Metadata document missing causing NullpointerException

[cbra-pwl]

We saw this error last year, but have only seen it once, so it has been prioritized pretty low,. But we thought we should report it anyway. We got a NullPointerException:

DEBUG 2022-09-22 07:52:02,256 7234ms [27] Log4NetTraceListener Write - dk.nita.saml20 Information: 0 :
DEBUG 2022-09-22 07:52:02,272 7250ms [27] Log4NetTraceListener WriteLine - dk.nita.saml20.protocol.Saml20SignonHandler.Handle() called
INFO 2022-09-22 07:52:02,272 7250ms [27] OIOSAML_AUDIT_LOGGER LogEntry - Session id: , Direction: IN, Operation: ACCESS, User IP: 93.176.79.130, Idp ID: , Assertion ID: , Message: User accessing resource: /IdentityHub/saml-sign-on?forceAuthn=True without authentication., Data:
INFO 2022-09-22 07:52:02,272 7250ms [11] OIOSAML_AUDIT_LOGGER LogEntry - Session id: , Direction: IN, Operation: ACCESS, User IP: 83.151.151.55, Idp ID: , Assertion ID: , Message: User accessing resource: /IdentityHub/saml-sign-on?forceAuthn=True without authentication., Data:
INFO 2022-09-22 07:52:02,272 7250ms [25] OIOSAML_AUDIT_LOGGER LogEntry - Session id: , Direction: IN, Operation: ACCESS, User IP: 83.151.151.55, Idp ID: , Assertion ID: , Message: User accessing resource: /IdentityHub/saml-sign-on without authentication., Data:
DEBUG 2022-09-22 07:52:02,288 7266ms [27] Log4NetTraceListener Write - dk.nita.saml20 Information: 0 :
DEBUG 2022-09-22 07:52:02,288 7266ms [27] Log4NetTraceListener WriteLine - dk.nita.saml20.protocol.Saml20SignonHandler.SendRequest() called
DEBUG 2022-09-22 07:52:02,288 7266ms [11] Log4NetTraceListener Write - dk.nita.saml20 Information: 0 :
DEBUG 2022-09-22 07:52:02,288 7266ms [11] Log4NetTraceListener WriteLine - dk.nita.saml20.protocol.Saml20SignonHandler.SendRequest() called
INFO 2022-09-22 07:52:02,288 7266ms [27] OIOSAML_AUDIT_LOGGER LogEntry - Session id: 9c7fdd5a-fefe-410a-89a9-9d075fd71034, Direction: IN, Operation: DISCOVER, User IP: 93.176.79.130, Idp ID: , Assertion ID: , Message: No IdP selected in Common Domain Cookie, using default IdP: https://sts.windows.net/2e91ef12-3cbc-456a-8637-b8d139d5d3a7/, Data:
INFO 2022-09-22 07:52:02,288 7266ms [11] OIOSAML_AUDIT_LOGGER LogEntry - Session id: b3465bf8-33f3-47c9-88d0-31dfa135ed49, Direction: IN, Operation: DISCOVER, User IP: 83.151.151.55, Idp ID: , Assertion ID: , Message: No IdP selected in Common Domain Cookie, using default IdP: https://sts.windows.net/2e91ef12-3cbc-456a-8637-b8d139d5d3a7/, Data:
INFO 2022-09-22 07:52:02,272 7250ms [23] OIOSAML_AUDIT_LOGGER LogEntry - Session id: , Direction: IN, Operation: ACCESS, User IP: 93.176.79.130, Idp ID: , Assertion ID: , Message: User accessing resource: /IdentityHub/saml-sign-on without authentication., Data:
INFO 2022-09-22 07:52:02,272 7250ms [10] OIOSAML_AUDIT_LOGGER LogEntry - Session id: , Direction: IN, Operation: ACCESS, User IP: 83.151.151.55, Idp ID: , Assertion ID: , Message: User accessing resource: /IdentityHub/saml-sign-on without authentication., Data:
DEBUG 2022-09-22 07:52:02,303 7281ms [27] Log4NetTraceListener Write - dk.nita.saml20 Error: 0 :
DEBUG 2022-09-22 07:52:02,303 7281ms [27] Log4NetTraceListener WriteLine - Error: System.NullReferenceException: Object reference not set to an instance of an object.
at dk.nita.saml20.protocol.Saml20AbstractEndpointHandler.<>c__DisplayClass10_0.b__0(IDPEndPointElement el) in E:\Projects\bob3-f2-8.6\OIOSAML.NET\src\dk.nita.saml20\dk.nita.saml20\Protocol\Saml20AbstractEndpointHandler.cs:line 203
at System.Collections.Generic.List1.FindIndex(Int32 startIndex, Int32 count, Predicate1 match)
at System.Collections.Generic.List1.Exists(Predicate1 match)
at dk.nita.saml20.protocol.Saml20AbstractEndpointHandler.DetermineEndpointConfiguration(SAMLBinding defaultBinding, IDPEndPointElement config, List`1 metadata) in E:\Projects\bob3-f2-8.6\OIOSAML.NET\src\dk.nita.saml20\dk.nita.saml20\Protocol\Saml20AbstractEndpointHandler.cs:line 203
at dk.nita.saml20.protocol.Saml20SignonHandler.TransferClient(IDPEndPoint idpEndpoint, Saml20AuthnRequest request, HttpContext context) in E:\Projects\bob3-f2-8.6\OIOSAML.NET\src\dk.nita.saml20\dk.nita.saml20\Protocol\Saml20SignonHandler.cs:line 658
at dk.nita.saml20.protocol.Saml20SignonHandler.SendRequest(HttpContext context) in E:\Projects\bob3-f2-8.6\OIOSAML.NET\src\dk.nita.saml20\dk.nita.saml20\Protocol\Saml20SignonHandler.cs:line 218
at dk.nita.saml20.protocol.Saml20SignonHandler.Handle(HttpContext context) in E:\Projects\bob3-f2-8.6\OIOSAML.NET\src\dk.nita.saml20\dk.nita.saml20\Protocol\Saml20SignonHandler.cs:line 110
at dk.nita.saml20.protocol.Saml20AbstractEndpointHandler.ProcessRequest(HttpContext context) in E:\Projects\bob3-f2-8.6\OIOSAML.NET\src\dk.nita.saml20\dk.nita.saml20\Protocol\Saml20AbstractEndpointHandler.cs:line 49

and after that all subsequent login attempts failed and the service had to be restarted. It looks to me like some sort of concurrency problem where data gets corrupted, otherwise I cannot see how the NullPointerException can occur where it does.