Abstract unix socket control

[l0kod]

It would be nice to be able to scope access to abstract unix sockets the same way ptrace is restricted (but this time it would be opt-in).

See https://lore.kernel.org/all/20231023.ahphah4Wii4v@digikod.net/ and https://lore.kernel.org/all/20231102.MaeWaepav8nu@digikod.net/

Approach similar to #8

v6: https://lore.kernel.org/all/Zn32CYZiu7pY+rdI@tahera-OptiPlex-5000/ and https://lore.kernel.org/all/Zn32KKIJrY7Zi51K@tahera-OptiPlex-5000/
v5: https://lore.kernel.org/all/ZnSZnhGBiprI6FRk@tahera-OptiPlex-5000/
v4: https://lore.kernel.org/all/ZnNcE3ph2SWi1qmd@tahera-OptiPlex-5000/
v3: https://lore.kernel.org/all/ZmJJ7lZdQuQop7e5@tahera-OptiPlex-5000/
v2: https://lore.kernel.org/all/ZgX5TRTrSDPrJFfF@tahera-OptiPlex-5000/
v1: https://lore.kernel.org/all/ZgXN5fi6A1YQKiAQ@tahera-OptiPlex-5000/

[tahifahimi]

Hi @l0kod,
I start working on this, and read almost all of the related docs & explanations :)
quick question, besides following the landlock logic from task.c (which is ptrace.c in staging branch) and scope changes that should apply to net.c, do we need to modify any other file?

[l0kod]

Hi @tahifahimi,

Hi @l0kod, I start working on this, and read almost all of the related docs & explanations :)

Great!

besides following the landlock logic from task.c (which is ptrace.c in staging branch) and scope changes that should apply to net.c, do we need to modify any other file?

I think most changes should be in task.c/ptrace.c. The net.c file is dedicated to network rule management (only TCP bind/connect for now), but the abstract unix socket restrictions should be implemented as scopes like for ptrace restrictions (e.g. no new Landlock rule type but only a ruleset's flag, no sockaddr parsing...). Moreover, I consider abstract unix sockets to be more an IPC mechanism rather than a network feature. task.c contains the main helpers that should be used (and extended): task_is_scoped() and domain_scope_le().

About the flag design, see #8 (comment). Updating this interface should lead you to the other files that will need some changes.

[tahifahimi]

Thanks for your comments! Based on you suggested, I had a look; please correct me if I am wrong.
First I have to add a struct field to the landlock_ruleset in landlock/ruleset.h (a struct field same as hierarchy which is used for ptrace). Then I should edit the "landlock/ptrace.c" and add landlock_hooks for unix_stream_connect and unix_may_send and write the respective helpers (same thing we have for ptrace_traceme and ptrace_access_check for ptrace).

[l0kod]

Looks good! One important thing to keep in mind is that because abstract unix socket scoping will be optional, you might need to implement new checks in the current domain_scope_le() helper and related data structures/calls.

BTW, the rename of ptrace.c to task.c is now merged: 35e886e

[l0kod]

I'm assigning this issue to you. Please regularly update it with your progress. This doesn't need to be long but just enough to make sure you are not blocked.