[v7,4/5] keys: asymmetric: Add tpm2_key_rsa

* Asymmetric TPM2 RSA key with signing and verification.
* Encryption and decryption when pcks1 encoding is used.
* Enabled with CONFIG_ASYMMETRIC_TPM2_KEY_ECDSA_SUBTYPE.

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

On Wed May 29, 2024 at 12:08 AM EEST, 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.
>
> Signed-off-by: James Prestwood <prestwoj@gmail.com>
> Co-developed-by: Jarkko Sakkinen <jarkko@kernel.org>
> Signed-off-by: Jarkko Sakkinen <jarkko@kernel.org>

To be addressed in v8:

"
4970b8d723c3af Jarkko Sakkinen 2024-05-26  634  	key = tpm2_key_decode(prep->data, prep->datalen);
4970b8d723c3af Jarkko Sakkinen 2024-05-26  635  	if (IS_ERR(key))
4970b8d723c3af Jarkko Sakkinen 2024-05-26 @636  		return ret;
                                                                ^^^^^^^^^^
Same.  return PTR_ERR(key);
" - https://lore.kernel.org/all/cbae0ed0-e0a6-41ba-9671-a9f48e8f07f3@moroto.mountain/

BR, Jarkko

On Fri May 31, 2024 at 4:10 AM EEST, Stefan Berger wrote:
>
>
> 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 !

Thanks, note taken.

>
> > 
> > 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 ?

Ack.

>
> >   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 !

+1


>
>
> > + *
> > + * 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

+1


>
> > +	 * 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)

+1

>
> > +		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.

Good catch, thanks.

>
> > +		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,

Yeah, all remarks make total sense to me, thank you.

BR, Jarkko

On Fri Jun 7, 2024 at 1:58 PM EEST, Herbert Xu wrote:
> On Wed, May 29, 2024 at 12:08:09AM +0300, Jarkko Sakkinen wrote:
> >
> > +/*
> > + * 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);
>
> Could you please explain why this can't be done through pkcs1pad
> instead of going to raw RSA?

Sorry was away couple of weeks from here. I replace this with TPM2_Sign
as is done already in the ECDSA module, so I guess that is a "yes".

BR, Jarkko