[RFC PATCH 0/2] landlock network implementation cover letter

[Konstantin Meskhidze]

Hi, all!

This is a new bunch of RFC patches related to Landlock LSM network confinement.
Here are previous discussions:
1. https://lore.kernel.org/linux-security-module/20211210072123.386713-1-konstantin.meskhidze@huawei.com/
2. https://lore.kernel.org/linux-security-module/20211228115212.703084-1-konstantin.meskhidze@huawei.com/

As in previous RFCs, 2 hooks are supported:
  - hook_socket_bind()
  - hook_socket_connect()

Selftest are provided in tools/testing/selftests/landlock/network_test.c;
Implementation was tested in QEMU invironment with 5.13 kernel version:
 1. base_test - passed all tests
 2. fs_test - passed 44/46 tests. 2 tests related to overlayfs failed.
    Probably, I have wrong config options for overlayfs.
 3. network_test - passed all tests.
    Please give your suggestions about test cover in network_test.c

Implementation related issues
=============================

1. Access masks array refactored into 1D one and changed
to 32 bits. Filesystem masks occupy 16 lower bits and network
masks reside in 16 upper bits.

      struct landlock_ruleset {
            ...
            ...
            u32 access_masks[];
      }

2. Refactor API functions in ruleset.c:
    1. Add (void *)object argument.
    2. Add u16 rule_type argument.

  - In filesystem case the "object" is defined by underlying inode.
  In network case the "object" is defined by a port. There is
  a union containing either a struct landlock_object pointer or a
  raw data (here a u16 port):
    union {
        struct landlock_object *ptr;
        uintptr_t data;
    } object;

  - Everytime when a rule is inserted it's needed to provide a rule type:

    landlock_insert_rule(ruleset, (void *)object, access, rule_type)
      1. A rule_type could be or LANDLOCK_RULE_NET_SERVICE or
      LANDLOCK_RULE_PATH_BENEATH;
      2. (void *) object - is either landlock_object *ptr or port value;

3. Use two rb_trees in ruleset structure:
    1. root_inode - for filesystem objects (inodes).
    2. root_net_port - for network port objects.

Konstantin Meskhidze (2):
  landlock: TCP network hooks implementation
  landlock: selftests for bind and connect hooks

 include/uapi/linux/landlock.h                 |  52 +++
 security/landlock/Makefile                    |   2 +-
 security/landlock/fs.c                        |  12 +-
 security/landlock/limits.h                    |   6 +
 security/landlock/net.c                       | 175 +++++++++
 security/landlock/net.h                       |  21 ++
 security/landlock/ruleset.c                   | 167 ++++++---
 security/landlock/ruleset.h                   |  40 +-
 security/landlock/setup.c                     |   3 +
 security/landlock/syscalls.c                  | 142 ++++---
 .../testing/selftests/landlock/network_test.c | 346 ++++++++++++++++++
 11 files changed, 860 insertions(+), 106 deletions(-)
 create mode 100644 security/landlock/net.c
 create mode 100644 security/landlock/net.h
 create mode 100644 tools/testing/selftests/landlock/network_test.c

--
2.25.1