1*4882a593Smuzhiyun // SPDX-License-Identifier: GPL-2.0
2*4882a593Smuzhiyun #define pr_fmt(fmt) "TPM-PARSER: "fmt
3*4882a593Smuzhiyun #include <linux/module.h>
4*4882a593Smuzhiyun #include <linux/kernel.h>
5*4882a593Smuzhiyun #include <linux/export.h>
6*4882a593Smuzhiyun #include <linux/slab.h>
7*4882a593Smuzhiyun #include <linux/err.h>
8*4882a593Smuzhiyun #include <keys/asymmetric-subtype.h>
9*4882a593Smuzhiyun #include <keys/asymmetric-parser.h>
10*4882a593Smuzhiyun #include <crypto/asym_tpm_subtype.h>
11*4882a593Smuzhiyun #include "tpm.asn1.h"
12*4882a593Smuzhiyun
13*4882a593Smuzhiyun struct tpm_parse_context {
14*4882a593Smuzhiyun const void *blob;
15*4882a593Smuzhiyun u32 blob_len;
16*4882a593Smuzhiyun };
17*4882a593Smuzhiyun
18*4882a593Smuzhiyun /*
19*4882a593Smuzhiyun * Note the key data of the ASN.1 blob.
20*4882a593Smuzhiyun */
tpm_note_key(void * context,size_t hdrlen,unsigned char tag,const void * value,size_t vlen)21*4882a593Smuzhiyun int tpm_note_key(void *context, size_t hdrlen,
22*4882a593Smuzhiyun unsigned char tag,
23*4882a593Smuzhiyun const void *value, size_t vlen)
24*4882a593Smuzhiyun {
25*4882a593Smuzhiyun struct tpm_parse_context *ctx = context;
26*4882a593Smuzhiyun
27*4882a593Smuzhiyun ctx->blob = value;
28*4882a593Smuzhiyun ctx->blob_len = vlen;
29*4882a593Smuzhiyun
30*4882a593Smuzhiyun return 0;
31*4882a593Smuzhiyun }
32*4882a593Smuzhiyun
33*4882a593Smuzhiyun /*
34*4882a593Smuzhiyun * Parse a TPM-encrypted private key blob.
35*4882a593Smuzhiyun */
tpm_parse(const void * data,size_t datalen)36*4882a593Smuzhiyun static struct tpm_key *tpm_parse(const void *data, size_t datalen)
37*4882a593Smuzhiyun {
38*4882a593Smuzhiyun struct tpm_parse_context ctx;
39*4882a593Smuzhiyun long ret;
40*4882a593Smuzhiyun
41*4882a593Smuzhiyun memset(&ctx, 0, sizeof(ctx));
42*4882a593Smuzhiyun
43*4882a593Smuzhiyun /* Attempt to decode the private key */
44*4882a593Smuzhiyun ret = asn1_ber_decoder(&tpm_decoder, &ctx, data, datalen);
45*4882a593Smuzhiyun if (ret < 0)
46*4882a593Smuzhiyun goto error;
47*4882a593Smuzhiyun
48*4882a593Smuzhiyun return tpm_key_create(ctx.blob, ctx.blob_len);
49*4882a593Smuzhiyun
50*4882a593Smuzhiyun error:
51*4882a593Smuzhiyun return ERR_PTR(ret);
52*4882a593Smuzhiyun }
53*4882a593Smuzhiyun /*
54*4882a593Smuzhiyun * Attempt to parse a data blob for a key as a TPM private key blob.
55*4882a593Smuzhiyun */
tpm_key_preparse(struct key_preparsed_payload * prep)56*4882a593Smuzhiyun static int tpm_key_preparse(struct key_preparsed_payload *prep)
57*4882a593Smuzhiyun {
58*4882a593Smuzhiyun struct tpm_key *tk;
59*4882a593Smuzhiyun
60*4882a593Smuzhiyun /*
61*4882a593Smuzhiyun * TPM 1.2 keys are max 2048 bits long, so assume the blob is no
62*4882a593Smuzhiyun * more than 4x that
63*4882a593Smuzhiyun */
64*4882a593Smuzhiyun if (prep->datalen > 256 * 4)
65*4882a593Smuzhiyun return -EMSGSIZE;
66*4882a593Smuzhiyun
67*4882a593Smuzhiyun tk = tpm_parse(prep->data, prep->datalen);
68*4882a593Smuzhiyun
69*4882a593Smuzhiyun if (IS_ERR(tk))
70*4882a593Smuzhiyun return PTR_ERR(tk);
71*4882a593Smuzhiyun
72*4882a593Smuzhiyun /* We're pinning the module by being linked against it */
73*4882a593Smuzhiyun __module_get(asym_tpm_subtype.owner);
74*4882a593Smuzhiyun prep->payload.data[asym_subtype] = &asym_tpm_subtype;
75*4882a593Smuzhiyun prep->payload.data[asym_key_ids] = NULL;
76*4882a593Smuzhiyun prep->payload.data[asym_crypto] = tk;
77*4882a593Smuzhiyun prep->payload.data[asym_auth] = NULL;
78*4882a593Smuzhiyun prep->quotalen = 100;
79*4882a593Smuzhiyun return 0;
80*4882a593Smuzhiyun }
81*4882a593Smuzhiyun
82*4882a593Smuzhiyun static struct asymmetric_key_parser tpm_key_parser = {
83*4882a593Smuzhiyun .owner = THIS_MODULE,
84*4882a593Smuzhiyun .name = "tpm_parser",
85*4882a593Smuzhiyun .parse = tpm_key_preparse,
86*4882a593Smuzhiyun };
87*4882a593Smuzhiyun
tpm_key_init(void)88*4882a593Smuzhiyun static int __init tpm_key_init(void)
89*4882a593Smuzhiyun {
90*4882a593Smuzhiyun return register_asymmetric_key_parser(&tpm_key_parser);
91*4882a593Smuzhiyun }
92*4882a593Smuzhiyun
tpm_key_exit(void)93*4882a593Smuzhiyun static void __exit tpm_key_exit(void)
94*4882a593Smuzhiyun {
95*4882a593Smuzhiyun unregister_asymmetric_key_parser(&tpm_key_parser);
96*4882a593Smuzhiyun }
97*4882a593Smuzhiyun
98*4882a593Smuzhiyun module_init(tpm_key_init);
99*4882a593Smuzhiyun module_exit(tpm_key_exit);
100*4882a593Smuzhiyun
101*4882a593Smuzhiyun MODULE_DESCRIPTION("TPM private key-blob parser");
102*4882a593Smuzhiyun MODULE_LICENSE("GPL v2");
103