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Fix Spotify API authorization #66

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Fix Spotify API authorization #66

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62 changes: 44 additions & 18 deletions spotify-backup.py
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Original file line number Diff line number Diff line change
Expand Up @@ -13,10 +13,28 @@
import urllib.parse
import urllib.request
import webbrowser
import secrets
import string
import base64
import hashlib

logging.basicConfig(level=20, datefmt='%I:%M:%S', format='[%(asctime)s] %(message)s')


def generate_pkce_pair(length: int = 64) -> tuple[str, str]:
# https://developer.spotify.com/documentation/web-api/tutorials/code-pkce-flow#code-verifier
chars = string.ascii_letters + string.digits
code_verifier = ''.join(secrets.choice(chars) for _ in range(length))

digest = hashlib.sha256(code_verifier.encode("utf-8")).digest()
code_challenge = (
base64.urlsafe_b64encode(digest)
.rstrip(b"=")
.decode("ascii")
)

return code_verifier, code_challenge

class SpotifyAPI:

# Requires an OAuth token.
Expand Down Expand Up @@ -64,11 +82,15 @@ def list(self, url, params={}):
# Pops open a browser window for a user to log in and authorize API access.
@staticmethod
def authorize(client_id, scope):
code_verifier, code_challenge = generate_pkce_pair()

url = 'https://accounts.spotify.com/authorize?' + urllib.parse.urlencode({
'response_type': 'token',
'response_type': 'code',
'client_id': client_id,
'scope': scope,
'redirect_uri': 'http://127.0.0.1:{}/redirect'.format(SpotifyAPI._SERVER_PORT)
'redirect_uri': 'http://127.0.0.1:{}/redirect'.format(SpotifyAPI._SERVER_PORT),
'code_challenge_method': 'S256',
'code_challenge': code_challenge,
})
logging.info(f'Logging in (click if it doesn\'t open automatically): {url}')
webbrowser.open(url)
Expand All @@ -79,7 +101,19 @@ def authorize(client_id, scope):
while True:
server.handle_request()
except SpotifyAPI._Authorization as auth:
return SpotifyAPI(auth.access_token)
# https://developer.spotify.com/documentation/web-api/tutorials/code-pkce-flow#request-an-access-token
body = bytes(urllib.parse.urlencode({
'grant_type': 'authorization_code',
'code': auth.access_code,
'redirect_uri': 'http://127.0.0.1:{}/redirect'.format(SpotifyAPI._SERVER_PORT),
'client_id': client_id,
'code_verifier': code_verifier,
}), encoding='utf-8')
req = urllib.request.Request("https://accounts.spotify.com/api/token", data=body)
req.add_header('content-type', 'application/x-www-form-urlencoded')
res = urllib.request.urlopen(req)
reader = codecs.getreader('utf-8')
return SpotifyAPI(json.load(reader(res))['access_token'])

# The port that the local server listens on. Don't change this,
# as Spotify only will redirect to certain predefined URLs.
Expand All @@ -95,25 +129,17 @@ def handle_error(self, request, client_address):

class _AuthorizationHandler(http.server.BaseHTTPRequestHandler):
def do_GET(self):
# The Spotify API has redirected here, but access_token is hidden in the URL fragment.
# Read it using JavaScript and send it to /token as an actual query string...
if self.path.startswith('/redirect'):
self.send_response(200)
self.send_header('Content-Type', 'text/html')
self.end_headers()
self.wfile.write(b'<script>location.replace("token?" + location.hash.slice(1));</script>')

# Read access_token and use an exception to kill the server listening...
elif self.path.startswith('/token?'):
if self.path.startswith('/redirect?code'):
self.send_response(200)
self.send_header('Content-Type', 'text/html')
self.end_headers()
self.wfile.write(b'<script>close()</script>Thanks! You may now close this window.')

access_token = re.search('access_token=([^&]*)', self.path).group(1)
logging.info(f'Received access token from Spotify: {access_token}')
raise SpotifyAPI._Authorization(access_token)

code = re.search('code=([^&]*)', self.path).group(1)
logging.info(f'Received access code from Spotify: {code}')

raise SpotifyAPI._Authorization(code)
else:
self.send_error(404)

Expand All @@ -122,8 +148,8 @@ def log_message(self, format, *args):
pass

class _Authorization(Exception):
def __init__(self, access_token):
self.access_token = access_token
def __init__(self, access_code):
self.access_code = access_code


def main():
Expand Down