linux/security/keys/permission.c
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   1/* permission.c: key permission determination
   2 *
   3 * Copyright (C) 2005 Red Hat, Inc. All Rights Reserved.
   4 * Written by David Howells (dhowells@redhat.com)
   5 *
   6 * This program is free software; you can redistribute it and/or
   7 * modify it under the terms of the GNU General Public License
   8 * as published by the Free Software Foundation; either version
   9 * 2 of the License, or (at your option) any later version.
  10 */
  11
  12#include <linux/module.h>
  13#include <linux/security.h>
  14#include "internal.h"
  15
  16/*****************************************************************************/
  17/*
  18 * check to see whether permission is granted to use a key in the desired way,
  19 * but permit the security modules to override
  20 */
  21int key_task_permission(const key_ref_t key_ref,
  22                        struct task_struct *context,
  23                        key_perm_t perm)
  24{
  25        struct key *key;
  26        key_perm_t kperm;
  27        int ret;
  28
  29        key = key_ref_to_ptr(key_ref);
  30
  31        /* use the second 8-bits of permissions for keys the caller owns */
  32        if (key->uid == context->fsuid) {
  33                kperm = key->perm >> 16;
  34                goto use_these_perms;
  35        }
  36
  37        /* use the third 8-bits of permissions for keys the caller has a group
  38         * membership in common with */
  39        if (key->gid != -1 && key->perm & KEY_GRP_ALL) {
  40                if (key->gid == context->fsgid) {
  41                        kperm = key->perm >> 8;
  42                        goto use_these_perms;
  43                }
  44
  45                task_lock(context);
  46                ret = groups_search(context->group_info, key->gid);
  47                task_unlock(context);
  48
  49                if (ret) {
  50                        kperm = key->perm >> 8;
  51                        goto use_these_perms;
  52                }
  53        }
  54
  55        /* otherwise use the least-significant 8-bits */
  56        kperm = key->perm;
  57
  58use_these_perms:
  59        /* use the top 8-bits of permissions for keys the caller possesses
  60         * - possessor permissions are additive with other permissions
  61         */
  62        if (is_key_possessed(key_ref))
  63                kperm |= key->perm >> 24;
  64
  65        kperm = kperm & perm & KEY_ALL;
  66
  67        if (kperm != perm)
  68                return -EACCES;
  69
  70        /* let LSM be the final arbiter */
  71        return security_key_permission(key_ref, context, perm);
  72
  73} /* end key_task_permission() */
  74
  75EXPORT_SYMBOL(key_task_permission);
  76
  77/*****************************************************************************/
  78/*
  79 * validate a key
  80 */
  81int key_validate(struct key *key)
  82{
  83        struct timespec now;
  84        int ret = 0;
  85
  86        if (key) {
  87                /* check it's still accessible */
  88                ret = -EKEYREVOKED;
  89                if (test_bit(KEY_FLAG_REVOKED, &key->flags) ||
  90                    test_bit(KEY_FLAG_DEAD, &key->flags))
  91                        goto error;
  92
  93                /* check it hasn't expired */
  94                ret = 0;
  95                if (key->expiry) {
  96                        now = current_kernel_time();
  97                        if (now.tv_sec >= key->expiry)
  98                                ret = -EKEYEXPIRED;
  99                }
 100        }
 101
 102 error:
 103        return ret;
 104
 105} /* end key_validate() */
 106
 107EXPORT_SYMBOL(key_validate);
 108