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 * key_task_permission - Check a key can be used 19 * @key_ref: The key to check 20 * @cred: The credentials to use 21 * @perm: The permissions to check for 22 * 23 * Check to see whether permission is granted to use a key in the desired way, 24 * but permit the security modules to override. 25 * 26 * The caller must hold either a ref on cred or must hold the RCU readlock or a 27 * spinlock. 28 */ 29 int key_task_permission(const key_ref_t key_ref, const struct cred *cred, 30 key_perm_t perm) 31 { 32 struct key *key; 33 key_perm_t kperm; 34 int ret; 35 36 key = key_ref_to_ptr(key_ref); 37 38 /* use the second 8-bits of permissions for keys the caller owns */ 39 if (key->uid == cred->fsuid) { 40 kperm = key->perm >> 16; 41 goto use_these_perms; 42 } 43 44 /* use the third 8-bits of permissions for keys the caller has a group 45 * membership in common with */ 46 if (key->gid != -1 && key->perm & KEY_GRP_ALL) { 47 if (key->gid == cred->fsgid) { 48 kperm = key->perm >> 8; 49 goto use_these_perms; 50 } 51 52 ret = groups_search(cred->group_info, key->gid); 53 if (ret) { 54 kperm = key->perm >> 8; 55 goto use_these_perms; 56 } 57 } 58 59 /* otherwise use the least-significant 8-bits */ 60 kperm = key->perm; 61 62 use_these_perms: 63 64 /* use the top 8-bits of permissions for keys the caller possesses 65 * - possessor permissions are additive with other permissions 66 */ 67 if (is_key_possessed(key_ref)) 68 kperm |= key->perm >> 24; 69 70 kperm = kperm & perm & KEY_ALL; 71 72 if (kperm != perm) 73 return -EACCES; 74 75 /* let LSM be the final arbiter */ 76 return security_key_permission(key_ref, cred, perm); 77 78 } /* end key_task_permission() */ 79 80 EXPORT_SYMBOL(key_task_permission); 81 82 /*****************************************************************************/ 83 /* 84 * validate a key 85 */ 86 int key_validate(struct key *key) 87 { 88 struct timespec now; 89 int ret = 0; 90 91 if (key) { 92 /* check it's still accessible */ 93 ret = -EKEYREVOKED; 94 if (test_bit(KEY_FLAG_REVOKED, &key->flags) || 95 test_bit(KEY_FLAG_DEAD, &key->flags)) 96 goto error; 97 98 /* check it hasn't expired */ 99 ret = 0; 100 if (key->expiry) { 101 now = current_kernel_time(); 102 if (now.tv_sec >= key->expiry) 103 ret = -EKEYEXPIRED; 104 } 105 } 106 107 error: 108 return ret; 109 110 } /* end key_validate() */ 111 112 EXPORT_SYMBOL(key_validate); 113