5.4.4 Ensure default user umask is 027 or more restrictive - /etc/profile /etc/profile.d/*.sh

Information

The default umask determines the permissions of files created by users. The user creating
the file has the discretion of making their files and directories readable by others via the
chmod command. Users who wish to allow their files and directories to be readable by
others by default may choose a different default umask by inserting the umask command
into the standard shell configuration files ( .profile , .bashrc , etc.) in their home
directories.

Rationale:

Setting a very secure default value for umask ensures that users make a conscious choice
about their file permissions. A default umask setting of 077 causes files and directories
created by users to not be readable by any other user on the system. A umask of 027 would
make files and directories readable by users in the same Unix group, while a umask of 022
would make files readable by every user on the system.

Solution

Edit the /etc/bashrc, /etc/profile and /etc/profile.d/*.sh files (and the appropriate
files for any other shell supported on your system) and add or edit any umask parameters
as follows:

umask 027

Notes:

The audit and remediation in this recommendation apply to bash and shell. If other shells
are supported on the system, it is recommended that their configuration files also are
checked.

Other methods of setting a default user umask exist however the shell configuration files
are the last run and will override other settings if they exist therefor our recommendation
is to configure in the shell configuration files. If other methods are in use in your
environment they should be audited and the shell configs should be verified to not
override.

See Also

https://workbench.cisecurity.org/files/2420

Item Details

Category: CONFIGURATION MANAGEMENT, SYSTEM AND COMMUNICATIONS PROTECTION

References: 800-53|CM-6, 800-53|SC-7(10), CSCv6|13, CSCv7|5.1, CSCv7|13

Plugin: Unix

Control ID: 88ac52170a0897a93d6ce9971e968ba10d4cf6cfdca2f203926e1e89f769b4fa