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20 KiB

Ansible role bertvv.samba

Build Status

An Ansible role for setting up Samba as a file server. It is tested on CentOS, Debian, Ubuntu and Arch Linux. Specifically, the responsibilities of this role are to:

  • Install the necessary packages
  • Configure SELinux settings (when SELinux is active)
  • Create share directories
  • Manage Samba users and passwords
  • Manage access to shares

The following are not considered concerns of this role, and you should configure these using another role (e.g. bertvv.rh-base:

  • Managing firewall settings.
  • Creating system users. Samba users should already exist as system users.

If you like/use this role, please consider giving it a star! Thanks!

CVE-2017-7494

A remote code execution vulnerability may affect your Samba server installation. Samba versions 3.5.0 and before 4.6.4 are affected. If SELinux is enabled on your system, it is NOT vulnerable.

This role will check if the installed version of Samba is affected by the vulnerability and apply the proposed workaround: adding nt pipe support = no to the [global] section of the configuration. Remark that this disables share browsing by Windows clients.

You can explicitly disable the fix if necessary, by setting the role variable samba_mitigate_cve_2017_7494 to false.

More info: https://access.redhat.com/security/cve/cve-2017-7494

Requirements

No specific requirements

Role Variables

Variable Default Comments
samba_apple_extensions no When yes, enables support for Apple specific SMB extensions. Required for Time Machine support to work (see below)
samba_create_varwww_symlinks false When true, symlinks are created in web docroot to the shares. (var/www/ or /var/www/html depending on platform)
samba_cups_server localhost:631 Value for the global option cups server (only needed when samba_printer_type is "cups")
samba_domain_master true When true, smbd enables WAN-wide browse list collation
samba_global_include - Samba-compatible configuration file with options to be loaded to [global] section (see below)
samba_guest_account - Guest account for unknown users
samba_homes_include - Samba-compatible configuration file with options to be loaded to [homes] section (see below)
samba_interfaces [] List of network interfaces used for browsing, name registration, etc.
samba_load_homes false When true, user home directories are accessible.
samba_load_printers false When true, printers attached to the host are shared
samba_local_master true When true, nmbd will try & become local master of the subnet
samba_log - Set the log file. If left undefined, logging is done through syslog.
samba_log_size 5000 Set the maximum size of the log file.
samba_log_level 0 Set Samba log level, 0 is least verbose and 10 is a flood of debug output.
samba_map_to_guest bad user Behaviour when unregistered users access the shares.
samba_mitigate_cve_2017_7494 true CVE-2017-7494 mitigation breaks some clients, such as macOS High Sierra.
samba_netbios_name {{ ansible_hostname }} The NetBIOS name of this server.
samba_passdb_backend tdbsam Password database backend.
samba_preferred_master true When true, indicates nmbd is a preferred master browser for workgroup
samba_realm - Realm domain name
samba_printer_type cups value for the global option printing and printcap name
samba_security user Samba security setting
samba_server_max_protocol - Specify a maximum protocol version offered by the server.
samba_server_min_protocol - Specify a minimum protocol version offered by the server.
samba_server_string fileserver %m Comment string for the server.
samba_shares_root /srv/shares Directories for the shares are created under this directory.
samba_shares [] List of dicts containing share definitions. See below for details.
samba_users [] List of dicts defining users that can access shares.
samba_wins_support true When true, Samba will act as a WINS server
samba_workgroup WORKGROUP Name of the server workgroup.

Defining users

In order to allow users to access the shares, they need to get a password specifically for Samba:

samba_users:
  - name: alice
    password: ecila
  - name: bob
    password: bob
  - name: charlie
    password: eilrahc

Unfortunately, passwords have to be in plain text for now. Also, remark that this role will not change the password of an existing user.

These users should already have an account on the host! Creating system users is not a concern of this role, so you should do this separately. A possibility is my role bertvv.rh-base. An example:

rhbase_users:
  - name: alice
    comment: 'Alice'
    password: !!
    shell: /sbin/nologin
    groups:
      [...]

This user is not allowed to log in on the system (e.g. with SSH) and would only get access to the Samba shares.

Defining shares

Defining Samba shares and configuring access control can be challenging, since it involves not only getting the Samba configuration right, but also user and file permissions, and SELinux settings. This role attempts to simplify the process.

To specify a share, you should at least give it a name:

samba_shares:
  - name: readonlyshare

This will create a share with only read access for registered users. Guests will not be able to see the contents of the share.

A good way to configure write access for a share is to create a system user group, add users to that group, and make sure they have write access to the directory of the share. This role assumes groups are already set up and users are members of the groups that control write access. Let's assume you have two users jack and teach, members of the group pirates. This share definition will give both read and write access to the pirates:

samba_shares:
  - name: piratecove
    comment: 'A place for pirates to hang out'
    group: pirates
    write_list: +pirates

Guests have no access to this share, registered users can read. You can further tweak access control. Read access can be extended to guests (add public: yes) or restricted to specified users or groups (add valid_users: +pirates). Write access can be restricted to individual pirates (e.g. write_list: jack). Files added to the share will be added to the specified group and group write access will be granted by default.

This is an example of configuring multiple vfs object modules to share a glusterfs volume. VFS object options are optional. The necessary VFS object modules must be present/installed outside this role. In this case samba-glusterfs was installed on centos. See samba documentation for how to install or what the default VFS object modules are.

samba_shares:
  - name: gluster-app_deploys
    comment: 'For samba share of volume app_deploys'
    vfs_objects:
      - name: audit
        options:
          - name: facility
            value: LOCAL1
          - name: priority
            value: NOTICE
      - name: glusterfs
        options:
          - name: volume
            value: app_deploys
          - name: logfile
            value: /var/log/samba/glusterfs-app_deploys.%M.log
          - name: loglevel
            value: 7
    path: /
    read_only: no
    guest_ok: yes
    write_list: tomcat
    group: tomcat

A complete overview of share options follows below. Only name is required, the rest is optional.

Option Default Comment
browseable - Controls whether this share appears in file browser.
comment - A comment string for the share
create_mode 0664 See the Samba documentation for details.
directory_mode 0775 See the Samba documentation for details.
include_file - Samba combatible configuration file with options to be included for this share (see below).
force_create_mode 0664 See the Samba documentation for details.
force_directory_mode 0775 See the Samba documentation for details.
group users The user group files in the share will be added to.
guest_ok - Allow guest access.
name (required) - The name of the share.
owner root Set the owner of the path
path /{{samba_shares_root}}/{{name}} The path to the share directory.
public no Controls read access for guest users
setype samba_share_t The SELinux type of the share directory
valid_users - Controls read access for registered users. Use the syntax of the corresponding Samba setting.
vfs_objects - See the Samba documentation for details.
writable - Writable for guests.
write_list - Controls write access for registered users. Use the syntax of the corresponding Samba setting.

The values for valid_users and write_list should be a comma separated list of users. Names prepended with + or @ are interpreted as groups. The documentation for the Samba configuration has more details on these options.

Adding arbitrary configuration files

You can add settings that are not supported by this role out-of-the-box through custom configuration files that will be included from the main configuration file. There are three types of include files: for the global section, for the homes section, and for individual shares. Put your custom configuration files in a subdirectory templates, relative to your master playbook location. Then, specify them in the variables samba_global_include, samba_homes_include, or include_file in the samba_shares definition.

Your custom configuration files are considered to be Jinja templates, so you can use Ansible variables inside them. The configuration files will be validated to ensure they are syntactically correct.

For example, to include templates/global-include.conf, set:

samba_global_include: global-include.conf

Remark that is it not necessary to specify the templates/ directory.

Likewise, to include templates/piratecove-include.conf, specific for the piratecove share (see the example above); set:

samba_shares:
  - name: piratecove
    comment: 'A place for pirates to hang out'
    group: pirates
    write_list: +pirates
    include_file: piratecove-include.conf

The test playbook has some examples. The custom configuration files can be found in the docker-tests branch.

Dependencies

No dependencies.

Example Playbook

See the test playbook

Testing

This role is tested using Ansible Molecule. Tests are launched automatically on Travis CI after each commit and PR.

This Molecule configuration will:

  • Run Yamllint and Ansible Lint
  • Create a Docker container
  • Run a syntax check
  • Apply the role with a test playbook
  • Run acceptance tests with BATS

This process is repeated for the supported Linux distributions.

Local test environment

If you want to set up a local test environment, you can use this reproducible setup based on Vagrant+VirtualBox: https://github.com/bertvv/ansible-testenv. Steps to install the necessary tools manually:

  1. Docker, BATS and smbclient should be installed on your machine (assumed to run Linux). No Docker containers should be running when you start the test.
  2. As recommended by Molecule, create a python virtual environment
  3. Install the software tools python3 -m pip install molecule docker yamllint ansible-lint
  4. Navigate to the root of the role directory and run molecule test

Molecule automatically deletes the containers after a test. If you would like to check out the containers yourself, run molecule converge followed by molecule login --host HOSTNAME.

The Docker containers are based on images created by Jeff Geerling, specifically for Ansible testing (look for images named geerlingguy/docker-DISTRO-ansible). You can use any of his images, but only the distributions mentioned in meta/main.yml are supported.

The default config will start a Centos 7 container. Choose another distro by setting the MOLECULE_DISTRO variable with the command, e.g.:

MOLECULE_DISTRO=debian9 molecule test

or

MOLECULE_DISTRO=debian9 molecule converge

You can run the acceptance tests on both servers with molecule verify or manually with

SUT_IP=172.17.0.2 bats molecule/default/files/samba.bats

You need to initialise the variable SUT_IP, the system under test's IP address. The server, smb1, should have IP address 172.17.0.2.

Contributing

Issues, feature requests, ideas are appreciated and can be posted in the Issues section.

Pull requests are also very welcome. The best way to submit a PR is by first creating a fork of this Github project, then creating a topic branch for the suggested change and pushing that branch to your own fork. Github can then easily create a PR based on that branch. Don't forget to add yourself to the list of contributors below!

License

2-clause BSD license, see LICENSE.md

Contributors

This role could only have been realized thanks to the contributions of the people listed below. If you have an idea to improve it even further, don't hesitate to pitch in!

Issues, feature requests, ideas, suggestions, etc. can be posted in the Issues section.

Pull requests are also very welcome. Please create a topic branch for your proposed changes. If you don't, this will create conflicts in your fork after the merge. Don't hesitate to add yourself to the contributor list below in your PR!

Ben Tomasik, Bengt Giger, Bert Van Vreckem (maintainer), Birgit Croux, DarkStar1973, George Hartzell, Ian Young, Jonas Heinrich, Jonathan Underwood, Karl Goetz, morbidick, Paul Montero, Slavek Jurkowski, Sven Eeckeman, Tiemo Kieft, Tobias Wolter, Tomohiko Ozawa, Robin Ophalvens.