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d5e72745ca
For TPM based keys, the only standard seems to be described here: http://david.woodhou.se/draft-woodhouse-cert-best-practice.html#rfc.section.4.4 Quote from the relevant section: "Rather, a common form of storage for "wrapped" keys is to encode the binary TCPA_KEY structure in a single ASN.1 OCTET-STRING, and store the result in PEM format with the tag "-----BEGIN TSS KEY BLOB-----". " This patch implements the above behavior. It is assumed that the PEM encoding is stripped out by userspace and only the raw DER/BER format is provided. This is similar to how PKCS7, PKCS8 and X.509 keys are handled. Signed-off-by: Denis Kenzior <denkenz@gmail.com> Signed-off-by: David Howells <dhowells@redhat.com> Tested-by: Marcel Holtmann <marcel@holtmann.org> Reviewed-by: Marcel Holtmann <marcel@holtmann.org> Signed-off-by: James Morris <james.morris@microsoft.com>
103 lines
2.2 KiB
C
103 lines
2.2 KiB
C
// SPDX-License-Identifier: GPL-2.0
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#define pr_fmt(fmt) "TPM-PARSER: "fmt
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#include <linux/module.h>
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#include <linux/kernel.h>
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#include <linux/export.h>
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#include <linux/slab.h>
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#include <linux/err.h>
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#include <keys/asymmetric-subtype.h>
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#include <keys/asymmetric-parser.h>
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#include <crypto/asym_tpm_subtype.h>
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#include "tpm.asn1.h"
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struct tpm_parse_context {
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const void *blob;
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u32 blob_len;
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};
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/*
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* Note the key data of the ASN.1 blob.
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*/
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int tpm_note_key(void *context, size_t hdrlen,
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unsigned char tag,
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const void *value, size_t vlen)
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{
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struct tpm_parse_context *ctx = context;
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ctx->blob = value;
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ctx->blob_len = vlen;
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return 0;
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}
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/*
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* Parse a TPM-encrypted private key blob.
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*/
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static struct tpm_key *tpm_parse(const void *data, size_t datalen)
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{
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struct tpm_parse_context ctx;
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long ret;
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memset(&ctx, 0, sizeof(ctx));
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/* Attempt to decode the private key */
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ret = asn1_ber_decoder(&tpm_decoder, &ctx, data, datalen);
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if (ret < 0)
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goto error;
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return tpm_key_create(ctx.blob, ctx.blob_len);
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error:
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return ERR_PTR(ret);
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}
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/*
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* Attempt to parse a data blob for a key as a TPM private key blob.
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*/
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static int tpm_key_preparse(struct key_preparsed_payload *prep)
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{
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struct tpm_key *tk;
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/*
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* TPM 1.2 keys are max 2048 bits long, so assume the blob is no
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* more than 4x that
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*/
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if (prep->datalen > 256 * 4)
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return -EMSGSIZE;
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tk = tpm_parse(prep->data, prep->datalen);
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if (IS_ERR(tk))
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return PTR_ERR(tk);
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/* We're pinning the module by being linked against it */
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__module_get(asym_tpm_subtype.owner);
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prep->payload.data[asym_subtype] = &asym_tpm_subtype;
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prep->payload.data[asym_key_ids] = NULL;
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prep->payload.data[asym_crypto] = tk;
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prep->payload.data[asym_auth] = NULL;
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prep->quotalen = 100;
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return 0;
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}
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static struct asymmetric_key_parser tpm_key_parser = {
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.owner = THIS_MODULE,
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.name = "tpm_parser",
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.parse = tpm_key_preparse,
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};
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static int __init tpm_key_init(void)
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{
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return register_asymmetric_key_parser(&tpm_key_parser);
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}
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static void __exit tpm_key_exit(void)
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{
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unregister_asymmetric_key_parser(&tpm_key_parser);
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}
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module_init(tpm_key_init);
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module_exit(tpm_key_exit);
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MODULE_DESCRIPTION("TPM private key-blob parser");
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MODULE_LICENSE("GPL v2");
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