(Go) Get E-way Bill System Access Token

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

Chilkat Go Downloads Go Package for Windows, MacOS, Linux, Alpine Linux, Solaris

    // 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 := chilkat.NewPublicKey()
    success := pubkey.LoadFromFile("qa_data/pem/eway_publickey.pem")
    if success != true {
        fmt.Println(pubkey.LastErrorText())
        pubkey.DisposePublicKey()
        return
    }

    // Encrypt the password using the RSA public key provided by eway..
    password := "my_wepgst_password"
    rsa := chilkat.NewRsa()
    rsa.SetCharset("utf-8")
    rsa.SetEncodingMode("base64")

    success = rsa.ImportPublicKeyObj(pubkey)
    if success != true {
        fmt.Println(rsa.LastErrorText())
        pubkey.DisposePublicKey()
        rsa.DisposeRsa()
        return
    }

    // Returns the encrypted password as base64 (because the EncodingMode = "base64")
    encPassword := rsa.EncryptStringENC(password,false)
    if rsa.LastMethodSuccess() != true {
        fmt.Println(rsa.LastErrorText())
        pubkey.DisposePublicKey()
        rsa.DisposeRsa()
        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.
    prng := chilkat.NewPrng()
    // Generate a random string containing some numbers, uppercase, and lowercase.
    app_key := prng.RandomString(32,true,true,true)

    fmt.Println("app_key = ", *app_key)

    // RSA encrypt the app_key.
    encAppKey := rsa.EncryptStringENC(*app_key,false)
    if rsa.LastMethodSuccess() != true {
        fmt.Println(rsa.LastErrorText())
        pubkey.DisposePublicKey()
        rsa.DisposeRsa()
        prng.DisposePrng()
        return
    }

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

    http := chilkat.NewHttp()

    // 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.SetAccept("application/json")

    // POST the JSON...
    resp := http.PostJson2("http://ewb.wepgst.com/api/Authenticate","application/json",*jsonBody.Emit())
    if http.LastMethodSuccess() != true {
        fmt.Println(http.LastErrorText())
        pubkey.DisposePublicKey()
        rsa.DisposeRsa()
        prng.DisposePrng()
        jsonBody.DisposeJsonObject()
        http.DisposeHttp()
        return
    }

    respStatusCode := resp.StatusCode()
    fmt.Println("response status code =", respStatusCode)
    fmt.Println("response body:")
    fmt.Println(resp.BodyStr())

    if respStatusCode != 200 {
        resp.DisposeHttpResponse()
        fmt.Println("Failed in some unknown way.")
        pubkey.DisposePublicKey()
        rsa.DisposeRsa()
        prng.DisposePrng()
        jsonBody.DisposeJsonObject()
        http.DisposeHttp()
        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.
    json := chilkat.NewJsonObject()
    json.Load(resp.BodyStr())
    resp.DisposeHttpResponse()

    status := json.IntOf("status")
    fmt.Println("status = ", status)

    if status != 1 {
        // Failed.  Base64 decode the error
        // {"status":"0","error":"eyJlcnJvckNvZGVzIjoiMTA4In0="}
        // For an invalid password, the error is: {"errorCodes":"108"}
        sbError := chilkat.NewStringBuilder()
        json.StringOfSb("error",sbError)
        sbError.Decode("base64","utf-8")
        fmt.Println("error: ", *sbError.GetAsString())
        pubkey.DisposePublicKey()
        rsa.DisposeRsa()
        prng.DisposePrng()
        jsonBody.DisposeJsonObject()
        http.DisposeHttp()
        json.DisposeJsonObject()
        sbError.DisposeStringBuilder()
        return
    }

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

    // Decrypt the sek key using our app_key.
    crypt := chilkat.NewCrypt2()
    crypt.SetCryptAlgorithm("aes")
    crypt.SetCipherMode("ecb")
    crypt.SetKeyLength(256)
    crypt.SetEncodedKey(*app_key,"us-ascii")
    crypt.SetEncodingMode("base64")

    bdSek := chilkat.NewBinData()
    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.
    jsonEwayAuth := chilkat.NewJsonObject()
    jsonEwayAuth.UpdateString("authToken",*authToken)
    jsonEwayAuth.UpdateString("decryptedSek",*bdSek.GetEncoded("base64"))
    jsonEwayAuth.SetEmitCompact(false)

    fac := chilkat.NewFileAccess()
    fac.WriteEntireTextFile("qa_data/tokens/ewayAuth.json",*jsonEwayAuth.Emit(),"utf-8",false)

    fmt.Println("Saved:")
    fmt.Println(*jsonEwayAuth.Emit())

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

    pubkey.DisposePublicKey()
    rsa.DisposeRsa()
    prng.DisposePrng()
    jsonBody.DisposeJsonObject()
    http.DisposeHttp()
    json.DisposeJsonObject()
    sbError.DisposeStringBuilder()
    crypt.DisposeCrypt2()
    bdSek.DisposeBinData()
    jsonEwayAuth.DisposeJsonObject()
    fac.DisposeFileAccess()