[TUHS] Who's behind the UNIX filesystem permission implementation

[Arthur Krewat]

On 7/31/2019 12:49 PM, Rodrigo G. López wrote:
> Multics had modes per file (https://multicians.org/fjcc4.html) but i 
> don't know about the origins. the simpler approach of 
> owner/group/other is a purely Unix creation and i would bet Ken 
> Thompson is behind it all.

TOPS-10 had a 3 octal digit file protection code:

<xxx> - <Owner, Project, Everyone else> - Logins are PPNs - [Project, 
Programmer] - So if I was [76,5], another user with [76,10] was in the 
same project. Much like UNIX groups.

Owner Protection Codes
7*, 6* - You can execute, read, or change the protection code of the file.
5* - You have unlimited access to the file, except for renaming it.
4* - You have unlimited access to the file.
3 - You can execute, read, or change the protection code of the file.
2 - You have unlimited access to the file, except for renaming it.
1, 0 - You have unlimited access.
* The File Daemon is called on a protection failure on this file (my 
memory is a little fuzzy on this, but I believe it allowed finer grained 
protections).

Protection Codes for Fields 2 and 3
7 - The user cannot access the file.
6 - The user can only execute the file.
5 - The user can execute or read the file.
4 - The user can execute, read, or append to the file.
3 - The user can execute, read, append to, or update the file.
2 - The user can execute, read, append to, update, and write to the file.
1 - The user can execute, read, append to, update, write to, and rename 
the file.
0 - Unlimited access, including changing the protection code of the file.

The name TOPS-10 was first used in 1970, but the monitor itself dates 
back to 1964. I'm not sure when these protection codes came into being, 
though.