiJodHRwOi8vZXhhbXBsZS5vcmciLCJzdWIiOiJKb2huIiwiYXVkIjoiaHR0cDovL2V4YW1wbGUuY29tIiwiaWF0IjoxNDYzNDMxODEyLCJuYmYiOjE0NjM0MzE4MTIsImV4cCI6MTQ2MzQzNTQxMn0.SHnMJ11qJH5pbp22YchT_9fL2HIx0koHiUHLG67_foU";

    // First verify the signature.
    // The password used to create this JWT was "secret".
    bool sigVerified = jwt.VerifyJwt(token,"secret");
    strOut.append("with correct password: ");
    strOut.appendInt(sigVerified);
    strOut.append("\r\n");

    // Now try with a different password:
    sigVerified = jwt.VerifyJwt(token,"secret2");
    strOut.append("with incorrect password ");
    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;
    bool 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());

    }