User Authentication Method and Apparatus

A session management function entity, comprising:

• a receiver, configured to receive a session establishment request message, wherein the session establishment request message is used to request to establish a session for a terminal device;
• a processor, configured to determine, based on the session establishment request message, to perform user authentication on a user using the terminal device;
• and
• a transmitter, configured to send a session establishment message to a user plane function entity, wherein the session establishment message is used to establish a first session for the terminal device, and a session attribute of the first session is:
• a session used to transmit only a user authentication message, wherein
• the transmitter is further configured to send an indication message to the terminal device, wherein the indication message is used to indicate the session attribute of the first session.

A terminal device, comprising:

• a receiver, configured to receive an indication message from a session management function entity, wherein the indication message is used to indicate that a session attribute of a first session is:
• a session used to transmit only a user authentication message;
• and
• a transmitter, configured to send the user authentication message through the first session, wherein
• the receiver is further configured to receive the user authentication message through the first session.