[Summary] Reasons and solutions for phpCAS ticket authentication failure

[Foreword]

When performing CAS single sign-on, phpCAS is a very popular solution. However, many people are at a loss if they encounter the problem of ticket authentication failure. This article will introduce the reasons and solutions for phpCAS ticket authentication failure.

[Problem Description]

When using phpCAS for single sign-on, sometimes you will encounter the following problems:

1. Cannot log in normally
2. Authentication failed
3. An error message appears during authentication jump
4. Displays errors such as "Invalid Session" or "Session Expired"

What these problems have in common is that they all Related to bills.

[Introduction to Tickets]

Tickets are a core concept in single sign-on. In CAS single sign-on, tickets refer to TGT (Ticket-granting Ticket) and ST (Service Ticket).

TGT is the ticket issued by the CAS server when the user authenticates for the first time. It represents the user's login credentials and can be used to generate ST. ST is a service credential generated by the CAS server based on TGT when a user accesses a service. Users must hold ST to access services.

[Reason for bill authentication failure]

1. Bill expiration
   TGT and ST have validity periods, and they cannot be used if they expire. In phpCAS, you can use $CAS_CLIENT->isAuthenticated() to determine whether it has expired.
2. No ticket is carried
   When a user accesses a service, he or she needs to carry ST to access it. If ST is not carried, ticket authentication failure will occur. In phpCAS, you can use $CAS_CLIENT->hasServiceTicket() to determine whether ST is carried.
3. Ticket verification failed
   When a user logs in, the CAS server will verify the user's username and password and issue a TGT. When a user brings a TGT to access other services, the CAS server will verify whether the TGT is legal and issue an ST. If the verification fails, there will be a problem of ticket authentication failure.

[Solution]

1. Ticket Expiration
   If the ticket expires, you need to obtain the ticket again. In phpCAS, tickets can be reacquired via $CAS_CLIENT->renewTicket().
2. No ticket is carried
   If ST is not carried, ST needs to be regenerated. In phpCAS, ST can be regenerated via $CAS_CLIENT->forceAuthentication().
3. Ticket verification failed
   If ticket verification fails, you need to check the following aspects:

① Check whether the CAS server configuration is correct.
② Check whether the phpCAS client configuration is correct.
③ Check whether the user's username and password are correct.
④ Check whether the TGT is legal.
⑤ Check whether ST is legal.

If the above aspects are correct, then please contact the CAS server administrator or phpCAS developer for help.

[Summary]

phpCAS ticket authentication failure is a common problem, and the solution is also very simple. You need to pay attention to issues such as expired tickets, not carrying tickets, and failed ticket verification, and solve them one by one. CAS single sign-on is a commonly used login method, and developers also need to master its common problems and solutions.

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