On Thu, 3 Oct 2024 at 15:51, Raymond Mao raymond.mao@linaro.org wrote:
Integrate MbedTLS v3.6 LTS (currently v3.6.0) with U-Boot.
Motivations:
- MbedTLS is well maintained with LTS versions.
- LWIP is integrated with MbedTLS and easily to enable HTTPS.
- 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:
- Decoding of Microsoft Authentication Code.
- Decoding of PKCS#9 Authenticate Attributes.
- Extending MbedTLS PKCS#7 lib to support multiple signer's certificates.
- 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