Re: [PATCH v4 17/29] mbedtls: add public key porting layer

On Tue, 2 Jul 2024 at 21:30, Raymond Mao raymond.mao@linaro.org wrote:

Add porting layer for public key on top of MbedTLS X509 library. Introduce _LEGACY and _MBEDTLS kconfigs for public key legacy and MbedTLS implementations respectively.

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

Changes in v2

• Move the porting layer to MbedTLS dir.

Changes in v3

• None.

Changes in v4

• Introduce _LEGACY and _MBEDTLS kconfigs for public key legacy and MbedTLS implementations respectively.
• Move common functions to helper.

lib/mbedtls/Kconfig | 50 ++++++++++++++++++++++++ lib/mbedtls/Makefile | 7 +++- lib/mbedtls/public_key.c | 82 ++++++++++++++++++++++++++++++++++++++++ 3 files changed, 138 insertions(+), 1 deletion(-) create mode 100644 lib/mbedtls/public_key.c

diff --git a/lib/mbedtls/Kconfig b/lib/mbedtls/Kconfig index 0cdf0135667..6f29b0c81a2 100644 --- a/lib/mbedtls/Kconfig +++ b/lib/mbedtls/Kconfig @@ -122,9 +122,35 @@ endif # LEGACY_CRYPTO_BASIC

config LEGACY_CRYPTO_CERT bool "legacy certificate libraries"

•   select ASYMMETRIC_PUBLIC_KEY_SUBTYPE_LEGACY if \
  

•           ASYMMETRIC_PUBLIC_KEY_SUBTYPE
  

•   select SPL_ASYMMETRIC_PUBLIC_KEY_SUBTYPE_LEGACY if \
  

•           ASYMMETRIC_PUBLIC_KEY_SUBTYPE && SPL
    help
      Enable legacy certificate libraries.
  
  

+if LEGACY_CRYPTO_CERT

+config ASYMMETRIC_PUBLIC_KEY_SUBTYPE_LEGACY

•   bool "Asymmetric public key crypto with legacy certificate library"
  

•   depends on LEGACY_CRYPTO_CERT && ASYMMETRIC_PUBLIC_KEY_SUBTYPE
  

•   help
  

•     This option chooses legacy certificate library for asymmetric public
  

•     key crypto algorithm.
  

+if SPL

+config SPL_ASYMMETRIC_PUBLIC_KEY_SUBTYPE_LEGACY

subtype is either legacy or mbedTLS? If yes I think you can get rid of it and have SPL_ASYMMETRIC_PUBLIC_KEY_LEGACY and ASYMMETRIC_PUBLIC_KEY_MBEDTLS

•   bool "Asymmetric public key crypto with legacy certificate library in SPL"
  

•   depends on LEGACY_CRYPTO_CERT && SPL_ASYMMETRIC_PUBLIC_KEY_SUBTYPE
  

•   help
  

•     This option chooses legacy certificate library for asymmetric public
  

•     key crypto algorithm in SPL.
  

+endif # SPL

+endif # LEGACY_CRYPTO_CERT

endif # LEGACY_CRYPTO

if MBEDTLS_LIB @@ -232,7 +258,31 @@ endif # MBEDTLS_LIB_CRYPTO

config MBEDTLS_LIB_X509 bool "MbedTLS certificate libraries"

•   select ASYMMETRIC_PUBLIC_KEY_SUBTYPE_MBEDTLS if \
  

•           ASYMMETRIC_PUBLIC_KEY_SUBTYPE
  

•   select SPL_ASYMMETRIC_PUBLIC_KEY_SUBTYPE_MBEDTLS if \
  

•           ASYMMETRIC_PUBLIC_KEY_SUBTYPE && SPL
  

Why do we have to select SPL here and in the Kconfig above for the legacy option?

    help
      Enable MbedTLS certificate libraries.

+if MBEDTLS_LIB_X509

+config ASYMMETRIC_PUBLIC_KEY_SUBTYPE_MBEDTLS

•   bool "Asymmetric public key crypto with MbedTLS certificate library"
  

•   help
  

•     This option chooses MbedTLS certificate library for asymmetric public
  

•     key crypto algorithm.
  

+if SPL

+config SPL_ASYMMETRIC_PUBLIC_KEY_SUBTYPE_MBEDTLS

•   bool "Asymmetric public key crypto with MbedTLS certificate library in SPL"
  

•   help
  

•     This option chooses MbedTLS certificate library for asymmetric public
  

•     key crypto algorithm in SPL.
  

+endif # SPL

+endif # MBEDTLS_LIB_X509

endif # MBEDTLS_LIB diff --git a/lib/mbedtls/Makefile b/lib/mbedtls/Makefile index 32a98b7f4ca..f06d0704502 100644 --- a/lib/mbedtls/Makefile +++ b/lib/mbedtls/Makefile @@ -20,6 +20,11 @@ hash_mbedtls-$(CONFIG_$(SPL_)SHA1_MBEDTLS) += sha1.o hash_mbedtls-$(CONFIG_$(SPL_)SHA256_MBEDTLS) += sha256.o hash_mbedtls-$(CONFIG_$(SPL_)SHA512_MBEDTLS) += sha512.o

+# x509 libraries +obj-$(CONFIG_MBEDTLS_LIB_X509) += x509_mbedtls.o +x509_mbedtls-$(CONFIG_$(SPL_)ASYMMETRIC_PUBLIC_KEY_SUBTYPE_MBEDTLS) += \

•   public_key.o
  

# MbedTLS crypto library obj-$(CONFIG_MBEDTLS_LIB_CRYPTO) += mbedtls_lib_crypto.o mbedtls_lib_crypto-y += \ @@ -45,7 +50,7 @@ mbedtls_lib_x509-$(CONFIG_$(SPL_)RSA_PUBLIC_KEY_PARSER) += \ $(MBEDTLS_LIB_DIR)/bignum_core.o \ $(MBEDTLS_LIB_DIR)/rsa.o \ $(MBEDTLS_LIB_DIR)/rsa_alt_helpers.o -mbedtls_lib_x509-$(CONFIG_$(SPL_)ASYMMETRIC_PUBLIC_KEY_SUBTYPE) += \ +mbedtls_lib_x509-$(CONFIG_$(SPL_)ASYMMETRIC_PUBLIC_KEY_SUBTYPE_MBEDTLS) += \ $(MBEDTLS_LIB_DIR)/pk.o \ $(MBEDTLS_LIB_DIR)/pk_wrap.o \ $(MBEDTLS_LIB_DIR)/pkparse.o diff --git a/lib/mbedtls/public_key.c b/lib/mbedtls/public_key.c new file mode 100644 index 00000000000..076a61862cb --- /dev/null +++ b/lib/mbedtls/public_key.c @@ -0,0 +1,82 @@ +// SPDX-License-Identifier: GPL-2.0+ +/*

• • Public key helper functions using MbedTLS X509 library
• • Copyright (c) 2024 Linaro Limited
• • Author: Raymond Mao raymond.mao@linaro.org
• */

+#include <linux/compat.h> +#include <crypto/public_key.h>

+int public_key_verify_signature(const struct public_key *pkey,

•                           const struct public_key_signature *sig)
  

+{

•   mbedtls_md_type_t mb_hash_algo;
  

•   mbedtls_pk_context pk_ctx;
  

•   int ret;
  

•   if (!pkey || !sig || pkey->key_is_private)
  

•           return -EINVAL;
  

•   /*
  

•    * ECRDSA (Elliptic Curve RedDSA) from Red Hat is not supported by
  

•    * MbedTLS
  

•    */
  

That's not Redhat AFAICT. That's Elliptic Curve (Russian) Digital Signature Algorithm described in GOST 34.10-2018, GOST R 34.10-2012, RFC 7091, ISO/IEC 14888-3:2018

•   if (strcmp(pkey->pkey_algo, "rsa")) {
  

•           pr_err("Encryption is not RSA: %s\n", sig->pkey_algo);
  

•           return -EINVAL;
  

•   }
  

•   /*
  

•    * Can be pkcs1 or raw, but pkcs1 is expected.
  

•    * This is just for argument checking, not necessarily passed to MbedTLS,
  

•    * For RSA signatures, MbedTLS typically supports the PKCS#1 v1.5
  

•    * (aka. pkcs1) encoding by default.
  

•    * The library internally handles the details of decoding and verifying
  

•    * the signature according to the expected encoding for the specified algorithm.
  

•    */
  

•   if (strcmp(sig->encoding, "pkcs1")) {
  

•           pr_err("Encoding %s is not supported, only supports pkcs1\n",
  

•                  sig->encoding);
  

•           return -EINVAL;
  

•   }
  

•   if (!strcmp(sig->hash_algo, "sha1"))
  

•           mb_hash_algo = MBEDTLS_MD_SHA1;
  

•   else if (!strcmp(sig->hash_algo, "sha224"))
  

•           mb_hash_algo = MBEDTLS_MD_SHA224;
  

•   else if (!strcmp(sig->hash_algo, "sha256"))
  

•           mb_hash_algo = MBEDTLS_MD_SHA256;
  

•   else if (!strcmp(sig->hash_algo, "sha384"))
  

•           mb_hash_algo = MBEDTLS_MD_SHA384;
  

•   else if (!strcmp(sig->hash_algo, "sha512"))
  

•           mb_hash_algo = MBEDTLS_MD_SHA512;
  

•   else    /* Unknown or unsupported hash algorithm */
  

•           return -EINVAL;
  

•   /* Initialize the mbedtls_pk_context with RSA key type */
  

•   mbedtls_pk_init(&pk_ctx);
  

•   /* Parse the DER-encoded public key */
  

•   ret = mbedtls_pk_parse_public_key(&pk_ctx, pkey->key, pkey->keylen);
  

•   if (ret) {
  

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

•           ret = -EINVAL;
  

•           goto err_key;
  

•   }
  

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

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

•           pr_err("Only RSA keys are supported\n");
  

•           ret = -EKEYREJECTED;
  

•           goto err_key;
  

•   }
  

•   /* Verify the hash */
  

•   ret = mbedtls_pk_verify(&pk_ctx, mb_hash_algo, sig->digest,
  

•                           sig->digest_size, sig->s, sig->s_size);
  

+err_key:

•   mbedtls_pk_free(&pk_ctx);
  

•   return ret;
  

+}

2.25.1

Thanks /Ilias