Almost all folders and files including home folder have suddenly had their sharing and permissions privileges switched to read only
No indication of why this happened. Tedious to go through each item, enter password, add parties and change to read and write.
Is there a quick fix?
Run Verify Disk in Disk Utility.
If it's just your home folder where this is happening, reset home folder permissions.
Sounds like your ACL's are messed up.
The procedure to fix them varies by OS version. You should google resetting ACL's for the OS version you use.
Retrieving data ...