(Unicode C++) Get E-way Bill System Access Token

Sends a request to get an E-way bill system access token.

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#include <CkPublicKeyW.h>
#include <CkRsaW.h>
#include <CkPrngW.h>
#include <CkJsonObjectW.h>
#include <CkHttpW.h>
#include <CkHttpResponseW.h>
#include <CkStringBuilderW.h>
#include <CkCrypt2W.h>
#include <CkBinDataW.h>
#include <CkFileAccessW.h>

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

    //  First load the public key provided by the E-way bill System
    CkPublicKeyW pubkey;
    bool success = pubkey.LoadFromFile(L"qa_data/pem/eway_publickey.pem");
    if (success != true) {
        wprintf(L"%s\n",pubkey.lastErrorText());
        return;
    }

    //  Encrypt the password using the RSA public key provided by eway..
    const wchar_t *password = L"my_wepgst_password";
    CkRsaW rsa;
    rsa.put_Charset(L"utf-8");
    rsa.put_EncodingMode(L"base64");

    success = rsa.ImportPublicKeyObj(pubkey);
    if (success != true) {
        wprintf(L"%s\n",rsa.lastErrorText());
        return;
    }

    //  Returns the encrypted password as base64 (because the EncodingMode = "base64")
    const wchar_t *encPassword = rsa.encryptStringENC(password,false);
    if (rsa.get_LastMethodSuccess() != true) {
        wprintf(L"%s\n",rsa.lastErrorText());
        return;
    }

    //  Generate a random app_key.  This should be 32 bytes (us-ascii chars)
    //  We need 32 bytes because we'll be doing 256-bit AES ECB encryption, and 32 bytes = 256 bits.
    CkPrngW prng;
    //  Generate a random string containing some numbers, uppercase, and lowercase.
    const wchar_t *app_key = prng.randomString(32,true,true,true);

    wprintf(L"app_key = %s\n",app_key);

    //  RSA encrypt the app_key.
    const wchar_t *encAppKey = rsa.encryptStringENC(app_key,false);
    if (rsa.get_LastMethodSuccess() != true) {
        wprintf(L"%s\n",rsa.lastErrorText());
        return;
    }

    //  Prepare the JSON body for the HTTP POST that gets the access token.
    CkJsonObjectW jsonBody;
    jsonBody.UpdateString(L"action",L"ACCESSTOKEN");
    //  Use your username instead of "09ABDC24212B1FK".
    jsonBody.UpdateString(L"username",L"09ABDC24212B1FK");
    jsonBody.UpdateString(L"password",encPassword);
    jsonBody.UpdateString(L"app_key",encAppKey);

    CkHttpW http;

    //  Add required headers.
    //  Use your ewb-user-id instead of "03AEXPR16A9M010"
    http.SetRequestHeader(L"ewb-user-id",L"03AEXPR16A9M010");
    //  The Gstin should be the same as the username in the jsonBody above.
    http.SetRequestHeader(L"Gstin",L"09ABDC24212B1FK");
    http.put_Accept(L"application/json");

    //  POST the JSON...
    CkHttpResponseW *resp = http.PostJson2(L"http://ewb.wepgst.com/api/Authenticate",L"application/json",jsonBody.emit());
    if (http.get_LastMethodSuccess() != true) {
        wprintf(L"%s\n",http.lastErrorText());
        return;
    }

    int respStatusCode = resp->get_StatusCode();
    wprintf(L"response status code =%d\n",respStatusCode);
    wprintf(L"response body:\n");
    wprintf(L"%s\n",resp->bodyStr());

    if (respStatusCode != 200) {
        delete resp;
        wprintf(L"Failed in some unknown way.\n");
        return;
    }

    //  When the response status code = 200, we'll have either
    //  success response like this:
    //   {"status":"1","authtoken":"...","sek":"..."}
    // 
    //  or a failed response like this:
    // 
    //  {"status":"0","error":"eyJlcnJvckNvZGVzIjoiMTA4In0="}

    //  Load the response body into a JSON object.
    CkJsonObjectW json;
    json.Load(resp->bodyStr());
    delete resp;

    int status = json.IntOf(L"status");
    wprintf(L"status = %d\n",status);

    if (status != 1) {
        //  Failed.  Base64 decode the error
        // {"status":"0","error":"eyJlcnJvckNvZGVzIjoiMTA4In0="}
        //  For an invalid password, the error is: {"errorCodes":"108"}
        CkStringBuilderW sbError;
        json.StringOfSb(L"error",sbError);
        sbError.Decode(L"base64",L"utf-8");
        wprintf(L"error: %s\n",sbError.getAsString());
        return;
    }

    //  At this point, we know the request was entirely successful.
    const wchar_t *authToken = json.stringOf(L"authtoken");

    //  Decrypt the sek key using our app_key.
    CkCrypt2W crypt;
    crypt.put_CryptAlgorithm(L"aes");
    crypt.put_CipherMode(L"ecb");
    crypt.put_KeyLength(256);
    crypt.SetEncodedKey(app_key,L"us-ascii");
    crypt.put_EncodingMode(L"base64");

    CkBinDataW bdSek;
    bdSek.AppendEncoded(json.stringOf(L"sek"),L"base64");
    crypt.DecryptBd(bdSek);

    //  bdSek now contains the decrypted symmetric encryption key...
    //  We'll use it to encrypt the JSON payloads we send.

    //  Let's persist our authtoken and decrypted sek (symmetric encryption key).
    //  To send EWAY requests (such as to create an e-way bill), we'll just load
    //  and use these pre-obtained credentials.
    CkJsonObjectW jsonEwayAuth;
    jsonEwayAuth.UpdateString(L"authToken",authToken);
    jsonEwayAuth.UpdateString(L"decryptedSek",bdSek.getEncoded(L"base64"));
    jsonEwayAuth.put_EmitCompact(false);

    CkFileAccessW fac;
    fac.WriteEntireTextFile(L"qa_data/tokens/ewayAuth.json",jsonEwayAuth.emit(),L"utf-8",false);

    wprintf(L"Saved:\n");
    wprintf(L"%s\n",jsonEwayAuth.emit());

    //  Sample output:
    //  {
    //    "authToken": "IBTeFtxNfVurg71LTzZ2r0xK7",
    //    "decryptedSek": "5g1TyTie7yoslU3DrbYATa7mWyPazlODE7cEh5Vy4Ho="
    //  }
    }