SELinux: policy selectable handling of unknown classes and perms

Allow policy to select, in much the same way as it selects MLS support, how
the kernel should handle access decisions which contain either unknown
classes or unknown permissions in known classes.  The three choices for the
policy flags are

0 - Deny unknown security access. (default)
2 - reject loading policy if it does not contain all definitions
4 - allow unknown security access

The policy's choice is exported through 2 booleans in
selinuxfs.  /selinux/deny_unknown and /selinux/reject_unknown.

Signed-off-by: Eric Paris <eparis@redhat.com>
Acked-by: Stephen Smalley <sds@tycho.nsa.gov>
Signed-off-by: James Morris <jmorris@namei.org>

1 files changed, 26 insertions, 0 deletions

diff --git a/security/selinux/selinuxfs.c b/security/selinux/selinuxfs.c
index c9e92daedee2..f5f3e6da5da7 100644
--- a/security/selinux/selinuxfs.c
+++ b/security/selinux/selinuxfs.c
@@ -103,6 +103,8 @@ enum sel_inos {
         SEL_MEMBER,     /* compute polyinstantiation membership decision */
         SEL_CHECKREQPROT, /* check requested protection, not kernel-applied one */
         SEL_COMPAT_NET, /* whether to use old compat network packet controls */
+        SEL_REJECT_UNKNOWN, /* export unknown reject handling to userspace */
+        SEL_DENY_UNKNOWN, /* export unknown deny handling to userspace */
         SEL_INO_NEXT,   /* The next inode number to use */
 };
 
@@ -177,6 +179,23 @@ static const struct file_operations sel_enforce_ops = {
         .write          = sel_write_enforce,
 };
 
+static ssize_t sel_read_handle_unknown(struct file *filp, char __user *buf,
+                                        size_t count, loff_t *ppos)
+{
+        char tmpbuf[TMPBUFLEN];
+        ssize_t length;
+        ino_t ino = filp->f_path.dentry->d_inode->i_ino;
+        int handle_unknown = (ino == SEL_REJECT_UNKNOWN) ?
+                security_get_reject_unknown() : !security_get_allow_unknown();
+
+        length = scnprintf(tmpbuf, TMPBUFLEN, "%d", handle_unknown);
+        return simple_read_from_buffer(buf, count, ppos, tmpbuf, length);
+}
+
+static const struct file_operations sel_handle_unknown_ops = {
+        .read           = sel_read_handle_unknown,
+};
+
 #ifdef CONFIG_SECURITY_SELINUX_DISABLE
 static ssize_t sel_write_disable(struct file * file, const char __user * buf,
                                  size_t count, loff_t *ppos)
@@ -309,6 +328,11 @@ static ssize_t sel_write_load(struct file * file, const char __user * buf,
                 length = count;
 
 out1:
+
+        printk(KERN_INFO "SELinux: policy loaded with handle_unknown=%s\n",
+               (security_get_reject_unknown() ? "reject" :
+                (security_get_allow_unknown() ? "allow" : "deny")));
+
         audit_log(current->audit_context, GFP_KERNEL, AUDIT_MAC_POLICY_LOAD,
                 "policy loaded auid=%u",
                 audit_get_loginuid(current->audit_context));
@@ -1575,6 +1599,8 @@ static int sel_fill_super(struct super_block * sb, void * data, int silent)
                 [SEL_MEMBER] = {"member", &transaction_ops, S_IRUGO|S_IWUGO},
                 [SEL_CHECKREQPROT] = {"checkreqprot", &sel_checkreqprot_ops, S_IRUGO|S_IWUSR},
                 [SEL_COMPAT_NET] = {"compat_net", &sel_compat_net_ops, S_IRUGO|S_IWUSR},
+                [SEL_REJECT_UNKNOWN] = {"reject_unknown", &sel_handle_unknown_ops, S_IRUGO},
+                [SEL_DENY_UNKNOWN] = {"deny_unknown", &sel_handle_unknown_ops, S_IRUGO},
                 /* last one */ {""}
         };
         ret = simple_fill_super(sb, SELINUX_MAGIC, selinux_files);