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 "internal.h" 14 15 /*****************************************************************************/ 16 /* 17 * check to see whether permission is granted to use a key in the desired way, 18 * but permit the security modules to override 19 */ 20 int key_task_permission(const key_ref_t key_ref, 21 struct task_struct *context, 22 key_perm_t perm) 23 { 24 struct key *key; 25 key_perm_t kperm; 26 int ret; 27 28 key = key_ref_to_ptr(key_ref); 29 30 /* use the second 8-bits of permissions for keys the caller owns */ 31 if (key->uid == context->fsuid) { 32 kperm = key->perm >> 16; 33 goto use_these_perms; 34 } 35 36 /* use the third 8-bits of permissions for keys the caller has a group 37 * membership in common with */ 38 if (key->gid != -1 && key->perm & KEY_GRP_ALL) { 39 if (key->gid == context->fsgid) { 40 kperm = key->perm >> 8; 41 goto use_these_perms; 42 } 43 44 task_lock(context); 45 ret = groups_search(context->group_info, key->gid); 46 task_unlock(context); 47 48 if (ret) { 49 kperm = key->perm >> 8; 50 goto use_these_perms; 51 } 52 } 53 54 /* otherwise use the least-significant 8-bits */ 55 kperm = key->perm; 56 57 use_these_perms: 58 /* use the top 8-bits of permissions for keys the caller possesses 59 * - possessor permissions are additive with other permissions 60 */ 61 if (is_key_possessed(key_ref)) 62 kperm |= key->perm >> 24; 63 64 kperm = kperm & perm & KEY_ALL; 65 66 return kperm == perm; 67 68 } /* end key_task_permission() */ 69 70 EXPORT_SYMBOL(key_task_permission); 71