(Python) Get E-way Bill System Access Token

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

Chilkat Python Downloads install with pip pip3 install chilkat or download... Python Module for Windows, MacOS, Linux, Alpine Linux, Solaris

import sys
import chilkat

#  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.CkPublicKey()
success = pubkey.LoadFromFile("qa_data/pem/eway_publickey.pem")
if (success != True):
    print(pubkey.lastErrorText())
    sys.exit()

#  Encrypt the password using the RSA public key provided by eway..
password = "my_wepgst_password"
rsa = chilkat.CkRsa()
rsa.put_Charset("utf-8")
rsa.put_EncodingMode("base64")

success = rsa.ImportPublicKeyObj(pubkey)
if (success != True):
    print(rsa.lastErrorText())
    sys.exit()

#  Returns the encrypted password as base64 (because the EncodingMode = "base64")
encPassword = rsa.encryptStringENC(password,False)
if (rsa.get_LastMethodSuccess() != True):
    print(rsa.lastErrorText())
    sys.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 = chilkat.CkPrng()
#  Generate a random string containing some numbers, uppercase, and lowercase.
app_key = prng.randomString(32,True,True,True)

print("app_key = " + app_key)

#  RSA encrypt the app_key.
encAppKey = rsa.encryptStringENC(app_key,False)
if (rsa.get_LastMethodSuccess() != True):
    print(rsa.lastErrorText())
    sys.exit()

#  Prepare the JSON body for the HTTP POST that gets the access token.
jsonBody = chilkat.CkJsonObject()
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.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.put_Accept("application/json")

#  POST the JSON...
# resp is a CkHttpResponse
resp = http.PostJson2("http://ewb.wepgst.com/api/Authenticate","application/json",jsonBody.emit())
if (http.get_LastMethodSuccess() != True):
    print(http.lastErrorText())
    sys.exit()

respStatusCode = resp.get_StatusCode()
print("response status code =" + str(respStatusCode))
print("response body:")
print(resp.bodyStr())

if (respStatusCode != 200):

    print("Failed in some unknown way.")
    sys.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 = chilkat.CkJsonObject()
json.Load(resp.bodyStr())

status = json.IntOf("status")
print("status = " + str(status))

if (status != 1):
    #  Failed.  Base64 decode the error
    # {"status":"0","error":"eyJlcnJvckNvZGVzIjoiMTA4In0="}
    #  For an invalid password, the error is: {"errorCodes":"108"}
    sbError = chilkat.CkStringBuilder()
    json.StringOfSb("error",sbError)
    sbError.Decode("base64","utf-8")
    print("error: " + sbError.getAsString())
    sys.exit()

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

#  Decrypt the sek key using our app_key.
crypt = chilkat.CkCrypt2()
crypt.put_CryptAlgorithm("aes")
crypt.put_CipherMode("ecb")
crypt.put_KeyLength(256)
crypt.SetEncodedKey(app_key,"us-ascii")
crypt.put_EncodingMode("base64")

bdSek = chilkat.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.
jsonEwayAuth = chilkat.CkJsonObject()
jsonEwayAuth.UpdateString("authToken",authToken)
jsonEwayAuth.UpdateString("decryptedSek",bdSek.getEncoded("base64"))
jsonEwayAuth.put_EmitCompact(False)

fac = chilkat.CkFileAccess()
fac.WriteEntireTextFile("qa_data/tokens/ewayAuth.json",jsonEwayAuth.emit(),"utf-8",False)

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

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