Classic ASP Requires Chilkat v11.0.0+
Get E-way Bill System Access Token

Sends a request to get an E-way bill system access token.
Chilkat Classic ASP Downloads

Classic ASP
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<meta http-equiv="Content-Type" content="text/html; charset=utf-8">
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<%
success = 0

'  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
set pubkey = Server.CreateObject("Chilkat.PublicKey")
success = pubkey.LoadFromFile("qa_data/pem/eway_publickey.pem")
If (success = 0) Then
    Response.Write "<pre>" & Server.HTMLEncode( pubkey.LastErrorText) & "</pre>"
    Response.End
End If

'  Encrypt the password using the RSA public key provided by eway..
password = "my_wepgst_password"
set rsa = Server.CreateObject("Chilkat.Rsa")
rsa.Charset = "utf-8"
rsa.EncodingMode = "base64"

success = rsa.UsePublicKey(pubkey)
If (success = 0) Then
    Response.Write "<pre>" & Server.HTMLEncode( rsa.LastErrorText) & "</pre>"
    Response.End
End If

'  Returns the encrypted password as base64 (because the EncodingMode = "base64")
encPassword = rsa.EncryptStringENC(password,0)
If (rsa.LastMethodSuccess = 0) Then
    Response.Write "<pre>" & Server.HTMLEncode( rsa.LastErrorText) & "</pre>"
    Response.End
End If

'  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.
set prng = Server.CreateObject("Chilkat.Prng")
'  Generate a random string containing some numbers, uppercase, and lowercase.
app_key = prng.RandomString(32,1,1,1)

Response.Write "<pre>" & Server.HTMLEncode( "app_key = " & app_key) & "</pre>"

'  RSA encrypt the app_key.
encAppKey = rsa.EncryptStringENC(app_key,0)
If (rsa.LastMethodSuccess = 0) Then
    Response.Write "<pre>" & Server.HTMLEncode( rsa.LastErrorText) & "</pre>"
    Response.End
End If

'  Prepare the JSON body for the HTTP POST that gets the access token.
set jsonBody = Server.CreateObject("Chilkat.JsonObject")
success = jsonBody.UpdateString("action","ACCESSTOKEN")
'  Use your username instead of "09ABDC24212B1FK".
success = jsonBody.UpdateString("username","09ABDC24212B1FK")
success = jsonBody.UpdateString("password",encPassword)
success = jsonBody.UpdateString("app_key",encAppKey)

set http = Server.CreateObject("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...
set resp = Server.CreateObject("Chilkat.HttpResponse")
success = http.HttpJson("POST","http://ewb.wepgst.com/api/Authenticate",jsonBody,"application/json",resp)
If (success = 0) Then
    Response.Write "<pre>" & Server.HTMLEncode( http.LastErrorText) & "</pre>"
    Response.End
End If

respStatusCode = resp.StatusCode
Response.Write "<pre>" & Server.HTMLEncode( "response status code =" & respStatusCode) & "</pre>"
Response.Write "<pre>" & Server.HTMLEncode( "response body:") & "</pre>"
Response.Write "<pre>" & Server.HTMLEncode( resp.BodyStr) & "</pre>"

If (respStatusCode <> 200) Then
    Response.Write "<pre>" & Server.HTMLEncode( "Failed in some unknown way.") & "</pre>"
    Response.End
End If

'  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.
set json = Server.CreateObject("Chilkat.JsonObject")
success = json.Load(resp.BodyStr)

status = json.IntOf("status")
Response.Write "<pre>" & Server.HTMLEncode( "status = " & status) & "</pre>"

If (status <> 1) Then
    '  Failed.  Base64 decode the error
    '  {"status":"0","error":"eyJlcnJvckNvZGVzIjoiMTA4In0="}
    '  For an invalid password, the error is: {"errorCodes":"108"}
    set sbError = Server.CreateObject("Chilkat.StringBuilder")
    success = json.StringOfSb("error",sbError)
    success = sbError.Decode("base64","utf-8")
    Response.Write "<pre>" & Server.HTMLEncode( "error: " & sbError.GetAsString()) & "</pre>"
    Response.End
End If

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

'  Decrypt the sek key using our app_key.
set crypt = Server.CreateObject("Chilkat.Crypt2")
crypt.CryptAlgorithm = "aes"
crypt.CipherMode = "ecb"
crypt.KeyLength = 256
crypt.SetEncodedKey app_key,"us-ascii"
crypt.EncodingMode = "base64"

set bdSek = Server.CreateObject("Chilkat.BinData")
success = bdSek.AppendEncoded(json.StringOf("sek"),"base64")
success = 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.
set jsonEwayAuth = Server.CreateObject("Chilkat.JsonObject")
success = jsonEwayAuth.UpdateString("authToken",authToken)
success = jsonEwayAuth.UpdateString("decryptedSek",bdSek.GetEncoded("base64"))
jsonEwayAuth.EmitCompact = 0

set fac = Server.CreateObject("Chilkat.FileAccess")
success = fac.WriteEntireTextFile("qa_data/tokens/ewayAuth.json",jsonEwayAuth.Emit(),"utf-8",0)

Response.Write "<pre>" & Server.HTMLEncode( "Saved:") & "</pre>"
Response.Write "<pre>" & Server.HTMLEncode( jsonEwayAuth.Emit()) & "</pre>"

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

%>
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