Method and apparatus for handling non-integrity protected reject messages in non-public networks

1. An apparatus comprising:

at least one processor; and

at least one memory including computer program code, the at least one memory and the computer program code configured to, with the at least one processor, cause the apparatus to at least:

receive, in a standalone non-public network (SNPN), in response to a request message sent via an access node of the SNPN, a reject message, wherein information in the reject message indicates that the apparatus is not allowed to access the SNPN by subscription; and

cause storage of one or more identifiers associated with the SNPN in a list of forbidden SNPNs associated with the access node via which the apparatus sent the request.

2. The apparatus of claim 1 , wherein the information in the reject message indicates at least one of non-3rd Generation Partnership Project (non-3GPP) access to Fifth Generation Core Network (5GCN) not allowed, temporarily not authorized for the SNPN, or permanently not authorized for the SNPN.

3. The apparatus of claim 1 , wherein the at least one memory and the computer program code are further configured to, with the at least one processor, cause the apparatus to at least:

set an update status to indicate that roaming is not allowed by said apparatus;

cause storage of said update status; and

delete one or more of a Globally Unique Temporary Identity (GUTI), a last visited registered tracking area identity (TAI), a TAI list, or a key set identifier (ngKSI).

4. The apparatus of claim 1 , wherein the at least one memory and the computer program code are further configured to, with the at least one processor, cause the apparatus to at least:

cause the apparatus to enter a deregistered state or a deregistered and network searching state; and

cause the apparatus to perform a selection of at least one other SNPN.

5. The apparatus of claim 1 , wherein the at least one memory and the computer program code are further configured to, with the at least one processor, cause the apparatus to at least:

determine whether said reject message has been successfully integrity checked within a non-access stratum (NAS); and

in an instance in which said reject message has been successfully integrity checked within the NAS, set a SNPN-specific attempt counter for non-3rd Generation Partnership Project (non-3GPP) access for said SNPN to a user equipment implementation-specific maximum value.

6. The apparatus of claim 1 , wherein the list of forbidden SNPNs comprises one or more of: a list of permanently forbidden SNPNs, a list of temporarily forbidden SNPNs, a list of permanently forbidden SNPNs for non-3GPP access, or a list of temporarily forbidden SNPNs for non-3GPP access.

7. A method comprising:

receiving, at user equipment, in a standalone non-public network (SNPN), in response to a request message sent via an access node of the SNPN, a reject message, wherein information in the reject message indicates that the user equipment is not allowed to access the SNPN by subscription; and

causing storage of one or more identifiers associated with the SNPN in a list of forbidden SNPNs associated with the access node via which the user equipment sent the request.

8. The method of claim 7 , wherein the information in the reject message indicates at least one of non-3rd Generation Partnership Project (non-3GPP) access to Fifth Generation Core Network (5GCN) not allowed, temporarily not authorized for the SNPN, or permanently not authorized for the SNPN.

9. The method of claim 7 , further comprising:

setting an update status to indicate that roaming is not allowed by the user equipment;

causing storage of said update status; and

deleting one or more of a Globally Unique Temporary Identity (GUTI), a last visited registered tracking area identity (TAI), a TAI list, or a key set identifier (ngKSI).

10. The method of claim 7 , further comprising:

causing the user equipment to enter a deregistered state or a deregistered and network searching state; and

causing the user equipment to perform a selection of at least one other SNPN.

11. The method of claim 7 , further comprising:

determining whether said reject message has been successfully integrity checked within a non-access stratum (NAS); and

in an instance in which said reject message has been successfully integrity checked within the NAS, setting a SNPN-specific attempt counter for non-3rd Generation Partnership Project (non-3GPP) access for said SNPN to a user equipment implementation-specific maximum value.

12. The method of claim 7 , wherein the list of forbidden SNPNs comprises one or more of: a list of permanently forbidden SNPNs, a list of temporarily forbidden SNPNs, a list of permanently forbidden SNPNs for non-3GPP access, or a list of temporarily forbidden SNPNs for non-3GPP access.

13. A non-transitory computer readable medium including program code which, when executed, causes operations comprising:

receiving, in a standalone non-public network (SNPN), in response to a request message sent from user equipment, via an access node of the SNPN, a reject message, wherein information in the reject message indicates that the user equipment is not allowed to access the SNPN by subscription; and

causing storage of one or more identifiers associated with the SNPN in a list of forbidden SNPNs associated with the access node via which the user equipment sent the request.