From: Roland Hieber <rhi@pengutronix.de>
To: ptxdist@pengutronix.de
Cc: Roland Hieber <rhi@pengutronix.de>
Subject: [ptxdist] [PATCH v2 2/3] kernel: add support for module signing
Date: Fri, 23 Jul 2021 16:29:55 +0200 [thread overview]
Message-ID: <20210723142956.31879-2-rhi@pengutronix.de> (raw)
In-Reply-To: <20210723142956.31879-1-rhi@pengutronix.de>
Use the code signing role 'kernel-modules' to supply the kernel with the
key for kernel module singing. This only works if kernel module signing
is enabled in the kernel config file, so write a short paragraph for the
"daily use" chapter in the docs what has to be considered when using
module signing in PTXdist.
Signed-off-by: Roland Hieber <rhi@pengutronix.de>
---
PATCH v2:
- rebase to current master
- split trusted key handling into its own patch (see previous patch)
- add CONFIG_MODULE_SIG_KEY to KENREL_BASE_OPT instead of
KERNEL_SIGN_OPT, and only if module signing is enabled in the
platformconfig
- fix some typos and adapt documentation
PATCH v1: https://lore.ptxdist.org/ptxdist/20210719183053.3799-1-rhi@pengutronix.de
doc/daily_work.inc | 38 ++++++++++++++++++++++++++++++++++++++
platforms/kernel.in | 15 +++++++++++++++
rules/kernel.make | 4 ++++
3 files changed, 57 insertions(+)
diff --git a/doc/daily_work.inc b/doc/daily_work.inc
index 4562b5ca70b9..37bb9bc48180 100644
--- a/doc/daily_work.inc
+++ b/doc/daily_work.inc
@@ -157,6 +157,44 @@ add those certificates to the kernel trust root.
:ref:`cs_append_ca_from_pem`, or :ref:`cs_append_ca_from_uri` with the
``kernel-trusted`` role to supply those certificates.)
+Note that the kernel also always adds the module signing key to the trust root
+(see :ref:`kernel_module_signing` below).
+If the EVM key is signed by the module signing key (or if the two keys are the
+same *and* it is self-signed), no additional trust CA is necessary.
+
+.. _kernel_module_signing:
+
+Kernel Module Signing
+~~~~~~~~~~~~~~~~~~~~~
+
+The kernel's build system can generate cryptographic signatures for all
+kernel modules during the build process.
+This can ensure that all modules loaded on the target at runtime have been
+built by a trustworthy source.
+
+If ``PTXCONF_KERNEL_MODULES_SIGN`` ("sign modules") is enabled in the
+platformconfig, PTXdist augments the kernel config with the following config
+options during the `kernel.compile` and `kernel.install` stages:
+
+* ``CONFIG_MODULE_SIG_KEY`` ("File name or PKCS#11 URI of module signing key"):
+ PTXdist supplies the URI from the ``kernel-modules`` role of the configured
+ code signing provider.
+ (The code signing provider should use :ref:`cs_set_uri` to set the URI.)
+
+However, additional settings must also be enabled in the kernel config:
+
+* ``CONFIG_MODULE_SIG=y`` ("Module signature verification"):
+ Enable this option for module signing, and to get access to its sub-options.
+* ``CONFIG_MODULE_SIG_ALL=y`` ("Automatically sign all modules"):
+ Enable this option so that the kernel's build system signs the modules during
+ PTXdist's `kernel.install` stage.
+* Additionally, ``CONFIG_MODULE_SIG_FORCE`` ("Require modules to be validly
+ signed") can be useful so that the kernel refuses loading modules with
+ invalid, untrusted, or no signature.
+
+For the full overview, refer to the `kernel's module signing documentation
+<https://www.kernel.org/doc/html/latest/admin-guide/module-signing.html>`_.
+
Discovering Runtime Dependencies
--------------------------------
diff --git a/platforms/kernel.in b/platforms/kernel.in
index 8fe47b741fa7..ff3cc8df4f47 100644
--- a/platforms/kernel.in
+++ b/platforms/kernel.in
@@ -39,6 +39,21 @@ config KERNEL_MODULES_INSTALL
prompt "Install modules into /lib/modules"
depends on KERNEL_MODULES
+config KERNEL_MODULES_SIGN
+ bool
+ depends on KERNEL_MODULES
+ select KERNEL_CODE_SIGNING
+ select KERNEL_MODULES_INSTALL
+ prompt "sign modules"
+ help
+ If enabled, kernel modules are signed during the install stage with
+ the key specified by the code signing provider in the "kernel-modules"
+ role.
+
+ See the section "Kernel module signing" in the "Daily Work" chapter in
+ the PTXdist manual for use cases and more infos about what needs to be
+ enabled in the kernel config file.
+
config KERNEL_VERSION
prompt "kernel version"
string
diff --git a/rules/kernel.make b/rules/kernel.make
index ac27450832df..9caff677918e 100644
--- a/rules/kernel.make
+++ b/rules/kernel.make
@@ -76,6 +76,10 @@ KERNEL_BASE_OPT += \
$(if $(shell cs_get_ca kernel-trusted), \
CONFIG_SYSTEM_TRUSTED_KEYS=$(shell cs_get_ca kernel-trusted))
endif
+ifdef PTXCONF_KERNEL_MODULES_SIGN
+KERNEL_BASE_OPT += \
+ CONFIG_MODULE_SIG_KEY='"$(shell cs_get_uri kernel-modules)"'
+endif
# Intermediate option. This will be used by kernel module packages.
KERNEL_MODULE_OPT = \
--
2.30.2
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next prev parent reply other threads:[~2021-07-23 14:30 UTC|newest]
Thread overview: 6+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-07-23 14:29 [ptxdist] [PATCH v2 1/3] kernel: add CAs from the code signing provider to the kernel trust root Roland Hieber
2021-07-23 14:29 ` Roland Hieber [this message]
2021-07-27 6:21 ` [ptxdist] [APPLIED] kernel: add support for module signing Michael Olbrich
2021-07-23 14:29 ` [ptxdist] [PATCH v2 3/3] host-ptx-code-signing-dev: version bump 0.5 -> 0.6 Roland Hieber
2021-07-27 6:21 ` [ptxdist] [APPLIED] " Michael Olbrich
2021-07-27 6:21 ` [ptxdist] [APPLIED] kernel: add CAs from the code signing provider to the kernel trust root Michael Olbrich
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