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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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