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");