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Message-ID: <8a13796d-1274-4cb0-b5aa-08f366d95ed7@linux.ibm.com>
Date: Thu, 30 May 2024 21:10:30 -0400
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Subject: Re: [PATCH v7 4/5] keys: asymmetric: Add tpm2_key_rsa
To: Jarkko Sakkinen <jarkko@kernel.org>,
        Herbert Xu <herbert@gondor.apana.org.au>
Cc: linux-integrity@vger.kernel.org, keyrings@vger.kernel.org,
        Andreas.Fuchs@infineon.com, James Prestwood <prestwoj@gmail.com>,
        David Woodhouse <dwmw2@infradead.org>,
        Eric Biggers <ebiggers@kernel.org>,
        James Bottomley <James.Bottomley@hansenpartnership.com>,
        linux-crypto@vger.kernel.org,
        Lennart Poettering <lennart@poettering.net>,
        "David S. Miller" <davem@davemloft.net>,
        open list <linux-kernel@vger.kernel.org>,
        David Howells
 <dhowells@redhat.com>, Ard Biesheuvel <ardb@kernel.org>,
        Mario Limonciello <mario.limonciello@amd.com>
References: <20240528210823.28798-1-jarkko@kernel.org>
 <20240528210823.28798-5-jarkko@kernel.org>
Content-Language: en-US
From: Stefan Berger <stefanb@linux.ibm.com>
In-Reply-To: <20240528210823.28798-5-jarkko@kernel.org>
Content-Type: text/plain; charset=UTF-8; format=flowed
Content-Transfer-Encoding: 7bit


On 5/28/24 17:08, Jarkko Sakkinen wrote:
> * Asymmetric TPM2 RSA key with signing and verification.
> * Encryption and decryption when pcks1 encoding is used.
> * Enabled with CONFIG_ASYMMETRIC_TPM2_KEY_ECDSA_SUBTYPE.

s/ECDSA/RSA !

> 
> Signed-off-by: James Prestwood <prestwoj@gmail.com>
> Co-developed-by: Jarkko Sakkinen <jarkko@kernel.org>
> Signed-off-by: Jarkko Sakkinen <jarkko@kernel.org>
> ---
> v6:
> * Validate RSA parameters, and also that the blob has space for
>    them.
> * Fix tpm2_key_rsa_destroy() memory corruption: cast to tpm2_key_rsa
> * Allocate temporary buffers from heap.
> * Rename tpm2_key_rsa_extract_pub to tpm2_key_rsa_probe.
> * While pre-parsing, return -EBADMSG when the probing fails. This
>    translates to "not detected" for the framework, i.e. should not
>    be considered as an error but instead "move on". E.g. TPM_ALG_RSA
>    is checked and if it is instead TPM_ALG_ECDSA, then it is passed
>    to that module.
> v5:
> * akcipher has two *undocumented* parameters. Document this clearly.
> * Remove unused variable.
> v4:
> * Just put the values to the buffer instead of encoding them.
> * Adjust buffer sizes.
> * Make tpm2_rsa_key_encode() not to allocate from heap and simplify
>    the serialization.
> v3:
> * Drop the special case for null handle i.e. do not define policy.
> * Remove extra empty line.
> v2:
> * Remove two spurios pr_info() messsages that I forgot to remove.
> * Clean up padding functions and add additional checks for length
>    also in tpm2_unpad_pcks1().
> * Add the missing success check kzalloc() in tpm2_key_rsa_decrypt().
> * Check that params->out_len for capacity before copying the result.
> ---
>   crypto/asymmetric_keys/Kconfig        |  15 +
>   crypto/asymmetric_keys/Makefile       |   1 +
>   crypto/asymmetric_keys/tpm2_key_rsa.c | 678 ++++++++++++++++++++++++++
>   include/linux/tpm.h                   |   2 +
>   4 files changed, 696 insertions(+)
>   create mode 100644 crypto/asymmetric_keys/tpm2_key_rsa.c
> 
> diff --git a/crypto/asymmetric_keys/Kconfig b/crypto/asymmetric_keys/Kconfig
> index e1345b8f39f1..9d88c1190621 100644
> --- a/crypto/asymmetric_keys/Kconfig
> +++ b/crypto/asymmetric_keys/Kconfig
> @@ -15,6 +15,7 @@ config ASYMMETRIC_PUBLIC_KEY_SUBTYPE
>   	select MPILIB
>   	select CRYPTO_HASH_INFO
>   	select CRYPTO_AKCIPHER
> +	select CRYPTO_RSA
>   	select CRYPTO_SIG
>   	select CRYPTO_HASH
>   	help
> @@ -23,6 +24,20 @@ config ASYMMETRIC_PUBLIC_KEY_SUBTYPE
>   	  appropriate hash algorithms (such as SHA-1) must be available.
>   	  ENOPKG will be reported if the requisite algorithm is unavailable.
>   
> +config ASYMMETRIC_TPM2_KEY_RSA_SUBTYPE
> +	tristate "Asymmetric TPM2 RSA crypto algorithm subtype"
> +	depends on TCG_TPM
> +	select CRYPTO_RSA
> +	select CRYPTO_SHA256
> +	select CRYPTO_HASH_INFO
> +	select CRYPTO_TPM2_KEY
> +	select ASN1
> +	help
> +	  This option provides support for asymmetric TPM2 key type handling.
> +	  If signature generation and/or verification are to be used,
> +	  appropriate hash algorithms (such as SHA-256) must be available.
> +	  ENOPKG will be reported if the requisite algorithm is unavailable.
> +

s/requisite/required ?

>   config X509_CERTIFICATE_PARSER
>   	tristate "X.509 certificate parser"
>   	depends on ASYMMETRIC_PUBLIC_KEY_SUBTYPE
> diff --git a/crypto/asymmetric_keys/Makefile b/crypto/asymmetric_keys/Makefile
> index bc65d3b98dcb..c6da84607824 100644
> --- a/crypto/asymmetric_keys/Makefile
> +++ b/crypto/asymmetric_keys/Makefile
> @@ -11,6 +11,7 @@ asymmetric_keys-y := \
>   	signature.o
>   
>   obj-$(CONFIG_ASYMMETRIC_PUBLIC_KEY_SUBTYPE) += public_key.o
> +obj-$(CONFIG_ASYMMETRIC_TPM2_KEY_RSA_SUBTYPE) += tpm2_key_rsa.o
>   
>   #
>   # X.509 Certificate handling
> diff --git a/crypto/asymmetric_keys/tpm2_key_rsa.c b/crypto/asymmetric_keys/tpm2_key_rsa.c
> new file mode 100644
> index 000000000000..4bc322580037
> --- /dev/null
> +++ b/crypto/asymmetric_keys/tpm2_key_rsa.c
> @@ -0,0 +1,678 @@
> +// SPDX-License-Identifier: GPL-2.0-or-later
> +/* TPM2 asymmetric public-key crypto subtype
> + *
> + * Asymmetric TPM2 RSA key:
> + * - Decrypts RSA with TPM2_RSA_Decrypt.
> + * - Signs with PKCS#1 1.5 padding. Signing is implemented with
> + *   TPM2_RSA_Decrypt operation.
> + * - Encrypts with the akcipher rsa-pcks1pad.

s/pcks1pad/pkcs1pad !


> + *
> + * See Documentation/crypto/asymmetric-keys.rst
> + *
> + * Copyright (c) 2020 Intel Corporation
> + */
> +
> +#include <asm/unaligned.h>
> +#include <crypto/akcipher.h>
> +#include <crypto/public_key.h>
> +#include <crypto/rsa-pkcs1pad.h>
> +#include <crypto/tpm2_key.h>
> +#include <keys/asymmetric-parser.h>
> +#include <keys/asymmetric-subtype.h>
> +#include <keys/trusted-type.h>
> +#include <linux/keyctl.h>
> +#include <linux/module.h>
> +#include <linux/scatterlist.h>
> +#include <linux/slab.h>
> +#include <linux/tpm.h>
> +
> +#undef pr_fmt
> +#define pr_fmt(fmt) "tpm2_key_rsa: "fmt
> +
> +#define PKCS1_PAD_MIN_SIZE 11
> +
> +/* TPM2 Structures 12.2.3.5: TPMS_RSA_PARMS */
> +struct tpm2_rsa_parms {
> +	__be16 symmetric;
> +	__be16 scheme;
> +	__be16 key_bits;
> +	__be32 exponent;
> +	__be16 modulus_size;
> +} __packed;
> +
> +/*
> + * Fill the data with PKCS#1 v1.5 padding.
> + */
> +static int tpm2_pad_pkcs1(const u8 *in, int in_len, u8 *out, int out_len)
> +{
> +	unsigned int prefix_len = out_len - in_len - 3;
> +
> +	if (in_len > out_len - PKCS1_PAD_MIN_SIZE)
> +		return -EBADMSG;
> +
> +	/* prefix */
> +	out[0] = 0;
> +	out[1] = 1;
> +	memset(&out[2], 0xff, prefix_len);
> +	out[2 + prefix_len] = 0;
> +	/* payload */
> +	memcpy(&out[2 + prefix_len + 1], in, in_len);
> +
> +	return 0;
> +}
> +
> +/*
> + * RFC 3447 - Section 7.2.2
> + * Size of the input data should be checked against public key size by
> + * the caller.
> + */
> +static const u8 *tpm2_unpad_pkcs1(const u8 *in, int in_len, int *out_len)
> +{
> +	int i;
> +
> +	if (in[0] != 0 || in[1] != 2)
> +		return NULL;
> +
> +	i = 2;
> +	while (in[i] != 0 && i < in_len)
> +		i++;
> +
> +	if (i == in_len || i < (PKCS1_PAD_MIN_SIZE - 1))
> +		return NULL;
> +
> +	*out_len = in_len - i - 1;
> +	return in + i + 1;
> +}
> +
> +/*
> + * Outputs the cipher algorithm name on success, and retuns -ENOPKG
> + * on failure.
> + */
> +static int tpm2_key_get_akcipher(const char *encoding, const char *hash_algo,
> +				 char *cipher)
> +{
> +	ssize_t ret;
> +
> +	if (strcmp(encoding, "pkcs1") == 0) {
> +		if (!hash_algo) {
> +			strcpy(cipher, "pkcs1pad(rsa)");
> +			return 0;
> +		}
> +
> +		ret = snprintf(cipher, CRYPTO_MAX_ALG_NAME,
> +			       "pkcs1pad(rsa,%s)",
> +			       hash_algo);
> +		if (ret >= CRYPTO_MAX_ALG_NAME)
> +			return -ENOPKG;
> +
> +		return 0;
> +	}
> +
> +	if (strcmp(encoding, "raw") == 0) {
> +		strcpy(cipher, "rsa");
> +		return 0;
> +	}
> +
> +	return -ENOPKG;
> +}
> +
> +static int tpm2_key_rsa_encode(const struct tpm2_key *key, u8 *buf)
> +{
> +	const off_t o = key->priv_len + 2 + sizeof(*key->desc);
> +	const struct tpm2_rsa_parms *p =
> +		(const struct tpm2_rsa_parms *)&key->data[o];
> +	const u16 mod_size = be16_to_cpu(p->modulus_size);
> +	const void *mod = &key->data[o + sizeof(*p)];
> +
> +	u8 *start = &buf[4];
> +	u8 *work = &buf[4];
> +	u32 seq_len;
> +
> +	work[0] = 0x02;			/* INTEGER */
> +	work[1] = 0x82;			/* u16 */
> +	work[2] = mod_size >> 8;
> +	work[3] = mod_size & 0xff;
> +	work = &work[4];
> +	memcpy(work, mod, mod_size);
> +	work = &work[mod_size];
> +	work[0] = 0x02;			/* INTEGER */
> +	work[1] = 3;			/* < 128 */
> +	work[2] = 1;			/* 65537 */
> +	work[3] = 0;
> +	work[4]	= 1;
> +	work = &work[5];
> +	seq_len = work - start;
> +	buf[0] = 0x30;			/* SEQUENCE */
> +	buf[1] = 0x82;			/* u16 */
> +	buf[2] = seq_len >> 8;
> +	buf[3] = seq_len & 0xff;
> +
> +	/*
> +	 * ABI requires this according include/crypto/akcipher.h, which says

according to

> +	 * that there is epilogue with algorithm OID and parameters length.

is an epilogue

> +	 * Neither size nor semantics is documented *anywhere*, and there's no
> +	 * struct to hold them.
> +	 *
> +	 * So zeroing out the last eight bytes after the key blob seems like the
> +	 * best bet, given no better (or any) information. The size of the
> +	 * parameters (two u32's) was found from crypto/asymmetric/public_key.c.
> +	 */
> +	memset(work, 0, 8);
> +
> +	return seq_len + 4;
> +}
> +
> +/*
> + * Encryption operation is performed with the public key.  Hence it is done
> + * in software
> + */
> +static int tpm2_key_rsa_encrypt(struct tpm2_key *key,
> +				struct kernel_pkey_params *params,
> +				const void *in, void *out)
> +{
> +	char cipher[CRYPTO_MAX_ALG_NAME];
> +	struct scatterlist in_sg, out_sg;
> +	struct akcipher_request *req;
> +	struct crypto_akcipher *tfm;
> +	struct crypto_wait cwait;
> +	u8 *buf;
> +	int ret;
> +
> +	buf = kzalloc(TPM2_KEY_BYTES_MAX, GFP_KERNEL);
> +	if (!buf)
> +		return -ENOMEM;
> +
> +	ret = tpm2_key_get_akcipher(params->encoding, params->hash_algo, cipher);
> +	if (ret < 0)
> +		goto err_buf;
> +
> +	tfm = crypto_alloc_akcipher(cipher, 0, 0);
> +	if (IS_ERR(tfm)) {
> +		ret = PTR_ERR(tfm);
> +		goto err_buf;
> +	}
> +
> +	ret = tpm2_key_rsa_encode(key, buf);
> +	if (ret < 0)
> +		goto err_tfm;
> +
> +	ret = crypto_akcipher_set_pub_key(tfm, buf, ret);
> +	if (ret < 0)
> +		goto err_tfm;
> +
> +	req = akcipher_request_alloc(tfm, GFP_KERNEL);
> +	if (!req) {
> +		ret = -ENOMEM;
> +		goto err_tfm;
> +	}
> +
> +	sg_init_one(&in_sg, in, params->in_len);
> +	sg_init_one(&out_sg, out, params->out_len);
> +	akcipher_request_set_crypt(req, &in_sg, &out_sg, params->in_len,
> +				   params->out_len);
> +
> +	crypto_init_wait(&cwait);
> +	akcipher_request_set_callback(req, CRYPTO_TFM_REQ_MAY_BACKLOG |
> +				      CRYPTO_TFM_REQ_MAY_SLEEP,
> +				      crypto_req_done, &cwait);
> +
> +	ret = crypto_akcipher_encrypt(req);
> +	if (ret)
> +		goto err_tfm;
> +
> +	ret = crypto_wait_req(ret, &cwait);
> +	if (!ret)
> +		ret = req->dst_len;
> +
> +	akcipher_request_free(req);
> +
> +err_tfm:
> +	crypto_free_akcipher(tfm);
> +
> +err_buf:
> +	kfree(buf);
> +	return ret;
> +}
> +
> +static int __tpm2_key_rsa_decrypt(struct tpm_chip *chip,
> +				  struct tpm2_key *key,
> +				  struct kernel_pkey_params *params,
> +				  const void *in, int in_len, void *out)
> +{
> +	u32 key_handle = 0;
> +	struct tpm_buf buf;
> +	u16 decrypted_len;
> +	u8 *pos;
> +	int ret;
> +
> +	ret = tpm_try_get_ops(chip); > +	if (ret)

if (ret < 0)

> +		return ret;
> +
> +	ret = tpm2_start_auth_session(chip);
> +	if (ret)

Uh, this one can return TPM error codes it seems from 
tpm_transmit_cmd()? You probably have to do something with ret here in 
case it's positive because I saw a caller of __tpm2_key_rsa_decrypt 
relying on ret < 0 as error.

> +		goto err_ops;
> +
> +	ret = tpm_buf_init(&buf, TPM2_ST_SESSIONS, TPM2_CC_LOAD);
> +	if (ret < 0)
> +		goto err_auth;
> +
> +	tpm_buf_append_name(chip, &buf, key->parent, NULL);
> +	tpm_buf_append_hmac_session(chip, &buf, TPM2_SA_CONTINUE_SESSION |
> +				    TPM2_SA_ENCRYPT, NULL, 0);
> +	tpm_buf_append(&buf, &key->data[0], key->priv_len + key->pub_len);
> +	if (buf.flags & TPM_BUF_OVERFLOW) {
> +		ret = -E2BIG;
> +		goto err_buf;
> +	}
> +	tpm_buf_fill_hmac_session(chip, &buf);
> +	ret = tpm_transmit_cmd(chip, &buf, 4, "TPM2_CC_LOAD");
> +	ret = tpm_buf_check_hmac_response(chip, &buf, ret);
> +	if (ret) {
> +		ret = -EIO;
> +		goto err_buf;
> +	}
> +	key_handle = be32_to_cpup((__be32 *)&buf.data[TPM_HEADER_SIZE]);
> +
> +	tpm_buf_reset(&buf, TPM2_ST_SESSIONS, TPM2_CC_RSA_DECRYPT);
> +	tpm_buf_append_name(chip, &buf, key_handle, NULL);
> +	tpm_buf_append_hmac_session(chip, &buf, TPM2_SA_DECRYPT, NULL, 0);
> +	tpm_buf_append_u16(&buf, in_len);
> +	tpm_buf_append(&buf, in, in_len);
> +	tpm_buf_append_u16(&buf, TPM_ALG_NULL);
> +	tpm_buf_append_u16(&buf, 0);
> +	tpm_buf_fill_hmac_session(chip, &buf);
> +	ret = tpm_transmit_cmd(chip, &buf, 4, "TPM2_RSA_DECRYPT");
> +	ret = tpm_buf_check_hmac_response(chip, &buf, ret);
> +	if (ret) {
> +		ret = -EIO;
> +		goto err_blob;
> +	}
> +
> +	pos = buf.data + TPM_HEADER_SIZE + 4;
> +	decrypted_len = be16_to_cpup((__be16 *)pos);
> +	pos += 2;
> +
> +	if (params->out_len < decrypted_len) {
> +		ret = -EMSGSIZE;
> +		goto err_blob;
> +	}
> +
> +	memcpy(out, pos, decrypted_len);
> +	ret = decrypted_len;
> +
> +err_blob:
> +	tpm2_flush_context(chip, key_handle);
> +
> +err_buf:
> +	tpm_buf_destroy(&buf);
> +
> +err_auth:
> +	if (ret < 0)
> +		tpm2_end_auth_session(chip);
> +
> +err_ops:
> +	tpm_put_ops(chip);
> +	return ret;
> +}
> +
> +static int tpm2_key_rsa_decrypt(struct tpm_chip *chip, struct tpm2_key *key,
> +				struct kernel_pkey_params *params,
> +				const void *in, void *out)
> +{
> +	const u8 *ptr;
> +	int out_len;
> +	u8 *work;
> +	int ret;
> +
> +	work = kzalloc(TPM2_KEY_BYTES_MAX, GFP_KERNEL);
> +	if (!work)
> +		return -ENOMEM;
> +
> +	ret = __tpm2_key_rsa_decrypt(chip, key, params, in, params->in_len,
> +				     work);
> +	if (ret < 0)
> +		goto err;
> +
> +	ptr = tpm2_unpad_pkcs1(work, ret, &out_len);
> +	if (!ptr) {
> +		ret = -EINVAL;
> +		goto err;
> +	}
> +
> +	if (out_len > params->out_len) {

I suppose params->out_len describes the size of void *out buffer..

> +		ret = -EMSGSIZE;
> +		goto err;
> +	}
> +
> +	memcpy(out, ptr, out_len);
> +	kfree(work);
> +	return out_len;
> +
> +err:
> +	kfree(work);
> +	return ret;
> +}
> +
> +/*
> + * Sign operation is an encryption using the TPM's private key. With RSA the
> + * only difference between encryption and decryption is where the padding goes.
> + * Since own padding can be used, TPM2_RSA_Decrypt can be repurposed to do
> + * encryption.
> + */
> +static int tpm2_key_rsa_sign(struct tpm_chip *chip, struct tpm2_key *key,
> +			     struct kernel_pkey_params *params,
> +			     const void *in, void *out)
> +{
> +	const off_t o = key->priv_len + 2 + sizeof(*key->desc);
> +	const struct tpm2_rsa_parms *p =
> +		(const struct tpm2_rsa_parms *)&key->data[o];
> +	const u16 mod_size = be16_to_cpu(p->modulus_size);
> +	const struct rsa_asn1_template *asn1;
> +	u32 in_len = params->in_len;
> +	void *asn1_wrapped = NULL;
> +	u8 *padded;
> +	int ret;
> +
> +	if (strcmp(params->encoding, "pkcs1") != 0) {
> +		ret = -ENOPKG;
> +		goto err;
> +	}
> +
> +	if (params->hash_algo) {
> +		asn1 = rsa_lookup_asn1(params->hash_algo);
> +		if (!asn1) {
> +			ret = -ENOPKG;
> +			goto err;
> +		}
> +
> +		/* Request enough space for the ASN.1 template + input hash */
> +		asn1_wrapped = kzalloc(in_len + asn1->size, GFP_KERNEL);
> +		if (!asn1_wrapped) {
> +			ret = -ENOMEM;
> +			goto err;
> +		}
> +
> +		/* Copy ASN.1 template, then the input */
> +		memcpy(asn1_wrapped, asn1->data, asn1->size);
> +		memcpy(asn1_wrapped + asn1->size, in, in_len);
> +
> +		in = asn1_wrapped;
> +		in_len += asn1->size;
> +	}
> +
> +	/* with padding: * > +	padded = kmalloc(mod_size, GFP_KERNEL);

check NULL pointer?

> +	tpm2_pad_pkcs1(in, in_len, padded, mod_size);
> +	ret = __tpm2_key_rsa_decrypt(chip, key, params, padded, mod_size, out);
> +	kfree(padded);
> +
> +err:
> +	kfree(asn1_wrapped);
> +	return ret;
> +}
> +
> +static void tpm2_key_rsa_describe(const struct key *asymmetric_key,
> +				  struct seq_file *m)
> +{
> +	struct tpm2_key *key = asymmetric_key->payload.data[asym_crypto];
> +
> +	if (!key) {
> +		pr_err("key blob missing");
> +		return;
> +	}
> +
> +	seq_puts(m, "TPM2/RSA");
> +}
> +
> +static void tpm2_key_rsa_destroy(void *payload0, void *payload3)
> +{
> +	struct tpm2_key *key = payload0;
> +
> +	if (!key)
> +		return;

This seems unnecessary.

> +
> +	kfree(key);
> +}
> +
> +static int tpm2_key_rsa_eds_op(struct kernel_pkey_params *params,
> +			       const void *in, void *out)
> +{
> +	struct tpm2_key *key = params->key->payload.data[asym_crypto];
> +	struct tpm_chip *chip = tpm_default_chip();
> +
> +	if (!chip)
> +		return -ENODEV;
> +
> +	switch (params->op) {
> +	case kernel_pkey_encrypt:
> +		return tpm2_key_rsa_encrypt(key, params, in, out);
> +	case kernel_pkey_decrypt:
> +		return tpm2_key_rsa_decrypt(chip, key, params, in, out);
> +	case kernel_pkey_sign:
> +		return tpm2_key_rsa_sign(chip, key, params, in, out);

Missing verify here?

> +	default:
> +		return -EOPNOTSUPP;
> +	}
> +}
> +
> +static int tpm2_key_rsa_verify(const struct key *key,
> +			       const struct public_key_signature *sig)
> +{
> +	const struct tpm2_key *tpm2_key = key->payload.data[asym_crypto];
> +	char alg_name[CRYPTO_MAX_ALG_NAME];
> +	struct akcipher_request *req;
> +	struct scatterlist src_sg[2];
> +	struct crypto_akcipher *tfm;
> +	struct crypto_wait cwait;
> +	u8 *buf;
> +	int ret;
> +
> +	if (!sig->digest)
> +		return -ENOPKG;
> +
> +	ret = tpm2_key_get_akcipher(sig->encoding, sig->hash_algo, alg_name);
> +	if (ret < 0)
> +		return ret;
> +
> +	buf = kzalloc(TPM2_KEY_BYTES_MAX, GFP_KERNEL);
> +	if (!buf)
> +		return -ENOMEM;
> +
> +	tfm = crypto_alloc_akcipher(alg_name, 0, 0);
> +	if (IS_ERR(tfm)) {
> +		ret = PTR_ERR(tfm);
> +		goto err_buf;
> +	}
> +
> +	ret = tpm2_key_rsa_encode(tpm2_key, buf);
> +	if (ret < 0)
> +		goto err_tfm;
> +
> +	ret = crypto_akcipher_set_pub_key(tfm, buf, ret);
> +	if (ret < 0)
> +		goto err_tfm;
> +
> +	ret = -ENOMEM;
> +	req = akcipher_request_alloc(tfm, GFP_KERNEL);
> +	if (!req)
> +		goto err_tfm;
> +
> +	sg_init_table(src_sg, 2);
> +	sg_set_buf(&src_sg[0], sig->s, sig->s_size);
> +	sg_set_buf(&src_sg[1], sig->digest, sig->digest_size);
> +	akcipher_request_set_crypt(req, src_sg, NULL, sig->s_size,
> +				   sig->digest_size);
> +	crypto_init_wait(&cwait);
> +	akcipher_request_set_callback(req, CRYPTO_TFM_REQ_MAY_BACKLOG |
> +				      CRYPTO_TFM_REQ_MAY_SLEEP,
> +				      crypto_req_done, &cwait);
> +	ret = crypto_wait_req(crypto_akcipher_verify(req), &cwait);
> +
> +	akcipher_request_free(req);
> +
> +err_tfm:
> +	crypto_free_akcipher(tfm);
> +
> +err_buf:
> +	kfree(buf);
> +	return ret;
> +}
> +
> +static int tpm2_key_rsa_query(const struct kernel_pkey_params *params,
> +			      struct kernel_pkey_query *info)
> +{
> +	const struct tpm2_key *key = params->key->payload.data[asym_crypto];
> +	const off_t o = key->priv_len + 2 + sizeof(*key->desc);
> +	const struct tpm2_rsa_parms *p =
> +		(const struct tpm2_rsa_parms *)&key->data[o];
> +	const u16 mod_size = be16_to_cpu(p->modulus_size);
> +	char alg_name[CRYPTO_MAX_ALG_NAME];
> +	struct crypto_akcipher *tfm;
> +	unsigned int len;
> +	u8 *buf;
> +	int ret;
> +
> +	ret = tpm2_key_get_akcipher(params->encoding, params->hash_algo, alg_name);
> +	if (ret < 0)
> +		return ret;
> +
> +	buf = kzalloc(TPM2_KEY_BYTES_MAX, GFP_KERNEL);
> +	if (!buf)
> +		return -ENOMEM;
> +
> +	tfm = crypto_alloc_akcipher(alg_name, 0, 0);
> +	if (IS_ERR(tfm)) {
> +		ret = PTR_ERR(tfm);
> +		goto err_buf;
> +	}
> +
> +	ret = tpm2_key_rsa_encode(key, buf);
> +	if (ret < 0)
> +		goto err_tfm;
> +
> +	ret = crypto_akcipher_set_pub_key(tfm, buf, ret);
> +	if (ret < 0)
> +		goto err_tfm;
> +
> +	len = crypto_akcipher_maxsize(tfm);
> +
> +	info->key_size = mod_size * 8;
> +	info->max_data_size = mod_size;
> +	info->max_sig_size = len;
> +	info->max_enc_size = len;
> +	info->max_dec_size = mod_size;
> +
> +	info->supported_ops = KEYCTL_SUPPORTS_SIGN | KEYCTL_SUPPORTS_VERIFY;
> +
> +	if (!strcmp(params->encoding, "pkcs1")) {
> +		pr_info("pkcs1\n");
> +		info->supported_ops =
> +			KEYCTL_SUPPORTS_ENCRYPT | KEYCTL_SUPPORTS_DECRYPT;
> +	}
> +
> +err_tfm:
> +	crypto_free_akcipher(tfm);
> +	return ret;
> +
> +err_buf:
> +	kfree(buf);
> +	return ret;
> +}
> +
> +struct asymmetric_key_subtype tpm2_key_rsa_subtype = {
> +	.owner			= THIS_MODULE,
> +	.name			= "tpm2_key_rsa",
> +	.name_len		= sizeof("tpm2_key_rsa") - 1,
> +	.describe		= tpm2_key_rsa_describe,
> +	.destroy		= tpm2_key_rsa_destroy,
> +	.query			= tpm2_key_rsa_query,
> +	.eds_op			= tpm2_key_rsa_eds_op,
> +	.verify_signature	= tpm2_key_rsa_verify,
> +};
> +EXPORT_SYMBOL_GPL(tpm2_key_rsa_subtype);
> +
> +static int __tpm2_key_rsa_preparse(struct tpm2_key *key)
> +{
> +	const off_t o = key->priv_len + 2 + sizeof(*key->desc);
> +	const struct tpm2_rsa_parms *p =
> +		(const struct tpm2_rsa_parms *)&key->data[o];
> +
> +	if (tpm2_key_type(key) != TPM_ALG_RSA)
> +		return -EBADMSG;
> +
> +	if (tpm2_key_policy_size(key) != 0)
> +		return -EBADMSG;
> +
> +	if (be16_to_cpu(p->symmetric) != TPM_ALG_NULL)
> +		return -EBADMSG;
> +
> +	if (be16_to_cpu(p->scheme) != TPM_ALG_NULL)
> +		return -EBADMSG;
> +
> +	if (be16_to_cpu(p->key_bits) != 2048 &&
> +	    be16_to_cpu(p->key_bits) != 3072 &&
> +	    be16_to_cpu(p->key_bits) != 4096)
> +		return -EBADMSG;
> +
> +	if (be32_to_cpu(p->exponent) != 0x00000000 &&
> +	    be32_to_cpu(p->exponent) != 0x00010001)
> +		return -EBADMSG;
> +
> +	pr_debug("modulus_size=%u\n", be16_to_cpu(p->modulus_size));
> +	return 0;
> +}
> +
> +/*
> + * Attempt to parse a data blob for a key as a TPM private key blob.
> + */
> +static int tpm2_key_rsa_preparse(struct key_preparsed_payload *prep)
> +{
> +	struct tpm2_key *key;
> +	int ret;
> +
> +	key = tpm2_key_decode(prep->data, prep->datalen);
> +	if (IS_ERR(key))
> +		return ret;
> +
> +	if (key->oid != OID_TPMLoadableKey) {
> +		kfree(key);
> +		return -EBADMSG;
> +	}
> +
> +	ret = __tpm2_key_rsa_preparse(key);
> +	if (ret < 0) {
> +		kfree(key);
> +		return ret;
> +	}
> +
> +	prep->payload.data[asym_subtype] = &tpm2_key_rsa_subtype;
> +	prep->payload.data[asym_key_ids] = NULL;
> +	prep->payload.data[asym_crypto] = key;
> +	prep->payload.data[asym_auth] = NULL;
> +	prep->quotalen = 100;
> +
> +	return 0;
> +}
> +
> +static struct asymmetric_key_parser tpm2_key_rsa_parser = {
> +	.owner	= THIS_MODULE,
> +	.name	= "tpm2_key_rsa_parser",
> +	.parse	= tpm2_key_rsa_preparse,
> +};
> +
> +static int __init tpm2_key_rsa_init(void)
> +{
> +	return register_asymmetric_key_parser(&tpm2_key_rsa_parser);
> +}
> +
> +static void __exit tpm2_key_rsa_exit(void)
> +{
> +	unregister_asymmetric_key_parser(&tpm2_key_rsa_parser);
> +}
> +
> +module_init(tpm2_key_rsa_init);
> +module_exit(tpm2_key_rsa_exit);
> +
> +MODULE_DESCRIPTION("Asymmetric TPM2 RSA key");
> +MODULE_LICENSE("GPL");
> diff --git a/include/linux/tpm.h b/include/linux/tpm.h
> index 21a67dc9efe8..d0860af7a56d 100644
> --- a/include/linux/tpm.h
> +++ b/include/linux/tpm.h
> @@ -43,6 +43,7 @@ enum tpm2_session_types {
>   /* if you add a new hash to this, increment TPM_MAX_HASHES below */
>   enum tpm_algorithms {
>   	TPM_ALG_ERROR		= 0x0000,
> +	TPM_ALG_RSA		= 0x0001,
>   	TPM_ALG_SHA1		= 0x0004,
>   	TPM_ALG_AES		= 0x0006,
>   	TPM_ALG_KEYEDHASH	= 0x0008,
> @@ -271,6 +272,7 @@ enum tpm2_command_codes {
>   	TPM2_CC_NV_READ                 = 0x014E,
>   	TPM2_CC_CREATE		        = 0x0153,
>   	TPM2_CC_LOAD		        = 0x0157,
> +	TPM2_CC_RSA_DECRYPT	        = 0x0159,
>   	TPM2_CC_SEQUENCE_UPDATE         = 0x015C,
>   	TPM2_CC_UNSEAL		        = 0x015E,
>   	TPM2_CC_CONTEXT_LOAD	        = 0x0161,