Chapter 11 Privileges (Tasks)

This chapter provides step-by-step instructions for managing privileges and using privileges on your system. The following is a list of the information in this chapter.

• Managing and Using Privileges (Task Map)

• Managing Privileges (Task Map)

• Determining Your Privileges (Task Map)

For an overview of privileges, see Privileges (Overview). For reference information, see Chapter 12, Privileges (Reference).

Managing and Using Privileges (Task Map)

The following task map points to task maps for managing privileges and for using privileges.

Managing Privileges (Task Map)

The following task map points to procedures for viewing privileges, assigning privileges, and running a script that contains privileged commands.

Managing Privileges

The most secure way to manage privileges for users and roles is to confine use of privilege to commands in a rights profile. The rights profile is then included in a role. The role is assigned to a user. When the user assumes the assigned role, the privileged commands are available to be run in a profile shell. The following procedures show how to assign privileges, remove privileges, and debug privilege use.

How to Determine the Privileges on a Process

This procedure shows how to determine which privileges are available to your processes. The listing does not include privileges that have been assigned to particular commands.

1. List the privileges that are available to your shell's process.

   % ppriv pid $ ppriv -v pid

   pid

   Is the process number. Use a double dollar sign ($$) to pass the process number of the parent shell to the command.

   -v

   Provides a verbose listing of the privilege names.

Example 11–1 Determining the Privileges in Your Current Shell

In the following example, the privileges in the parent process of the user's shell process are listed. In the second example, the full names of the privileges are listed. The single letters in the output refer to the following privilege sets:

E

Is the effective privilege set.

I

Is the inheritable privilege set.

P

Is the permitted privilege set.

L

Is the limit privilege set.

% ppriv $$
1200:   -csh
flags = <none>
        E: basic
        I: basic
        P: basic
        L: all
% ppriv -v $$
1200:   -csh
flags = <none>
        E: file_link_any,net_access,proc_exec,proc_fork,proc_info,proc_session
        I: file_link_any,net_access,proc_exec,proc_fork,proc_info,proc_session
        P: file_link_any,net_access,proc_exec,proc_fork,proc_info,proc_session
        L: cpc_cpu,dtrace_kernel,dtrace_proc,dtrace_user,…,sys_time

Example 11–2 Determining the Privileges of a Role That You Can Assume

Roles use an administrative shell, or profile shell. You must assume a role and use the role's shell to list the privileges that have been directly assigned to the role. In the following example, the role sysadmin has no directly assigned privileges.

% su - sysadmin
Password: <Type sysadmin password>
$ /usr/ucb/whoami
sysadmin
$ ppriv -v $$
1400:   pfksh
flags = <none>
        E: file_link_any,net_access,proc_exec,proc_fork,proc_info,proc_session
        I: file_link_any,net_access,proc_exec,proc_fork,proc_info,proc_session
        P: file_link_any,net_access,proc_exec,proc_fork,proc_info,proc_session
        L: cpc_cpu,dtrace_kernel,dtrace_proc,dtrace_user,…,sys_time

How to Determine Which Privileges a Program Requires

This procedure determines which privileges a command or process requires to succeed.

Before You Begin

The command or process must have failed for this procedure to work.

1. Type the command that is failing as an argument to the ppriv debugging command.

   % ppriv -eD touch /etc/acct/yearly touch[11365]: missing privilege "file_dac_write" (euid = 130, syscall = 224) needed at ufs_direnter_cm+0x27c touch: /etc/acct/yearly cannot create

2. Determine which system call is failing by finding the syscall number in the /etc/name_to_sysnum file.

   % grep 224 /etc/name_to_sysnum creat64 224

Example 11–3 Using the truss Command to Examine Privilege Use

The truss command can debug privilege use in a regular shell. For example, the following command debugs the failing touch process:

% truss -t creat touch /etc/acct/yearly
creat64("/etc/acct/yearly", 0666)            
                       Err#13 EACCES [file_dac_write]
touch: /etc/acct/yearly cannot create

The extended /proc interfaces report the missing privilege after the error code in truss output.

Example 11–4 Using the ppriv Command to Examine Privilege Use in a Profile Shell

The ppriv command can debug privilege use in a profile shell. If you assign a rights profile to a user, and the rights profile includes commands with privileges, the commands must be typed in a profile shell. When the privileged commands are typed in a regular shell, the commands do not execute with privilege.

In this example, the jdoe user can assume the role objadmin. The objadmin role includes the Object Access Management rights profile. This rights profile allows the objadmin role to change permissions on files that objadmin does not own.

In the following excerpt, jdoe fails to change the permissions on the useful.script file:

jdoe% ls -l useful.script
-rw-r--r--  1 aloe  staff  2303 Apr 10 10:10 useful.script
jdoe% chown objadmin useful.script
chown: useful.script: Not owner
jdoe% ppriv -eD chown objadmin useful.script
chown[11444]: missing privilege "file_chown" 
            (euid = 130, syscall = 16) needed at ufs_setattr+0x258
chown: useful.script: Not owner

When jdoe assumes the objadmin role, the permissions on the file are changed:

jdoe% su - objadmin
Password: <Type objadmin password>
$ ls -l useful.script
-rw-r--r--  1 aloe  staff  2303 Apr 10 10:10 useful.script
$ chown objadmin useful.script
$ ls -l useful.script
-rw-r--r--  1 objadmin  staff  2303 Apr 10 10:10 useful.script
$ chgrp admin useful.script
$ ls -l objadmin.script
-rw-r--r--  1 objadmin  admin  2303 Apr 10 10:11 useful.script

Example 11–5 Changing a File Owned by the root User

This example illustrates the protections against privilege escalation. For a discussion, see Prevention of Privilege Escalation. The file is owned by the root user. The less powerful role, objadmin role needs all privileges to change the file's ownership, so the operation fails.

jdoe% su - objadmin
Password: <Type objadmin password>
$ cd /etc; ls -l system
-rw-r--r--  1 root  sys   1883 Oct 10 10:20 system
$ chown objadmin system
chown: system: Not owner
$ ppriv -eD chown objadmin system
chown[11481]: missing privilege "ALL" 
     (euid = 101, syscall = 16) needed at ufs_setattr+0x258
chown: system: Not owner

How to Add Privileges to a Command

You add privileges to a command when you are adding the command to a rights profile. The privileges enable the role that includes the rights profile to run the administrative command, while not gaining any other superuser capabilities.

Before You Begin

The command or program must be privilege-aware. For a fuller discussion, see How Processes Get Privileges.

1. Become superuser or assume an equivalent role.

   Roles contain authorizations and privileged commands. For more information about roles, see Configuring RBAC (Task Map).

2. Open the Solaris Management Console GUI.

   For instructions, see How to Assume a Role in the Solaris Management Console.

3. Use the Rights tool to update an appropriate profile.

   Select the command to include. For each included command, add the privileges that the command requires.

   ---

   Caution –

   When you include commands in a rights profile and add privileges to the commands, the commands execute with those privileges when the commands are run in a profile shell.

   The order of profiles is important. The profile shell executes a command or action with the security attributes that are specified in the earliest profile in the account's list of profiles. For example, if the chgrp command is in the Object Access Management rights profile with privileges, and Object Access Management is the first profile in which the chgrp command is found, then the chgrp command executes with the privileges specified in the Object Access Management profile.

   ---

How to Assign Privileges to a User or Role

You might trust some users with a particular privilege all the time. Very specific privileges that affect a small part of the system are good candidates for assigning to a user. For a discussion of the implications of directly assigned privileges, see Security Considerations When Directly Assigning Security Attributes.

The following procedure enables user jdoe to use high resolution timers.

1. Assume the Primary Administrator role, or become superuser.

   The Primary Administrator role includes the Primary Administrator profile. To create the role and assign the role to a user, see Chapter 2, Working With the Solaris Management Console (Tasks), in System Administration Guide: Basic Administration.

2. Add the privilege that affects high resolution times to the user's initial inheritable set of privileges.

   $ usermod -K defaultpriv=basic,proc_clock_highres jdoe

   The values for the defaultpriv keyword replace the existing values. Therefore, for the user to retain the basic privileges, the value basic must be specified. In the default configuration, all users have basic privileges.

3. Read the resulting user_attr entry.

   $ grep jdoe /etc/user_attr jdoe::::type=normal;defaultpriv=basic,proc_clock_highres

Example 11–6 Creating a Role With Privileges to Configure System Time

In this example, a role is created whose only task is to handle time on the system.

$ /usr/sadm/bin/smrole -D nisplus:/examplehost/example.domain \
-r primaryadm -l <Type primaryadm password> \
add -- -n clockmgr \
-c "Role that sets system time" \
-F "Clock Manager" \
-s /bin/pfksh \
-u 108 \
-P <Type clockmgr password> \
-K defaultpriv=basic,proc_priocntl,sys_cpu_config,
proc_clock_highres,sys_time

The -K line is wrapped for display purposes.

If the role was created locally, the user_attr entry for the role would appear similar to the following:

clockmgr:::Role that sets system time:
type=role;defaultpriv=basic,proc_priocntl,sys_cpu_config,
proc_clock_highres,sys_time

How to Limit a User's or Role's Privileges

You can limit the privileges that are available to a user or role by reducing the basic set, or by reducing the limit set. You should have good reason to limit the user's privileges in this way, because such limitations can have unintended side effects.

You should thoroughly test any user's capabilities where the basic set or the limit set has been modified for a user.

• When the basic set is less than the default, users can be prevented from using the system.

• When the limit set is less than all privileges, processes that need to run with an effective UID=0 might fail.

1. Determine the privileges in a user's basic set and limit set.

   For the procedure, see How to Determine the Privileges on a Process.

2. (Optional) Remove one of the privileges from the basic set.

   $ usermod -K defaultpriv=basic,!priv-name username

   By removing the proc_session privilege, you prevent the user from examining any processes outside the user's current session. By removing the file_link_any privilege, you prevent the user from making hard links to files that are not owned by the user.

   ---

   Caution –

   Do not remove the proc_fork or the proc_exec privilege. Without these privileges, the user would not be able to use the system. In fact, these two privileges are only reasonably removed from daemons that should not fork() or exec() other processes.

   ---

3. (Optional) Remove one of the privileges from the limit set.

   $ usermod -K limitpriv=all,!priv-name username

4. Test the capabilities of username.

   Log in as username and try to perform the tasks that username must perform on the system.

Example 11–7 Removing Privileges From a User's Limit Set

In the following example, all sessions that originate from jdoe's initial login are prevented from using the sys_linkdir privilege. That is, the user cannot make hard links to directories, nor can the user unlink directories, even after the user runs the su command.

$ usermod -K limitpriv=all,!sys_linkdir jdoe
$ grep jdoe /etc/user_attr
jdoe::::type=normal;defaultpriv=basic;limitpriv=all,!sys_linkdir

Example 11–8 Removing Privileges From a User's Basic Set

In the following example, all sessions that originate from jdoe's initial login are prevented from using the proc_session privilege. That is, the user cannot examine any processes outside the user's session, even after the user runs the su command.

$ usermod -K defaultpriv=basic,!proc_session jdoe

$ grep jdoe /etc/user_attr
jdoe::::type=normal;defaultpriv=basic,!proc_session;limitpriv=all

How to Run a Shell Script With Privileged Commands

When you create a shell script that runs commands with inherited privileges, the appropriate rights profile must contain the commands with privileges assigned to them.

1. Start the script with /bin/pfsh, or any other profile shell, on the first line.

   #!/bin/pfsh # Copyright (c) 2009 by Sun Microsystems, Inc.

2. Determine the privileges that the commands in the script need.

   % ppriv -eD script-full-path

3. Open the Solaris Management Console GUI.

   For instructions, see How to Assume a Role in the Solaris Management Console. Choose a role, such as Primary Administrator, that can create a rights profile.

4. Use the Rights tool to create or update an appropriate profile.

   Select the script, and include in the rights profile each of the commands in the shell script that need privileges to run. For each included command, add the privileges that the command requires.

   ---

   Caution –

   The order of rights profiles is important. The profile shell executes the earliest instance of a command in the list of profiles. For example, if the chgrp command is in the Object Access Management rights profile, and Object Access Management is the first profile in which the chgrp command is found, then the chgrp command executes with the privileges that are specified in the Object Access Management profile.

   ---

5. Add the rights profile to a role and assign the role to a user.

   To execute the profile, the user assumes the role and runs the script in the role's profile shell.

Determining Your Privileges (Task Map)

The following task map points to procedures for using the privileges that have been assigned to you.

Determining Your Assigned Privileges

When a user is directly assigned privileges, the privileges are in effect in every shell. When a user is not directly assigned privileges, then the user must open a profile shell. For example, when commands with assigned privileges are in a rights profile that is in the user's list of rights profiles, then the user must execute the command in a profile shell.

How to Determine the Privileges That You Have Been Directly Assigned

The following procedure shows how to determine if you have been directly assigned privileges.

Inappropriate use of directly assigned privileges can result in unintentional breaches of security. For a discussion, see Security Considerations When Directly Assigning Security Attributes.

1. List the privileges that your processes can use.

   See How to Determine the Privileges on a Process for the procedure.

2. Invoke actions and run commands in any shell.

   The privileges that are listed in the effective set are in effect throughout your session. If you have been directly assigned privileges in addition to the basic set, the privileges are listed in the effective set.

Example 11–9 Determining Your Directly-Assigned Privileges

If you have been directly assigned privileges, then your basic set contains more than the default basic set. In this example, the user always has access to the proc_clock_highres privilege.

% /usr/ucb/whoami
jdoe
% ppriv -v $$
1800:   pfksh
flags = <none>
        E: file_link_any,…,proc_clock_highres,proc_session
        I: file_link_any,…,proc_clock_highres,proc_session
        P: file_link_any,…,proc_clock_highres,proc_session
        L: cpc_cpu,dtrace_kernel,dtrace_proc,dtrace_user,…,sys_time
% ppriv -vl proc_clock_highres
        Allows a process to use high resolution timers.

Example 11–10 Determining a Role's Directly-Assigned Privileges

Roles use an administrative shell, or profile shell. Users who assume a role can use the role's shell to list the privileges that have been directly assigned to the role. In the following example, the role realtime has been directly assigned privileges to handle date and time programs.

% su - realtime
Password: <Type realtime password>
$ /usr/ucb/whoami
realtime
$ ppriv -v $$
1600:   pfksh
flags = <none>
        E: file_link_any,…,proc_clock_highres,proc_session,sys_time
        I: file_link_any,…,proc_clock_highres,proc_session,sys_time
        P: file_link_any,…,proc_clock_highres,proc_session,sys_time
        L: cpc_cpu,dtrace_kernel,dtrace_proc,dtrace_user,…,sys_time

How to Determine the Privileged Commands That You Can Run

When a user is not directly assigned privileges, then the user gets access to privileged commands through a rights profile. Commands in a rights profile must be executed in a profile shell.

Before You Begin

The user or role who authenticates to the Solaris Management Console must have the solaris.admin.usermgr.read authorization. The Basic Solaris User rights profile includes this authorization.

1. Determine the rights profiles that you have been assigned.

   $ /usr/sadm/bin/smuser list -- -n username -l

   Authenticating as user: admin … Please enter a string value for: password :: … User name: username User ID (UID): 130 Primary group: staff Secondary groups: Comment: object mgt jobs Login Shell: /bin/sh Home dir server: system Home directory: /export/home/username AutoHome setup: True Mail server: system Rights: Object Access Management Assigned Roles:

2. Locate the line that begins with “Rights:”.

   The “Rights” line lists the names of the rights profiles that have been directly assigned to you.

3. Find the names of the rights profiles in the exec_attr database.

   $ cd /etc/security $ grep "Object Access Management" exec_attr Object Access Management:solaris:cmd:::/usr/bin/chgrp:privs=file_chown Object Access Management:solaris:cmd:::/usr/bin/chown:privs=file_chown Object Access Management:suser:cmd:::/usr/bin/chgrp:euid=0 Object Access Management:suser:cmd:::/usr/bin/chmod:euid=0 …

   The commands with added privileges are listed at the end of solaris policy entries.

4. Type the commands that require privileges in a profile shell.

   When the commands are typed in a regular shell, the commands do not run with privilege, and do not succeed.

   % pfsh $

Example 11–11 Running Privileged Commands in a Profile Shell

In the following example, the user jdoe cannot change the group permissions on a file from his regular shell. However, jdoe can change the permissions when typing the command in a profile shell.

% whoami
jdoe
% ls -l useful.script
-rwxr-xr-- 1 nodoe eng 262 Apr 2 10:52 useful.script
chgrp staff useful.script
chgrp: useful.script: Not owner
% pfksh
$ /usr/ucb/whoami
jdoe
$ chgrp staff useful.script
$ chown jdoe useful.script
$ ls -l useful.script
-rwxr-xr-- 1 jdoe staff 262 Apr 2 10:53 useful.script

How to Determine the Privileged Commands That a Role Can Run

A role gets access to privileged commands through a rights profile that contains commands with assigned privileges. The most secure way to provide a user with access to privileged commands is to assign a role to them. After assuming the role, the user can execute all the privileged commands that are included in the rights profiles for that role.

Before You Begin

The user or role who authenticates to the Solaris Management Console must have the solaris.admin.usermgr.read authorization. The Basic Solaris User rights profile includes this authorization.

1. Determine the roles that you can assume.

   $ /usr/sadm/bin/smuser list -- -n username -l Authenticating as user: primadmin … User name: username User ID (UID): 110 Primary group: staff Secondary groups: Comment: Has admin roles Login Shell: /bin/sh … Rights: Assigned Roles: primadmin, admin

2. Locate the line that begins with “Assigned Roles:”.

   The “Assigned Roles” line lists the roles that you can assume.

3. Determine the rights profiles that are included in one of your roles.

   $ /usr/sadm/bin/smuser list -- -n admin -l Authenticating as user: primadmin … User name: admin User ID (UID): 101 Primary group: sysadmin Secondary groups: Comment: system administrator Login Shell: /bin/pfksh … Rights: System Administrator Assigned Roles:

4. Locate the names of the rights profiles for the role in the “Rights:” line.

5. Find the rights profiles in the prof_attr database.

   Because the System Administrator profile is a collection of profiles, you need to list the profiles in the System Administrator profile.

   $ cd /etc/security $ grep "System Administrator" prof_attr System Administrator:::Can perform most non-security administrative tasks:profiles=Audit Review,Printer Management,Cron Management, Device Management,File System Management,Mail Management,Maintenance and Repair,Media Backup,Media Restore,Name Service Management,Network Management,Object Access Management,Process Management,Software Installation,User Management,All;help=RtSysAdmin.html

6. For each rights profile, find the rights profiles in the exec_attr database.

   For example, the Network Management profile is a supplementary profile of the System Administrator profile. The Network Management profile includes a number of privileged commands.

   $ cd /etc/security $ grep "Network Management" exec_attr Network Management:solaris:cmd:::/usr/sbin/ifconfig:privs=sys_net_config Network Management:solaris:cmd:::/usr/sbin/route:privs=sys_net_config …

   The commands and their assigned privileges are the final two fields of solaris policy entries. You can run these commands in the profile shell of your role.

Example 11–12 Running the Privileged Commands in Your Role

When a user assumes a role, the shell becomes a profile shell. Therefore, the commands are executed with the privileges that were assigned to the commands. In the following example, the admin role can change the permissions on the useful.script file.

% whoami
jdoe
% ls -l useful.script
-rwxr-xr-- 1 elsee eng 262 Apr 2 10:52 useful.script
chgrp admin useful.script
chgrp: useful.script: Not owner
% su - admin
Password: <Type admin password>
$ /usr/ucb/whoami
admin
$ chgrp admin useful.script
$ chown admin useful.script
$ ls -l useful.script
-rwxr-xr-- 1 admin admin 262 Apr 2 10:53 useful.script