Re: [PATCH v9 00/12] Network support for Landlock

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2/24/2023 1:17 AM, Günther Noack пишет:
Hello Konstantin!

Sorry for asking such fundamental questions again so late in the review.

After playing with patch V9 with the Go-Landlock library, I'm still
having trouble understanding these questions -- they probably have
good answers, but I also did not see them explained in the
documentation. Maybe it would help to clarify it there?

* What is the use case for permitting processes to connect to a given
   TCP port, but leaving unspecified what the IP address is?

   Example: If a Landlock ruleset permits connecting to TCP port 53,
   that makes it possible to talk to any IP address on the internet (at
   least if the process runs on a normal Linux desktop machine), and we
   can't really control whether that is the system's proper (TCP-)DNS
   server or whether that is an attacker-controlled service for
   accepting leaked secrets from the process...?

   Is the plan that IP address support should be added in a follow-up
   patch?  Will it become part of the landlock_net_service_attr struct?

     In the beginning I introduced the idea with IP address to
Mickaël but he suggested to use port-based granularity. So with ports it's worth using Landlock in containerized applications working within one IP address. Anyway it's possible to use netfilter to control incoming traffic. It's a good question - we should discuss it carefuly.

* Given the list of obscure network protocols listed in the socket(2)
   man page, I find it slightly weird to have rules for the use of TCP,
   but to leave less prominent protocols unrestricted.

   For example, a process with an enabled Landlock network ruleset may
   connect only to certain TCP ports, but at the same time it can
   happily use Bluetooth/CAN bus/DECnet/IPX or other protocols?

We also have started a discussion about UDP protocol, but it's more complicated since UDP sockets does not establish connections between each other. There is a performance problem on the first place here.

I'm not familiar with Bluetooth/CAN bus/DECnet/IPX but let's discuss it.
Any ideas here?

   I'm mentioning these more obscure protocols, because I doubt that
   Landlock will grow more sophisticated support for them anytime soon,
   so maybe the best option would be to just make it possible to
   disable these?  Is that also part of the plan?

   (I think there would be a lot of value in restricting network
   access, even when it's done very broadly.  There are many programs
   that don't need network at all, and among those that do need
   network, most only require IP networking.

   Btw, the argument for more broad disabling of network access was
   already made at in the
     Thanks for the link. I will read it.

* This one is more of an implementation question: I don't understand
   why we are storing the networking rules in the same RB tree as the
   file system rules. - It looks a bit like "YAGNI" to me...?

     Actually network rules are stored in a different RB tree.
     You can check it in struct landlock_ruleset (ruleset.h):
     - struct rb_root root_inodeis for fs rules

     - struct rb_root root_net_port is for network rules;

   Would it be more efficient to keep the file system rules in the
   existing RB tree, and store the networking rules *separately* next
   to it in a different RB tree, or even in a more optimized data
   structure? In pseudocode:

     struct fast_lookup_int_set bind_tcp_ports;
     struct fast_lookup_int_set connect_tcp_ports;
     struct landlock_rb_tree fs_rules;

   It seems that there should be a data structure that supports this
   well and which uses the fact that we only need to store small

Thnaks for the question. From my point of view it depends on a real scenario - how many ports we want to allow by Landlock for a proccess - thousands, hundreds or less. If it's just 10 ports - do we really need some optimized data structure? Do we get some performance gain here?
What do you think?


P.S.: Apologies if some of it was discussed previously. I did my best
to catch up on previous threads, but it's long, and it's possible that
I missed parts of the discussion.

On Mon, Jan 16, 2023 at 04:58:06PM +0800, Konstantin Meskhidze wrote:
This is a new V9 patch related to Landlock LSM network confinement.
It is based on the landlock's -next branch on top of v6.2-rc3 kernel version:

It brings refactoring of previous patch version V8.
Mostly there are fixes of logic and typos, adding new tests.

All test were run in QEMU evironment and compiled with
 -static flag.
 1. network_test: 32/32 tests passed.
 2. base_test: 7/7 tests passed.
 3. fs_test: 78/78 tests passed.
 4. ptrace_test: 8/8 tests passed.

Previous versions:

Konstantin Meskhidze (11):
  landlock: Make ruleset's access masks more generic
  landlock: Refactor landlock_find_rule/insert_rule
  landlock: Refactor merge/inherit_ruleset functions
  landlock: Move and rename umask_layers() and init_layer_masks()
  landlock: Refactor _unmask_layers() and _init_layer_masks()
  landlock: Refactor landlock_add_rule() syscall
  landlock: Add network rules and TCP hooks support
  selftests/landlock: Share enforce_ruleset()
  selftests/landlock: Add 10 new test suites dedicated to network
  samples/landlock: Add network demo
  landlock: Document Landlock's network support

Mickaël Salaün (1):
  landlock: Allow filesystem layout changes for domains without such
    rule type

 Documentation/userspace-api/landlock.rst     |   72 +-
 include/uapi/linux/landlock.h                |   49 +
 samples/landlock/sandboxer.c                 |  131 +-
 security/landlock/Kconfig                    |    1 +
 security/landlock/Makefile                   |    2 +
 security/landlock/fs.c                       |  255 ++--
 security/landlock/limits.h                   |    7 +-
 security/landlock/net.c                      |  200 +++
 security/landlock/net.h                      |   26 +
 security/landlock/ruleset.c                  |  409 +++++--
 security/landlock/ruleset.h                  |  185 ++-
 security/landlock/setup.c                    |    2 +
 security/landlock/syscalls.c                 |  165 ++-
 tools/testing/selftests/landlock/base_test.c |    2 +-
 tools/testing/selftests/landlock/common.h    |   10 +
 tools/testing/selftests/landlock/config      |    4 +
 tools/testing/selftests/landlock/fs_test.c   |   75 +-
 tools/testing/selftests/landlock/net_test.c  | 1157 ++++++++++++++++++
 18 files changed, 2398 insertions(+), 354 deletions(-)
 create mode 100644 security/landlock/net.c
 create mode 100644 security/landlock/net.h
 create mode 100644 tools/testing/selftests/landlock/net_test.c



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