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// SPDX-License-Identifier: GPL-2.0
#define pr_fmt(fmt) "TPM-PARSER: "fmt
#include <linux/module.h>
#include <linux/kernel.h>
#include <linux/export.h>
#include <linux/slab.h>
#include <linux/err.h>
#include <keys/asymmetric-subtype.h>
#include <keys/asymmetric-parser.h>
#include <crypto/asym_tpm_subtype.h>
#include "tpm.asn1.h"
struct tpm_parse_context {
const void *blob;
u32 blob_len;
};
/*
* Note the key data of the ASN.1 blob.
*/
int tpm_note_key(void *context, size_t hdrlen,
unsigned char tag,
const void *value, size_t vlen)
{
struct tpm_parse_context *ctx = context;
ctx->blob = value;
ctx->blob_len = vlen;
return 0;
}
/*
* Parse a TPM-encrypted private key blob.
*/
static struct tpm_key *tpm_parse(const void *data, size_t datalen)
{
struct tpm_parse_context ctx;
long ret;
memset(&ctx, 0, sizeof(ctx));
/* Attempt to decode the private key */
ret = asn1_ber_decoder(&tpm_decoder, &ctx, data, datalen);
if (ret < 0)
goto error;
return tpm_key_create(ctx.blob, ctx.blob_len);
error:
return ERR_PTR(ret);
}
/*
* Attempt to parse a data blob for a key as a TPM private key blob.
*/
static int tpm_key_preparse(struct key_preparsed_payload *prep)
{
struct tpm_key *tk;
/*
* TPM 1.2 keys are max 2048 bits long, so assume the blob is no
* more than 4x that
*/
if (prep->datalen > 256 * 4)
return -EMSGSIZE;
tk = tpm_parse(prep->data, prep->datalen);
if (IS_ERR(tk))
return PTR_ERR(tk);
/* We're pinning the module by being linked against it */
__module_get(asym_tpm_subtype.owner);
prep->payload.data[asym_subtype] = &asym_tpm_subtype;
prep->payload.data[asym_key_ids] = NULL;
prep->payload.data[asym_crypto] = tk;
prep->payload.data[asym_auth] = NULL;
prep->quotalen = 100;
return 0;
}
static struct asymmetric_key_parser tpm_key_parser = {
.owner = THIS_MODULE,
.name = "tpm_parser",
.parse = tpm_key_preparse,
};
static int __init tpm_key_init(void)
{
return register_asymmetric_key_parser(&tpm_key_parser);
}
static void __exit tpm_key_exit(void)
{
unregister_asymmetric_key_parser(&tpm_key_parser);
}
module_init(tpm_key_init);
module_exit(tpm_key_exit);
MODULE_DESCRIPTION("TPM private key-blob parser");
MODULE_LICENSE("GPL v2");
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