NAME

Linux::Landlock::Ruleset - A higher level interface to the Linux Landlock API

DESCRIPTION

Landlock is a sandboxing feature specific to Linux that allows a process to restrict its own access to the file system. Since the restrictions are set at runtime, from within the process itself, you can take into account dynamic information, like log or file system spool locations defined in your current configuration.

Once set, restrictions cannot be undone and they are inherited by all future child processes.

This module provides an object-oriented interface to the Linux Landlock API. It uses the lower-level interface provided by Linux::Landlock::Direct.

See https://docs.kernel.org/userspace-api/landlock.html for more information about Landlock.

SYNOPSIS

  use Linux::Landlock::Ruleset;

  my $ruleset = Linux::Landlock::Ruleset->new();
  $ruleset->add_path_rule('/etc/fstab', qw(read_file));
  $ruleset->add_net_rule(22222, qw(bind_tcp));
  $ruleset->apply();

  print -r '/etc/fstab' ? "allowed\n" : "not allowed\n"; # allowed ...
  IO::File->new('/etc/fstab', 'r') and print "succeeded: $!\n"; # ... and opening works
  print -r '/etc/passwd' ? "allowed\n" : "not allowed\n"; # allowed ...
  IO::File->new('/etc/passwd', 'r') or print "failed\n"; # ... but opening fails because of Landlock

  system('/usr/bin/cat /etc/fstab') and print "failed: $!\n"; # this fails, because we cannot execute cat

  IO::Socket::INET->new(LocalPort => 33333, Proto => 'tcp') or print "failed: $!\n"; # failed
  IO::Socket::INET->new(LocalPort => 22222, Proto => 'tcp') and print "succeeded\n"; # succeeded

METHODS

• apply()

  Apply the ruleset to the current process and all future children. Dies on error.

• get_abi_version()

  Int, returns the ABI version of the Landlock kernel module. Can be called as a static method. A version < 1 means that Landlock is not available.

• add_path_beneath_rule($path, @allowed)

  Add a rule to the ruleset that allows the specified access to the given path. $path can be a file or a directory. @allowed is a list of access rights to allow.

  Possible access rights are:

    execute
    write_file
    read_file
    read_dir
    remove_dir
    remove_file
    make_char
    make_dir
    make_reg
    make_sock
    make_fifo
    make_block
    make_sym
    refer
    truncate
  

  See https://docs.kernel.org/userspace-api/landlock.html for all possible access rights.

• add_net_port_rule($port, @allowed)

  Add a rule to the ruleset that allows the specified access to the given port. $port is allowed port, @allowed is a list of allowed operations.

  Possible operations are:

    bind_tcp
    connect_tcp
  

• allow_perl_inc_access()

  A convenience method that adds rules to allow reading files and directories in all directories in @INC.

• new([handled_fs_actions => \@fs_actions, handled_net_actions => \@net_actions])

  Create a new Linux::Landlock::Ruleset instance.

  handled_fs_actions and handled_net_actions restrict the set of actions that can be used in rules and that will be prevented if not allowed by any rule.

  By default, all actions supported by the kernel and known to this module are covered. This should usually not be changed.

LIMITATIONS

This module requires a Linux system supporting the Landlock functionality. As of 2024, this is the case for almost all distributions, however, the version of the available Landlock ABI varies.

Notably, the TRUNCATE access right is only supported by the kernel since ABI version 3 (kernel version 6.2 or newer, unless backported).

Network functionality is only available since ABI version 4.

AUTHOR

Marc Ballarin, ballarin.marc@gmx.de

COPYRIGHT AND LICENSE

Copyright (C) 2024 by Marc Ballarin

This library is free software; you can redistribute it and/or modify it under the same terms as Perl itself.