[PATCH v6 00/28] Integrate MbedTLS v3.6 LTS with U-Boot

[Raymond Mao]

Hi Simon,

On Thu, 5 Sept 2024 at 20:43, Simon Glass <sjg at chromium.org> wrote:

> Hi Raymond,
>
> On Tue, 3 Sept 2024 at 08:59, Raymond Mao <raymond.mao at linaro.org> wrote:
> >
> > Hi Simon,
> >
> > On Sat, 17 Aug 2024 at 11:58, Simon Glass <sjg at chromium.org> wrote:
> >>
> >> Hi Raymond,
> >>
> >> On Fri, 16 Aug 2024 at 15:44, Raymond Mao <raymond.mao at linaro.org>
> wrote:
> >> >
> >> > Integrate MbedTLS v3.6 LTS (currently v3.6.0) with U-Boot.
> >> >
> >> > Motivations:
> >> > ------------
> >> >
> >> > 1. MbedTLS is well maintained with LTS versions.
> >> > 2. LWIP is integrated with MbedTLS and easily to enable HTTPS.
> >> > 3. MbedTLS recently switched license back to GPLv2.
> >> >
> >> > Prerequisite:
> >> > -------------
> >> >
> >> > This patch series requires mbedtls git repo to be added as a
> >> > subtree to the main U-Boot repo via:
> >> >     $ git subtree add --prefix lib/mbedtls/external/mbedtls \
> >> >           https://github.com/Mbed-TLS/mbedtls.git \
> >> >           v3.6.0 --squash
> >> > Moreover, due to the Windows-style files from mbedtls git repo,
> >> > we need to convert the CRLF endings to LF and do a commit manually:
> >> >     $ git add --renormalize .
> >> >     $ git commit
> >> >
> >> > New Kconfig options:
> >> > --------------------
> >> >
> >> > `MBEDTLS_LIB` is for MbedTLS general switch.
> >> > `MBEDTLS_LIB_CRYPTO` is for replacing original digest and crypto libs
> with
> >> > MbedTLS.
> >> > `MBEDTLS_LIB_X509` is for replacing original X509, PKCS7, MSCode,
> ASN1,
> >> > and Pubkey parser with MbedTLS.
> >> > `LEGACY_CRYPTO` is introduced as a main switch for legacy crypto
> library.
> >> > `LEGACY_CRYPTO_BASIC` is for the basic crypto functionalities and
> >> > `LEGACY_CRYPTO_CERT` is for the certificate related functionalities.
> >> > For each of the algorithm, a pair of `<alg>_LEGACY` and
> `<alg>_MBEDTLS`
> >> > Kconfig options are introduced. Meanwhile, `SPL_` Kconfig options are
> >> > introduced.
> >> >
> >> > In this patch set, MBEDTLS_LIB, MBEDTLS_LIB_CRYPTO and
> MBEDTLS_LIB_X509
> >> > are by default enabled in qemu_arm64_defconfig and sandbox_defconfig
> >> > for testing purpose.
> >> >
> >> > Patches for external MbedTLS project:
> >> > -------------------------------------
> >> >
> >> > Since U-Boot uses Microsoft Authentication Code to verify PE/COFFs
> >> > executables which is not supported by MbedTLS at the moment,
> >> > addtional patches for MbedTLS are created to adapt with the EFI
> loader:
> >> > 1. Decoding of Microsoft Authentication Code.
> >> > 2. Decoding of PKCS#9 Authenticate Attributes.
> >> > 3. Extending MbedTLS PKCS#7 lib to support multiple signer's
> certificates.
> >> > 4. MbedTLS native test suites for PKCS#7 signer's info.
> >> >
> >> > All above 4 patches (tagged with `mbedtls/external`) are submitted to
> >> > MbedTLS project and being reviewed, eventually they should be part of
> >> > MbedTLS LTS release.
> >> > But before that, please merge them into U-Boot, otherwise the building
> >> > will be broken when MBEDTLS_LIB_X509 is enabled.
> >> >
> >> > See below PR link for the reference:
> >> > https://github.com/Mbed-TLS/mbedtls/pull/9001
> >> >
> >> > Miscellaneous:
> >> > --------------
> >> >
> >> > Optimized MbedTLS library size by tailoring the config file
> >> > and disabling all unnecessary features for EFI loader.
> >> > From v2, original libs (rsa, asn1_decoder, rsa_helper, md5, sha1,
> sha256,
> >> > sha512) are completely replaced when MbedTLS is enabled.
> >> > From v3, the size-growth is slightly reduced by refactoring Hash
> functions.
> >> > From v6, smaller implementations for SHA256 and SHA512 are enabled and
> >> > target size reduce significantly.
> >> > Target(QEMU arm64) size-growth when enabling MbedTLS:
> >> > v1: 6.03%
> >> > v2: 4.66%
> >> > v3 - v5: 4.55%
> >> > v6: 2.90%
> >> >
> >> > Please see the latest output from buildman for size-growth on QEMU
> arm64,
> >> > Sandbox and Nanopi A64. [1]
> >> >
> >> > Tests done:
> >> > -----------
> >> >
> >> > EFI Secure Boot test (EFI variables loading and verifying, EFI signed
> image
> >> > verifying and booting) via U-Boot console.
> >> > EFI Secure Boot and Capsule sandbox test passed.
> >> >
> >> > Known issues:
> >> > -------------
> >> >
> >> > None.
> >>
> >> I wonder if we could leave out the SHA stuff? The algorithms are
> >> stable and this would seem to avoid much of the size growth, and all
> >> the pain of trying to integrate another yet another hashing layer (we
> >> already have normal, progressive and h/w acceleration, plus
> >> UCLASS_HASH which h/w acceleration should use but that migration never
> >> happened). I struggle to see any benefit in replacing U-Boot's very
> >> solid hashing infra with something else, particularly as this series
> >> adds yet another. Better to invest the time to refactor it. I asked
> >> about this before and was told that it would happen 'later'. Let's
> >> just not change it at all, then it is more likely someone will sort it
> >> out.
> >>
> > Unfortunately, MbedTLS depends on its own digest layer. Unless we patch
> MbedTLS
> > to allow an external digest library from U-Boot ...
>
> Yes that sounds best. It looks like only a few call sites, so it
> should be a matter of leaving out the MbedTLS code and adding some
> static inlines.
>
> Inspired by Ilias's reply to patch #7, though we can use the MbedTLS hash
alternative options,
we still need to convert all U-Boot hash APIs to adapt to the MbedTLS style.
This will impact all callers in U-Boot and I don't think it worth to do, at
least now.
As the first patch set to introduce MbedTLS to U-Boot with turning on all
necessary features,
I think this patch set is in the best way with an overall consideration.

[snip]

Raymond