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

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

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#include <C_CkHttp.h>
#include <C_CkStringBuilder.h>
#include <C_CkJsonObject.h>
#include <C_CkPublicKey.h>
#include <C_CkJwt.h>

void ChilkatSample(void)
    {
    HCkHttp http;
    HCkStringBuilder sbJsonKeys;
    BOOL success;
    HCkJsonObject jsonKeys;
    HCkJsonObject jsonKey1;
    HCkPublicKey pubKey1;
    HCkJwt jwt;
    const char *token;
    BOOL sigVerified;
    int leeway;
    BOOL bTimeValid;
    const char *payload;
    HCkJsonObject json;
    const char *joseHeader;

    // 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) {
        printf("%s\n",CkHttp_lastErrorText(http));
        CkHttp_Dispose(http);
        CkStringBuilder_Dispose(sbJsonKeys);
        return;
    }

    jsonKeys = CkJsonObject_Create();
    CkJsonObject_LoadSb(jsonKeys,sbJsonKeys);
    CkJsonObject_putEmitCompact(jsonKeys,FALSE);
    printf("%s\n",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_ObjectOf(jsonKeys,"keys[0]");
    if (CkJsonObject_getLastMethodSuccess(jsonKeys) == FALSE) {
        printf("Did not get the 1st JSON public key.\n");
        CkHttp_Dispose(http);
        CkStringBuilder_Dispose(sbJsonKeys);
        CkJsonObject_Dispose(jsonKeys);
        return;
    }

    pubKey1 = CkPublicKey_Create();
    success = CkPublicKey_LoadFromString(pubKey1,CkJsonObject_emit(jsonKey1));
    if (success == FALSE) {
        printf("%s\n",CkPublicKey_lastErrorText(pubKey1));
        CkHttp_Dispose(http);
        CkStringBuilder_Dispose(sbJsonKeys);
        CkJsonObject_Dispose(jsonKeys);
        CkPublicKey_Dispose(pubKey1);
        return;
    }

    CkJsonObject_Dispose(jsonKey1);

    printf("Success\n");

    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);
    printf("verified: %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));


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

    }