76 lines
1.9 KiB
C
76 lines
1.9 KiB
C
/* permission.c: key permission determination
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*
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* Copyright (C) 2005 Red Hat, Inc. All Rights Reserved.
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* Written by David Howells (dhowells@redhat.com)
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*
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* This program is free software; you can redistribute it and/or
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* modify it under the terms of the GNU General Public License
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* as published by the Free Software Foundation; either version
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* 2 of the License, or (at your option) any later version.
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*/
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#include <linux/module.h>
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#include <linux/security.h>
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#include "internal.h"
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/*****************************************************************************/
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/*
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* check to see whether permission is granted to use a key in the desired way,
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* but permit the security modules to override
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*/
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int key_task_permission(const key_ref_t key_ref,
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struct task_struct *context,
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key_perm_t perm)
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{
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struct key *key;
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key_perm_t kperm;
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int ret;
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key = key_ref_to_ptr(key_ref);
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/* use the second 8-bits of permissions for keys the caller owns */
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if (key->uid == context->fsuid) {
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kperm = key->perm >> 16;
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goto use_these_perms;
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}
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/* use the third 8-bits of permissions for keys the caller has a group
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* membership in common with */
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if (key->gid != -1 && key->perm & KEY_GRP_ALL) {
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if (key->gid == context->fsgid) {
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kperm = key->perm >> 8;
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goto use_these_perms;
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}
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task_lock(context);
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ret = groups_search(context->group_info, key->gid);
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task_unlock(context);
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if (ret) {
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kperm = key->perm >> 8;
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goto use_these_perms;
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}
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}
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/* otherwise use the least-significant 8-bits */
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kperm = key->perm;
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use_these_perms:
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/* use the top 8-bits of permissions for keys the caller possesses
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* - possessor permissions are additive with other permissions
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*/
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if (is_key_possessed(key_ref))
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kperm |= key->perm >> 24;
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kperm = kperm & perm & KEY_ALL;
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if (kperm != perm)
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return -EACCES;
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/* let LSM be the final arbiter */
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return security_key_permission(key_ref, context, perm);
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} /* end key_task_permission() */
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EXPORT_SYMBOL(key_task_permission);
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