Re: [PATCH v4 00/29] Integrate MbedTLS v3.6 LTS with U-Boot

[Tom Rini <trini@konsulko.com>]

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On Wed, Jul 24, 2024 at 10:34:50AM -0400, Raymond Mao wrote:
> Hi Tom,
> 
> On Tue, 2 Jul 2024 at 21:26, Tom Rini <trini@konsulko.com> wrote:
> 
> > On Tue, Jul 02, 2024 at 11:22:36AM -0700, Raymond Mao wrote:
> >
> > > Integrate MbedTLS v3.6 LTS (currently v3.6.0-RC1) 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.
> > > `MBEDTLS_LIB_TLS` is for SSL/TLS (Disabled until LWIP port for MbedTLS is
> > > ready).
> > > `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 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.
> > >
> > > Target(QEMU arm64) size-growth when enabling MbedTLS:
> > > v1: 6.03%
> > > v2: 4.66%
> > > v3 & v4: 4.55%
> > >
> > > Please see the latest output of bloat-o-meter for the reference of the
> > > size-growth on QEMU arm64 target [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.
> > >
> > > [1]: bloat-o-meter output between disabling/enabling MbedTLS (QEMU arm64)
> > > ```
> > > add/remove: 206/81 grow/shrink: 19/17 up/down: 55548/-17495 (38053)
> >
> > bloat-o-meter is a bit off then, since buildman shows:
> > u-boot: add: 243/-17, grow: 18/-17 bytes: 65723/-8480 (57243)
> >
> > (Please use buildman for the size comparisons in the future).
> >
> > The reason that buildman is showing more growth is because I enable
> "CONFIG_EFI_SECURE_BOOT=y" in my patch, which is off by default
> for qemu_arm64.
> Since the buildman is always comparing one local branch with the
> 'upstream' (I didn't find a way to let it compare two local branches or
> maybe
> I am wrong), I guess I have to first merge one commit with just enabling
> CONFIG_EFI_SECURE_BOOT to solve this. But I get this makes less
> value...
> 
> I think it is better to use sandbox for comparison from v5,
> and I will add one more platform (e.g. imx8mp) for reference.

Please note that I check the world before/after, not just single
platforms, for size growth. I'll note some examples of issues when I
find them, typically. And with the wrapper I posted, sometimes I will
"--all" a platform to see which commit increases things.

-- 
Tom

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