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Subject[PATCH 4.14 088/118] apparmor: fix ptrace label match when matching stacked labels
Date
4.14-stable review patch.  If anyone has any objections, please let me know.

------------------

From: John Johansen <john.johansen@canonical.com>

commit 0dda0b3fb255048a221f736c8a2a24c674da8bf3 upstream.

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: 290f458a4f16 ("apparmor: allow ptrace checks to be finer grained than just capability")
Reported-by: Matthew Garrett <mjg59@google.com>
Tested-by: Matthew Garrett <mjg59@google.com>
Signed-off-by: John Johansen <john.johansen@canonical.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

---
security/apparmor/include/perms.h | 3 ++
security/apparmor/ipc.c | 53 ++++++++++++++++++++++----------------
2 files changed, 35 insertions(+), 21 deletions(-)

--- a/security/apparmor/include/perms.h
+++ b/security/apparmor/include/perms.h
@@ -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);
--- a/security/apparmor/ipc.c
+++ b/security/apparmor/ipc.c
@@ -64,40 +64,48 @@ static void audit_ptrace_cb(struct audit
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 common_audit_data *sa)
+ 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,
- struct common_audit_data *sa)
+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_p
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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