[GIT PULL] MODSIGN: Use PKCS#7 for module signatures [ver #7a]

From: David Howells
Date: Tue Aug 11 2015 - 16:03:57 EST

Hi James,

Can you pull this into security/next please? Its aim is twofold: firstly,
make the module signatures of PKCS#7/CMS format rather than a home-brewed
format and secondly to pave the way for use of the signing code for
firmware signatures (to follow later).

Note that the openssl-devel package is now a requirement for building the
kernel if module signing is enabled as the sign-file program now uses the
OpenSSL libraries directly rather than scripting calls to the openssl

To this end, the patchset effects the following changes:

(1) Extracts both parts of an X.509 AuthorityKeyIdentifier (AKID)
extension. We already extract the bit that can match the
subjectKeyIdentifier (SKID) of the parent X.509 cert, but we currently
ignore the bits that can match the issuer and serialNumber.

Looks up an X.509 cert by issuer and serialNumber if those are
provided in the AKID. If the keyIdentifier is also provided, checks
that the subjectKeyIdentifier of the cert found matches that also.

If no issuer and serialNumber are provided in the AKID, looks up an
X.509 cert by SKID using the AKID keyIdentifier.

This allows module signing to be done with certificates that don't
have an SKID by which they can be looked up.

(2) Makes use of the PKCS#7 facility to provide module signatures.

sign-file is replaced with a program that generates a PKCS#7 message
that has no X.509 certs embedded and that has detached data (the
module content) and adds it onto the message with magic string and

(3) The PKCS#7 message supplies all the information that is needed to
select the X.509 cert to be used to verify the signature by standard
means (including selection of digest algorithm and public key
algorithm). No kernel-specific magic values are required.

(4) Makes it possible to get sign-file to just write out a file containing
the PKCS#7 signature blob. This can be used for debugging and
potentially for firmware signing.

(5) Extracts the function that does PKCS#7 signature verification on a
blob from the module signing code and put it somewhere more general so
that other things, such as firmware signing, can make use of it
without depending on module config options.

(6) Adds support for CMS messages in place of PKCS#7 (they're very similar
ASN.1) and makes sign-file create CMS messages instead of PKCS#7.
This allows signatures to refer to the verifying key by X.509 cert
SKID instead of X.509 cert issuer and serial number.

(7) Provides support for providing a password/pin for an encrypted private
key to sign-file.

(8) Makes it possible to use PKCS#11 with sign-file, thus allowing the use
of cryptographic hardware.

(9) Overhauls the way the module signing key is handled. If the name in
CONFIG_MODULE_SIG_KEY is "signing_key.pem" then a key will be
automatically generated and placed in the build directory. If the
name is different, autogeneration is suppressed and the file is
presumed to be a PEM file containing both the private key and X.509

(10) Overhauls the way auxiliary trusted keys are added to the kernel.
Files matching the pattern "*.x509" are no longer just gathered up and
cat'd together. Now CONFIG_SYSTEM_TRUSTED_KEYS must be set to point
to a single PEM file containing a set of X.509 certs cat'd together if
this facility is desired.

(11) Severely restricts what authenticateAttributes are permitted in a PKCS#7
or CMS message and what content type may be used. This is selected by
the in-kernel user with the appropriate VERIFYING_*_SIGNATURE constant.

Note that the revised sign-file program no longer supports the "-s
<signature>" option to add an externally generated signature. This is
deprecated in favour of using PKCS#11. Note also that the format of the
signature file that would be passed to -s has changed.

There are two changes since the modsign-pkcs7-20150807 tag: a documentation
patch has been added noting the extra dependency and an extra review line
has been added.

The following changes since commit 459c15e53cf7e4e88a78ecfb109af5a267c5500a:

Merge tag 'asn1-fixes-20150805' of git://git.kernel.org/pub/scm/linux/kernel/git/dhowells/linux-fs into next (2015-08-07 13:27:58 +1000)

are available in the git repository at:

git://git.kernel.org/pub/scm/linux/kernel/git/dhowells/linux-fs.git tags/modsign-pkcs7-20150811

for you to fetch changes up to f81977b461ed8e077aa7ad71cb0bb04382f32373:

sign-file: Document dependency on OpenSSL devel libraries (2015-08-11 20:09:06 +0100)

Module signing with PKCS#7

David Howells (17):
ASN.1: Add an ASN.1 compiler option to dump the element tree
ASN.1: Copy string names to tokens in ASN.1 compiler
X.509: Extract both parts of the AuthorityKeyIdentifier
X.509: Support X.509 lookup by Issuer+Serial form AuthorityKeyIdentifier
PKCS#7: Allow detached data to be supplied for signature checking purposes
MODSIGN: Provide a utility to append a PKCS#7 signature to a module
MODSIGN: Use PKCS#7 messages as module signatures
system_keyring.c doesn't need to #include module-internal.h
MODSIGN: Extract the blob PKCS#7 signature verifier from module signing
PKCS#7: Check content type and versions
X.509: Change recorded SKID & AKID to not include Subject or Issuer
PKCS#7: Support CMS messages also [RFC5652]
sign-file: Generate CMS message as signature instead of PKCS#7
PKCS#7: Improve and export the X.509 ASN.1 time object decoder
KEYS: Add a name for PKEY_ID_PKCS7
PKCS#7: Appropriately restrict authenticated attributes and content type
sign-file: Document dependency on OpenSSL devel libraries

David Woodhouse (9):
modsign: Abort modules_install when signing fails
modsign: Allow password to be specified for signing key
modsign: Allow signing key to be PKCS#11
modsign: Allow external signing key to be specified
modsign: Extract signing cert from CONFIG_MODULE_SIG_KEY if needed
modsign: Use single PEM file for autogenerated key
modsign: Add explicit CONFIG_SYSTEM_TRUSTED_KEYS option
extract-cert: Cope with multiple X.509 certificates in a single file
modsign: Use extract-cert to process CONFIG_SYSTEM_TRUSTED_KEYS

Luis R. Rodriguez (1):
sign-file: Add option to only create signature file

.gitignore | 1 +
Documentation/kbuild/kbuild.txt | 5 +
Documentation/module-signing.txt | 54 +++-
Makefile | 8 +-
arch/x86/kernel/kexec-bzimage64.c | 4 +-
crypto/asymmetric_keys/Makefile | 8 +-
crypto/asymmetric_keys/asymmetric_type.c | 11 +
crypto/asymmetric_keys/pkcs7.asn1 | 22 +-
crypto/asymmetric_keys/pkcs7_key_type.c | 14 +-
crypto/asymmetric_keys/pkcs7_parser.c | 269 ++++++++++++++++++-
crypto/asymmetric_keys/pkcs7_parser.h | 20 +-
crypto/asymmetric_keys/pkcs7_trust.c | 10 +-
crypto/asymmetric_keys/pkcs7_verify.c | 145 ++++++++--
crypto/asymmetric_keys/public_key.c | 1 +
crypto/asymmetric_keys/verify_pefile.c | 7 +-
crypto/asymmetric_keys/x509_akid.asn1 | 35 +++
crypto/asymmetric_keys/x509_cert_parser.c | 231 ++++++++++------
crypto/asymmetric_keys/x509_parser.h | 12 +-
crypto/asymmetric_keys/x509_public_key.c | 95 ++++---
include/crypto/pkcs7.h | 13 +-
include/crypto/public_key.h | 18 +-
include/keys/system_keyring.h | 7 +
include/linux/oid_registry.h | 4 +-
include/linux/verify_pefile.h | 6 +-
init/Kconfig | 58 +++-
kernel/Makefile | 112 +++++---
kernel/module_signing.c | 213 ++-------------
kernel/system_certificates.S | 3 +
kernel/system_keyring.c | 53 +++-
scripts/Makefile | 4 +
scripts/Makefile.modinst | 2 +-
scripts/asn1_compiler.c | 229 ++++++++++------
scripts/extract-cert.c | 166 ++++++++++++
scripts/sign-file | 421 ------------------------------
scripts/sign-file.c | 260 ++++++++++++++++++
35 files changed, 1593 insertions(+), 928 deletions(-)
create mode 100644 crypto/asymmetric_keys/x509_akid.asn1
create mode 100644 scripts/extract-cert.c
delete mode 100755 scripts/sign-file
create mode 100755 scripts/sign-file.c

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