Re: [PATCH v6 24/28] mbedtls: add RSA helper layer on MbedTLS

On Sat, 17 Aug 2024 at 00:54, Raymond Mao raymond.mao@linaro.org wrote:

Add RSA helper layer on top on MbedTLS PK and RSA library. Introduce _LEGACY and _MBEDTLS kconfigs for RSA helper legacy and MbedTLS implementations respectively.

Signed-off-by: Raymond Mao raymond.mao@linaro.org

Changes in v2

• Initial patch.

Changes in v3

• None.

Changes in v4

• Introduce _LEGACY and _MBEDTLS kconfigs for RSA helper legacy and MbedTLS implementations respectively.
• Remove unnecessary type casting.

Changes in v5

• Correct header file include directories.
• Correct kconfig dependence.
• Kconfig rename.
• Refactored MbedTLS makefile.

Changes in v6

• None.

lib/mbedtls/Kconfig | 36 +++++++++++++++ lib/mbedtls/Makefile | 3 +- lib/mbedtls/rsa_helper.c | 95 ++++++++++++++++++++++++++++++++++++++++ 3 files changed, 133 insertions(+), 1 deletion(-) create mode 100644 lib/mbedtls/rsa_helper.c

diff --git a/lib/mbedtls/Kconfig b/lib/mbedtls/Kconfig index ecdf4d3008f..797da0df938 100644 --- a/lib/mbedtls/Kconfig +++ b/lib/mbedtls/Kconfig @@ -119,11 +119,13 @@ config LEGACY_CRYPTO_CERT bool "legacy certificate libraries" select ASYMMETRIC_PUBLIC_KEY_LEGACY if \ ASYMMETRIC_PUBLIC_KEY_SUBTYPE

•   select RSA_PUBLIC_KEY_PARSER_LEGACY if RSA_PUBLIC_KEY_PARSER
    select X509_CERTIFICATE_PARSER_LEGACY if X509_CERTIFICATE_PARSER
    select PKCS7_MESSAGE_PARSER_LEGACY if PKCS7_MESSAGE_PARSER
    select MSCODE_PARSER_LEGACY if MSCODE_PARSER
    select SPL_ASYMMETRIC_PUBLIC_KEY_LEGACY if \
            SPL_ASYMMETRIC_PUBLIC_KEY_SUBTYPE
  

•   select SPL_RSA_PUBLIC_KEY_PARSER_LEGACY if SPL_RSA_PUBLIC_KEY_PARSER
    help
      Enable legacy certificate libraries.
  
  

@@ -136,6 +138,14 @@ config ASYMMETRIC_PUBLIC_KEY_LEGACY This option chooses legacy certificate library for asymmetric public key crypto algorithm.

+config RSA_PUBLIC_KEY_PARSER_LEGACY

•   bool "RSA public key parser with legacy certificate library"
  

•   depends on ASYMMETRIC_PUBLIC_KEY_LEGACY
  

•   select ASN1_DECODER_LEGACY
  

•   help
  

•     This option chooses legacy certificate library for RSA public key
  

•     parser.
  

config X509_CERTIFICATE_PARSER_LEGACY bool "X.509 certificate parser with legacy certificate library" depends on ASYMMETRIC_PUBLIC_KEY_LEGACY @@ -169,6 +179,14 @@ config SPL_ASYMMETRIC_PUBLIC_KEY_LEGACY This option chooses legacy certificate library for asymmetric public key crypto algorithm in SPL.

+config SPL_RSA_PUBLIC_KEY_PARSER_LEGACY

•   bool "RSA public key parser with legacy certificate library in SPL"
  

•   depends on SPL_ASYMMETRIC_PUBLIC_KEY_LEGACY
  

•   select SPL_ASN1_DECODER_LEGACY
  

•   help
  

•     This option chooses legacy certificate library for RSA public key
  

•     parser in SPL.
  

endif # SPL

endif # LEGACY_CRYPTO_CERT @@ -301,11 +319,13 @@ config MBEDTLS_LIB_X509 bool "MbedTLS certificate libraries" select ASYMMETRIC_PUBLIC_KEY_MBEDTLS if \ ASYMMETRIC_PUBLIC_KEY_SUBTYPE

•   select RSA_PUBLIC_KEY_PARSER_MBEDTLS if RSA_PUBLIC_KEY_PARSER
    select X509_CERTIFICATE_PARSER_MBEDTLS if X509_CERTIFICATE_PARSER
    select PKCS7_MESSAGE_PARSER_MBEDTLS if PKCS7_MESSAGE_PARSER
    select MSCODE_PARSER_MBEDTLS if MSCODE_PARSER
    select SPL_ASYMMETRIC_PUBLIC_KEY_MBEDTLS if \
            SPL_ASYMMETRIC_PUBLIC_KEY_SUBTYPE
  

•   select SPL_RSA_PUBLIC_KEY_PARSER_MBEDTLS if SPL_RSA_PUBLIC_KEY_PARSER
    help
      Enable MbedTLS certificate libraries.
  
  

@@ -318,6 +338,14 @@ config ASYMMETRIC_PUBLIC_KEY_MBEDTLS This option chooses MbedTLS certificate library for asymmetric public key crypto algorithm.

+config RSA_PUBLIC_KEY_PARSER_MBEDTLS

•   bool "RSA public key parser with MbedTLS certificate library"
  

•   depends on ASYMMETRIC_PUBLIC_KEY_MBEDTLS
  

•   select ASN1_DECODER_MBEDTLS
  

•   help
  

•     This option chooses MbedTLS certificate library for RSA public key
  

•     parser.
  

config X509_CERTIFICATE_PARSER_MBEDTLS bool "X.509 certificate parser with MbedTLS certificate library" depends on ASYMMETRIC_PUBLIC_KEY_MBEDTLS @@ -351,6 +379,14 @@ config SPL_ASYMMETRIC_PUBLIC_KEY_MBEDTLS This option chooses MbedTLS certificate library for asymmetric public key crypto algorithm in SPL.

+config SPL_RSA_PUBLIC_KEY_PARSER_MBEDTLS

•   bool "RSA public key parser with MbedTLS certificate library in SPL"
  

•   depends on SPL_ASYMMETRIC_PUBLIC_KEY_MBEDTLS
  

•   select SPL_ASN1_DECODER_MBEDTLS
  

•   help
  

•     This option chooses MbedTLS certificate library for RSA public key
  

•     parser in SPL.
  

endif # SPL

endif # MBEDTLS_LIB_X509 diff --git a/lib/mbedtls/Makefile b/lib/mbedtls/Makefile index 83333b1b6a5..40031994708 100644 --- a/lib/mbedtls/Makefile +++ b/lib/mbedtls/Makefile @@ -18,6 +18,7 @@ obj-$(CONFIG_$(SPL_)X509_CERTIFICATE_PARSER_MBEDTLS) += \ x509_cert_parser.o obj-$(CONFIG_$(SPL_)PKCS7_MESSAGE_PARSER_MBEDTLS) += pkcs7_parser.o obj-$(CONFIG_$(SPL_)MSCODE_PARSER_MBEDTLS) += mscode_parser.o +obj-$(CONFIG_$(SPL_)RSA_PUBLIC_KEY_PARSER_MBEDTLS) += rsa_helper.o

# MbedTLS crypto library obj-$(CONFIG_MBEDTLS_LIB_CRYPTO) += mbedtls_lib_crypto.o @@ -39,7 +40,7 @@ mbedtls_lib_x509-$(CONFIG_$(SPL_)ASN1_DECODER) += \ $(MBEDTLS_LIB_DIR)/asn1parse.o \ $(MBEDTLS_LIB_DIR)/asn1write.o \ $(MBEDTLS_LIB_DIR)/oid.o -mbedtls_lib_x509-$(CONFIG_$(SPL_)RSA_PUBLIC_KEY_PARSER) += \ +mbedtls_lib_x509-$(CONFIG_$(SPL_)RSA_PUBLIC_KEY_PARSER_MBEDTLS) += \ $(MBEDTLS_LIB_DIR)/bignum.o \ $(MBEDTLS_LIB_DIR)/bignum_core.o \ $(MBEDTLS_LIB_DIR)/rsa.o \ diff --git a/lib/mbedtls/rsa_helper.c b/lib/mbedtls/rsa_helper.c new file mode 100644 index 00000000000..3d94eee9954 --- /dev/null +++ b/lib/mbedtls/rsa_helper.c @@ -0,0 +1,95 @@ +// SPDX-License-Identifier: GPL-2.0+ +/*

• • RSA helper functions using MbedTLS
• • Copyright (c) 2024 Linaro Limited
• • Author: Raymond Mao raymond.mao@linaro.org
• */

+#include <linux/err.h> +#include <crypto/internal/rsa.h> +#include <library/common.h> +#include <mbedtls/pk.h> +#include <mbedtls/rsa.h> +#include <mbedtls/asn1.h>

+/**

• • rsa_parse_pub_key() - decodes the BER encoded buffer and stores in the

• •                   provided struct rsa_key, pointers to the raw key as is,
    

• •                   so that the caller can copy it or MPI parse it, etc.
    

• • @rsa_key: struct rsa_key key representation
• • @key: key in BER format
• • @key_len: length of key
• • Return: 0 on success or error code in case of error
• */

+int rsa_parse_pub_key(struct rsa_key *rsa_key, const void *key,

•                 unsigned int key_len)
  

+{

•   int ret = 0;
  

•   mbedtls_pk_context pk;
  

•   mbedtls_rsa_context *rsa;
  

•   mbedtls_pk_init(&pk);
  

•   ret = mbedtls_pk_parse_public_key(&pk, (const unsigned char *)key,
  

•                                     key_len);
  

•   if (ret) {
  

•           pr_err("Failed to parse public key, ret:-0x%04x\n", -ret);
  

•           ret = -EINVAL;
  

•           goto clean_pubkey;
  

•   }
  

•   /* Ensure that it is a RSA key */
  

•   if (mbedtls_pk_get_type(&pk) != MBEDTLS_PK_RSA) {
  

•           pr_err("Non-RSA keys are not supported\n");
  

•           ret = -EKEYREJECTED;
  

•           goto clean_pubkey;
  

•   }
  

•   /* Get RSA key context */
  

•   rsa = mbedtls_pk_rsa(pk);
  

•   if (!rsa) {
  

•           pr_err("Failed to get RSA key context, ret:-0x%04x\n", -ret);
  

•           ret = -EINVAL;
  

•           goto clean_pubkey;
  

•   }
  

•   /* Parse modulus (n) */
  

•   rsa_key->n_sz = mbedtls_mpi_size(&rsa->N);
  

•   rsa_key->n = kzalloc(rsa_key->n_sz, GFP_KERNEL);
  

•   if (!rsa_key->n) {
  

•           ret = -ENOMEM;
  

•           goto clean_pubkey;
  

•   }
  

•   ret = mbedtls_mpi_write_binary(&rsa->N, (unsigned char *)rsa_key->n,
  

•                                  rsa_key->n_sz);
  

•   if (ret) {
  

•           pr_err("Failed to parse modulus (n), ret:-0x%04x\n", -ret);
  

•           ret = -EINVAL;
  

•           goto clean_modulus;
  

•   }
  

•   /* Parse public exponent (e) */
  

•   rsa_key->e_sz = mbedtls_mpi_size(&rsa->E);
  

•   rsa_key->e = kzalloc(rsa_key->e_sz, GFP_KERNEL);
  

•   if (!rsa_key->e) {
  

•           ret = -ENOMEM;
  

•           goto clean_modulus;
  

•   }
  

•   ret = mbedtls_mpi_write_binary(&rsa->E, (unsigned char *)rsa_key->e,
  

•                                  rsa_key->e_sz);
  

•   if (!ret)
  

•           return 0;
  

•   pr_err("Failed to parse public exponent (e), ret:-0x%04x\n", -ret);
  

•   ret = -EINVAL;
  

•   kfree(rsa_key->e);
  

+clean_modulus:

•   kfree(rsa_key->n);
  

+clean_pubkey:

•   mbedtls_pk_free(&pk);
  

•   return ret;
  

+}

2.25.1

Acked-by: Ilias Apalodimas ilias.apalodimas@linaro.org