A web application I've been developing has a new use case that has me searching for something easier than username/password authentication.
For this new use case, some subset of users will now only be entering data during a 90-day period that happens once a year. Most of the time this means they'll only be doing this for one day, maybe two, a year.
Because it will be easy for them to forget the password they set after logging in with the temp password I would like to try something like a unique URL that expires. The URL needs to be valid for 90-days (or at least until they've finished entering their data if we can figure out how to measure that).
Each year they get a new email with unique URL to start that 90-day period.
The security drawbacks here are the typical ones:
- Unique URL shows up in bookmarks and browser history
- Unique URL shows up in server logs
- User might forward the email to another mailbox and the message is not transported securely.
- Need to guard against SQL injection in URL
Normally unique URL schemes are valid for short periods like 24 hours, so I'm worried that a 90 day period is just too long.
As for risks: if an unauthorized person gains access there would be very little information leakage (and certainly nothing that is PII) but there is still some "loss of trust" concerns.
Is this secure enough? If not, are there any other authentication methods we might use here?