1// SPDX-License-Identifier: GPL-2.0-only
2/*
3 * Copyright (C) 2019 Microsoft Corporation.
4 *
5 * Author:  Jaskaran Singh Khurana <jaskarankhurana@linux.microsoft.com>
6 *
7 */
8#include <linux/device-mapper.h>
9#include <linux/verification.h>
10#include <keys/user-type.h>
11#include <linux/module.h>
12#include "dm-verity.h"
13#include "dm-verity-verify-sig.h"
14
15#define DM_VERITY_VERIFY_ERR(s) DM_VERITY_ROOT_HASH_VERIFICATION " " s
16
17static bool require_signatures;
18module_param(require_signatures, bool, 0444);
19MODULE_PARM_DESC(require_signatures,
20		"Verify the roothash of dm-verity hash tree");
21
22#define DM_VERITY_IS_SIG_FORCE_ENABLED() \
23	(require_signatures != false)
24
25bool verity_verify_is_sig_opt_arg(const char *arg_name)
26{
27	return (!strcasecmp(arg_name,
28			    DM_VERITY_ROOT_HASH_VERIFICATION_OPT_SIG_KEY));
29}
30
31static int verity_verify_get_sig_from_key(const char *key_desc,
32					struct dm_verity_sig_opts *sig_opts)
33{
34	struct key *key;
35	const struct user_key_payload *ukp;
36	int ret = 0;
37
38	key = request_key(&key_type_user,
39			key_desc, NULL);
40	if (IS_ERR(key))
41		return PTR_ERR(key);
42
43	down_read(&key->sem);
44
45	ukp = user_key_payload_locked(key);
46	if (!ukp) {
47		ret = -EKEYREVOKED;
48		goto end;
49	}
50
51	sig_opts->sig = kmalloc(ukp->datalen, GFP_KERNEL);
52	if (!sig_opts->sig) {
53		ret = -ENOMEM;
54		goto end;
55	}
56	sig_opts->sig_size = ukp->datalen;
57
58	memcpy(sig_opts->sig, ukp->data, sig_opts->sig_size);
59
60end:
61	up_read(&key->sem);
62	key_put(key);
63
64	return ret;
65}
66
67int verity_verify_sig_parse_opt_args(struct dm_arg_set *as,
68				     struct dm_verity *v,
69				     struct dm_verity_sig_opts *sig_opts,
70				     unsigned int *argc,
71				     const char *arg_name)
72{
73	struct dm_target *ti = v->ti;
74	int ret = 0;
75	const char *sig_key = NULL;
76
77	if (!*argc) {
78		ti->error = DM_VERITY_VERIFY_ERR("Signature key not specified");
79		return -EINVAL;
80	}
81
82	sig_key = dm_shift_arg(as);
83	(*argc)--;
84
85	ret = verity_verify_get_sig_from_key(sig_key, sig_opts);
86	if (ret < 0)
87		ti->error = DM_VERITY_VERIFY_ERR("Invalid key specified");
88
89	v->signature_key_desc = kstrdup(sig_key, GFP_KERNEL);
90	if (!v->signature_key_desc)
91		return -ENOMEM;
92
93	return ret;
94}
95
96/*
97 * verify_verify_roothash - Verify the root hash of the verity hash device
98 *			     using builtin trusted keys.
99 *
100 * @root_hash: For verity, the roothash/data to be verified.
101 * @root_hash_len: Size of the roothash/data to be verified.
102 * @sig_data: The trusted signature that verifies the roothash/data.
103 * @sig_len: Size of the signature.
104 *
105 */
106int verity_verify_root_hash(const void *root_hash, size_t root_hash_len,
107			    const void *sig_data, size_t sig_len)
108{
109	int ret;
110
111	if (!root_hash || root_hash_len == 0)
112		return -EINVAL;
113
114	if (!sig_data  || sig_len == 0) {
115		if (DM_VERITY_IS_SIG_FORCE_ENABLED())
116			return -ENOKEY;
117		else
118			return 0;
119	}
120
121	ret = verify_pkcs7_signature(root_hash, root_hash_len, sig_data,
122				sig_len,
123#ifdef CONFIG_DM_VERITY_VERIFY_ROOTHASH_SIG_SECONDARY_KEYRING
124				VERIFY_USE_SECONDARY_KEYRING,
125#else
126				NULL,
127#endif
128				VERIFYING_UNSPECIFIED_SIGNATURE, NULL, NULL);
129
130	return ret;
131}
132
133void verity_verify_sig_opts_cleanup(struct dm_verity_sig_opts *sig_opts)
134{
135	kfree(sig_opts->sig);
136	sig_opts->sig = NULL;
137	sig_opts->sig_size = 0;
138}
139