| | 1 | // SPDX-License-Identifier: GPL-2.0-or-later |
| | 2 | /* Key permission checking |
| | 3 | * |
| | 4 | * Copyright (C) 2005 Red Hat, Inc. All Rights Reserved. |
| | 5 | * Written by David Howells (dhowells@redhat.com) |
| | 6 | */ |
| | 7 | |
| | 8 | #include <linux/export.h> |
| | 9 | #include <linux/security.h> |
| | 10 | #include "internal.h" |
| | 11 | |
| | 12 | /** |
| | 13 | * key_task_permission - Check a key can be used |
| | 14 | * @key_ref: The key to check. |
| | 15 | * @cred: The credentials to use. |
| | 16 | * @perm: The permissions to check for. |
| | 17 | * |
| | 18 | * Check to see whether permission is granted to use a key in the desired way, |
| | 19 | * but permit the security modules to override. |
| | 20 | * |
| | 21 | * The caller must hold either a ref on cred or must hold the RCU readlock. |
| | 22 | * |
| | 23 | * Returns 0 if successful, -EACCES if access is denied based on the |
| | 24 | * permissions bits or the LSM check. |
| | 25 | */ |
| | 26 | int key_task_permission(const key_ref_t key_ref, const struct cred *cred, |
| | 27 | unsigned perm) |
| | 28 | { |
| | 29 | struct key *key; |
| | 30 | key_perm_t kperm; |
| | 31 | int ret; |
| | 32 | |
| | 33 | key = key_ref_to_ptr(key_ref); |
| | 34 | |
| | 35 | /* use the second 8-bits of permissions for keys the caller owns */ |
| | 36 | if (uid_eq(key->uid, cred->fsuid)) { |
| | 37 | kperm = key->perm >> 16; |
| | 38 | goto use_these_perms; |
| | 39 | } |
| | 40 | |
| | 41 | /* use the third 8-bits of permissions for keys the caller has a group |
| | 42 | * membership in common with */ |
| | 43 | if (gid_valid(key->gid) && key->perm & KEY_GRP_ALL) { |
| | 44 | if (gid_eq(key->gid, cred->fsgid)) { |
| | 45 | kperm = key->perm >> 8; |
| | 46 | goto use_these_perms; |
| | 47 | } |
| | 48 | |
| | 49 | ret = groups_search(cred->group_info, key->gid); |
| | 50 | if (ret) { |
| | 51 | kperm = key->perm >> 8; |
| | 52 | goto use_these_perms; |
| | 53 | } |
| | 54 | } |
| | 55 | |
| | 56 | /* otherwise use the least-significant 8-bits */ |
| | 57 | kperm = key->perm; |
| | 58 | |
| | 59 | use_these_perms: |
| | 60 | |
| | 61 | /* use the top 8-bits of permissions for keys the caller possesses |
| | 62 | * - possessor permissions are additive with other permissions |
| | 63 | */ |
| | 64 | if (is_key_possessed(key_ref)) |
| | 65 | kperm |= key->perm >> 24; |
| | 66 | |
| | 67 | kperm = kperm & perm & KEY_NEED_ALL; |
| | 68 | |
| | 69 | if (kperm != perm) |
| | 70 | return -EACCES; |
| | 71 | |
| | 72 | /* let LSM be the final arbiter */ |
| | 73 | return security_key_permission(key_ref, cred, perm); |
| | 74 | } |
| | 75 | EXPORT_SYMBOL(key_task_permission); |
| | 76 | |
| | 77 | /** |
| | 78 | * key_validate - Validate a key. |
| | 79 | * @key: The key to be validated. |
| | 80 | * |
| | 81 | * Check that a key is valid, returning 0 if the key is okay, -ENOKEY if the |
| | 82 | * key is invalidated, -EKEYREVOKED if the key's type has been removed or if |
| | 83 | * the key has been revoked or -EKEYEXPIRED if the key has expired. |
| | 84 | */ |
| | 85 | int key_validate(const struct key *key) |
| | 86 | { |
| | 87 | unsigned long flags = READ_ONCE(key->flags); |
| | 88 | time64_t expiry = READ_ONCE(key->expiry); |
| | 89 | |
| | 90 | if (flags & (1 << KEY_FLAG_INVALIDATED)) |
| | 91 | return -ENOKEY; |
| | 92 | |
| | 93 | /* check it's still accessible */ |
| | 94 | if (flags & ((1 << KEY_FLAG_REVOKED) | |
| | 95 | (1 << KEY_FLAG_DEAD))) |
| | 96 | return -EKEYREVOKED; |
| | 97 | |
| | 98 | /* check it hasn't expired */ |
| | 99 | if (expiry) { |
| | 100 | if (ktime_get_real_seconds() >= expiry) |
| | 101 | return -EKEYEXPIRED; |
| | 102 | } |
| | 103 | |
| | 104 | return 0; |
| | 105 | } |
| | 106 | EXPORT_SYMBOL(key_validate); |
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