Beyond Linux® From Scratch - Version svn-20070421

Chapter 4. Security

Sudo-1.6.8p12

Introduction to Sudo

The sudo package allows a system administrator to give certain users (or groups of users) the ability to run some (or all) commands as root or another user while logging the commands and arguments.

Package Information

Additional Downloads

User Notes: http://wiki.linuxfromscratch.org/blfs/wiki/sudo

Installation of Sudo

Install sudo by running the following commands: 

patch -Np1 -i ../sudo-1.6.8p12-envvar_fix-1.patch &&
./configure --prefix=/usr --libexecdir=/usr/lib \
    --enable-noargs-shell --with-ignore-dot --with-all-insults \
    --enable-shell-sets-home &&
make

Now, as the root user: 

make install

Command Explanations

--enable-noargs-shell: This switch allows sudo to run a shell if invoked with no arguments.

--with-ignore-dot: This switch causes sudo to ignore '.' in the PATH.

--with-all-insults: This switch includes all the sudo insult sets.

--enable-shell-sets-home: This switch sets HOME to the target user in shell mode.

[Note]

Note

There are many options to sudo's configure command. Check the configure --help output for a complete list.

Configuring Sudo

Config File

/etc/sudoers

Configuration Information

The sudoers file can be quite complicated. It is composed of two types of entries: aliases (basically variables) and user specifications (which specify who may run what). The installation installs a default configuration that has no privileges installed for any user.

One example usage is to allow the system administrator to execute any program without typing a password each time root privileges are needed. This can be configured as: 

# User alias specification
User_Alias  ADMIN = YourLoginId

# Allow people in group ADMIN to run all commands without a password
ADMIN       ALL = NOPASSWD: ALL

For details, see man sudoers.

[Note]

Note

The Sudo developers highly recommend using the visudo program to edit the sudoers file. This will provide basic sanity checking like syntax parsing and file permission to avoid some possible mistakes that could lead to a vulnerable configuration.

Contents

Installed Programs: sudo, sudoedit, and visudo
Installed Library: sudo_noexec.so
Installed Directories: None

Short Descriptions

sudo

executes a command as another user as permitted by the /etc/sudoers configuration file.

sudoedit

is a hard link to sudo that implies the -e option to invoke an editor as another user.

visudo

allows for safer editing of the sudoers file.

sudo_noexec.so

enables support for the "noexec" functionality which prevents a dynamically-linked program being run by sudo from executing another program (think shell escapes).

Last updated on 2007-04-04 21:42:53 +0200