Dart Requires Chilkat v11.0.0+

Get E-way Bill System Access Token

See more HTTP Misc Examples

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

import 'package:chilkat/chilkat.dart';

void main() {
  // 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
  final pubkey = CkPublicKey();
  try {
    pubkey.loadFromFile('qa_data/pem/eway_publickey.pem');
  } on ChilkatException catch (e) {
    print(e.lastErrorText);
    return;
  }

  // Encrypt the password using the RSA public key provided by eway..
  final password = 'my_wepgst_password';
  final rsa = CkRsa();
  rsa.charset = 'utf-8';
  rsa.encodingMode = 'base64';

  try {
    rsa.usePublicKey(pubkey);
  } on ChilkatException catch (e) {
    print(e.lastErrorText);
    return;
  }

  // Returns the encrypted password as base64 (because the EncodingMode = "base64")
  final String encPassword;
  try {
    encPassword = rsa.encryptStringENC(password, false);
  } on ChilkatException catch (e) {
    print(e.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.
  final prng = CkPrng();
  // Generate a random string containing some numbers, uppercase, and lowercase.
  final appKey = prng.randomString(32, true, true, true);

  print('app_key = $appKey');

  // RSA encrypt the app_key.
  final String encAppKey;
  try {
    encAppKey = rsa.encryptStringENC(appKey, false);
  } on ChilkatException catch (e) {
    print(e.lastErrorText);
    return;
  }

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

  final http = CkHttp();

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

  // POST the JSON...
  final resp = CkHttpResponse();
  try {
    http.httpJson('POST', 'http://ewb.wepgst.com/api/Authenticate', jsonBody, 'application/json', resp);
  } on ChilkatException catch (e) {
    print(e.lastErrorText);
    return;
  }

  final respStatusCode = resp.statusCode;
  print('response status code =$respStatusCode');
  print('response body:');
  print(resp.bodyStr);

  if (respStatusCode != 200) {
    print('Failed in some unknown way.');
    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.
  final json = CkJsonObject();
  json.load(resp.bodyStr);

  final status = json.intOf('status');
  print('status = $status');

  if (status != 1) {
    // Failed.  Base64 decode the error
    // {"status":"0","error":"eyJlcnJvckNvZGVzIjoiMTA4In0="}
    // For an invalid password, the error is: {"errorCodes":"108"}
    final sbError = CkStringBuilder();
    json.stringOfSb('error', sbError);
    sbError.decode('base64', 'utf-8');
    print('error: ${sbError.getAsString()}');
    return;
  }

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

  // Decrypt the sek key using our app_key.
  final crypt = CkCrypt2();
  crypt.cryptAlgorithm = 'aes';
  crypt.cipherMode = 'ecb';
  crypt.keyLength = 256;
  crypt.setEncodedKey(appKey, 'us-ascii');
  crypt.encodingMode = 'base64';

  final bdSek = CkBinData();
  bdSek.appendEncoded(json.stringOf('sek'), '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.
  final jsonEwayAuth = CkJsonObject();
  jsonEwayAuth.updateString('authToken', authToken);
  jsonEwayAuth.updateString('decryptedSek', bdSek.getEncoded('base64'));
  jsonEwayAuth.emitCompact = false;

  final fac = CkFileAccess();
  fac.writeEntireTextFile('qa_data/tokens/ewayAuth.json', jsonEwayAuth.emit(), 'utf-8', false);

  print('Saved:');
  print(jsonEwayAuth.emit());

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