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Date: Mon, 7 Mar 2022 14:48:52 +0200
From: Jarkko Sakkinen <jarkko@...nel.org>
To: Nayna Jain <nayna@...ux.ibm.com>
Cc: linux-integrity@...r.kernel.org, keyrings@...r.kernel.org,
dhowells@...hat.com, zohar@...ux.ibm.com,
linux-security-module@...r.kernel.org,
linux-kernel@...r.kernel.org, dimitri.ledkov@...onical.com,
seth@...shee.me, rnsastry@...ux.ibm.com
Subject: Re: [PATCH v10 3/3] integrity: support including firmware
".platform" keys at build time
On Sun, Mar 06, 2022 at 03:51:00PM -0500, Nayna Jain wrote:
> Allow firmware keys to be embedded in the Linux kernel and loaded onto
> the ".platform" keyring on boot.
>
> The firmware keys can be specified in a file as a list of PEM encoded
> certificates using new config INTEGRITY_PLATFORM_KEYS. The certificates
> are embedded in the image by converting the PEM-formatted certificates
> into DER(binary) and generating
> security/integrity/platform_certs/platform_certificate_list file at
> build time. On boot, the embedded certs from the image are loaded onto
> the ".platform" keyring at late_initcall(), ensuring the platform keyring
> exists before loading the keys.
>
> Reviewed-by: Mimi Zohar <zohar@...ux.ibm.com>
> Signed-off-by: Nayna Jain <nayna@...ux.ibm.com>
> ---
> security/integrity/Kconfig | 10 ++++++++
> security/integrity/Makefile | 15 +++++++++++-
> security/integrity/integrity.h | 3 +++
> .../integrity/platform_certs/platform_cert.S | 23 +++++++++++++++++++
> .../platform_certs/platform_keyring.c | 23 +++++++++++++++++++
> 5 files changed, 73 insertions(+), 1 deletion(-)
> create mode 100644 security/integrity/platform_certs/platform_cert.S
>
> diff --git a/security/integrity/Kconfig b/security/integrity/Kconfig
> index 599429f99f99..77b2c22c0e1b 100644
> --- a/security/integrity/Kconfig
> +++ b/security/integrity/Kconfig
> @@ -62,6 +62,16 @@ config INTEGRITY_PLATFORM_KEYRING
> provided by the platform for verifying the kexec'ed kerned image
> and, possibly, the initramfs signature.
>
> +config INTEGRITY_PLATFORM_KEYS
> + string "Builtin X.509 keys for .platform keyring"
> + depends on KEYS
> + depends on ASYMMETRIC_KEY_TYPE
> + depends on INTEGRITY_PLATFORM_KEYRING
> + help
> + If set, this option should be the filename of a PEM-formatted file
> + containing X.509 certificates to be loaded onto the ".platform"
> + keyring.
> +
> config INTEGRITY_MACHINE_KEYRING
> bool "Provide a keyring to which Machine Owner Keys may be added"
> depends on SECONDARY_TRUSTED_KEYRING
> diff --git a/security/integrity/Makefile b/security/integrity/Makefile
> index d0ffe37dc1d6..65bd93301a3a 100644
> --- a/security/integrity/Makefile
> +++ b/security/integrity/Makefile
> @@ -3,13 +3,17 @@
> # Makefile for caching inode integrity data (iint)
> #
>
> +quiet_cmd_extract_certs = CERT $@
> + cmd_extract_certs = certs/extract-cert $(2) $@
> +
> obj-$(CONFIG_INTEGRITY) += integrity.o
>
> integrity-y := iint.o
> integrity-$(CONFIG_INTEGRITY_AUDIT) += integrity_audit.o
> integrity-$(CONFIG_INTEGRITY_SIGNATURE) += digsig.o
> integrity-$(CONFIG_INTEGRITY_ASYMMETRIC_KEYS) += digsig_asymmetric.o
> -integrity-$(CONFIG_INTEGRITY_PLATFORM_KEYRING) += platform_certs/platform_keyring.o
> +integrity-$(CONFIG_INTEGRITY_PLATFORM_KEYRING) += platform_certs/platform_keyring.o \
> + platform_certs/platform_cert.o
> integrity-$(CONFIG_INTEGRITY_MACHINE_KEYRING) += platform_certs/machine_keyring.o
> integrity-$(CONFIG_LOAD_UEFI_KEYS) += platform_certs/efi_parser.o \
> platform_certs/load_uefi.o \
> @@ -20,3 +24,12 @@ integrity-$(CONFIG_LOAD_PPC_KEYS) += platform_certs/efi_parser.o \
> platform_certs/keyring_handler.o
> obj-$(CONFIG_IMA) += ima/
> obj-$(CONFIG_EVM) += evm/
> +
> +$(obj)/platform_certs/platform_cert.o: $(obj)/platform_certs/platform_certificate_list
> +
> +targets += platform_certificate_list
> +
> +$(obj)/platform_certs/platform_certificate_list: $(CONFIG_INTEGRITY_PLATFORM_KEYS) certs/extract-cert FORCE
> + $(call if_changed,extract_certs,$(if $(CONFIG_INTEGRITY_PLATFORM_KEYS),$<,""))
> +
> +clean-files := platform_certs/platform_certificate_list
> diff --git a/security/integrity/integrity.h b/security/integrity/integrity.h
> index 76e9a9515f99..219da29fecf7 100644
> --- a/security/integrity/integrity.h
> +++ b/security/integrity/integrity.h
> @@ -282,6 +282,9 @@ integrity_audit_log_start(struct audit_context *ctx, gfp_t gfp_mask, int type)
> #endif
>
> #ifdef CONFIG_INTEGRITY_PLATFORM_KEYRING
> +extern __initconst const u8 platform_certificate_list[];
> +extern __initconst const unsigned long platform_certificate_list_size;
> +
> void __init add_to_platform_keyring(const char *source, const void *data,
> size_t len);
> #else
> diff --git a/security/integrity/platform_certs/platform_cert.S b/security/integrity/platform_certs/platform_cert.S
> new file mode 100644
> index 000000000000..20bccce5dc5a
> --- /dev/null
> +++ b/security/integrity/platform_certs/platform_cert.S
> @@ -0,0 +1,23 @@
> +/* SPDX-License-Identifier: GPL-2.0 */
> +#include <linux/export.h>
> +#include <linux/init.h>
> +
> + __INITRODATA
> +
> + .align 8
> +#ifdef CONFIG_INTEGRITY_PLATFORM_KEYRING
> + .globl platform_certificate_list
> +platform_certificate_list:
> +__cert_list_start:
> + .incbin "security/integrity/platform_certs/platform_certificate_list"
> +__cert_list_end:
> +#endif
> +
> + .align 8
> + .globl platform_certificate_list_size
> +platform_certificate_list_size:
> +#ifdef CONFIG_64BIT
> + .quad __cert_list_end - __cert_list_start
> +#else
> + .long __cert_list_end - __cert_list_start
> +#endif
> diff --git a/security/integrity/platform_certs/platform_keyring.c b/security/integrity/platform_certs/platform_keyring.c
> index bcafd7387729..c2368912fd1b 100644
> --- a/security/integrity/platform_certs/platform_keyring.c
> +++ b/security/integrity/platform_certs/platform_keyring.c
> @@ -12,6 +12,7 @@
> #include <linux/cred.h>
> #include <linux/err.h>
> #include <linux/slab.h>
> +#include <keys/system_keyring.h>
> #include "../integrity.h"
>
> /**
> @@ -37,6 +38,28 @@ void __init add_to_platform_keyring(const char *source, const void *data,
> pr_info("Error adding keys to platform keyring %s\n", source);
> }
>
> +static __init int load_platform_certificate_list(void)
> +{
> + const u8 *p;
> + unsigned long size;
> + int rc;
> + struct key *keyring;
> +
> + p = platform_certificate_list;
> + size = platform_certificate_list_size;
> +
> + keyring = integrity_keyring_from_id(INTEGRITY_KEYRING_PLATFORM);
> + if (IS_ERR(keyring))
> + return PTR_ERR(keyring);
> +
> + rc = load_certificate_list(p, size, keyring);
> + if (rc)
> + pr_info("Error adding keys to platform keyring %d\n", rc);
> +
> + return rc;
> +}
> +late_initcall(load_platform_certificate_list);
> +
> /*
> * Create the trusted keyrings.
> */
> --
> 2.27.0
>
There's zero tested-by's for this, i.e. cannot be applied before someone
has tested this. Mimi, do not mean to be rude, but I don't frankly
understand why you ask to pick a patch set that is *untested*.
So I generated a self-signed certificate:
openssl req -x509 -out localhost.crt -keyout localhost.key \
-newkey rsa:2048 -nodes -sha256 \
-subj '/CN=localhost' -extensions EXT -config <( \
printf "[dn]\nCN=localhost\n[req]\ndistinguished_name = dn\n[EXT]\nsubjectAltName=DNS:localhost\nkeyUsage=digitalSignature\nextendedKeyUsage=serverAuth")
(by courtesy of letsencrypt: https://letsencrypt.org/docs/certificates-for-localhost/)
openssl x509 -in localhost.crt -out localhost.pem -outform PEM
And starting with tinyconfig I added minimal options to enable this
feature. The config is attached.
The end result is:
make[2]: *** No rule to make target 'certs/extract-cert', needed by 'security/integrity/platform_certs/platform_certificate_list'. Stop.
make[1]: *** [scripts/Makefile.build:550: security/integrity] Error 2
make: *** [Makefile:1831: security] Error 2
BR, Jarkko
View attachment ".config" of type "text/plain" (35368 bytes)
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