Functions to create and use an eBay digital signature in Python

.ebay_digital_signature.py

#!/usr/bin/env python3

from base64 import b64encode
from urllib.parse import urlparse
import sys
import time
import requests
from Crypto.PublicKey import ECC
from Crypto.Signature import eddsa
from Crypto.Hash import SHA256
from requests.exceptions import HTTPError


def get_content_digest(content: str) -> str:
    hasher = SHA256.new()
    hasher.update(bytes(content, encoding="utf-8"))
    return b64encode(hasher.digest()).decode()


def get_digital_signature(
    ebay_private_key: str,
    ebay_public_key_jwe: str,
    request_url: str,
    signature_params: str,
) -> str:
    url = urlparse(request_url)
    params = (
        f'"x-ebay-signature-key": {ebay_public_key_jwe}\n'
        f'"@method": GET\n'
        f'"@path": {url.path}\n'
        f'"@authority": {url.netloc}\n'
        f'"@signature-params": {signature_params}'
    ).encode()

    try:
        private_key = ECC.import_key(
            f"""-----BEGIN PRIVATE KEY-----\n{ebay_private_key}\n-----END PRIVATE KEY-----"""
        )
        signer = eddsa.new(private_key, mode="rfc8032")
        signature = signer.sign(params)
        return b64encode(signature).decode()
    except ValueError as error:
        sys.exit(f"Error creating digital signature: {error}")


def send_signed_api_request(
    ebay_private_key: str,
    ebay_public_key_jwe: str,
    access_token: str,
    request_url: str
) -> None:
    creation_time = int(time.time())
    signature_input = (
        '("x-ebay-signature-key" "@method" "@path" "@authority");'
        f"created={creation_time}"
    )

    signature = get_digital_signature(
        ebay_private_key=ebay_private_key,
        ebay_public_key_jwe=ebay_public_key_jwe,
        request_url=request_url,
        signature_params=signature_input,
    )

    headers = {
        "Authorization": "Bearer " + access_token,
        "Signature-Input": f"sig1={signature_input}",
        "Signature": f"sig1=:{signature}:",
        "x-ebay-signature-key": ebay_public_key_jwe,
        "x-ebay-enforce-signature": "true",
    }

    try:
        response = requests.get(request_url, headers=headers, timeout=10)
        response.raise_for_status()
        print(response.text)
        sys.exit()
    except HTTPError as error:
        sys.exit(f"Unable to send request: {error}")

README.md

This gist contains functions to work with eBay digital signatures in Python. Feel free to use this code however you wish.

For a functional demo and more in-depth overview, check out this repo: https://github.com/carlansell94/ebay-digital-signature-demo