libsepol: add compile-time constraint for mutual exclusive attributes

cgzones · fishilico · commit e5a22627c35d · 2022-06-19T23:01:18.000+02:00
Add a new compile-time constraint, similar to neverallow, which enables to specify two or more type attributes to be mutual exclusive. This means no type can be associated with more than one of them. The constraints are stored as a linked-list in the policy for modular policies, by a new modular policy version, and are discarded in kernel policies, not needing any kernel support. Some Reference Policy examples: unpriv_userdomain, admindomain: <no violations> client_packet_type, server_packet_type: <no violations> auth_file_type, non_auth_file_type: <no violations> pseudofs, xattrfs, noxattrfs: <no violations> reserved_port_type, unreserved_port_type: <no violations> security_file_type, non_security_file_type: libsepol.check_segregate_attributes: segregate_attributes violated by type dnssec_t associated with attributes security_file_type and non_security_file_type ibendport_type, packet_type, sysctl_type, device_node, ibpkey_type, sysfs_types, domain, boolean_type, netif_type, file_type, node_type, proc_type, port_type: libsepol.check_segregate_attributes: segregate_attributes violated by type virt_content_t associated with attributes device_node and file_type libsepol.check_segregate_attributes: segregate_attributes violated by type sysctl_fs_t associated with attributes sysctl_type and file_type libsepol.check_segregate_attributes: segregate_attributes violated by type initrc_devpts_t associated with attributes device_node and file_type libsepol.check_segregate_attributes: segregate_attributes violated by type qemu_image_t associated with attributes device_node and file_type libsepol.check_segregate_attributes: segregate_attributes violated by type user_devpts_t associated with attributes device_node and file_type libsepol.check_segregate_attributes: segregate_attributes violated by type dockerc_t associated with attributes domain and file_type libsepol.check_segregate_attributes: segregate_attributes violated by type cpu_online_t associated with attributes sysfs_types and file_type libsepol.check_segregate_attributes: segregate_attributes violated by type cardmgr_dev_t associated with attributes device_node and file_type libsepol.check_segregate_attributes: segregate_attributes violated by type sysctl_t associated with attributes sysctl_type and file_type libsepol.check_segregate_attributes: segregate_attributes violated by type bootloader_tmp_t associated with attributes device_node and file_type libsepol.check_segregate_attributes: segregate_attributes violated by type xen_image_t associated with attributes device_node and file_type libsepol.check_segregate_attributes: segregate_attributes violated by type svirt_prot_exec_image_t associated with attributes device_node and file_type libsepol.check_segregate_attributes: segregate_attributes violated by type xen_devpts_t associated with attributes device_node and file_type libsepol.check_segregate_attributes: segregate_attributes violated by type proc_t associated with attributes file_type and proc_type libsepol.check_segregate_attributes: segregate_attributes violated by type sysfs_t associated with attributes sysfs_types and file_type libsepol.check_segregate_attributes: segregate_attributes violated by type proc_xen_t associated with attributes file_type and proc_type libsepol.check_segregate_attributes: segregate_attributes violated by type svirt_image_t associated with attributes device_node and file_type libsepol.check_segregate_attributes: segregate_attributes violated by type virt_image_t associated with attributes device_node and file_type libsepol.check_segregate_attributes: segregate_attributes violated by type container_file_t associated with attributes device_node and file_type libsepol.check_assertions: 20 segregate attribute failures occurred Closes: SELinuxProject#42 Signed-off-by: Christian Göttsche <cgzones@googlemail.com>
diff --git a/libsepol/include/sepol/policydb/policydb.h b/libsepol/include/sepol/policydb/policydb.h
@@ -192,6 +192,16 @@ typedef struct type_datum {
 	uint32_t bounds;	/* bounds type, if exist */
 } type_datum_t;
 
+/* Mutual exclusive attributes */
+typedef struct segregate_attribute {
+	ebitmap_t attrs;	/* mutual exclusive attributes */
+	unsigned long line;	/* line number from policy.conf where this rule originated  */
+	/* source file name and line number (e.g. .te file) */
+	char *source_filename;
+	unsigned long source_line;
+	struct segregate_attribute *next;
+} segregate_attribute_t;
+
 /*
  * Properties of type_datum
  * available on the policy version >= (MOD_)POLICYDB_VERSION_BOUNDARY
@@ -605,6 +615,9 @@ typedef struct policydb {
 	   bitmaps.  Someday the 0 bit may be used for global permissive */
 	ebitmap_t permissive_map;
 
+	/* mutual exclusive attributes (not preserved in kernel policy) */
+	segregate_attribute_t *segregate_attributes;
+
 	unsigned policyvers;
 
 	unsigned handle_unknown;
@@ -696,6 +709,8 @@ extern void level_datum_init(level_datum_t * x);
 extern void level_datum_destroy(level_datum_t * x);
 extern void cat_datum_init(cat_datum_t * x);
 extern void cat_datum_destroy(cat_datum_t * x);
+extern void segregate_attribute_init(segregate_attribute_t * x);
+extern void segregate_attribute_destroy(segregate_attribute_t * x);
 extern int check_assertion(policydb_t *p, avrule_t *avrule);
 extern int check_assertions(sepol_handle_t * handle,
 			    policydb_t * p, avrule_t * avrules);
@@ -783,9 +798,10 @@ extern int policydb_set_target_platform(policydb_t *p, int platform);
 #define MOD_POLICYDB_VERSION_INFINIBAND		19
 #define MOD_POLICYDB_VERSION_GLBLUB		20
 #define MOD_POLICYDB_VERSION_SELF_TYPETRANS	21
+#define MOD_POLICYDB_VERSION_SEGREGATEATTRIBUTE	22
 
 #define MOD_POLICYDB_VERSION_MIN MOD_POLICYDB_VERSION_BASE
-#define MOD_POLICYDB_VERSION_MAX MOD_POLICYDB_VERSION_SELF_TYPETRANS
+#define MOD_POLICYDB_VERSION_MAX MOD_POLICYDB_VERSION_SEGREGATEATTRIBUTE
 
 #define POLICYDB_CONFIG_MLS    1
 
diff --git a/libsepol/src/assertion.c b/libsepol/src/assertion.c
@@ -36,7 +36,7 @@ struct avtab_match_args {
 	unsigned long errors;
 };
 
-static const char* policy_name(policydb_t *p) {
+static const char* policy_name(const policydb_t *p) {
 	const char *policy_file = "policy.conf";
 	if (p->name) {
 		policy_file = p->name;
@@ -535,6 +535,53 @@ int check_assertion(policydb_t *p, avrule_t *avrule)
 	return rc;
 }
 
+static int check_segregate_attributes(sepol_handle_t *handle, const policydb_t *p)
+{
+	int errors = 0;
+	const segregate_attribute_t *sattr;
+
+	for (sattr = p->segregate_attributes; sattr; sattr = sattr->next) {
+		ebitmap_node_t *first_node;
+		unsigned int first_bit;
+
+		ebitmap_for_each_positive_bit(&sattr->attrs, first_node, first_bit) {
+			ebitmap_node_t *second_node;
+			unsigned int second_bit;
+
+			ebitmap_for_each_positive_bit_starting(&sattr->attrs, first_node, first_bit, second_node, second_bit) {
+				ebitmap_t attr_union;
+				ebitmap_node_t *type_node;
+				unsigned int type_bit;
+
+				if (ebitmap_and(&attr_union, &p->attr_type_map[first_bit], &p->attr_type_map[second_bit]))
+					return -1;
+
+				ebitmap_for_each_positive_bit(&attr_union, type_node, type_bit) {
+					if (sattr->source_filename)
+						ERR(handle, "segregate_attributes on line %lu of %s (or line %lu of %s) violated by "
+							"type %s associated with attributes %s and %s",
+							sattr->source_line, sattr->source_filename, sattr->line, policy_name(p),
+							p->p_type_val_to_name[type_bit], p->p_type_val_to_name[first_bit], p->p_type_val_to_name[second_bit]);
+					else if (sattr->line)
+						ERR(handle, "segregate_attributes on line %lu of %s violated by "
+							"type %s associated with attributes %s and %s",
+							sattr->line, policy_name(p),
+							p->p_type_val_to_name[type_bit], p->p_type_val_to_name[first_bit], p->p_type_val_to_name[second_bit]);
+					else
+						ERR(handle, "segregate_attributes violated by "
+							"type %s associated with attributes %s and %s",
+							p->p_type_val_to_name[type_bit], p->p_type_val_to_name[first_bit], p->p_type_val_to_name[second_bit]);
+					errors++;
+				}
+
+				ebitmap_destroy(&attr_union);
+			}
+		}
+	}
+
+	return errors;
+}
+
 int check_assertions(sepol_handle_t * handle, policydb_t * p,
 		     avrule_t * avrules)
 {
@@ -570,5 +617,15 @@ int check_assertions(sepol_handle_t * handle, policydb_t * p,
 	if (errors)
 		ERR(handle, "%lu neverallow failures occurred", errors);
 
+	rc = check_segregate_attributes(handle, p);
+	if (rc < 0) {
+		ERR(handle, "Error occurred while checking segregate attributes");
+		return -1;
+	}
+	if (rc) {
+		ERR(handle, "%d segregate attribute failures occurred", rc);
+		errors += rc;
+	}
+
 	return errors ? -1 : 0;
 }
diff --git a/libsepol/src/expand.c b/libsepol/src/expand.c
@@ -56,7 +56,7 @@ static void expand_state_init(expand_state_t * state)
 	memset(state, 0, sizeof(expand_state_t));
 }
 
-static int map_ebitmap(ebitmap_t * src, ebitmap_t * dst, uint32_t * map)
+static int map_ebitmap(const ebitmap_t * src, ebitmap_t * dst, const uint32_t * map)
 {
 	unsigned int i;
 	ebitmap_node_t *tnode;
@@ -2341,6 +2341,56 @@ static int genfs_copy(expand_state_t * state)
 	return 0;
 }
 
+static int segregate_attribute_copy(expand_state_t *state)
+{
+	const segregate_attribute_t *old;
+	segregate_attribute_t *list = NULL;
+
+	for (old = state->base->segregate_attributes; old; old = old->next) {
+		segregate_attribute_t *new;
+
+		new = calloc(1, sizeof(segregate_attribute_t));
+		if (!new) {
+			ERR(state->handle, "Out of memory!");
+			return -1;
+		}
+
+		new->next = NULL;
+		new->line = old->line;
+		new->source_line = old->source_line;
+		if (old->source_filename) {
+			new->source_filename = strdup(old->source_filename);
+			if (!new->source_filename) {
+				ERR(state->handle, "Out of memory!");
+				free(new);
+				return -1;
+			}
+		}
+
+		if (map_ebitmap(&old->attrs, &new->attrs, state->typemap)) {
+			ERR(state->handle, "out of memory");
+			ebitmap_destroy(&new->attrs);
+			free(new->source_filename);
+			free(new);
+			return -1;
+		}
+
+		if (list)
+			list->next = new;
+		else {
+			if (state->out->segregate_attributes) {
+				segregate_attribute_t *s;
+				for (s = state->out->segregate_attributes; s->next; s = s->next) {}
+				s->next = new;
+			} else
+				state->out->segregate_attributes = new;
+		}
+		list = new;
+	}
+
+	return 0;
+}
+
 static int type_attr_map(hashtab_key_t key
 			 __attribute__ ((unused)), hashtab_datum_t datum,
 			 void *ptr)
@@ -3173,6 +3223,10 @@ int expand_module(sepol_handle_t * handle,
 	if (genfs_copy(&state))
 		goto cleanup;
 
+	/* copy segregate attributes */
+	if (segregate_attribute_copy(&state))
+		goto cleanup;
+
 	/* Build the type<->attribute maps and remove attributes. */
 	state.out->attr_type_map = calloc(state.out->p_types.nprim,
 					  sizeof(ebitmap_t));
diff --git a/libsepol/src/link.c b/libsepol/src/link.c
@@ -1857,6 +1857,58 @@ static int scope_copy_callback(hashtab_key_t key, hashtab_datum_t datum,
 	return -1;
 }
 
+static int copy_segregate_attributes(link_state_t * state, const policy_module_t *module)
+{
+	const segregate_attribute_t *src_sattr;
+	segregate_attribute_t *list = NULL;
+
+	for (src_sattr = module->policy->segregate_attributes; src_sattr; src_sattr = src_sattr->next) {
+		segregate_attribute_t *new_sattr;
+
+		new_sattr = calloc(1, sizeof(segregate_attribute_t));
+		if (!new_sattr) {
+			ERR(state->handle, "Out of memory!");
+			return -1;
+		}
+
+		ebitmap_init(&new_sattr->attrs);
+		if (ebitmap_convert(&src_sattr->attrs, &new_sattr->attrs, module->map[SYM_TYPES])) {
+			ebitmap_destroy(&new_sattr->attrs);
+			free(new_sattr);
+			ERR(state->handle, "Out of memory!");
+			return -1;
+		}
+
+		new_sattr->line = src_sattr->line;
+
+		if (src_sattr->source_filename) {
+			new_sattr->source_filename = strdup(src_sattr->source_filename);
+			if (!new_sattr->source_filename) {
+				ebitmap_destroy(&new_sattr->attrs);
+				free(new_sattr);
+				ERR(state->handle, "Out of memory!");
+				return -1;
+			}
+		}
+
+		new_sattr->source_line = src_sattr->source_line;
+
+		if (list)
+			list->next = new_sattr;
+		else {
+			if (state->base->segregate_attributes) {
+				segregate_attribute_t *s;
+				for (s = state->base->segregate_attributes; s->next; s = s->next) {}
+				s->next = new_sattr;
+			} else
+				state->base->segregate_attributes = new_sattr;
+		}
+		list = new_sattr;
+	}
+
+	return 0;
+}
+
 /* Copy a module over to a base, remapping all values within.  After
  * all identifiers and rules are done, copy the scoping information.
  * This is when it checks for duplicate declarations. */
@@ -1891,6 +1943,11 @@ static int copy_module(link_state_t * state, policy_module_t * module)
 		}
 	}
 
+	ret = copy_segregate_attributes(state, module);
+	if (ret) {
+		return ret;
+	}
+
 	return 0;
 }
 
diff --git a/libsepol/src/policydb.c b/libsepol/src/policydb.c
@@ -334,6 +334,13 @@ static const struct policydb_compat_info policydb_compat[] = {
 	 .ocon_num = OCON_IBENDPORT + 1,
 	 .target_platform = SEPOL_TARGET_SELINUX,
 	},
+	{
+	 .type = POLICY_BASE,
+	 .version = MOD_POLICYDB_VERSION_SEGREGATEATTRIBUTE,
+	 .sym_num = SYM_NUM,
+	 .ocon_num = OCON_IBENDPORT + 1,
+	 .target_platform = SEPOL_TARGET_SELINUX,
+	},
 	{
 	 .type = POLICY_MOD,
 	 .version = MOD_POLICYDB_VERSION_BASE,
@@ -460,6 +467,13 @@ static const struct policydb_compat_info policydb_compat[] = {
 	 .ocon_num = 0,
 	 .target_platform = SEPOL_TARGET_SELINUX,
 	},
+	{
+	 .type = POLICY_MOD,
+	 .version = MOD_POLICYDB_VERSION_SEGREGATEATTRIBUTE,
+	 .sym_num = SYM_NUM,
+	 .ocon_num = 0,
+	 .target_platform = SEPOL_TARGET_SELINUX,
+	},
 };
 
 #if 0
@@ -760,6 +774,21 @@ void avrule_list_destroy(avrule_t * x)
 	}
 }
 
+void segregate_attribute_init(segregate_attribute_t * x)
+{
+	memset(x, 0, sizeof(segregate_attribute_t));
+	ebitmap_init(&x->attrs);
+}
+
+
+void segregate_attribute_destroy(segregate_attribute_t * x)
+{
+	if (!x)
+		return;
+	ebitmap_destroy(&x->attrs);
+	free(x->source_filename);
+}
+
 /* 
  * Initialize the role table by implicitly adding role 'object_r'.  If
  * the policy is a module, set object_r's scope to be SCOPE_REQ,
@@ -1492,6 +1521,7 @@ void policydb_destroy(policydb_t * p)
 	unsigned int i;
 	role_allow_t *ra, *lra = NULL;
 	role_trans_t *tr, *ltr = NULL;
+	segregate_attribute_t *sattr, *sattr_next;
 
 	if (!p)
 		return;
@@ -1585,6 +1615,12 @@ void policydb_destroy(policydb_t * p)
 		free(p->attr_type_map);
 	}
 
+	for (sattr = p->segregate_attributes; sattr; sattr = sattr_next) {
+		sattr_next = sattr->next;
+		segregate_attribute_destroy(sattr);
+		free(sattr);
+	}
+
 	return;
 }
 
@@ -4174,6 +4210,39 @@ static int scope_read(policydb_t * p, int symnum, struct policy_file *fp)
 	return -1;
 }
 
+static int segregate_attributes_read(policydb_t * p, struct policy_file *fp)
+{
+	segregate_attribute_t *list = NULL;
+	uint32_t buf, nel, i;
+	int rc;
+
+	rc = next_entry(&buf, fp, sizeof(uint32_t));
+	if (rc < 0)
+		return -1;
+	nel = le32_to_cpu(buf);
+	for (i = 0; i < nel; i++) {
+		segregate_attribute_t *sattr;
+
+		sattr = calloc(1, sizeof(segregate_attribute_t));
+		if (!sattr)
+			return -1;
+
+		if (ebitmap_read(&sattr->attrs, fp) < 0) {
+			ebitmap_destroy(&sattr->attrs);
+			free(sattr);
+			return -1;
+		}
+
+		if (list)
+			list->next = sattr;
+		else
+			p->segregate_attributes = sattr;
+		list = sattr;
+	}
+
+	return 0;
+}
+
 static sepol_security_class_t policydb_string_to_security_class(
 	struct policydb *policydb,
 	const char *class_name)
@@ -4570,6 +4639,12 @@ int policydb_read(policydb_t * p, struct policy_file *fp, unsigned verbose)
 		}
 	}
 
+	if (p->policyvers >= MOD_POLICYDB_VERSION_SEGREGATEATTRIBUTE &&
+	    p->policy_type != POLICY_KERN) {
+		if (segregate_attributes_read(p, fp))
+			return POLICYDB_ERROR;
+	}
+
 	if (validate_policydb(fp->handle, p))
 		goto bad;
 
diff --git a/libsepol/src/policydb_validate.c b/libsepol/src/policydb_validate.c
diff --git a/libsepol/src/write.c b/libsepol/src/write.c
