apparmor: revalidate files during exec
Instead of running file revalidation lazily when read/write are called
copy selinux and revalidate the file table on exec. This avoids
extra mediation overhead in read/write and also prevents file handles
being passed through to a grand child unchecked.
Signed-off-by: John Johansen <john.johansen@canonical.com>
diff --git a/security/apparmor/file.c b/security/apparmor/file.c
index 2e128c2..bf50879 100644
--- a/security/apparmor/file.c
+++ b/security/apparmor/file.c
@@ -12,8 +12,13 @@
* License.
*/
+#include <linux/tty.h>
+#include <linux/fdtable.h>
+#include <linux/file.h>
+
#include "include/apparmor.h"
#include "include/audit.h"
+#include "include/context.h"
#include "include/file.h"
#include "include/match.h"
#include "include/path.h"
@@ -445,3 +450,70 @@ int aa_file_perm(const char *op, struct aa_profile *profile, struct file *file,
return aa_path_perm(op, profile, &file->f_path, PATH_DELEGATE_DELETED,
request, &cond);
}
+
+static void revalidate_tty(struct aa_profile *profile)
+{
+ struct tty_struct *tty;
+ int drop_tty = 0;
+
+ tty = get_current_tty();
+ if (!tty)
+ return;
+
+ spin_lock(&tty->files_lock);
+ if (!list_empty(&tty->tty_files)) {
+ struct tty_file_private *file_priv;
+ struct file *file;
+ /* TODO: Revalidate access to controlling tty. */
+ file_priv = list_first_entry(&tty->tty_files,
+ struct tty_file_private, list);
+ file = file_priv->file;
+
+ if (aa_file_perm(OP_INHERIT, profile, file,
+ MAY_READ | MAY_WRITE))
+ drop_tty = 1;
+ }
+ spin_unlock(&tty->files_lock);
+ tty_kref_put(tty);
+
+ if (drop_tty)
+ no_tty();
+}
+
+static int match_file(const void *p, struct file *file, unsigned int fd)
+{
+ struct aa_profile *profile = (struct aa_profile *)p;
+
+ if (aa_file_perm(OP_INHERIT, profile, file,
+ aa_map_file_to_perms(file)))
+ return fd + 1;
+ return 0;
+}
+
+
+/* based on selinux's flush_unauthorized_files */
+void aa_inherit_files(const struct cred *cred, struct files_struct *files)
+{
+ struct aa_profile *profile = aa_get_newest_cred_profile(cred);
+ struct file *devnull = NULL;
+ unsigned int n;
+
+ revalidate_tty(profile);
+
+ /* Revalidate access to inherited open files. */
+ n = iterate_fd(files, 0, match_file, profile);
+ if (!n) /* none found? */
+ goto out;
+
+ devnull = dentry_open(&aa_null, O_RDWR, cred);
+ if (IS_ERR(devnull))
+ devnull = NULL;
+ /* replace all the matching ones with this */
+ do {
+ replace_fd(n - 1, devnull, 0);
+ } while ((n = iterate_fd(files, n, match_file, profile)) != 0);
+ if (devnull)
+ fput(devnull);
+out:
+ aa_put_profile(profile);
+}