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facade.py
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102 lines (79 loc) · 2.99 KB
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import base64
import binascii
import hashlib
import hmac
from logging import Logger
from urllib import parse
from django.conf import settings
_key_bytes = settings.DISCOURSE_SSO_SECRET.encode('utf-8')
__all__ = (
'generate_discourse_login_url',
'InvalidSOOPayload',
'MissingDiscourseAPICredentials',
'generate_sso_payload_and_signature'
)
class InvalidSOOPayload(Exception):
pass
class MissingDiscourseAPICredentials(Exception):
pass
logger = Logger(__file__)
def generate_discourse_login_url(user, payload, signature):
"""
Generate Discourse login url if payload matches signature
It will raise InvalidSOOPayload otherwise
:param user: Django's User
:param payload: payload to be validated
:param signature: payload signature
:return: url to login user
"""
decoded = _decode_payload(payload, signature)
_check_nonce_is_present(decoded)
nonce = parse.parse_qs(decoded)['nonce'][0]
return _generate_discourse_login_url(nonce, user)
def _generate_discourse_login_url(nonce, user):
params = {
'nonce': nonce,
'email': user.email,
'external_id': user.id,
'require_activation': 'false',
'groups': ','.join(g.name for g in user.groups.all())
}
sso_payload, signature = generate_sso_payload_and_signature(params)
query_string = parse.urlencode({'sso': sso_payload, 'sig': signature})
url = f'{settings.DISCOURSE_BASE_URL}/session/sso_login'
url = f'{url}?{query_string}'
return url
def generate_sso_payload_and_signature(params):
sso_payload = base64.encodebytes(parse.urlencode(params).encode('utf-8'))
h = hmac.new(_key_bytes, sso_payload, digestmod=hashlib.sha256)
signature = h.hexdigest()
return sso_payload, signature
def _decode_payload(payload, signature):
_check_mandatory_params(payload, signature)
payload_bytes = parse.unquote(payload).encode('utf-8')
try:
decoded = base64.decodebytes(payload_bytes).decode('utf-8')
except binascii.Error as e:
msg = f'Invalid base64 payload: {payload}'
logger.warning(msg)
raise InvalidSOOPayload(msg) from e
else:
h = hmac.new(_key_bytes, payload_bytes, digestmod=hashlib.sha256)
calculated_signature = h.hexdigest()
_check_signature(calculated_signature, signature)
return decoded
def _check_signature(calculated_signature, signature):
if not hmac.compare_digest(calculated_signature, signature):
msg = f'Signatures mismatch: {signature} != {calculated_signature}'
logger.warning(msg)
raise InvalidSOOPayload(msg)
def _check_nonce_is_present(decoded):
if 'nonce' not in decoded:
msg = f'Nonce not in payload={decoded}'
logger.warning(msg)
raise InvalidSOOPayload(msg)
def _check_mandatory_params(payload, signature):
if payload is None or signature is None:
msg = f'Invalid SSO payload={payload} signature={signature}'
logger.warning(msg)
raise InvalidSOOPayload(msg)