[PATCH RFC v11 9/19] ipe: add permissive toggle

[Paul Moore]

On Oct  4, 2023 Fan Wu <wufan at linux.microsoft.com> wrote:
> 
> IPE, like SELinux, supports a permissive mode. This mode allows policy
> authors to test and evaluate IPE policy without it effecting their
> programs. When the mode is changed, a 1404 AUDIT_MAC_STATUS
> be reported.
> 
> This patch adds the following audit records:
> 
>     audit: MAC_STATUS enforcing=0 old_enforcing=1 auid=4294967295
>       ses=4294967295 enabled=1 old-enabled=1 lsm=ipe res=1
>     audit: MAC_STATUS enforcing=1 old_enforcing=0 auid=4294967295
>       ses=4294967295 enabled=1 old-enabled=1 lsm=ipe res=1
> 
> The audit record only emit when the value from the user input is
> different from the current enforce value.
> 
> Signed-off-by: Deven Bowers <deven.desai at linux.microsoft.com>
> Signed-off-by: Fan Wu <wufan at linux.microsoft.com>
> ---
> v2:
>   + Split evaluation loop, access control hooks,
>     and evaluation loop from policy parser and userspace
>     interface to pass mailing list character limit
> 
> v3:
>   + Move ipe_load_properties to patch 04.
>   + Remove useless 0-initializations
>   + Prefix extern variables with ipe_
>   + Remove kernel module parameters, as these are
>     exposed through sysctls.
>   + Add more prose to the IPE base config option
>     help text.
>   + Use GFP_KERNEL for audit_log_start.
>   + Remove unnecessary caching system.
>   + Remove comments from headers
>   + Use rcu_access_pointer for rcu-pointer null check
>   + Remove usage of reqprot; use prot only.
>   + Move policy load and activation audit event to 03/12
> 
> v4:
>   + Remove sysctls in favor of securityfs nodes
>   + Re-add kernel module parameters, as these are now
>     exposed through securityfs.
>   + Refactor property audit loop to a separate function.
> 
> v5:
>   + fix minor grammatical errors
>   + do not group rule by curly-brace in audit record,
>     reconstruct the exact rule.
> 
> v6:
>   + No changes
> 
> v7:
>   + Further split lsm creation into a separate commit from the
>     evaluation loop and audit system, for easier review.
>   + Propagating changes to support the new ipe_context structure in the
>     evaluation loop.
>   + Split out permissive functionality into a separate patch for easier
>     review.
>   + Remove permissive switch compile-time configuration option - this
>     is trivial to add later.
> 
> v8:
>   + Remove "IPE" prefix from permissive audit record
>   + align fields to the linux-audit field dictionary. This causes the
>     following fields to change:
>       enforce -> permissive
> 
>   + Remove duplicated information correlated with syscall record, that
>     will always be present in the audit event.
>   + Change audit types:
>     + AUDIT_TRUST_STATUS -> AUDIT_MAC_STATUS
>       + There is no significant difference in meaning between
>         these types.
> 
> v9:
>   + Clean up ipe_context related code
> 
> v10:
>   + Change audit format to comform with the existing format selinux is
>     using
>   + Remove the audit record emission during init to align with selinux,
>     which does not perform this action.
> 
> v11:
>   + Remove redundant code
> ---
>  security/ipe/audit.c | 22 ++++++++++++++
>  security/ipe/audit.h |  1 +
>  security/ipe/eval.c  | 14 +++++++--
>  security/ipe/eval.h  |  1 +
>  security/ipe/fs.c    | 68 ++++++++++++++++++++++++++++++++++++++++++++
>  5 files changed, 104 insertions(+), 2 deletions(-)

...

> diff --git a/security/ipe/eval.c b/security/ipe/eval.c
> index 499b6b3338f2..78c54ff1fdd3 100644
> --- a/security/ipe/eval.c
> +++ b/security/ipe/eval.c
> @@ -167,9 +172,12 @@ int ipe_evaluate_event(const struct ipe_eval_ctx *const ctx)
>  	ipe_audit_match(ctx, match_type, action, rule);
>  
>  	if (action == IPE_ACTION_DENY)
> -		return -EACCES;
> +		rc = -EACCES;
> +
> +	if (!enforcing)
> +		rc = 0;

Why the local @enforcing variable?  Why not:

  if (!READ_ONCE(enforce))
    rc = 0;

> -	return 0;
> +	return rc;
>  }
>  
>  /**
> @@ -198,3 +206,5 @@ void ipe_invalidate_pinned_sb(const struct super_block *mnt_sb)
>  
>  module_param(success_audit, bool, 0400);
>  MODULE_PARM_DESC(success_audit, "Start IPE with success auditing enabled");
> +module_param(enforce, bool, 0400);
> +MODULE_PARM_DESC(enforce, "Start IPE in enforce or permissive mode");

"enforcing"

--
paul-moore.com