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 (and matching X.509 cert) supply 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.
Note that the revised sign-file program no longer supports the "-s <signature>"
option as I'm not sure what the best way to deal with this is. Do we generate
a PKCS#7 cert from the signature given, or do we get given a PKCS#7 cert? I
lean towards the latter.
They can be found here also:
http://git.kernel.org/cgit/linux/kernel/git/dhowells/linux-fs.git/log/?h=modsign-pkcs7
These patches are based on the security tree's next branch.
Changes:
(*) Fixed a comment on x509_certificate::id to show the order of construction
correctly [thanks to Vivek Goyal].
(*) The 'id' argument to x509_request_asymmetric_key() can be NULL so needs to
be checked [thanks to Mimi Zohar].
(*) pkcs7_supply_detached_data() doesn't need exporting [thanks to Mimi
Zohar].
(*) Fixed "make install_modules" to not try to run sign-file under perl
[thanks to Dmitry Kasatkin].
(*) Fixed sign-file to handle binary X.509 certs as well as PEM-encoded X.509
certs.
David
---
David Howells (5):
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
Makefile | 2
crypto/asymmetric_keys/Makefile | 8 -
crypto/asymmetric_keys/pkcs7_trust.c | 10 -
crypto/asymmetric_keys/pkcs7_verify.c | 80 ++++--
crypto/asymmetric_keys/x509_akid.asn1 | 35 ++
crypto/asymmetric_keys/x509_cert_parser.c | 142 ++++++----
crypto/asymmetric_keys/x509_parser.h | 5
crypto/asymmetric_keys/x509_public_key.c | 86 ++++--
include/crypto/pkcs7.h | 3
include/crypto/public_key.h | 4
init/Kconfig | 1
kernel/module_signing.c | 220 +++------------
scripts/Makefile | 2
scripts/sign-file | 421 -----------------------------
scripts/sign-file.c | 206 ++++++++++++++
15 files changed, 524 insertions(+), 701 deletions(-)
create mode 100644 crypto/asymmetric_keys/x509_akid.asn1
delete mode 100755 scripts/sign-file
create mode 100755 scripts/sign-file.c
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