Decryption failed error while generating token

[coder-amogh]

My GST Suvidha Provider (GSP) is Chartered Information Systems Private Limited (CISPL) and their documentation is here.

First question is, how to generate a PEM file? I tried following help from CISPL article and ran these two commands to obtain the PEM file:

• $ openssl req -x509 -nodes -sha256 -days 3650 -newkey rsa:2048 -keyout AspDsc.key -out AspDsc.cer
• $ openssl x509 -in AspDsc.cer -pubkey -noout > public_key.pem

Is this the intended way? Would appreciate help and some documentation on this.

Then I uploaded the AspDsc.cer file to CISPL portal as per their documentation and I got their email with the ASP_PASSWORD which can be used in the API calls.

My code is as follows:

with open("certs/public_key.pem") as f:
    public_key = f.read()

print("Creating session...")

session = Session(
    TEST_GSTIN, 
    client_id=CLIENT_ID, 
    client_secret=ASP_PASSWORD, 
    username=TEST_USER, 
    password=TEST_PASS, 
    public_key=public_key,
    # use the sandbox url, or production url
    # or pass-through APIs provided by GSPs
    base_url="https://gstsandbox.charteredinfo.com", 
    gsp_headers={
        "aspid": CLIENT_ID,
        "password": CLIENT_SECRET,
    },
)

print("Creating token...")

session.generate_token() # FAILS HERE

Below is complete traceback error:

Creating session...
Creating token...
{   'Data': None,
    'ErrorDetails': [   {   'ErrorCode': '1020',
                            'ErrorMessage': 'Decryption failed'}],
    'InfoDtls': None,
    'Status': 0}
Traceback (most recent call last):
  File "/Users/amoghdatar/gst-app/test-einv.py", line 34, in <module>
    session.generate_token()
    ~~~~~~~~~~~~~~~~~~~~~~^^
  File "/Users/amoghdatar/gst-app/venv/lib/python3.13/site-packages/gst_irn/session.py", line 181, in generate_token
    data, app_key = _get_auth_token(self, force_regenerate_token)
                    ~~~~~~~~~~~~~~~^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/Users/amoghdatar/gst-app/venv/lib/python3.13/site-packages/gst_irn/session.py", line 94, in _get_auth_token
    data = _get_data_from_response(response, encryption_key=None)
  File "/Users/amoghdatar/gst-app/venv/lib/python3.13/site-packages/gst_irn/session.py", line 58, in _get_data_from_response
    _raise_formatted_error(response, "action failed")
    ~~~~~~~~~~~~~~~~~~~~~~^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/Users/amoghdatar/gst-app/venv/lib/python3.13/site-packages/gst_irn/session.py", line 45, in _raise_formatted_error
    raise RequestError(msg, err)
gst_irn.session.RequestError: ('action failed', {'Status': 0, 'ErrorDetails': [{'ErrorCode': '1020', 'ErrorMessage': 'Decryption failed'}], 'Data': None, 'InfoDtls': None})