[PATCH v8 00/27] Integrate MbedTLS v3.6 LTS with U-Boot

[Simon Glass]

On Thu, 3 Oct 2024 at 15:51, 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_CRYPTO_ALT` is for using original U-Boot crypto libs as
> MbedTLS crypto alternatives.
> `MBEDTLS_LIB_X509` is for replacing original X509, PKCS7, MSCode, ASN1,
> and Pubkey parser with MbedTLS.
> By default `MBEDTLS_LIB_CRYPTO_ALT` and `MBEDTLS_LIB_X509` are selected
> when `MBEDTLS_LIB` is enabled.
> `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.
>
> [1]: buildman output for size comparison (With both `MBEDTLS_LIB` and
> `MBEDTLS_LIB_CRYPTO` selected)
> (qemu_arm64, sandbox and nanopi_a64)
> ```
>    aarch64: (for 2/2 boards) all -1568.0 bss -8.0 data -64.0 rodata +200.0 text -1696.0
>             qemu_arm64     : all +4472 bss -16 data -64 rodata +200 text +4352
>                u-boot: add: 29/-14, grow: 6/-13 bytes: 12812/-8084 (4728)
>                  function                                   old     new   delta
>                  mbedtls_internal_sha1_process                -    4540   +4540

I am not going to review this version as others are on top of this. It
looks reasonable to me. We do need to tidy up the hashing in
common/hash.c at some point but this series doesn't add to the pain
there.

I do worry about the size growth, though. Do we want/need the mbed
algorithms? Why are they so large?

Regards,
Simon