Commit 0dda0b3f authored by John Johansen's avatar John Johansen
Browse files

apparmor: fix ptrace label match when matching stacked labels 



Given a label with a profile stack of
  A//&B or A//&C ...

A ptrace rule should be able to specify a generic trace pattern with
a rule like

  ptrace trace A//&**,

however this is failing because while the correct label match routine
is called, it is being done post label decomposition so it is always
being done against a profile instead of the stacked label.

To fix this refactor the cross check to pass the full peer label in to
the label_match.

Fixes: 290f458a ("apparmor: allow ptrace checks to be finer grained than just capability")
Cc: Stable <stable@vger.kernel.org>
Reported-by: default avatarMatthew Garrett <mjg59@google.com>
Tested-by: default avatarMatthew Garrett <mjg59@google.com>
Signed-off-by: default avatarJohn Johansen <john.johansen@canonical.com>
parent c92a9a46

security/apparmor/include/perms.h

+3 −0
Original line number Diff line number Diff line
@@ -133,6 +133,9 @@ extern struct aa_perms allperms; 
#define xcheck_labels_profiles(L1, L2, FN, args...)		\

	xcheck_ns_labels((L1), (L2), xcheck_ns_profile_label, (FN), args)



#define xcheck_labels(L1, L2, P, FN1, FN2)			\

	xcheck(fn_for_each((L1), (P), (FN1)), fn_for_each((L2), (P), (FN2)))





void aa_perm_mask_to_str(char *str, const char *chrs, u32 mask);

void aa_audit_perm_names(struct audit_buffer *ab, const char **names, u32 mask);

security/apparmor/ipc.c

+32 −21
Original line number Diff line number Diff line
@@ -64,40 +64,48 @@ static void audit_ptrace_cb(struct audit_buffer *ab, void *va) 
			FLAGS_NONE, GFP_ATOMIC);

}



/* assumes check for PROFILE_MEDIATES is already done */

/* TODO: conditionals */

static int profile_ptrace_perm(struct aa_profile *profile,

			       struct aa_profile *peer, u32 request,

			     struct aa_label *peer, u32 request,

			     struct common_audit_data *sa)

{

	struct aa_perms perms = { };



	/* need because of peer in cross check */

	if (profile_unconfined(profile) ||

	    !PROFILE_MEDIATES(profile, AA_CLASS_PTRACE))

		return 0;



	aad(sa)->peer = &peer->label;

	aa_profile_match_label(profile, &peer->label, AA_CLASS_PTRACE, request,

	aad(sa)->peer = peer;

	aa_profile_match_label(profile, peer, AA_CLASS_PTRACE, request,

			       &perms);

	aa_apply_modes_to_perms(profile, &perms);

	return aa_check_perms(profile, &perms, request, sa, audit_ptrace_cb);

}



static int cross_ptrace_perm(struct aa_profile *tracer,

			     struct aa_profile *tracee, u32 request,

static int profile_tracee_perm(struct aa_profile *tracee,

			       struct aa_label *tracer, u32 request,

			       struct common_audit_data *sa)

{

	if (profile_unconfined(tracee) || unconfined(tracer) ||

	    !PROFILE_MEDIATES(tracee, AA_CLASS_PTRACE))

		return 0;



	return profile_ptrace_perm(tracee, tracer, request, sa);

}



static int profile_tracer_perm(struct aa_profile *tracer,

			       struct aa_label *tracee, u32 request,

			       struct common_audit_data *sa)

{

	if (profile_unconfined(tracer))

		return 0;



	if (PROFILE_MEDIATES(tracer, AA_CLASS_PTRACE))

		return xcheck(profile_ptrace_perm(tracer, tracee, request, sa),

			      profile_ptrace_perm(tracee, tracer,

						  request << PTRACE_PERM_SHIFT,

						  sa));

	/* policy uses the old style capability check for ptrace */

	if (profile_unconfined(tracer) || tracer == tracee)

		return profile_ptrace_perm(tracer, tracee, request, sa);



	/* profile uses the old style capability check for ptrace */

	if (&tracer->label == tracee)

		return 0;



	aad(sa)->label = &tracer->label;

	aad(sa)->peer = &tracee->label;

	aad(sa)->peer = tracee;

	aad(sa)->request = 0;

	aad(sa)->error = aa_capable(&tracer->label, CAP_SYS_PTRACE, 1);
@@ -115,10 +123,13 @@ static int cross_ptrace_perm(struct aa_profile *tracer, 
int aa_may_ptrace(struct aa_label *tracer, struct aa_label *tracee,

		  u32 request)

{

	struct aa_profile *profile;

	u32 xrequest = request << PTRACE_PERM_SHIFT;

	DEFINE_AUDIT_DATA(sa, LSM_AUDIT_DATA_NONE, OP_PTRACE);



	return xcheck_labels_profiles(tracer, tracee, cross_ptrace_perm,

				      request, &sa);

	return xcheck_labels(tracer, tracee, profile,

			profile_tracer_perm(profile, tracee, request, &sa),

			profile_tracee_perm(profile, tracer, xrequest, &sa));

}

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