def _verify_signature(token, pkey_data):
try:
# construct the public key
public_key = jwk.construct(pkey_data)
except JOSEError as e:
raise TokenVerifyError(str(e)) from e
# get the last two sections of the token,
# message and signature (encoded in base64)
message, encoded_signature = str(token).rsplit(".", 1)
# decode the signature
decoded_signature = base64url_decode(encoded_signature.encode("utf-8"))
# verify the signature
if not public_key.verify(message.encode("utf8"), decoded_signature):
raise TokenVerifyError("Signature verification failed")
def _find_pkey(self, headers):
kid = headers["kid"]
# search for the kid in the downloaded public keys
key_index = -1
for i in range(len(self.jwk_keys)):
if kid == self.jwk_keys[i]["kid"]:
key_index = i
break
if key_index == -1:
raise TokenVerifyError("Public key not found in jwks.json")
return self.jwk_keys[key_index]
def verify(self, token, current_time=None):
""" https://github.com/awslabs/aws-support-tools/blob/master/Cognito/decode-verify-jwt/decode-verify-jwt.py """
if not token:
raise TokenVerifyError("No token provided")
headers = self._extract_headers(token)
pkey_data = self._find_pkey(headers)
self._verify_signature(token, pkey_data)
claims = self._extract_claims(token)
self._check_expiration(claims, current_time)
self._check_audience(claims)
self.claims = claims
def _check_audience(self, claims):
# and the Audience (use claims['client_id'] if verifying an access token)
audience = claims["aud"] if "aud" in claims else claims["client_id"]
if audience != self.user_pool_client_id:
raise TokenVerifyError("Token was not issued for this audience")
def _check_expiration(claims, current_time):
if not current_time:
current_time = time.time()
if current_time > claims["exp"]:
raise TokenVerifyError(
"Token is expired") # probably another exception
def _extract_claims(token):
try:
claims = jwt.get_unverified_claims(token)
return claims
except JOSEError as e:
raise TokenVerifyError(str(e)) from e
def _extract_headers(token):
try:
headers = jwt.get_unverified_headers(token)
return headers
except JOSEError as e:
raise TokenVerifyError(str(e)) from e
def verify(token):
if token != "good_token":
raise TokenVerifyError("test")
