1 /* Key permission checking 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 * key_task_permission - Check a key can be used 18 * @key_ref: The key to check. 19 * @cred: The credentials to use. 20 * @perm: The permissions to check for. 21 * 22 * Check to see whether permission is granted to use a key in the desired way, 23 * but permit the security modules to override. 24 * 25 * The caller must hold either a ref on cred or must hold the RCU readlock. 26 * 27 * Returns 0 if successful, -EACCES if access is denied based on the 28 * permissions bits or the LSM check. 29 */ 30 int key_task_permission(const key_ref_t key_ref, const struct cred *cred, 31 key_perm_t perm) 32 { 33 struct key *key; 34 key_perm_t kperm; 35 int ret; 36 37 key = key_ref_to_ptr(key_ref); 38 39 if (key->user->user_ns != cred->user->user_ns) 40 goto use_other_perms; 41 42 /* use the second 8-bits of permissions for keys the caller owns */ 43 if (key->uid == cred->fsuid) { 44 kperm = key->perm >> 16; 45 goto use_these_perms; 46 } 47 48 /* use the third 8-bits of permissions for keys the caller has a group 49 * membership in common with */ 50 if (key->gid != -1 && key->perm & KEY_GRP_ALL) { 51 if (key->gid == cred->fsgid) { 52 kperm = key->perm >> 8; 53 goto use_these_perms; 54 } 55 56 ret = groups_search(cred->group_info, key->gid); 57 if (ret) { 58 kperm = key->perm >> 8; 59 goto use_these_perms; 60 } 61 } 62 63 use_other_perms: 64 65 /* otherwise use the least-significant 8-bits */ 66 kperm = key->perm; 67 68 use_these_perms: 69 70 /* use the top 8-bits of permissions for keys the caller possesses 71 * - possessor permissions are additive with other permissions 72 */ 73 if (is_key_possessed(key_ref)) 74 kperm |= key->perm >> 24; 75 76 kperm = kperm & perm & KEY_ALL; 77 78 if (kperm != perm) 79 return -EACCES; 80 81 /* let LSM be the final arbiter */ 82 return security_key_permission(key_ref, cred, perm); 83 } 84 EXPORT_SYMBOL(key_task_permission); 85 86 /** 87 * key_validate - Validate a key. 88 * @key: The key to be validated. 89 * 90 * Check that a key is valid, returning 0 if the key is okay, -ENOKEY if the 91 * key is invalidated, -EKEYREVOKED if the key's type has been removed or if 92 * the key has been revoked or -EKEYEXPIRED if the key has expired. 93 */ 94 int key_validate(const struct key *key) 95 { 96 unsigned long flags = key->flags; 97 98 if (flags & (1 << KEY_FLAG_INVALIDATED)) 99 return -ENOKEY; 100 101 /* check it's still accessible */ 102 if (flags & ((1 << KEY_FLAG_REVOKED) | 103 (1 << KEY_FLAG_DEAD))) 104 return -EKEYREVOKED; 105 106 /* check it hasn't expired */ 107 if (key->expiry) { 108 struct timespec now = current_kernel_time(); 109 if (now.tv_sec >= key->expiry) 110 return -EKEYEXPIRED; 111 } 112 113 return 0; 114 } 115 EXPORT_SYMBOL(key_validate); 116