(PowerShell) Get E-way Bill System Access Token

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

Chilkat .NET Downloads Chilkat .NET Assemblies

Add-Type -Path "C:\chilkat\ChilkatDotNet47-9.5.0-x64\ChilkatDotNet47.dll"

# 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 = New-Object Chilkat.PublicKey
$success = $pubkey.LoadFromFile("qa_data/pem/eway_publickey.pem")
if ($success -ne $true) {
    $($pubkey.LastErrorText)
    exit
}

# Encrypt the password using the RSA public key provided by eway..
$password = "my_wepgst_password"
$rsa = New-Object Chilkat.Rsa
$rsa.Charset = "utf-8"
$rsa.EncodingMode = "base64"

$success = $rsa.ImportPublicKeyObj($pubkey)
if ($success -ne $true) {
    $($rsa.LastErrorText)
    exit
}

# Returns the encrypted password as base64 (because the EncodingMode = "base64")
$encPassword = $rsa.EncryptStringENC($password,$false)
if ($rsa.LastMethodSuccess -ne $true) {
    $($rsa.LastErrorText)
    exit
}

# 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 = New-Object Chilkat.Prng
# Generate a random string containing some numbers, uppercase, and lowercase.
$app_key = $prng.RandomString(32,$true,$true,$true)

$("app_key = " + $app_key)

# RSA encrypt the app_key.
$encAppKey = $rsa.EncryptStringENC($app_key,$false)
if ($rsa.LastMethodSuccess -ne $true) {
    $($rsa.LastErrorText)
    exit
}

# Prepare the JSON body for the HTTP POST that gets the access token.
$jsonBody = New-Object Chilkat.JsonObject
$jsonBody.UpdateString("action","ACCESSTOKEN")
# Use your username instead of "09ABDC24212B1FK".
$jsonBody.UpdateString("username","09ABDC24212B1FK")
$jsonBody.UpdateString("password",$encPassword)
$jsonBody.UpdateString("app_key",$encAppKey)

$http = New-Object Chilkat.Http

# 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...
$resp = $http.PostJson2("http://ewb.wepgst.com/api/Authenticate","application/json",$jsonBody.Emit())
if ($http.LastMethodSuccess -ne $true) {
    $($http.LastErrorText)
    exit
}

$respStatusCode = $resp.StatusCode
$("response status code =" + $respStatusCode)
$("response body:")
$($resp.BodyStr)

if ($respStatusCode -ne 200) {

    $("Failed in some unknown way.")
    exit
}

# 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 = New-Object Chilkat.JsonObject
$json.Load($resp.BodyStr)

$status = $json.IntOf("status")
$("status = " + $status)

if ($status -ne 1) {
    # Failed.  Base64 decode the error
    # {"status":"0","error":"eyJlcnJvckNvZGVzIjoiMTA4In0="}
    # For an invalid password, the error is: {"errorCodes":"108"}
    $sbError = New-Object Chilkat.StringBuilder
    $json.StringOfSb("error",$sbError)
    $sbError.Decode("base64","utf-8")
    $("error: " + $sbError.GetAsString())
    exit
}

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

# Decrypt the sek key using our app_key.
$crypt = New-Object Chilkat.Crypt2
$crypt.CryptAlgorithm = "aes"
$crypt.CipherMode = "ecb"
$crypt.KeyLength = 256
$crypt.SetEncodedKey($app_key,"us-ascii")
$crypt.EncodingMode = "base64"

$bdSek = New-Object Chilkat.BinData
$bdSek.AppendEncoded($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 = New-Object Chilkat.JsonObject
$jsonEwayAuth.UpdateString("authToken",$authToken)
$jsonEwayAuth.UpdateString("decryptedSek",$bdSek.GetEncoded("base64"))
$jsonEwayAuth.EmitCompact = $false

$fac = New-Object Chilkat.FileAccess
$fac.WriteEntireTextFile("qa_data/tokens/ewayAuth.json",$jsonEwayAuth.Emit(),"utf-8",$false)

$("Saved:")
$($jsonEwayAuth.Emit())

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