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

[Simon Glass <sjg@chromium.org>]

Hi Takahiro,

On Tue, 22 Oct 2019 at 23:43, AKASHI Takahiro
<takahiro.akashi@linaro.org> wrote:
>
> On Tue, Oct 22, 2019 at 07:50:20AM -0600, Simon Glass wrote:
> > Hi Takahiro,
> >
> > On Tue, 17 Sep 2019 at 20:59, AKASHI Takahiro
> > <takahiro.akashi@linaro.org> wrote:
> > >
> > > Simon,
> > >
> > > Overall, do you agree to my approach here?
> > >
> > > On Mon, Sep 16, 2019 at 10:48:07PM -0700, Simon Glass wrote:
> > > > Hi AKASHI,
> > > >
> > > > On Fri, 6 Sep 2019 at 00:06, AKASHI Takahiro <takahiro.akashi@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@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.
> > >
> > > Will add more description.
> > >
> > > > > +
> > > > >  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)
> >
> > Can you use if() instead of #if ?
>
> This code is for local variable declaration, and so changing as you suggested
> can be difficult. Or do you accept moving this stuff further down to the next
> "#if CONFIG_IS_ENABLED(FIT_SIGNATURE)":

Yes if you use if() then you don't need to #ifdef the variables.

> === 8< ===
> if (IS_ENABLED(CONFIG_RSA_VERIFY_WITH_PKEY) && !info->fdt_blob) {
>         /* don't rely on fdt properties */
>                 ret = rsa_verify_with_pkey(info, hash, sig, sig_len);
>
>                 return ret;
> }
>
> if (CONFIG_IS_ENABLED(FIT_SIGNATURE)) {
>         /*
>          * declare variables here!
>          */
>         const void *blob = info->fdt_blob;
>         int ndepth, noffset;
>         int sig_node, node;
>         char name[100];
>
>         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 */
>         ...
> }
> === >8 ===
>
> Otherwise, we will have to introduce another function, rsa_verify_with_fdt?,
> just for this purpose.
>

Regards,
Simon