/dev/rmt permissions - default

[ConnieK]

I have been notified by our security office of a "finding" in regard to the permissions granted on /dev/rmt/* (the tape devices). They have stated that the permissions that are set on each device/tape allow "others" to have access and possibly erase data on a tape. The permissions are now crw-rw-rw- (766) and need to be changed to 760. My questions are:
1. Will changing the permissions cause any problems?
2. Is this an HP default setting?
Thanks in advance for your responses!

[Antoanetta Naghiu]

The default is 666 under bin:bin ownership.
If changed to 660, that means you take away from users the possibility to backup/restore.
It is not a big issue, but as well I do not see a huge security problem here. Maybe other devices...

[Victor BERRIDGE]

As Antoanetta mentioned, it is read write for other in order to let anyone use the tape drive, not only backup purpose...I dont see anything wrong or issue to that...
Regards

[Bill Hassell · Accepted solution]

Each system admin should review the permissions on all device files. For a large server, tapes should never be accessible by users since most backup programs have no security code to allow reading of the tape. Consider a backup of porprietary data like personnel records or financial data. All the protection in unix through file and directory permissions is useless once the data is on a tape.

While the ordinary user can't restore files into directories owned by root, someone could restore these files into a local directory with simple commands like chroot. By restricting the tape device files to 600 or 660 (7 is meaningless as the tape device files are not executable), only root can read or write tapes.

Same thing for all disk device files. *NO* read or write permissions for ordinary users. If these device files were readable (whether lvols or physical disks), a hacker to read the raw data on any disk and bypass all file/directory protection.