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

Fan Wu
2023-11-02T22:56:56Z

On 10/23/2023 8:52 PM, Paul Moore wrote:
> On Oct 4, 2023 Fan Wu <wufan@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@linux.microsoft.com>
>> Signed-off-by: Fan Wu <wufan@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;
>

Yes the variable is unnecessary, I will remove it.
-Fan
>> - 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