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LTI authentication failing with large diff(server-oauth) values

LTI authentication failing with large diff(server-oauth) values

by Larry Riddle -
Number of replies: 2

We have been running our WeBWorK server with our classes for about a month now using LTI authentication between Canvas and WebWorK. This was working fine, but I received a report this week from one instructor that a student reported she was unable to access WeBWorK because the authentication failed. The instructor also said that "I've had other students telling me that the WeBWorK site keeps timing out for them and not loading."

Two screenshots of the WeBWorK warning message showed that diff(server-oauth) was 81 seconds in one case and 82 seconds in another case. Could this large time difference be causing the authentication to fail? If so, is there a way to increase the default time before authentication fails? I thought I would ask about this first before I try turning on the LTI debugging flag for further testing.

I had the instructor add me to her Canvas class as a student, and I was able to successfully authenticate to WeBWorK and access the homework sets. I tried 3 different assignments and each time connected to WeBWorK very quickly. So the diff(server-oauth) values in my cases were certainly very small. And so far I have not received any reports from other classes of students having authentication issues. So this may be just an isolated issue affecting just a few students, but I wanted to see if there was anything I could do on the server end to help them authenticate to WeBWorK.

In reply to Larry Riddle

Re: LTI authentication failing with large diff(server-oauth) values

by Glenn Rice -
The large time differential will certainly cause authentication failure. The default setting of the $NonceLifeTime in authen_LTI.conf is 60 seconds. Any time differential more than that will fail to authenticate. If your students are consistently seeing time differentials of more than 60 seconds, then you should increase that value.
In reply to Glenn Rice

Re: LTI authentication failing with large diff(server-oauth) values

by Larry Riddle -

Thanks. I'll increase that value until our IT department has resolved some wifi connection issues on campus, which I believe may be what is causing some students to run into the authentication failure with these large time differentials.