You can prevent you and your users from making unintentional errors in the following ways:
You can keep from running a Trojan horse by correctly setting the PATH variable.
You can assign a restricted shell to users. A restricted shell prevents user error by steering users to those parts of the system that the users need for their jobs. In fact, through careful setup, you can ensure that users access only those parts of the system that help the users work efficiently.
You can set restrictive permissions on files that users do not need to access.
Take care to correctly set the PATH variable. Otherwise, you can accidentally run a program that was introduced by someone else that creates a security hazard. The intruding program can corrupt your data or harm your system. This kind of program is referred to as a Trojan horse. For example, a substitute su program could be placed in a public directory where you, as system administrator, might run the substitute program. Such a script would look just like the regular su command. Because the script removes itself after execution, you would have little evidence to show that you have actually run a Trojan horse.
The PATH variable is automatically set at login time. The path is set through your initialization files, such as .bashrc and /etc/profile. When you set up the user search path so that the current directory (.) comes last, you are protected from running this type of Trojan horse. The PATH variable for the root account should not include the current directory at all.
The standard shell allows a user to open files, execute commands, and so on. The restricted shell limits the ability of a user to change directories and to execute commands. The restricted shell is invoked with the /usr/lib/rsh command. Note that the restricted shell is not the remote shell, which is /usr/sbin/rsh.
The restricted shell differs from a standard shell in the following ways:
User access is limited to the user's home directory, so the user cannot use the cd command to change directories. Therefore, the user cannot browse system files.
The user cannot change the PATH variable, so the user can use commands only in the path that is set by the system administrator. The user also cannot execute commands or scripts by using a complete path name.
The restricted shell enables you to limit a user's ability to stray into system files. The shell creates a limited environment for a user who needs to perform specific tasks. The restricted shell is not completely secure, however, and is intended only to keep unskilled users from inadvertently doing damage.
For information about the restricted shell, use the man -s1m rsh command to see the rsh(1M) man page.
Because Oracle Solaris is a multiuser environment, file system security is the most basic security risk on a system. You can use traditional UNIX file protections to protect your files. You can also use the more secure access control lists (ACLs).
You might want to allow some users to read some files, and give other users permission to change or delete some files. You might have some data that you do not want anyone else to see. Chapter 1, Controlling Access to Files, in Securing Files and Verifying File Integrity in Oracle Solaris 11.2 discusses how to set file permissions.