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This chapter is from the book

Apply Your Knowledge

Exercise

4.1 Creating a User and a Role

In this exercise, you’ll create a new role named admin1 and a profile called Shutdown. The Shutdown profile will be added to the role. A user account trng1 will be created and have the admin1 role assigned to it. The user will then assume the role and execute a privileged command to shut down the system.

Estimated time: 20 minutes

To create a user and a role, follow these steps:

  1. Create the role named admin1:

         # roleadd -u 2000 -g 10 -d /export/home/admin1 -m admin1<cr>
         # passwd admin1<cr>

    You are prompted to enter the password twice.

  2. Create a profile to allow the user to shut down a system.

    Edit the /etc/security/prof_attr file and enter the following line:

         Shutdown:::Permit system shutdown:

    Save and exit the file.

  3. Add the Shutdown and All profiles to the role:

         # rolemod -P Shutdown,All admin1<cr>
  4. Verify that the changes have been made to the user_attr database:

         # more /etc/user_attr<cr>
  5. Create the user account and assign it access to the admin1 role:

         # useradd -u 3000 -g 10 -d /export/home/trng1 -m -s /bin/ksh -R admin1 trng1<cr>
  6. Assign a password to the new user account:

         # passwd trng1<cr>

    You are prompted to enter the password twice.

  7. Verify that the entry has been made to the passwd, shadow, and user_attr files:

         # more /etc/passwd<cr>
         # more /etc/shadow<cr>
         # more /etc/user_attr<cr>
  8. Assign commands to the Shutdown profile:

    Edit the /etc/security/exec_attr file and add the following line:

         Shutdown:suser:cmd:::/usr/sbin/shutdown:uid=0

    Save and exit the file.

  9. Test the new role and user account as follows:

    1. Log in as trng1.
    2. List the roles that are granted to you by typing the following:

           $ roles<cr>
    3. Use the su command to assume the role admin1:

           $ su admin1<cr>

      You are prompted to enter the password for the role.

    4. List the profiles that are granted to you by typing the following:

           $ profiles<cr>
    5. Shut down the system:

           $ /usr/sbin/shutdown -i 0 -g 0<cr>

Exam Questions

  1. Which of the following commands is used to create a role?

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    A.

    useradd

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    B.

    makerole

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    C.

    roleadd

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    D.

    addrole

  2. In Role-Based Access Control, which file contains details of the user attributes?

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    A.

    /etc/security/prof_attr

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    B.

    /etc/user_attr

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    C.

    /etc/security/user_attr

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    D.

    /etc/shadow

  3. Which two statements about the roleadd command are true? (Choose two.)

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    A.

    roleadd looks similar to the useradd command.

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    B.

    roleadd uses the profile shell (pfsh) as the default shell.

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    C.

    The -A option associates an account with a profile.

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    D.

    An account created with roleadd is the same as a normal login account.

  4. Which component of RBAC associates users and roles with authorizations and profiles?

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    A.

    user_attr

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    B.

    prof_attr

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    C.

    auth_attr

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    D.

    exec_attr

  5. Which component of RBAC defines the privileged operations assigned to a profile?

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    A.

    user_attr

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    B.

    prof_attr

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    C.

    auth_attr

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    D.

    exec_attr

  6. In the execution attributes database, which of the following is not a valid value for the attr field?

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    A.

    euid

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    B.

    uid

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    C.

    egid

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    D.

    suid

  7. After creating an RBAC role, you find that the only commands that can be executed within the role are the privileged commands that you have set up. Ordinary nonprivileged commands are not available. The RBAC setup has a problem. What is the cause of this problem?

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    A.

    The role is not associated with a correct profile.

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    B.

    The access mechanism to the role is not initializing properly.

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    C.

    The role’s profile is not associated with the correct commands.

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    D.

    The file identifying the privileged commands has missing entries.

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    E.

    The role’s profile is not associated with the correct authorizations.

  8. Which of the following are valid RBAC databases? (Choose three.)

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    A.

    /etc/usr_attr

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    B.

    /etc/user_attr

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    C.

    /etc/security/exec_attr

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    D.

    /etc/security/prof_attr

  9. You want to enable a user to administer all user cron tables. This includes amending entries in any user’s crontab. Given due care to system security, what should you do to enable the user to carry out this duty?

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    A.

    Give the user the root password.

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    B.

    Set the suid on the crontab command.

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    C.

    Use RBAC to authorize the user to administer cron tables.

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    D.

    Use RBAC to give the user an ID of root when executing the crontab command.

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    E.

    Use the ACL mechanism to give the user RW access to each crontab table.

  10. Which command(s) grant a user access to a role account? (Choose two.)

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    A.

    roleadd

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    B.

    rolemod

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    C.

    useradd

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    D.

    usermod

  11. Which option to the rolemod command appends an authorization to an exiting list of authorizations?

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    A.

    -A

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    B.

    -P

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    C.

    -a

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    D.

    -o

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    E.

    None

  12. In which files are profiles defined? Choose all that apply. (Choose two.)

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    A.

    /etc/security/prof_attr

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    B.

    /etc/user_attr

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    C.

    /etc/security/exec_attr

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    D.

    /etc/security/auth_attr

  13. Which statements are true regarding the following line? (Choose all that apply.)

    Media Restore:suser:cmd:::/usr/lib/fs/ufs/ufsrestore:euid=0

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    A.

    It represents a profile in the exec_attr database.

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    B.

    Any role that has Media Restore as a profile can execute the ufsrestore command with an effective UID of root.

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    C.

    It represents a profile in the prof_attr database.

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    D.

    It represents a role definition in the user_attr database.

  14. In RBAC, which of the following is a bundling mechanism for grouping authorizations and commands with special attributes?

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    A.

    Profile

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    B.

    Role

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    C.

    Authorization

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    D.

    Group

Answers to Exam Questions

  1. C. Use the roleadd command to create a role account. For more information, see the “Using RBAC” section.
  2. B. /etc/user_attr contains details of the extended user attributes. For more information, see the “RBAC Components” section.
  3. A, B. The roleadd command looks very similar to the useradd command, but it uses the profile shell as the default shell. For more information, see the “Using RBAC” section.
  4. A. user_attr (extended user attributes database) associates users and roles with authorizations and profiles. For more information, see the “RBAC Components” section.
  5. D. exec_attr (profile attributes database) defines the privileged operations assigned to a profile. For more information, see the “RBAC Components” section.
  6. D. Six valid keys exist: euid, uid, egid, gid, privs, and limitprivs. For more information, see the “RBAC Components” section.
  7. A. If a role is not associated with a correct profile, the only commands that can be executed within the role are the privileged commands that you have set up. Ordinary nonprivileged commands are unavailable. For more information, see the “RBAC Components” section.
  8. B, C, D. The three valid RBAC databases are /etc/user_attr, /etc/security/exec_attr, and /etc/security/prof_attr. For more information, see the “RBAC Components” section.
  9. C. To enable a user to administer all user cron tables, configure RBAC to authorize the user to administer cron tables. For more information, see the “Using RBAC” section.
  10. C, D. Use the roleadd command to create a role account. Then, with the usermod command, assign the role to an existing user account using the -R option. If you are creating a new user account, use the useradd command with the -R option to assign the role to the new user account. For more information, see the “Using RBAC” section.
  11. E. The rolemod command does not add to the existing authorizations; it replaces any existing authorization setting. For more information, see the “Using RBAC” section.
  12. A, C. /etc/security/prof_attr (rights profile attributes database) defines profiles, lists the profile’s assigned authorizations, and identifies the associated help file.

    /etc/security/exec_attr (profile attributes database) defines the privileged operations assigned to a profile. For more information, see the “RBAC Components” section.

  13. A, B. The following entry in the exec_attr database represents a profile named Media Restore:

    Media Restore:suser:cmd:::/usr/lib/fs/ufs/ufsrestore:euid=0

    Any role that has Media Restore as a profile can execute the ufsrestore command with an effective UID of root. For more information, see the “RBAC Components” section.

  14. A. Execution profiles are bundling mechanisms for grouping authorizations and commands with special attributes. For more information, see the “RBAC Components” section.
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