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

From: Jarkko Sakkinen
Date: Tue Mar 08 2022 - 04:33:50 EST

On Mon, Mar 07, 2022 at 05:03:09PM -0500, Mimi Zohar wrote:
> [Cc'ing Masahiro Yamada]
>
> On Mon, 2022-03-07 at 14:48 +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
>
> I've reviewed and tested this patch set each time it was posted last
> fall/winter. Recent changes were limited to the cover letter and patch
> description. Only recently was "extract_cert" moved to the certs/
> directory and not built automatically. The commit message says the
> move was because it wasn't being used outside the certs directory.
> Refer to commit 340a02535ee7 ("certs: move scripts/extract-cert to
> certs/").
>
> Masahiro Yamada would you be ok with reverting the move?
>
> thanks,
>
> Mimi

OK, so I can add your tested-by? It was missing, that's where the
concern came from.

BR, Jarkko