[U-Boot] [RFC 3/3] lib: rsa: add rsa_verify_with_pkey()

[Simon Glass]

Hi AKASHI,

On Fri, 6 Sep 2019 at 00:06, AKASHI Takahiro <takahiro.akashi at linaro.org> wrote:
>
> This function, and hence rsa_verify(), will perform RSA verification
> with two essential parameters for a RSA public key in contract of
> rsa_verify_with_keynode(), which requires additional three parameters
> stored in FIT image.
>
> It will be used in implementing UEFI secure boot, i.e. image authentication
> and variable authentication.
>
> Signed-off-by: AKASHI Takahiro <takahiro.akashi at linaro.org>
> ---
>  lib/rsa/Kconfig      |  7 +++++
>  lib/rsa/Makefile     |  3 ++-
>  lib/rsa/rsa-verify.c | 63 ++++++++++++++++++++++++++++++++++++++------
>  3 files changed, 64 insertions(+), 9 deletions(-)
>
> diff --git a/lib/rsa/Kconfig b/lib/rsa/Kconfig
> index 338c8124da59..3c1986a26f8c 100644
> --- a/lib/rsa/Kconfig
> +++ b/lib/rsa/Kconfig
> @@ -25,6 +25,13 @@ config RSA_VERIFY
>         help
>           Add RSA signature verification support.
>
> +config RSA_VERIFY_WITH_PKEY
> +       bool "Execute RSA verification without key parameters from FDT"
> +       depends on RSA
> +       help
> +         This options enables RSA signature verification without
> +         using public key parameters which is embedded control FDT.

Please expand this, a lot. It is too brief.

> +
>  config RSA_SOFTWARE_EXP
>         bool "Enable driver for RSA Modular Exponentiation in software"
>         depends on DM
> diff --git a/lib/rsa/Makefile b/lib/rsa/Makefile
> index d66eef74c514..fd4592fd6a8a 100644
> --- a/lib/rsa/Makefile
> +++ b/lib/rsa/Makefile
> @@ -5,5 +5,6 @@
>  # (C) Copyright 2000-2007
>  # Wolfgang Denk, DENX Software Engineering, wd at denx.de.
>
> -obj-$(CONFIG_RSA_VERIFY) += rsa-verify.o rsa-checksum.o rsa-keyprop.o
> +obj-$(CONFIG_RSA_VERIFY) += rsa-verify.o rsa-checksum.o
> +obj-$(CONFIG_RSA_VERIFY_WITH_PKEY) += rsa-keyprop.o
>  obj-$(CONFIG_RSA_SOFTWARE_EXP) += rsa-mod-exp.o
> diff --git a/lib/rsa/rsa-verify.c b/lib/rsa/rsa-verify.c
> index 287fcc4d234d..80eabff3e940 100644
> --- a/lib/rsa/rsa-verify.c
> +++ b/lib/rsa/rsa-verify.c
> @@ -17,9 +17,14 @@
>  #include "mkimage.h"
>  #include <fdt_support.h>
>  #endif
> +#include <linux/kconfig.h>
>  #include <u-boot/rsa-mod-exp.h>
>  #include <u-boot/rsa.h>
>
> +#ifndef __UBOOT__ /* for host tools */
> +#undef CONFIG_RSA_VERIFY_WITH_PKEY
> +#endif
> +
>  /* Default public exponent for backward compatibility */
>  #define RSA_DEFAULT_PUBEXP     65537
>
> @@ -342,6 +347,34 @@ static int rsa_verify_key(struct image_sign_info *info,
>         return 0;
>  }
>
> +#ifdef CONFIG_RSA_VERIFY_WITH_PKEY
> +/**
> + * rsa_verify_with_pkey()
> + *
> + */
> +static int rsa_verify_with_pkey(struct image_sign_info *info,
> +                               const void *hash, uint8_t *sig, uint sig_len)
> +{
> +       struct key_prop *prop;
> +       int ret;
> +
> +       /* Public key is self-described to fill key_prop */
> +       prop = rsa_gen_key_prop(info->key, info->keylen);
> +       if (!prop) {
> +               debug("Generating necessary parameter for decoding failed\n");
> +               return -EACCES;
> +       }
> +
> +       ret = rsa_verify_key(info, prop, sig, sig_len, hash,
> +                            info->crypto->key_len);
> +
> +       rsa_free_key_prop(prop);
> +
> +       return ret;
> +}
> +#endif
> +
> +#if CONFIG_IS_ENABLED(FIT_SIGNATURE)
>  /**
>   * rsa_verify_with_keynode() - Verify a signature against some data using
>   * information in node with prperties of RSA Key like modulus, exponent etc.
> @@ -395,18 +428,21 @@ static int rsa_verify_with_keynode(struct image_sign_info *info,
>
>         return ret;
>  }
> +#endif
>
>  int rsa_verify(struct image_sign_info *info,
>                const struct image_region region[], int region_count,
>                uint8_t *sig, uint sig_len)
>  {
> -       const void *blob = info->fdt_blob;
>         /* Reserve memory for maximum checksum-length */
>         uint8_t hash[info->crypto->key_len];
> +       int ret = -EACCES;
> +#if CONFIG_IS_ENABLED(FIT_SIGNATURE)
> +       const void *blob = info->fdt_blob;
>         int ndepth, noffset;
>         int sig_node, node;
>         char name[100];
> -       int ret;
> +#endif
>
>         /*
>          * Verify that the checksum-length does not exceed the
> @@ -419,12 +455,6 @@ int rsa_verify(struct image_sign_info *info,
>                 return -EINVAL;
>         }
>
> -       sig_node = fdt_subnode_offset(blob, 0, FIT_SIG_NODENAME);
> -       if (sig_node < 0) {
> -               debug("%s: No signature node found\n", __func__);
> -               return -ENOENT;
> -       }
> -
>         /* Calculate checksum with checksum-algorithm */
>         ret = info->checksum->calculate(info->checksum->name,
>                                         region, region_count, hash);
> @@ -433,6 +463,22 @@ int rsa_verify(struct image_sign_info *info,
>                 return -EINVAL;
>         }
>
> +#ifdef CONFIG_RSA_VERIFY_WITH_PKEY

Can this use if() instead of #ifdef?

> +       if (!info->fdt_blob) {
> +               /* don't rely on fdt properties */
> +               ret = rsa_verify_with_pkey(info, hash, sig, sig_len);

Does this support required_keynode?

Please add to the documentation for secure boot in uImage, as this
seems to be a new case.

Also, how do we test this new code?


> +
> +               return ret;
> +       }
> +#endif
> +
> +#if CONFIG_IS_ENABLED(FIT_SIGNATURE)
> +       sig_node = fdt_subnode_offset(blob, 0, FIT_SIG_NODENAME);
> +       if (sig_node < 0) {
> +               debug("%s: No signature node found\n", __func__);
> +               return -ENOENT;
> +       }
> +
>         /* See if we must use a particular key */
>         if (info->required_keynode != -1) {
>                 ret = rsa_verify_with_keynode(info, hash, sig, sig_len,
> @@ -459,6 +505,7 @@ int rsa_verify(struct image_sign_info *info,
>                                 break;
>                 }
>         }
> +#endif
>
>         return ret;
>  }
> --
> 2.21.0
>