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 unsigned 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 /* use the second 8-bits of permissions for keys the caller owns */ 40 if (uid_eq(key->uid, cred->fsuid)) { 41 kperm = key->perm >> 16; 42 goto use_these_perms; 43 } 44 45 /* use the third 8-bits of permissions for keys the caller has a group 46 * membership in common with */ 47 if (gid_valid(key->gid) && key->perm & KEY_GRP_ALL) { 48 if (gid_eq(key->gid, cred->fsgid)) { 49 kperm = key->perm >> 8; 50 goto use_these_perms; 51 } 52 53 ret = groups_search(cred->group_info, key->gid); 54 if (ret) { 55 kperm = key->perm >> 8; 56 goto use_these_perms; 57 } 58 } 59 60 /* otherwise use the least-significant 8-bits */ 61 kperm = key->perm; 62 63 use_these_perms: 64 65 /* use the top 8-bits of permissions for keys the caller possesses 66 * - possessor permissions are additive with other permissions 67 */ 68 if (is_key_possessed(key_ref)) 69 kperm |= key->perm >> 24; 70 71 kperm = kperm & perm & KEY_NEED_ALL; 72 73 if (kperm != perm) 74 return -EACCES; 75 76 /* let LSM be the final arbiter */ 77 return security_key_permission(key_ref, cred, perm); 78 } 79 EXPORT_SYMBOL(key_task_permission); 80 81 /** 82 * key_validate - Validate a key. 83 * @key: The key to be validated. 84 * 85 * Check that a key is valid, returning 0 if the key is okay, -ENOKEY if the 86 * key is invalidated, -EKEYREVOKED if the key's type has been removed or if 87 * the key has been revoked or -EKEYEXPIRED if the key has expired. 88 */ 89 int key_validate(const struct key *key) 90 { 91 unsigned long flags = READ_ONCE(key->flags); 92 time64_t expiry = READ_ONCE(key->expiry); 93 94 if (flags & (1 << KEY_FLAG_INVALIDATED)) 95 return -ENOKEY; 96 97 /* check it's still accessible */ 98 if (flags & ((1 << KEY_FLAG_REVOKED) | 99 (1 << KEY_FLAG_DEAD))) 100 return -EKEYREVOKED; 101 102 /* check it hasn't expired */ 103 if (expiry) { 104 if (ktime_get_real_seconds() >= expiry) 105 return -EKEYEXPIRED; 106 } 107 108 return 0; 109 } 110 EXPORT_SYMBOL(key_validate); 111