2 files changed, 71 insertions, 0 deletions

diff --git a/security/keys/Makefile b/security/keys/Makefile
index c392d750b208..5145adfb6a05 100644
--- a/security/keys/Makefile
+++ b/security/keys/Makefile
@@ -6,6 +6,7 @@ obj-y := \
         key.o \
         keyring.o \
         keyctl.o \
+        permission.o \
         process_keys.o \
         request_key.o \
         request_key_auth.o \
diff --git a/security/keys/permission.c b/security/keys/permission.c
new file mode 100644
index 000000000000..1c3651670ce9
--- /dev/null
+++ b/security/keys/permission.c
@@ -0,0 +1,70 @@
+/* permission.c: key permission determination
+ *
+ * Copyright (C) 2005 Red Hat, Inc. All Rights Reserved.
+ * Written by David Howells (dhowells@redhat.com)
+ *
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU General Public License
+ * as published by the Free Software Foundation; either version
+ * 2 of the License, or (at your option) any later version.
+ */
+
+#include <linux/module.h>
+#include "internal.h"
+
+/*****************************************************************************/
+/*
+ * check to see whether permission is granted to use a key in the desired way,
+ * but permit the security modules to override
+ */
+int key_task_permission(const key_ref_t key_ref,
+                        struct task_struct *context,
+                        key_perm_t perm)
+{
+        struct key *key;
+        key_perm_t kperm;
+        int ret;
+
+        key = key_ref_to_ptr(key_ref);
+
+        /* use the top 8-bits of permissions for keys the caller possesses */
+        if (is_key_possessed(key_ref)) {
+                kperm = key->perm >> 24;
+                goto use_these_perms;
+        }
+
+        /* use the second 8-bits of permissions for keys the caller owns */
+        if (key->uid == context->fsuid) {
+                kperm = key->perm >> 16;
+                goto use_these_perms;
+        }
+
+        /* use the third 8-bits of permissions for keys the caller has a group
+         * membership in common with */
+        if (key->gid != -1 && key->perm & KEY_GRP_ALL) {
+                if (key->gid == context->fsgid) {
+                        kperm = key->perm >> 8;
+                        goto use_these_perms;
+                }
+
+                task_lock(context);
+                ret = groups_search(context->group_info, key->gid);
+                task_unlock(context);
+
+                if (ret) {
+                        kperm = key->perm >> 8;
+                        goto use_these_perms;
+                }
+        }
+
+        /* otherwise use the least-significant 8-bits */
+        kperm = key->perm;
+
+use_these_perms:
+        kperm = kperm & perm & KEY_ALL;
+
+        return kperm == perm;
+
+} /* end key_task_permission() */
+
+EXPORT_SYMBOL(key_task_permission);