(Delphi DLL) Get E-way Bill System Access Token

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

Chilkat for Delphi Downloads Chilkat non-ActiveX DLL for Delphi Chilkat ActiveX DLL for Delphi * The examples here use the non-ActiveX DLL.

uses
    Winapi.Windows, Winapi.Messages, System.SysUtils, System.Variants, System.Classes, Vcl.Graphics,
    Vcl.Controls, Vcl.Forms, Vcl.Dialogs, Vcl.StdCtrls, PublicKey, Prng, Crypt2, HttpResponse, Http, JsonObject, StringBuilder, FileAccess, Rsa, BinData;

...

procedure TForm1.Button1Click(Sender: TObject);
var
pubkey: HCkPublicKey;
success: Boolean;
password: PWideChar;
rsa: HCkRsa;
encPassword: PWideChar;
prng: HCkPrng;
app_key: PWideChar;
encAppKey: PWideChar;
jsonBody: HCkJsonObject;
http: HCkHttp;
resp: HCkHttpResponse;
respStatusCode: Integer;
json: HCkJsonObject;
status: Integer;
sbError: HCkStringBuilder;
authToken: PWideChar;
crypt: HCkCrypt2;
bdSek: HCkBinData;
jsonEwayAuth: HCkJsonObject;
fac: HCkFileAccess;

begin
//  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
pubkey := CkPublicKey_Create();
success := CkPublicKey_LoadFromFile(pubkey,'qa_data/pem/eway_publickey.pem');
if (success <> True) then
  begin
    Memo1.Lines.Add(CkPublicKey__lastErrorText(pubkey));
    Exit;
  end;

//  Encrypt the password using the RSA public key provided by eway..
password := 'my_wepgst_password';
rsa := CkRsa_Create();
CkRsa_putCharset(rsa,'utf-8');
CkRsa_putEncodingMode(rsa,'base64');

success := CkRsa_ImportPublicKeyObj(rsa,pubkey);
if (success <> True) then
  begin
    Memo1.Lines.Add(CkRsa__lastErrorText(rsa));
    Exit;
  end;

//  Returns the encrypted password as base64 (because the EncodingMode = "base64")
encPassword := CkRsa__encryptStringENC(rsa,password,False);
if (CkRsa_getLastMethodSuccess(rsa) <> True) then
  begin
    Memo1.Lines.Add(CkRsa__lastErrorText(rsa));
    Exit;
  end;

//  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.
prng := CkPrng_Create();
//  Generate a random string containing some numbers, uppercase, and lowercase.
app_key := CkPrng__randomString(prng,32,True,True,True);

Memo1.Lines.Add('app_key = ' + app_key);

//  RSA encrypt the app_key.
encAppKey := CkRsa__encryptStringENC(rsa,app_key,False);
if (CkRsa_getLastMethodSuccess(rsa) <> True) then
  begin
    Memo1.Lines.Add(CkRsa__lastErrorText(rsa));
    Exit;
  end;

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

http := CkHttp_Create();

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

//  POST the JSON...
resp := CkHttp_PostJson2(http,'http://ewb.wepgst.com/api/Authenticate','application/json',CkJsonObject__emit(jsonBody));
if (CkHttp_getLastMethodSuccess(http) <> True) then
  begin
    Memo1.Lines.Add(CkHttp__lastErrorText(http));
    Exit;
  end;

respStatusCode := CkHttpResponse_getStatusCode(resp);
Memo1.Lines.Add('response status code =' + IntToStr(respStatusCode));
Memo1.Lines.Add('response body:');
Memo1.Lines.Add(CkHttpResponse__bodyStr(resp));

if (respStatusCode <> 200) then
  begin
    CkHttpResponse_Dispose(resp);
    Memo1.Lines.Add('Failed in some unknown way.');
    Exit;
  end;

//  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.
json := CkJsonObject_Create();
CkJsonObject_Load(json,CkHttpResponse__bodyStr(resp));
CkHttpResponse_Dispose(resp);

status := CkJsonObject_IntOf(json,'status');
Memo1.Lines.Add('status = ' + IntToStr(status));

if (status <> 1) then
  begin
    //  Failed.  Base64 decode the error
    // {"status":"0","error":"eyJlcnJvckNvZGVzIjoiMTA4In0="}
    //  For an invalid password, the error is: {"errorCodes":"108"}
    sbError := CkStringBuilder_Create();
    CkJsonObject_StringOfSb(json,'error',sbError);
    CkStringBuilder_Decode(sbError,'base64','utf-8');
    Memo1.Lines.Add('error: ' + CkStringBuilder__getAsString(sbError));
    Exit;
  end;

//  At this point, we know the request was entirely successful.
authToken := CkJsonObject__stringOf(json,'authtoken');

//  Decrypt the sek key using our app_key.
crypt := CkCrypt2_Create();
CkCrypt2_putCryptAlgorithm(crypt,'aes');
CkCrypt2_putCipherMode(crypt,'ecb');
CkCrypt2_putKeyLength(crypt,256);
CkCrypt2_SetEncodedKey(crypt,app_key,'us-ascii');
CkCrypt2_putEncodingMode(crypt,'base64');

bdSek := CkBinData_Create();
CkBinData_AppendEncoded(bdSek,CkJsonObject__stringOf(json,'sek'),'base64');
CkCrypt2_DecryptBd(crypt,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.
jsonEwayAuth := CkJsonObject_Create();
CkJsonObject_UpdateString(jsonEwayAuth,'authToken',authToken);
CkJsonObject_UpdateString(jsonEwayAuth,'decryptedSek',CkBinData__getEncoded(bdSek,'base64'));
CkJsonObject_putEmitCompact(jsonEwayAuth,False);

fac := CkFileAccess_Create();
CkFileAccess_WriteEntireTextFile(fac,'qa_data/tokens/ewayAuth.json',CkJsonObject__emit(jsonEwayAuth),'utf-8',False);

Memo1.Lines.Add('Saved:');
Memo1.Lines.Add(CkJsonObject__emit(jsonEwayAuth));

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

CkPublicKey_Dispose(pubkey);
CkRsa_Dispose(rsa);
CkPrng_Dispose(prng);
CkJsonObject_Dispose(jsonBody);
CkHttp_Dispose(http);
CkJsonObject_Dispose(json);
    CkStringBuilder_Dispose(sbError);
CkCrypt2_Dispose(crypt);
CkBinData_Dispose(bdSek);
CkJsonObject_Dispose(jsonEwayAuth);
CkFileAccess_Dispose(fac);

end;