Re: [PATCH v10 3/3] integrity: support including firmware ".platform" keys at build time

From: Jarkko Sakkinen
Date: Mon Mar 07 2022 - 07:52:16 EST

On Mon, Mar 07, 2022 at 02:48:52PM +0200, Jarkko Sakkinen wrote:
> 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@xxxxxxxxxxxxx>
> > Signed-off-by: Nayna Jain <nayna@xxxxxxxxxxxxx>
> > ---
> > 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

At least for the next PR, I'm not including this, sorry.

BR, Jarkko