1// SPDX-License-Identifier: GPL-2.0
2#define pr_fmt(fmt) "TPM-PARSER: "fmt
3#include <linux/module.h>
4#include <linux/kernel.h>
5#include <linux/export.h>
6#include <linux/slab.h>
7#include <linux/err.h>
8#include <keys/asymmetric-subtype.h>
9#include <keys/asymmetric-parser.h>
10#include <crypto/asym_tpm_subtype.h>
11#include "tpm.asn1.h"
12
13struct tpm_parse_context {
14	const void	*blob;
15	u32		blob_len;
16};
17
18/*
19 * Note the key data of the ASN.1 blob.
20 */
21int tpm_note_key(void *context, size_t hdrlen,
22		   unsigned char tag,
23		   const void *value, size_t vlen)
24{
25	struct tpm_parse_context *ctx = context;
26
27	ctx->blob = value;
28	ctx->blob_len = vlen;
29
30	return 0;
31}
32
33/*
34 * Parse a TPM-encrypted private key blob.
35 */
36static struct tpm_key *tpm_parse(const void *data, size_t datalen)
37{
38	struct tpm_parse_context ctx;
39	long ret;
40
41	memset(&ctx, 0, sizeof(ctx));
42
43	/* Attempt to decode the private key */
44	ret = asn1_ber_decoder(&tpm_decoder, &ctx, data, datalen);
45	if (ret < 0)
46		goto error;
47
48	return tpm_key_create(ctx.blob, ctx.blob_len);
49
50error:
51	return ERR_PTR(ret);
52}
53/*
54 * Attempt to parse a data blob for a key as a TPM private key blob.
55 */
56static int tpm_key_preparse(struct key_preparsed_payload *prep)
57{
58	struct tpm_key *tk;
59
60	/*
61	 * TPM 1.2 keys are max 2048 bits long, so assume the blob is no
62	 * more than 4x that
63	 */
64	if (prep->datalen > 256 * 4)
65		return -EMSGSIZE;
66
67	tk = tpm_parse(prep->data, prep->datalen);
68
69	if (IS_ERR(tk))
70		return PTR_ERR(tk);
71
72	/* We're pinning the module by being linked against it */
73	__module_get(asym_tpm_subtype.owner);
74	prep->payload.data[asym_subtype] = &asym_tpm_subtype;
75	prep->payload.data[asym_key_ids] = NULL;
76	prep->payload.data[asym_crypto] = tk;
77	prep->payload.data[asym_auth] = NULL;
78	prep->quotalen = 100;
79	return 0;
80}
81
82static struct asymmetric_key_parser tpm_key_parser = {
83	.owner	= THIS_MODULE,
84	.name	= "tpm_parser",
85	.parse	= tpm_key_preparse,
86};
87
88static int __init tpm_key_init(void)
89{
90	return register_asymmetric_key_parser(&tpm_key_parser);
91}
92
93static void __exit tpm_key_exit(void)
94{
95	unregister_asymmetric_key_parser(&tpm_key_parser);
96}
97
98module_init(tpm_key_init);
99module_exit(tpm_key_exit);
100
101MODULE_DESCRIPTION("TPM private key-blob parser");
102MODULE_LICENSE("GPL v2");
103