[PATCH v4 25/29] mbedtls: add RSA helper layer on MbedTLS

Ilias Apalodimas ilias.apalodimas at linaro.org
Tue Jul 30 10:04:54 CEST 2024


Hi Raymond


On Tue, 2 Jul 2024 at 21:33, Raymond Mao <raymond.mao at 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 at 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.
> - Minor fix of the include directories.
>
>  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 d8a8f87e031..87c500d6ca9 100644
> --- a/lib/mbedtls/Kconfig
> +++ b/lib/mbedtls/Kconfig
> @@ -124,11 +124,13 @@ config LEGACY_CRYPTO_CERT
>         bool "legacy certificate libraries"
>         select ASYMMETRIC_PUBLIC_KEY_SUBTYPE_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_SUBTYPE_LEGACY if \
>                 ASYMMETRIC_PUBLIC_KEY_SUBTYPE && SPL
> +       select SPL_RSA_PUBLIC_KEY_PARSER_LEGACY if RSA_PUBLIC_KEY_PARSER && SPL

SPL shouldn't be selected. IIRC we discussed the same thing on another
patch, so I assume this is fixed already?

Cheers
/Ilias
>         help
>           Enable legacy certificate libraries.
>
> @@ -141,6 +143,14 @@ config ASYMMETRIC_PUBLIC_KEY_SUBTYPE_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_SUBTYPE_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_SUBTYPE_LEGACY
> @@ -174,6 +184,14 @@ config SPL_ASYMMETRIC_PUBLIC_KEY_SUBTYPE_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_SUBTYPE_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
> @@ -287,11 +305,13 @@ config MBEDTLS_LIB_X509
>         bool "MbedTLS certificate libraries"
>         select ASYMMETRIC_PUBLIC_KEY_SUBTYPE_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_SUBTYPE_MBEDTLS if \
>                 ASYMMETRIC_PUBLIC_KEY_SUBTYPE && SPL
> +       select SPL_RSA_PUBLIC_KEY_PARSER_MBEDTLS if RSA_PUBLIC_KEY_PARSER && SPL
>         help
>           Enable MbedTLS certificate libraries.
>
> @@ -303,6 +323,14 @@ config ASYMMETRIC_PUBLIC_KEY_SUBTYPE_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_SUBTYPE_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_SUBTYPE_MBEDTLS
> @@ -334,6 +362,14 @@ config SPL_ASYMMETRIC_PUBLIC_KEY_SUBTYPE_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_SUBTYPE_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 ac7c487449d..9c6991f8783 100644
> --- a/lib/mbedtls/Makefile
> +++ b/lib/mbedtls/Makefile
> @@ -28,6 +28,7 @@ x509_mbedtls-$(CONFIG_$(SPL_)X509_CERTIFICATE_PARSER_MBEDTLS) += \
>         x509_cert_parser.o
>  x509_mbedtls-$(CONFIG_$(SPL_)PKCS7_MESSAGE_PARSER_MBEDTLS) += pkcs7_parser.o
>  x509_mbedtls-$(CONFIG_$(SPL_)MSCODE_PARSER_MBEDTLS) += mscode_parser.o
> +x509_mbedtls-$(CONFIG_$(SPL_)RSA_PUBLIC_KEY_PARSER_MBEDTLS) += rsa_helper.o
>
>  # MbedTLS crypto library
>  obj-$(CONFIG_MBEDTLS_LIB_CRYPTO) += mbedtls_lib_crypto.o
> @@ -49,7 +50,7 @@ mbedtls_lib_x509-$(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 at 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
>


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