Information processing apparatus, system, and non-transitory computer-readable storage medium

A system in which an information processing apparatus, an authorization server, and a resource server are communicably connected, wherein

• the information processing apparatus comprises:
• a requesting unit configured to send, to the authorization server, a request for a token for usage of a service provided by the resource server, wherein the request includes an expiration time generated based on a time of the information processing apparatus or time information received from the authorization server;
• an obtaining unit configured to obtain time information of the resource server via a Network Time Protocol (NTP) server using the token obtained as a response to the request;
• and
• a correction unit configured to correct the time of the information processing apparatus based on the time information of the resource server,
• wherein the correction unit is configured to repeatedly correct the time of the information processing apparatus, within a predetermined time duration and for a plurality of times, to reduce a time difference between the time of the information processing apparatus and the time information of the resource server, and
• the authorization server comprises:
• a verification unit configured to, when a request for a token for using the service provided by the resource server is accepted from the information processing apparatus, verify the request;
• and
• an issuing unit configured to issue the token according to a result of verification by the verification unit,
• wherein, when it is determined by the verification unit that a setting of the expiration time of the request included in the request is not included in a range defined based on a time of the authorization server, the issuing unit sends time information of the authorization server to the information processing apparatus.

A non-transitory computer-readable medium storing a program for causing a computer to function as:

• a requesting unit configured to send, to an authorization server, a request for a token for usage of a service provided by a resource server, wherein the request includes an expiration time generated based on a time of the computer or time information received from the authorization server;
• an obtaining unit configured to obtain time information of the resource server via a Network Time Protocol (NTP) server using the token obtained as a response to the request;
• and
• a correction unit configured to correct the time of the computer based on the time information of the resource server,
• wherein the correction unit is configured to repeatedly correct the time of the computer, within a predetermined time duration and for a plurality of times, to reduce a time difference between the time of the computer and the time information of the resource server.