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_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, 57 make_kgid(current_user_ns(), key->gid)); 58 if (ret) { 59 kperm = key->perm >> 8; 60 goto use_these_perms; 61 } 62 } 63 64 use_other_perms: 65 66 /* otherwise use the least-significant 8-bits */ 67 kperm = key->perm; 68 69 use_these_perms: 70 71 /* use the top 8-bits of permissions for keys the caller possesses 72 * - possessor permissions are additive with other permissions 73 */ 74 if (is_key_possessed(key_ref)) 75 kperm |= key->perm >> 24; 76 77 kperm = kperm & perm & KEY_ALL; 78 79 if (kperm != perm) 80 return -EACCES; 81 82 /* let LSM be the final arbiter */ 83 return security_key_permission(key_ref, cred, perm); 84 } 85 EXPORT_SYMBOL(key_task_permission); 86 87 /** 88 * key_validate - Validate a key. 89 * @key: The key to be validated. 90 * 91 * Check that a key is valid, returning 0 if the key is okay, -ENOKEY if the 92 * key is invalidated, -EKEYREVOKED if the key's type has been removed or if 93 * the key has been revoked or -EKEYEXPIRED if the key has expired. 94 */ 95 int key_validate(const struct key *key) 96 { 97 unsigned long flags = key->flags; 98 99 if (flags & (1 << KEY_FLAG_INVALIDATED)) 100 return -ENOKEY; 101 102 /* check it's still accessible */ 103 if (flags & ((1 << KEY_FLAG_REVOKED) | 104 (1 << KEY_FLAG_DEAD))) 105 return -EKEYREVOKED; 106 107 /* check it hasn't expired */ 108 if (key->expiry) { 109 struct timespec now = current_kernel_time(); 110 if (now.tv_sec >= key->expiry) 111 return -EKEYEXPIRED; 112 } 113 114 return 0; 115 } 116 EXPORT_SYMBOL(key_validate); 117