selinux: support wildcard network interface names

Add support for wildcard matching of network interface names.  This is
useful for auto-generated interfaces, for example podman creates network
interfaces for containers with the naming scheme podman0, podman1,
podman2, ...

To maintain backward compatibility guard this feature with a new policy
capability 'netif_wildcard'.

Netifcon definitions are compared against in the order given by the
policy, so userspace tools should sort them in a reasonable order.

Signed-off-by: Christian Göttsche <cgzones@googlemail.com>
Signed-off-by: Paul Moore <paul@paul-moore.com>

Author: cgzones

security/selinux/include/policycap.h

@@ -15,6 +15,7 @@ enum {
 	POLICYDB_CAP_IOCTL_SKIP_CLOEXEC,
 	POLICYDB_CAP_USERSPACE_INITIAL_CONTEXT,
 	POLICYDB_CAP_NETLINK_XPERM,
+	POLICYDB_CAP_NETIF_WILDCARD,
 	__POLICYDB_CAP_MAX
 };
 #define POLICYDB_CAP_MAX (__POLICYDB_CAP_MAX - 1)

security/selinux/include/policycap_names.h

@@ -18,6 +18,7 @@ const char *const selinux_policycap_names[__POLICYDB_CAP_MAX] = {
 	"ioctl_skip_cloexec",
 	"userspace_initial_context",
 	"netlink_xperm",
+	"netif_wildcard",
 };
 /* clang-format on */
 

security/selinux/include/security.h

@@ -202,6 +202,12 @@ static inline bool selinux_policycap_netlink_xperm(void)
 		selinux_state.policycap[POLICYDB_CAP_NETLINK_XPERM]);
 }
 
+static inline bool selinux_policycap_netif_wildcard(void)
+{
+	return READ_ONCE(
+		selinux_state.policycap[POLICYDB_CAP_NETIF_WILDCARD]);
+}
+
 struct selinux_policy_convert_data;
 
 struct selinux_load_state {
@@ -301,7 +307,7 @@ int security_ib_pkey_sid(u64 subnet_prefix, u16 pkey_num, u32 *out_sid);
 
 int security_ib_endport_sid(const char *dev_name, u8 port_num, u32 *out_sid);
 
-int security_netif_sid(char *name, u32 *if_sid);
+int security_netif_sid(const char *name, u32 *if_sid);
 
 int security_node_sid(u16 domain, void *addr, u32 addrlen, u32 *out_sid);
 

security/selinux/ss/services.c

@@ -46,6 +46,7 @@
 #include <linux/in.h>
 #include <linux/sched.h>
 #include <linux/audit.h>
+#include <linux/parser.h>
 #include <linux/vmalloc.h>
 #include <linux/lsm_hooks.h>
 #include <net/netlabel.h>
@@ -2572,19 +2573,22 @@ int security_ib_endport_sid(const char *dev_name, u8 port_num, u32 *out_sid)
  * @name: interface name
  * @if_sid: interface SID
  */
-int security_netif_sid(char *name, u32 *if_sid)
+int security_netif_sid(const char *name, u32 *if_sid)
 {
 	struct selinux_policy *policy;
 	struct policydb *policydb;
 	struct sidtab *sidtab;
 	int rc;
 	struct ocontext *c;
+	bool wildcard_support;
 
 	if (!selinux_initialized()) {
 		*if_sid = SECINITSID_NETIF;
 		return 0;
 	}
 
+	wildcard_support = selinux_policycap_netif_wildcard();
+
 retry:
 	rc = 0;
 	rcu_read_lock();
@@ -2594,8 +2598,14 @@ int security_netif_sid(char *name, u32 *if_sid)
 
 	c = policydb->ocontexts[OCON_NETIF];
 	while (c) {
-		if (strcmp(name, c->u.name) == 0)
-			break;
+		if (wildcard_support) {
+			if (match_wildcard(c->u.name, name))
+				break;
+		} else {
+			if (strcmp(c->u.name, name) == 0)
+				break;
+		}
+
 		c = c->next;
 	}