Add max_age support

msal/application.py

@@ -558,6 +558,7 @@ def initiate_auth_code_flow(
             login_hint=None,  # type: Optional[str]
             domain_hint=None,  # type: Optional[str]
             claims_challenge=None,
+            max_age=None,
             ):
         """Initiate an auth code flow.
 
@@ -588,6 +589,17 @@ def initiate_auth_code_flow(
             `here <https://docs.microsoft.com/en-us/azure/active-directory/develop/v2-oauth2-auth-code-flow#request-an-authorization-code>`_ and
             `here <https://docs.microsoft.com/en-us/openspecs/windows_protocols/ms-oapx/86fb452d-e34a-494e-ac61-e526e263b6d8>`_.
 
+        :param int max_age:
+            OPTIONAL. Maximum Authentication Age.
+            Specifies the allowable elapsed time in seconds
+            since the last time the End-User was actively authenticated.
+            If the elapsed time is greater than this value,
+            Microsoft identity platform will actively re-authenticate the End-User.
+
+            MSAL Python will also automatically validate the auth_time in ID token.
+
+            New in version 1.15.
+
         :return:
             The auth code flow. It is a dict in this form::
 
@@ -617,6 +629,7 @@ def initiate_auth_code_flow(
             domain_hint=domain_hint,
             claims=_merge_claims_challenge_and_capabilities(
                 self._client_capabilities, claims_challenge),
+            max_age=max_age,
             )
         flow["claims_challenge"] = claims_challenge
         return flow
@@ -1403,6 +1416,7 @@ def acquire_token_interactive(
             timeout=None,
             port=None,
             extra_scopes_to_consent=None,
+            max_age=None,
             **kwargs):
         """Acquire token interactively i.e. via a local browser.
 
@@ -1448,6 +1462,17 @@ def acquire_token_interactive(
             in the same interaction, but for which you won't get back a
             token for in this particular operation.
 
+        :param int max_age:
+            OPTIONAL. Maximum Authentication Age.
+            Specifies the allowable elapsed time in seconds
+            since the last time the End-User was actively authenticated.
+            If the elapsed time is greater than this value,
+            Microsoft identity platform will actively re-authenticate the End-User.
+
+            MSAL Python will also automatically validate the auth_time in ID token.
+
+            New in version 1.15.
+
         :return:
             - A dict containing no "error" key,
               and typically contains an "access_token" key.
@@ -1466,6 +1491,7 @@ def acquire_token_interactive(
                 port=port or 0),
             prompt=prompt,
             login_hint=login_hint,
+            max_age=max_age,
             timeout=timeout,
             auth_params={
                 "claims": claims,

msal/oauth2cli/oidc.py

@@ -42,7 +42,7 @@ def decode_id_token(id_token, client_id=None, issuer=None, nonce=None, now=None)
     """
     decoded = json.loads(decode_part(id_token.split('.')[1]))
     err = None  # https://openid.net/specs/openid-connect-core-1_0.html#IDTokenValidation
-    _now = now or time.time()
+    _now = int(now or time.time())
     skew = 120  # 2 minutes
     if _now + skew < decoded.get("nbf", _now - 1):  # nbf is optional per JWT specs
         # This is not an ID token validation, but a JWT validation
@@ -67,14 +67,14 @@ def decode_id_token(id_token, client_id=None, issuer=None, nonce=None, now=None)
     # the Client and the Token Endpoint (which it is during _obtain_token()),
     # the TLS server validation MAY be used to validate the issuer
     # in place of checking the token signature.
-    if _now > decoded["exp"]:
+    if _now - skew > decoded["exp"]:
         err = "9. The current time MUST be before the time represented by the exp Claim."
     if nonce and nonce != decoded.get("nonce"):
         err = ("11. Nonce must be the same value "
             "as the one that was sent in the Authentication Request.")
     if err:
-        raise RuntimeError("%s The id_token was: %s" % (
-            err, json.dumps(decoded, indent=2)))
+        raise RuntimeError("%s Current epoch = %s.  The id_token was: %s" % (
+            err, _now, json.dumps(decoded, indent=2)))
     return decoded
 
 
@@ -187,6 +187,8 @@ def initiate_auth_code_flow(
         flow = super(Client, self).initiate_auth_code_flow(
             scope=_scope, nonce=_nonce_hash(nonce), **kwargs)
         flow["nonce"] = nonce
+        if kwargs.get("max_age") is not None:
+            flow["max_age"] = kwargs["max_age"]
         return flow
 
     def obtain_token_by_auth_code_flow(self, auth_code_flow, auth_response, **kwargs):
@@ -208,6 +210,26 @@ def obtain_token_by_auth_code_flow(self, auth_code_flow, auth_response, **kwargs
                 raise RuntimeError(
                     'The nonce in id token ("%s") should match our nonce ("%s")' %
                     (nonce_in_id_token, expected_hash))
+
+            if auth_code_flow.get("max_age") is not None:
+                auth_time = result.get("id_token_claims", {}).get("auth_time")
+                if not auth_time:
+                    raise RuntimeError(
+                        "13. max_age was requested, ID token should contain auth_time")
+                now = int(time.time())
+                skew = 120  # 2 minutes. Hardcoded, for now
+                if now - skew > auth_time + auth_code_flow["max_age"]:
+                    raise RuntimeError(
+                            "13. auth_time ({auth_time}) was requested, "
+                            "by using max_age ({max_age}) parameter, "
+                            "and now ({now}) too much time has elasped "
+                            "since last end-user authentication. "
+                            "The ID token was: {id_token}".format(
+                        auth_time=auth_time,
+                        max_age=auth_code_flow["max_age"],
+                        now=now,
+                        id_token=json.dumps(result["id_token_claims"], indent=2),
+                        ))
         return result
 
     def obtain_token_by_browser(