使用OAuth 2.0授权码流访问UNOS API时回调URI无法访问的问题

尝试使用OAuth 2.0授权码流程访问UNOS的特定API，但始终无法访问回调URI。以下是编写的Python脚本（已隐藏client_id和client_secret以保障安全），同时附上报错截图及API官方文档截图，文档明确了授权码请求、获取访问令牌等步骤的参数要求。

import base64
import hashlib
import os
import requests
from flask import Flask, request, redirect
from urllib.parse import urlencode, quote_plus


app = Flask(__name__)

def base64_urlencode(item):
    return base64.urlsafe_b64encode(item).rstrip(b'=')

def create_code_verifier(size=64):
    verifier = base64_urlencode(os.urandom(size)).decode('utf-8')
    return verifier

def create_code_challenge(verifier):
    sha256 = hashlib.sha256(verifier.encode('utf-8')).digest()
    return base64_urlencode(sha256).decode('utf-8')

code_verifier = create_code_verifier()
code_challenge = create_code_challenge(code_verifier)

# OAuth endpoints given in the UNOS OAuth documentation
authorization_url = "https://api.unos.org/login/v1/oauth2/authorize"
token_url = "https://api.unos.org/login/v1/oauth2/token"

# Client (application) credentials
client_id = ""
client_secret = ""
callback_uri = "https://api.transplantpro.org/api/unos"  # Update with your callback URI

# Prepare headers
auth_header = base64.b64encode(f'{client_id}:{client_secret}'.encode('utf-8')).decode('utf-8')
headers = {
    'Authorization': f'Basic {auth_header}',
    'Content-Type': 'application/x-www-form-urlencoded'
}

# Prepare request data
data = {
    'grant_type': 'authorization_code',
    'redirect_uri': callback_uri,
    'code_verifier': code_verifier
}

@app.route('/')
def index():
    authorize_params = {
        'response_type': 'code',
        'client_id': client_id,
        'redirect_uri': callback_uri,
        'code_challenge': code_challenge,
        'code_challenge_method': 'S256'
    }
    authorize_url = authorization_url + '?' + urlencode(authorize_params, quote_via=quote_plus)
    return redirect(authorize_url)

@app.route('/callback')
def callback():
    authorization_code = request.args.get('code')
    data['code'] = authorization_code

    try:
        # Make the request to obtain access token
        response = requests.post(token_url, headers=headers, data=data)
        response.raise_for_status()  # raise exception if invalid response
        auth_code = response.json()

        # Accessing the UNOS API
        api_url = 'https://api.unos.org/living-donor-tiedi/v1/donor-tiedi/v1/lookups/date-type'
        headers = {'Authorization': f'Bearer {auth_code["access_token"]}'}

        response = requests.get(api_url, headers=headers)
        response.raise_for_status()  # raise exception if invalid response
        return response.json()

    except requests.exceptions.HTTPError as err:
        return f"HTTP Error occurred: {err.response.status_code} - {err.response.text}"

    except Exception as err:
        return f"An error occurred: {err}"

if __name__ == '__main__':
    app.run()

报错截图：

API官方文档截图：

API文档参数说明：

• 请求授权码参数：response_type、client_id、redirect_uri、code_challenge
• 获取访问令牌参数：grant_type、code、redirect_uri、code_verifier
• 刷新令牌参数：access_token、token_type (Bearer)

内容的提问来源于stack exchange，提问作者NoobieDoobie365