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

[David Howells]

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).

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
     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) 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
     certificate.

(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.

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.

I can added the following to the patch set:

Tested-by: Luis R. Rodriguez <mcgrof@xxxxxxxx>

David
---
The following changes since commit fe6c59dc17908effd4e2caa666795b9ad984005b:

  Merge tag 'seccomp-next' of git://git.kernel.org/pub/scm/linux/kernel/git/kees/linux into next (2015-07-20 17:19:19 +1000)

are available in the git repository at:

  git://git.kernel.org/pub/scm/linux/kernel/git/dhowells/linux-fs.git tags/modsign-pkcs7-20150720

for you to fetch changes up to e8e9007e54dbaa1919fb3e0fad7e83782e0a4cd6:

  modsign: Use extract-cert to process CONFIG_SYSTEM_TRUSTED_KEYS (2015-07-20 21:16:34 +0100)

----------------------------------------------------------------
Module signing with PKCS#7

----------------------------------------------------------------
David Howells (13):
      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
      ASN.1: Add an ASN.1 compiler option to dump the element tree
      ASN.1: Fix handling of CHOICE in ASN.1 compiler
      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

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          |  51 +++-
 Makefile                                  |   8 +-
 crypto/asymmetric_keys/Makefile           |   8 +-
 crypto/asymmetric_keys/pkcs7.asn1         |  16 +-
 crypto/asymmetric_keys/pkcs7_parser.c     | 131 +++++++++-
 crypto/asymmetric_keys/pkcs7_parser.h     |   5 +-
 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 | 144 ++++++----
 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 +-
 include/keys/system_keyring.h             |   5 +
 init/Kconfig                              |  55 +++-
 kernel/Makefile                           | 112 +++++---
 kernel/module_signing.c                   | 212 ++-------------
 kernel/system_certificates.S              |   3 +
 kernel/system_keyring.c                   |  51 +++-
 scripts/Makefile                          |   4 +
 scripts/Makefile.modinst                  |   2 +-
 scripts/asn1_compiler.c                   | 104 ++++++--
 scripts/extract-cert.c                    | 166 ++++++++++++
 scripts/sign-file                         | 421 ------------------------------
 scripts/sign-file.c                       | 259 ++++++++++++++++++
 28 files changed, 1178 insertions(+), 808 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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