Here's a set of patches that does the following:
(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 descriptor.
(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) Provides support for providing a password/pin for an encrypted private
key to sign-file.
(7) Makes it possible to use PKCS#11 with sign-file, thus allowing the use of
cryptographic hardware.
(8) Overhauls the way the module signing key is handled. If the name in
CONFIG_MODULE_SIG_KEY is "signing_key.priv" 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 certificate.
(9) 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.
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.
David Woodhouse also has stated an intention to overhaul the makefile magic he
added to deal with quotes and quoting encountered when using CONFIG_* option
strings in the makefile.
The patches can be found here also:
http://git.kernel.org/cgit/linux/kernel/git/dhowells/linux-fs.git/log/?h=modsign-pkcs7
and are tagged with:
modsign-pkcs7-20150526
Additionally, the last four patches are provisionally added to support firmware
signing, but will need further modification (ie. registration of OIDs) before
they can be committed, but are included for comment:
(10) Add a PKCS#7 authenticated attribute to hold the name of the firmware blob
passed to request_key() so that this can be checked prior to permitting
the load.
(11) Add usage restriction markers to the extendedKeyUsage field of an X.509
certificate to indicate what may be checked with it.
(12) Parse the keyUsage extension of an X.509 certificate to detect CA keys
that are used for key signing.
(13) Implement a key usage restrictions. For instance, a keys specifically
restricted to module signature checking may not be used to verify firmware
blobs and a key specifically restricted to kexec image signature checking
may not be used for checking the signature on an X.509 certificate.
I have allowed that keys that have no restrictions noted can be used for
anything other than firmware, but possibly this should be restricted
further.
They can be found here also:
http://git.kernel.org/cgit/linux/kernel/git/dhowells/linux-fs.git/log/?h=fwsign-pkcs7
David
---
David Howells (11):
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: Add an optional authenticated attribute to hold firmware name
X.509: Restrict the usage of a key based on information in X.509
certificate
X.509: Parse the keyUsage extension to detect key-signing keys
KEYS: Restrict signature verification to keys appropriate to the purpose
David Woodhouse (7):
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
Luis R. Rodriguez (2):
sign-file: Add option to only create signature file
sign-file: use .p7s instead of .pkcs7 file extension
.gitignore | 1
Documentation/kbuild/kbuild.txt | 5
Documentation/module-signing.txt | 51 +++-
Makefile | 8 -
crypto/asymmetric_keys/Makefile | 12 +
crypto/asymmetric_keys/asymmetric_type.c | 12 +
crypto/asymmetric_keys/pkcs7_key_type.c | 19 +
crypto/asymmetric_keys/pkcs7_parser.c | 77 +++++
crypto/asymmetric_keys/pkcs7_parser.h | 1
crypto/asymmetric_keys/pkcs7_trust.c | 24 +-
crypto/asymmetric_keys/pkcs7_verify.c | 101 +++++--
crypto/asymmetric_keys/public_key.c | 78 +++++
crypto/asymmetric_keys/public_key.h | 3
crypto/asymmetric_keys/signature.c | 6
crypto/asymmetric_keys/x509_akid.asn1 | 35 ++
crypto/asymmetric_keys/x509_cert_parser.c | 255 ++++++++++++++----
crypto/asymmetric_keys/x509_extusage.asn1 | 3
crypto/asymmetric_keys/x509_parser.h | 8 -
crypto/asymmetric_keys/x509_public_key.c | 101 +++++--
include/crypto/pkcs7.h | 8 -
include/crypto/public_key.h | 19 +
include/keys/asymmetric-subtype.h | 6
include/keys/asymmetric-type.h | 13 +
include/keys/system_keyring.h | 8 +
include/linux/oid_registry.h | 6
init/Kconfig | 55 +++-
kernel/Makefile | 110 +++++---
kernel/module_signing.c | 213 +--------------
kernel/system_keyring.c | 78 +++++
lib/oid_registry.c | 1
scripts/Makefile | 3
scripts/Makefile.modinst | 2
scripts/extract-cert.c | 132 +++++++++
scripts/sign-file | 421 -----------------------------
scripts/sign-file.c | 284 ++++++++++++++++++++
35 files changed, 1356 insertions(+), 803 deletions(-)
create mode 100644 crypto/asymmetric_keys/x509_akid.asn1
create mode 100644 crypto/asymmetric_keys/x509_extusage.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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