[BUG] ut lib lib_rsa_verify_valid crashes on qemu_arm if RSA_VERIFY_WITH_PKEY=y

[Heiko Stübner]

Hi Akashi,

Am Dienstag, 9. Juni 2020, 11:22:35 CEST schrieb AKASHI Takahiro:
> Heinrich,
> 
> On Tue, Jun 09, 2020 at 03:54:44AM +0000, Heinrich Schuchardt wrote:
> > Am June 9, 2020 1:42:14 AM UTC schrieb AKASHI Takahiro <takahiro.akashi at linaro.org>:
> > >Heinrich,
> > >
> > >On Mon, Jun 08, 2020 at 11:08:53PM +0200, Heinrich Schuchardt wrote:
> > >> Hello Takahiro,
> > >> 
> > >> when trying to execute command
> > >> 
> > >> ut lib lib_rsa_verify_valid
> > >> 
> > >> on qemu_arm_defconfig with CONFIG_UNIT_TEST=y and
> > >> CONFIG_RSA_VERIFY_WITH_PKEY=y it crashes in
> > >> 
> > >> free((void *)prop->modulus) called from
> > >> rsa_free_key_prop() called from
> > >> rsa_verify_key() called from
> > >> rsa_verify_with_pkey().
> > >> 
> > >> Without CONFIG_RSA_VERIFY_WITH_PKEY=y the problem does not occur.
> > >> On qemu_arm64_defconfig the problem does not occur.
> > >
> > >I can't reproduce your problem on v2020.07-rc4 exactly with
> > >qemu_arm64_defconfig + PKEY=y:
> > >
> > >U-Boot 2020.07-rc4-dirty (Jun 09 2020 - 10:33:30 +0900)
> > >
> > >...
> > >
> > >=> ut lib
> > >Running 11 lib tests
> > >Test: lib_asn1_pkcs7
> > >Test: lib_asn1_pkey
> > >Test: lib_asn1_x509
> > >Test: lib_memcpy
> > >Test: lib_memmove
> > >Test: lib_memset
> > >Test: lib_rsa_verify_invalid
> > >Test: lib_rsa_verify_valid
> > >Test: lib_test_bin2hex
> > >Test: lib_test_hex2bin
> > >Test: lib_test_hex_to_bin
> > >Failures: 0
> > >
> > >
> > >-Takahiro Akashi
> > 
> > As said I only see the problem with 32 bit qemu_arm_defconfig.
> 
> Okay. I think that the size of rrtmp variable is not good enough
> and when it is handed over to br_i32_decode(), it accidentally
> destroys (*prop)->modulus.
> 
> Heiko's patch:
>   https://lists.denx.de/pipermail/u-boot/2020-May/413101.html
> will also fix this issue, but I'm not yet confident that
> the solution here, doubling max_rsa_size, is a right approach.

The algorithm does write outside its memory area with a big enough key
and I have to confess I had a hard time understanding it ;-) .

So what would be needed to get more confidence?

Because for me it looks like either the algorithm does strange things
or the memory area is too small - I don't really see a third option ;-) .


Heiko