[PATCH v3 19/25] mbedtls: add MSCode parser porting layer

[Ilias Apalodimas]

On Tue, 28 May 2024 at 17:17, Raymond Mao <raymond.mao at linaro.org> wrote:
>
> Add porting layer for MSCode on top of MbedTLS ASN1 library.
>
> Signed-off-by: Raymond Mao <raymond.mao at linaro.org>
> ---
> Changes in v2
> - Move the porting layer to MbedTLS dir.
> Changes in v3
> - None.
>
>  lib/mbedtls/Makefile        |   1 +
>  lib/mbedtls/mscode_parser.c | 111 ++++++++++++++++++++++++++++++++++++
>  2 files changed, 112 insertions(+)
>  create mode 100644 lib/mbedtls/mscode_parser.c
>
> diff --git a/lib/mbedtls/Makefile b/lib/mbedtls/Makefile
> index 005b8a25320..f0b8a1c4003 100644
> --- a/lib/mbedtls/Makefile
> +++ b/lib/mbedtls/Makefile
> @@ -26,6 +26,7 @@ obj-$(CONFIG_MBEDTLS_LIB_X509) += x509_mbedtls.o
>  x509_mbedtls-$(CONFIG_$(SPL_)ASYMMETRIC_PUBLIC_KEY_SUBTYPE) += public_key.o
>  x509_mbedtls-$(CONFIG_$(SPL_)X509_CERTIFICATE_PARSER) += x509_cert_parser.o
>  x509_mbedtls-$(CONFIG_$(SPL_)PKCS7_MESSAGE_PARSER) += pkcs7_parser.o
> +x509_mbedtls-$(CONFIG_$(SPL_)MSCODE_PARSER) += mscode_parser.o
>
>  obj-$(CONFIG_MBEDTLS_LIB_CRYPTO) += mbedtls_lib_crypto.o
>  mbedtls_lib_crypto-y := \
> diff --git a/lib/mbedtls/mscode_parser.c b/lib/mbedtls/mscode_parser.c
> new file mode 100644
> index 00000000000..34715f3a137
> --- /dev/null
> +++ b/lib/mbedtls/mscode_parser.c
> @@ -0,0 +1,111 @@
> +// SPDX-License-Identifier: GPL-2.0+
> +/*
> + * MSCode parser using MbedTLS ASN1 library
> + *
> + * Copyright (c) 2024 Linaro Limited
> + * Author: Raymond Mao <raymond.mao at linaro.org>
> + */
> +
> +#include <linux/kernel.h>
> +#include <linux/err.h>
> +#include <crypto/pkcs7.h>
> +#include <crypto/mscode.h>
> +
> +/*
> + * Parse a Microsoft Individual Code Signing blob
> + *
> + * U.P.SEQUENCE {
> + *    U.P.OBJECTIDENTIFIER 1.3.6.1.4.1.311.2.1.15 (SPC_PE_IMAGE_DATA_OBJID)
> + *    U.P.SEQUENCE {
> + *       U.P.BITSTRING NaN : 0 unused bit(s);
> + *       [C.P.0] {
> + *          [C.P.2] {
> + *             [C.P.0] <arbitrary string>
> + *          }
> + *       }
> + *    }
> + * }
> + * U.P.SEQUENCE {
> + *    U.P.SEQUENCE {
> + *       U.P.OBJECTIDENTIFIER <digest algorithm OID>
> + *       U.P.NULL
> + *    }
> + *    U.P.OCTETSTRING <PE image digest>
> + * }

You need to describe the function arguments as well on the comment

> + *
> + */
> +int mscode_parse(void *_ctx, const void *content_data, size_t data_len,
> +                size_t asn1hdrlen)
> +{
> +       struct pefile_context *ctx = _ctx;
> +       unsigned char *p = (unsigned char *)content_data;
> +       unsigned char *end = (unsigned char *)content_data + data_len;

Why are you dropping const here?

> +       size_t len = 0;
> +       int ret;
> +       unsigned char *inner_p;
> +       size_t seq_len = 0;
> +
> +       ret = mbedtls_asn1_get_tag(&p, end, &seq_len,
> +                                  MBEDTLS_ASN1_CONSTRUCTED |
> +                                  MBEDTLS_ASN1_SEQUENCE);
> +       if (ret)
> +               return ret;
> +
> +       inner_p = p;
> +       ret = mbedtls_asn1_get_tag(&inner_p, inner_p + seq_len, &len, MBEDTLS_ASN1_OID);
> +       if (ret)
> +               return ret;
> +
> +       /* Sanity check on the PE Image Data OID (1.3.6.1.4.1.311.2.1.15) */
> +       if (MBEDTLS_OID_CMP_RAW(MBEDTLS_OID_MICROSOFT_PEIMAGEDATA, inner_p, len))
> +               return -EINVAL;
> +
> +       p += seq_len;
> +       ret = mbedtls_asn1_get_tag(&p, end, &seq_len,
> +                                  MBEDTLS_ASN1_CONSTRUCTED |
> +                                  MBEDTLS_ASN1_SEQUENCE);
> +       if (ret)
> +               return ret;
> +
> +       ret = mbedtls_asn1_get_tag(&p, p + seq_len, &seq_len,
> +                                  MBEDTLS_ASN1_CONSTRUCTED |
> +                                  MBEDTLS_ASN1_SEQUENCE);
> +       if (ret)
> +               return ret;
> +
> +       inner_p = p;
> +
> +       /*
> +        * Check if the inner sequence contains a supported hash
> +        * algorithm OID
> +        */
> +       ret = mbedtls_asn1_get_tag(&inner_p, inner_p + seq_len, &len, MBEDTLS_ASN1_OID);
> +       if (ret)
> +               return ret;
> +
> +       if (!MBEDTLS_OID_CMP_RAW(MBEDTLS_OID_DIGEST_ALG_MD5, inner_p, len))
> +               ctx->digest_algo = "md5";
> +       else if (!MBEDTLS_OID_CMP_RAW(MBEDTLS_OID_DIGEST_ALG_SHA1, inner_p, len))
> +               ctx->digest_algo = "sha1";
> +       else if (!MBEDTLS_OID_CMP_RAW(MBEDTLS_OID_DIGEST_ALG_SHA224, inner_p, len))
> +               ctx->digest_algo = "sha224";
> +       else if (!MBEDTLS_OID_CMP_RAW(MBEDTLS_OID_DIGEST_ALG_SHA256, inner_p, len))
> +               ctx->digest_algo = "sha256";
> +       else if (!MBEDTLS_OID_CMP_RAW(MBEDTLS_OID_DIGEST_ALG_SHA384, inner_p, len))
> +               ctx->digest_algo = "sha384";
> +       else if (!MBEDTLS_OID_CMP_RAW(MBEDTLS_OID_DIGEST_ALG_SHA512, inner_p, len))
> +               ctx->digest_algo = "sha512";
> +
> +       if (!ctx->digest_algo)
> +               return -EINVAL;
> +
> +       p += seq_len;
> +       ret = mbedtls_asn1_get_tag(&p, end, &len, MBEDTLS_ASN1_OCTET_STRING);
> +       if (ret)
> +               return ret;
> +
> +       ctx->digest = p;
> +       ctx->digest_len = len;
> +
> +       return 0;
> +}
> --
> 2.25.1
>

Thanks
/Ilias