(Swift 3,4,5...) Get E-way Bill System Access Token

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

Chilkat Downloads for the Swift Programming Language MAC OS X (Cocoa) Objective-C/Swift Libs iOS Objective-C/Swift Libs

func chilkatTest() {
    // 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
    let pubkey = CkoPublicKey()!
    var success: Bool = pubkey.load(fromFile: "qa_data/pem/eway_publickey.pem")
    if success != true {
        print("\(pubkey.lastErrorText!)")
        return
    }

    // Encrypt the password using the RSA public key provided by eway..
    var password: String? = "my_wepgst_password"
    let rsa = CkoRsa()!
    rsa.charset = "utf-8"
    rsa.encodingMode = "base64"

    success = rsa.importPublicKeyObj(pubkey)
    if success != true {
        print("\(rsa.lastErrorText!)")
        return
    }

    // Returns the encrypted password as base64 (because the EncodingMode = "base64")
    var encPassword: String? = rsa.encryptStringENC(password, bUsePrivateKey: false)
    if rsa.lastMethodSuccess != true {
        print("\(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.
    let prng = CkoPrng()!
    // Generate a random string containing some numbers, uppercase, and lowercase.
    var app_key: String? = prng.randomString(32, bDigits: true, bLower: true, bUpper: true)

    print("app_key = \(app_key!)")

    // RSA encrypt the app_key.
    var encAppKey: String? = rsa.encryptStringENC(app_key, bUsePrivateKey: false)
    if rsa.lastMethodSuccess != true {
        print("\(rsa.lastErrorText!)")
        return
    }

    // Prepare the JSON body for the HTTP POST that gets the access token.
    let jsonBody = CkoJsonObject()!
    jsonBody.update("action", value: "ACCESSTOKEN")
    // Use your username instead of "09ABDC24212B1FK".
    jsonBody.update("username", value: "09ABDC24212B1FK")
    jsonBody.update("password", value: encPassword)
    jsonBody.update("app_key", value: encAppKey)

    let http = CkoHttp()!

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

    // POST the JSON...
    var resp: CkoHttpResponse? = http.postJson2("http://ewb.wepgst.com/api/Authenticate", contentType: "application/json", jsonText: jsonBody.emit())
    if http.lastMethodSuccess != true {
        print("\(http.lastErrorText!)")
        return
    }

    var respStatusCode: Int = resp!.statusCode.intValue
    print("response status code =\(respStatusCode)")
    print("response body:")
    print("\(resp!.bodyStr!)")

    if respStatusCode != 200 {
        resp = nil
        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.
    let json = CkoJsonObject()!
    json.load(resp!.bodyStr)
    resp = nil

    var status: Int = json.int(of: "status").intValue
    print("status = \(status)")

    if status != 1 {
        // Failed.  Base64 decode the error
        // {"status":"0","error":"eyJlcnJvckNvZGVzIjoiMTA4In0="}
        // For an invalid password, the error is: {"errorCodes":"108"}
        let sbError = CkoStringBuilder()!
        json.string(ofSb: "error", sb: sbError)
        sbError.decode("base64", charset: "utf-8")
        print("error: \(sbError.getAsString()!)")
        return
    }

    // At this point, we know the request was entirely successful.
    var authToken: String? = json.string(of: "authtoken")

    // Decrypt the sek key using our app_key.
    let crypt = CkoCrypt2()!
    crypt.cryptAlgorithm = "aes"
    crypt.cipherMode = "ecb"
    crypt.keyLength = 256
    crypt.setEncodedKey(app_key, encoding: "us-ascii")
    crypt.encodingMode = "base64"

    let bdSek = CkoBinData()!
    bdSek.appendEncoded(json.string(of: "sek"), encoding: "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.
    let jsonEwayAuth = CkoJsonObject()!
    jsonEwayAuth.update("authToken", value: authToken)
    jsonEwayAuth.update("decryptedSek", value: bdSek.getEncoded("base64"))
    jsonEwayAuth.emitCompact = false

    let fac = CkoFileAccess()!
    fac.writeEntireTextFile("qa_data/tokens/ewayAuth.json", fileData: jsonEwayAuth.emit(), charset: "utf-8", includePreamble: false)

    print("Saved:")
    print("\(jsonEwayAuth.emit()!)")

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

}