I have a Python script to create signature/token for API requests. It works fine.
I have written almost all lines from Python to Bash. Now I am not able to decode/translate below lines from Python to Bash so that correct signature gets created and I complete my bash script.

from Crypto.PublicKey import RSA
from Crypto.Signature import pss
from Crypto.Hash import SHA256

# Load private key
try:
    with open(private_key_location, 'r') as file:
        # Read the contents of the file
        private_key_string = file.read()

# Load private key
private_key = RSA.import_key(
private_key_string, passphrase=passphrase if passphrase else None)

# Sign
h = SHA256.new(signing_string.encode('utf-8'))
signature = pss.new(private_key).sign(h)

# Encode
encoded_signature = base64encode(signature)

First thing I get stuck is this line signing_string.encode('utf-8') as in Python it will create a byte string b'. I tried iconv in bash for byte string but doesn’t seem to fill the purpose. But I may be wrong.

Second thing I tried to sign and all is using below command in bash.

echo -n $MESSAGE |
openssl dgst -sha256 -hmac $SECRET -binary 
base64

This outputs a few characters but when I run the Python one it gives a lot of characters wrapped over multiple lines.

I tried the below too:

echo $MESSAGE |
openssl dgst -sha256 -sign private.pem |
base64

This gives a lot of characters wrapped in multiple lines like the Python one, but doesn’t generates the correct signature for server to authorize, so logic problem.

I need help in translating Python code above to Bash to be able to generate signature.

I know I can go ahead and use this whole code in Bash using python -c "" command etc, etc, but my goal is pure Bash script.