Teach audit2why to recognize type bounds failures. This required
updating libsepol sepol_compute_av_reason() to identify bounds
failures, and updating libsepol context_struct_compute_av() to
include the type bounds logic from the kernel.
This could potentially be further augmented to provide more detailed
reporting via the reason buffer to include information similar to
what security_dump_masked_av() reports in the kernel. However, it
is unclear if this is needed. It is already possible to get type
bounds checking at policy build time by enabling expand-check=1
in /etc/selinux/semanage.conf (or by default when compiling
monolithic policy).
Before:
type=AVC msg=audit(1480451925.038:3225): avc: denied { getattr } for pid=7118 comm="chmod" path="/home/sds/selinux-testsuite/tests/bounds/bounds_file_blue" dev="dm-2" ino=23337697 scontext=unconfined_u:unconfined_r:test_bounds_child_t:s0-s0:c0.c1023 tcontext=unconfined_u:object_r:test_bounds_file_blue_t:s0 tclass=file permissive=0
Was caused by:
Unknown - would be allowed by active policy
Possible mismatch between this policy and the one under which the audit message was generated.
Possible mismatch between current in-memory boolean settings vs. permanent ones.
After:
type=AVC msg=audit(1480451925.038:3225): avc: denied { getattr } for pid=7118 comm="chmod" path="/home/sds/selinux-testsuite/tests/bounds/bounds_file_blue" dev="dm-2" ino=23337697 scontext=unconfined_u:unconfined_r:test_bounds_child_t:s0-s0:c0.c1023 tcontext=unconfined_u:object_r:test_bounds_file_blue_t:s0 tclass=file permissive=0
Was caused by:
Typebounds violation.
Add an allow rule for the parent type.
Signed-off-by: Stephen Smalley <sds@xxxxxxxxxxxxx>
---
libselinux/src/audit2why.c | 5 ++
libsepol/include/sepol/policydb/services.h | 7 +--
libsepol/src/services.c | 77 ++++++++++++++++++++++++++++--
python/audit2allow/audit2allow | 5 ++
4 files changed, 86 insertions(+), 8 deletions(-)
diff --git a/libselinux/src/audit2why.c b/libselinux/src/audit2why.c
index 3d312a1..3135eed 100644
--- a/libselinux/src/audit2why.c
+++ b/libselinux/src/audit2why.c
@@ -28,6 +28,7 @@
#define BOOLEAN 3
#define CONSTRAINT 4
#define RBAC 5
+#define BOUNDS 6
struct boolean_t {
char *name;
@@ -425,6 +426,9 @@ static PyObject *analyze(PyObject *self __attribute__((unused)) , PyObject *args
if (reason & SEPOL_COMPUTEAV_RBAC)
RETURN(RBAC)
+ if (reason & SEPOL_COMPUTEAV_BOUNDS)
+ RETURN(BOUNDS)
+
RETURN(BADCOMPUTE)
}
@@ -481,6 +485,7 @@ PyMODINIT_FUNC initaudit2why(void)
PyModule_AddIntConstant(m,"BOOLEAN", BOOLEAN);
PyModule_AddIntConstant(m,"CONSTRAINT", CONSTRAINT);
PyModule_AddIntConstant(m,"RBAC", RBAC);
+ PyModule_AddIntConstant(m,"BOUNDS", BOUNDS);
#if PY_MAJOR_VERSION >= 3
return m;
diff --git a/libsepol/include/sepol/policydb/services.h b/libsepol/include/sepol/policydb/services.h
index 29f57cf..9162149 100644
--- a/libsepol/include/sepol/policydb/services.h
+++ b/libsepol/include/sepol/policydb/services.h
@@ -52,9 +52,10 @@ extern int sepol_compute_av(sepol_security_id_t ssid, /* IN */
/* Same as above, but also return the reason(s) for any
denials of the requested permissions. */
-#define SEPOL_COMPUTEAV_TE 1
-#define SEPOL_COMPUTEAV_CONS 2
-#define SEPOL_COMPUTEAV_RBAC 4
+#define SEPOL_COMPUTEAV_TE 0x1U
+#define SEPOL_COMPUTEAV_CONS 0x2U
+#define SEPOL_COMPUTEAV_RBAC 0x4U
+#define SEPOL_COMPUTEAV_BOUNDS 0x8U
extern int sepol_compute_av_reason(sepol_security_id_t ssid,
sepol_security_id_t tsid,
sepol_security_class_t tclass,
diff --git a/libsepol/src/services.c b/libsepol/src/services.c
index 068759d..03fb120 100644
--- a/libsepol/src/services.c
+++ b/libsepol/src/services.c
@@ -824,6 +824,67 @@ out:
return rc;
}
+/* Forward declaration */
+static int context_struct_compute_av(context_struct_t * scontext,
+ context_struct_t * tcontext,
+ sepol_security_class_t tclass,
+ sepol_access_vector_t requested,
+ struct sepol_av_decision *avd,
+ unsigned int *reason,
+ char **r_buf,
+ unsigned int flags);
+
+static void type_attribute_bounds_av(context_struct_t *scontext,
+ context_struct_t *tcontext,
+ sepol_security_class_t tclass,
+ sepol_access_vector_t requested,
+ struct sepol_av_decision *avd,
+ unsigned int *reason)
+{
+ context_struct_t lo_scontext;
+ context_struct_t lo_tcontext, *tcontextp = tcontext;
+ struct sepol_av_decision lo_avd;
+ type_datum_t *source;
+ type_datum_t *target;
+ sepol_access_vector_t masked = 0;
+
+ source = policydb->type_val_to_struct[scontext->type - 1];
+ if (!source->bounds)
+ return;
+
+ target = policydb->type_val_to_struct[tcontext->type - 1];
+
+ memset(&lo_avd, 0, sizeof(lo_avd));
+
+ memcpy(&lo_scontext, scontext, sizeof(lo_scontext));
+ lo_scontext.type = source->bounds;
+
+ if (target->bounds) {
+ memcpy(&lo_tcontext, tcontext, sizeof(lo_tcontext));
+ lo_tcontext.type = target->bounds;
+ tcontextp = &lo_tcontext;
+ }
+
+ context_struct_compute_av(&lo_scontext,
+ tcontextp,
+ tclass,
+ requested,
+ &lo_avd,
+ NULL, /* reason intentionally omitted */
+ NULL,
+ 0);
+
+ masked = ~lo_avd.allowed & avd->allowed;
+
+ if (!masked)
+ return; /* no masked permission */
+
+ /* mask violated permissions */
+ avd->allowed &= ~masked;
+
+ *reason |= SEPOL_COMPUTEAV_BOUNDS;
+}
+
/*
* Compute access vectors based on a context structure pair for
* the permissions in a particular class.
@@ -835,7 +896,7 @@ static int context_struct_compute_av(context_struct_t * scontext,
struct sepol_av_decision *avd,
unsigned int *reason,
char **r_buf,
- unsigned int flags)
+ unsigned int flags)
{
constraint_node_t *constraint;
struct role_allow *ra;
@@ -860,7 +921,8 @@ static int context_struct_compute_av(context_struct_t * scontext,
avd->auditallow = 0;
avd->auditdeny = 0xffffffff;
avd->seqno = latest_granting;
- *reason = 0;
+ if (reason)
+ *reason = 0;
/*
* If a specific type enforcement rule was defined for
@@ -899,7 +961,8 @@ static int context_struct_compute_av(context_struct_t * scontext,
}
if (requested & ~avd->allowed) {
- *reason |= SEPOL_COMPUTEAV_TE;
+ if (reason)
+ *reason |= SEPOL_COMPUTEAV_TE;
requested &= avd->allowed;
}
@@ -919,7 +982,8 @@ static int context_struct_compute_av(context_struct_t * scontext,
}
if (requested & ~avd->allowed) {
- *reason |= SEPOL_COMPUTEAV_CONS;
+ if (reason)
+ *reason |= SEPOL_COMPUTEAV_CONS;
requested &= avd->allowed;
}
@@ -942,10 +1006,13 @@ static int context_struct_compute_av(context_struct_t * scontext,
}
if (requested & ~avd->allowed) {
- *reason |= SEPOL_COMPUTEAV_RBAC;
+ if (reason)
+ *reason |= SEPOL_COMPUTEAV_RBAC;
requested &= avd->allowed;
}
+ type_attribute_bounds_av(scontext, tcontext, tclass, requested, avd,
+ reason);
return 0;
}
diff --git a/python/audit2allow/audit2allow b/python/audit2allow/audit2allow
index 4b50c5b..37ab23a 100644
--- a/python/audit2allow/audit2allow
+++ b/python/audit2allow/audit2allow
@@ -285,6 +285,11 @@ class AuditToPolicy:
print("\t\tAdd an allow rule for the role pair.\n")
continue
+ if rc == audit2why.BOUNDS:
+ print("\t\tTypebounds violation.\n")
+ print("\t\tAdd an allow rule for the parent type.\n")
+ continue
+
audit2why.finish()
return
--
2.7.4
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