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Message-Id: <20260113-module-hashes-v4-0-0b932db9b56b@weissschuh.net>
Date: Tue, 13 Jan 2026 13:28:44 +0100
From: Thomas Weißschuh <linux@...ssschuh.net>
To: Nathan Chancellor <nathan@...nel.org>, Arnd Bergmann <arnd@...db.de>,
Luis Chamberlain <mcgrof@...nel.org>, Petr Pavlu <petr.pavlu@...e.com>,
Sami Tolvanen <samitolvanen@...gle.com>,
Daniel Gomez <da.gomez@...sung.com>, Paul Moore <paul@...l-moore.com>,
James Morris <jmorris@...ei.org>, "Serge E. Hallyn" <serge@...lyn.com>,
Jonathan Corbet <corbet@....net>, Madhavan Srinivasan <maddy@...ux.ibm.com>,
Michael Ellerman <mpe@...erman.id.au>, Nicholas Piggin <npiggin@...il.com>,
Naveen N Rao <naveen@...nel.org>, Mimi Zohar <zohar@...ux.ibm.com>,
Roberto Sassu <roberto.sassu@...wei.com>,
Dmitry Kasatkin <dmitry.kasatkin@...il.com>,
Eric Snowberg <eric.snowberg@...cle.com>,
Nicolas Schier <nicolas.schier@...ux.dev>,
Daniel Gomez <da.gomez@...nel.org>, Aaron Tomlin <atomlin@...mlin.com>,
"Christophe Leroy (CS GROUP)" <chleroy@...nel.org>,
Nicolas Schier <nsc@...nel.org>,
Nicolas Bouchinet <nicolas.bouchinet@....cyber.gouv.fr>,
Xiu Jianfeng <xiujianfeng@...wei.com>, Nicolas Schier <nsc@...nel.org>,
Christophe Leroy <chleroy@...nel.org>
Cc: Fabian Grünbichler <f.gruenbichler@...xmox.com>,
Arnout Engelen <arnout@...t.net>, Mattia Rizzolo <mattia@...reri.org>,
kpcyrd <kpcyrd@...hlinux.org>, Christian Heusel <christian@...sel.eu>,
Câju Mihai-Drosi <mcaju95@...il.com>,
Sebastian Andrzej Siewior <bigeasy@...utronix.de>,
linux-kbuild@...r.kernel.org, linux-kernel@...r.kernel.org,
linux-arch@...r.kernel.org, linux-modules@...r.kernel.org,
linux-security-module@...r.kernel.org, linux-doc@...r.kernel.org,
linuxppc-dev@...ts.ozlabs.org, linux-integrity@...r.kernel.org,
Thomas Weißschuh <linux@...ssschuh.net>,
Coiby Xu <coxu@...hat.com>, kernel test robot <lkp@...el.com>
Subject: [PATCH v4 00/17] module: Introduce hash-based integrity checking
The current signature-based module integrity checking has some drawbacks
in combination with reproducible builds. Either the module signing key
is generated at build time, which makes the build unreproducible, or a
static signing key is used, which precludes rebuilds by third parties
and makes the whole build and packaging process much more complicated.
The goal is to reach bit-for-bit reproducibility. Excluding certain
parts of the build output from the reproducibility analysis would be
error-prone and force each downstream consumer to introduce new tooling.
Introduce a new mechanism to ensure only well-known modules are loaded
by embedding a merkle tree root of all modules built as part of the full
kernel build into vmlinux.
Interest has been proclaimed by NixOS, Arch Linux, Proxmox, SUSE and the
general reproducible builds community.
Compatibility with IMA modsig is not provided yet. It is still unclear
to me if it should be hooked up transparently without any changes to the
policy or it should require new policy options.
Further improvements:
* Use MODULE_SIG_HASH for configuration
* UAPI for discovery?
Signed-off-by: Thomas Weißschuh <linux@...ssschuh.net>
---
Changes in v4:
- Use as Merkle tree over a linera list of hashes.
- Provide compatibilith with INSTALL_MOD_STRIP
- Rework commit messages.
- Use vmlinux.unstripped over plain "vmlinux".
- Link to v3: https://lore.kernel.org/r/20250429-module-hashes-v3-0-00e9258def9e@weissschuh.net
Changes in v3:
- Rebase on v6.15-rc1
- Use openssl to calculate hash
- Avoid warning if no modules are built
- Simplify module_integrity_check() a bit
- Make incompatibility with INSTALL_MOD_STRIP explicit
- Update docs
- Add IMA cleanups
- Link to v2: https://lore.kernel.org/r/20250120-module-hashes-v2-0-ba1184e27b7f@weissschuh.net
Changes in v2:
- Drop RFC state
- Mention interested parties in cover letter
- Expand Kconfig description
- Add compatibility with CONFIG_MODULE_SIG
- Parallelize module-hashes.sh
- Update Documentation/kbuild/reproducible-builds.rst
- Link to v1: https://lore.kernel.org/r/20241225-module-hashes-v1-0-d710ce7a3fd1@weissschuh.net
---
Coiby Xu (1):
module: Only declare set_module_sig_enforced when CONFIG_MODULE_SIG=y
Thomas Weißschuh (16):
powerpc/ima: Drop unnecessary check for CONFIG_MODULE_SIG
ima: efi: Drop unnecessary check for CONFIG_MODULE_SIG/CONFIG_KEXEC_SIG
module: Make mod_verify_sig() static
module: Switch load_info::len to size_t
kbuild: add stamp file for vmlinux BTF data
kbuild: generate module BTF based on vmlinux.unstripped
module: Deduplicate signature extraction
module: Make module loading policy usable without MODULE_SIG
module: Move integrity checks into dedicated function
module: Move lockdown check into generic module loader
module: Move signature splitting up
module: Report signature type to users
lockdown: Make the relationship to MODULE_SIG a dependency
module: Introduce hash-based integrity checking
kbuild: move handling of module stripping to Makefile.lib
kbuild: make CONFIG_MODULE_HASHES compatible with module stripping
.gitignore | 2 +
Documentation/kbuild/reproducible-builds.rst | 5 +-
Makefile | 8 +-
arch/powerpc/kernel/ima_arch.c | 3 +-
include/asm-generic/vmlinux.lds.h | 11 +
include/linux/module.h | 20 +-
include/linux/module_hashes.h | 25 ++
include/linux/module_signature.h | 5 +-
kernel/module/Kconfig | 29 +-
kernel/module/Makefile | 1 +
kernel/module/hashes.c | 92 ++++++
kernel/module/hashes_root.c | 6 +
kernel/module/internal.h | 13 +-
kernel/module/main.c | 68 +++-
kernel/module/signing.c | 83 +----
kernel/module_signature.c | 49 ++-
scripts/.gitignore | 1 +
scripts/Makefile | 3 +
scripts/Makefile.lib | 32 ++
scripts/Makefile.modfinal | 28 +-
scripts/Makefile.modinst | 46 +--
scripts/Makefile.vmlinux | 6 +
scripts/link-vmlinux.sh | 20 +-
scripts/modules-merkle-tree.c | 467 +++++++++++++++++++++++++++
security/integrity/ima/ima_efi.c | 6 +-
security/integrity/ima/ima_modsig.c | 28 +-
security/lockdown/Kconfig | 2 +-
27 files changed, 884 insertions(+), 175 deletions(-)
---
base-commit: 8f0b4cce4481fb22653697cced8d0d04027cb1e8
change-id: 20241225-module-hashes-7a50a7cc2a30
Best regards,
--
Thomas Weißschuh <linux@...ssschuh.net>
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