[RFC PATCH v1 0/7] Landlock audit support

[Mickaël Salaün]

I talked about this patch series at the Kernel Recipes conference, and
you might want to take a look at the future work:
https://landlock.io/talks/2023-09-25_landlock-audit-kr.pdf

In a nutshell, new syscall flags:
* For landlock_create_ruleset() to opt-in for logging ruleset-related
  and domain-related use
* For landlock_add_rule() to opt-in for logging this rule if it granted
  the requested access
* For landlock_restrict_self() to opt-in for:
  * not log anything
  * handle a permissive mode to log actions that would have been denied
    (very useful to build a sandbox)


On Thu, Sep 21, 2023 at 08:16:34AM +0200, Mickaël Salaün wrote:
> Hi,
> 
> This patch series adds basic audit support to Landlock for most actions.
> Logging denied requests is useful for different use cases:
> * app developers: to ease and speed up sandboxing support
> * power users: to understand denials
> * sysadmins: to look for users' issues
> * tailored distro maintainers: to get usage metrics from their fleet
> * security experts: to detect attack attempts
> 
> To make logs useful, they need to contain the most relevant Landlock
> domain that denied an action, and the reason. This translates to the
> latest nested domain and the related missing access rights.
> 
> Two "Landlock permissions" are used to describe mandatory restrictions
> enforced on all domains:
> * fs_layout: change the view of filesystem with mount operations.
> * ptrace: tamper with a process.
> 
> Here is an example of logs, result of the sandboxer activity:
> tid=267 comm="sandboxer" op=create-ruleset ruleset=1 handled_access_fs=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
> tid=267 comm="sandboxer" op=restrict-self domain=2 ruleset=1 parent=0
> op=release-ruleset ruleset=1
> tid=267 comm="bash" domain=2 op=open errno=13 missing-fs-accesses=write_file,read_file missing-permission= path="/dev/tty" dev="devtmpfs" ino=9
> tid=268 comm="ls" domain=2 op=open errno=13 missing-fs-accesses=read_dir missing-permission= path="/" dev="vda2" ino=256
> tid=269 comm="touch" domain=2 op=mknod errno=13 missing-fs-accesses=make_reg missing-permission= path="/" dev="vda2" ino=256
> tid=270 comm="umount" domain=2 op=umount errno=1 missing-fs-accesses= missing-permission=fs_layout name="/" dev="tmpfs" ino=1
> tid=271 comm="strace" domain=2 op=ptrace errno=1 missing-fs-accesses= missing-permission=ptrace opid=1 ocomm="systemd"
> 
> As highlighted in comments, support for audit is not complete yet with
> this series: some actions are not logged (e.g. file reparenting), and
> rule additions are not logged neither.
> 
> I'm also not sure if we need to have seccomp-like features such as
> SECCOMP_FILTER_FLAG_LOG, SECCOMP_RET_LOG, and
> /proc/sys/kernel/seccomp/actions_logged
> 
> I'd like to get some early feedback on this proposal.
> 
> This series is based on v6.6-rc2
> 
> Regards,
> 
> Mickaël Salaün (7):
>   lsm: Add audit_log_lsm_data() helper
>   landlock: Factor out check_access_path()
>   landlock: Log ruleset creation and release
>   landlock: Log domain creation and enforcement
>   landlock: Log file-related requests
>   landlock: Log mount-related requests
>   landlock: Log ptrace requests
> 
>  include/linux/lsm_audit.h    |   2 +
>  include/uapi/linux/audit.h   |   1 +
>  security/landlock/Makefile   |   2 +
>  security/landlock/audit.c    | 283 +++++++++++++++++++++++++++++++++++
>  security/landlock/audit.h    |  88 +++++++++++
>  security/landlock/fs.c       | 169 ++++++++++++++++-----
>  security/landlock/ptrace.c   |  47 +++++-
>  security/landlock/ruleset.c  |   6 +
>  security/landlock/ruleset.h  |  10 ++
>  security/landlock/syscalls.c |  12 ++
>  security/lsm_audit.c         |  26 ++--
>  11 files changed, 595 insertions(+), 51 deletions(-)
>  create mode 100644 security/landlock/audit.c
>  create mode 100644 security/landlock/audit.h
> 
> 
> base-commit: ce9ecca0238b140b88f43859b211c9fdfd8e5b70
> -- 
> 2.42.0
>