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