Re: [PATCH 0/5] MODSIGN: Use PKCS#7 for module signatures
From: Dmitry Kasatkin
Date: Fri Nov 21 2014 - 08:01:17 EST
Before I go into reviewing the patches just want to let you know that
Integrity stuff seems to work fine with these changes.
On 20/11/14 18:53, David Howells wrote:
> 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:
> These patches are based on the security tree's next branch.
> 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
> crypto/asymmetric_keys/Makefile | 8 -
> crypto/asymmetric_keys/pkcs7_trust.c | 10 -
> crypto/asymmetric_keys/pkcs7_verify.c | 81 ++++--
> crypto/asymmetric_keys/x509_akid.asn1 | 35 ++
> crypto/asymmetric_keys/x509_cert_parser.c | 142 ++++++----
> crypto/asymmetric_keys/x509_parser.h | 3
> crypto/asymmetric_keys/x509_public_key.c | 85 ++++--
> 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 | 189 +++++++++++++
> 14 files changed, 505 insertions(+), 699 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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