[GIT PULL] Asymmetric keys and module signing

From: David Howells
Date: Mon Sep 24 2012 - 20:07:30 EST

Next message: David Howells: "Re: [GIT PULL] Asymmetric keys and module signing"
Previous message: Sebastian Hesselbarth: "[PATCH 4/6] ARM: dove: Restructure SoC device tree descriptor"
Next in thread: David Howells: "Re: [GIT PULL] Asymmetric keys and module signing"
Messages sorted by: [ date ] [ thread ] [ subject ] [ author ]

Hi Herbert, Rusty,

Here are my latest module signing patches on top of the asymmetric key crypto
patches, which I hope Herbert will consider taking, at least from the
crypto-keys-post-KS branch:

http://git.kernel.org/?p=linux/kernel/git/dhowells/linux-modsign.git;a=shortlog;h=refs/heads/crypto-keys-post-KS

The module signing patches go on top of those, and the set can be found here:

http://git.kernel.org/?p=linux/kernel/git/dhowells/linux-modsign.git;a=shortlog;h=refs/heads/modsign-post-KS

Do you want the patches posting to the lists? I've tried posting the series
as one, but there seems to be a problem posting the merge commit in the middle
because it has two parents:-/

Anyway...

The module signing patches provide:

- Some fixes to Rusty's patch. Also an additional patch to extend the policy
handling for modules signed with an unknown key and to handle FIPS mode.

- Module signature generation and checking. The signature format is:

<signer-id-string>
<binary-key-id>
<binary-signature>
<sig-information-block>

The fixed-length sig-information-block indicates the crypto algorithm (RSA
only for the moment), the hash type (SHA512 for example) and the identifier
scope (X.509 in this case), plus the lengths of the other three parts.

The binary-key-id could be rendered as hex and pasted onto the end of the
signer-id-string so that the kernel doesn't have to do the conversion.

A script is provided in one of the patches to generate the signer name and
key ID parts from the X.509 cert for later inclusion in module signatures
during the build.

- A transient X.509 cert will be automatically generated if one is not given
and will be used to automatically sign the modules after they've been
thoroughly stripped.

Note that this may prove not to be the best way for distributions to do
things. We're currently looking at the best way being to do the stripping
and signing manually from the RPM spec file after the make modules_install
step and after the debuginfo has been extracted, so automatic signing may
need to go away, or at least become optional.

To make this easier, a script is provided to sign a module and this can be
called either from the Makefile or the spec file.

- An 'extra_certificates' file can be placed in the root of the kernel build
containing a number of supplementary X.509 certs just cat'd together. These
will get added to the internal keyring and can then be used to check module
signatures also.

I have also fixed a number of things in the crypto patches:

- GeneralizedTime and GeneralString were transposed in the ASN.1 compiler
directive table and enum token_type ('S' comes before 'i' to strcmp()),
resulting in it not being possible to use either.

- I had made it a requirement that the X.509 certificate subjectKeyIdentifier
and authorityKeyIdentifier extensions exist so that we can validate the
X.509 signature if possible, but I hadn't put in any checks that they'd been
found before using the values extracted, leading to a crash.

- I fixed header length computation in ASN.1 decoder resulting making it
possible to discard one of the x509.asn1 callback actions (we can locate the
start of the TBS container directly now by subtraction).

- I got rid of the fingerprint bit at the end of the public_key struct as it's
superfluous (the asymmetric key type stores the fingerprint attached to
key->type_data.p[1]).

- I made the X.509 parser render the key description in a more compact manner:

The description is split into two parts: "<signer>: <key-id>".

The <key-id> is a hex rendering of the key identifier - in the case of X.509
that would be the contents of the subjectKeyIdentifier extension field with
the ASN.1 OctetString wrapper removed.

The <signer> is (in order) one of:

- The O and CN attributes as "<O-attr>: <CN-attr>" if the CN attribute
isn't prefixed with the O attribute, and, if longer, doesn't share
the same first seven chars (say a company name such as Red Hat Inc.).
I admit this is entirely arbitrary and biased towards companies with
7 chars or more in there name, but it does remove duplication of the
organisation's name if it's in both the O and the CN. Can anyone
suggest a better heuristic?

- The CN attribute.

- The O attribute.

- The email address.

- Omitted (with ": " omitted too).

As an example:

Magrathea: Glacier signing key: 5dd0839552bd6af498253f8af1e65da3472941c6

which is "<O-attr>: <CN-attr>: <key-id>" in form, or:

Red Hat Test Certificate: 3580cf35d76b3b667a40df66691cbcf87353b23c

which is just "<CN-attr>: <key-id>" in form.

- I no longer extract the bits of the X.509 certificate I don't currently use
(such as the version number).

Note, this implementation of the X.509 certificate parser uses a couple of
patterns to drive a reusable ASN.1 decoder. I do, however, have a direct
in-line decoder implementation also that can only decode X.509 certs. The
stack space usage is greater, but the code size is simpler and slightly smaller
and the code is less capable (it can't handle indefinite-length elements for
example), and it can't be reused for anything else (such as CIFS, netfilter,
PKCS#7, Kerberos tickets), whereas the pattern-based decoder can. I'll post
this separately to see what people think.

As far as testing goes, I have posted a number of testing scripts that I have
used to punish the crypto keys side of things. The "keyctl padd" command makes
this straightforward.

Hopefully, later this week the patches will appear in the Fedora 18 kernel.

David
---
The following changes since commit eeea3ac912207dcf759b95b2b4c36f96bce583bf:

Merge tag 'fixes-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/arm/arm-soc (2012-09-06 10:23:58 -0700)

are available in the git repository at:

git://git.kernel.org/pub/scm/linux/kernel/git/dhowells/linux-modsign.git modsign-post-KS

for you to fetch changes up to 8d4f62638e9aae069d1145dfeb7300c58077be49:

MODSIGN: Extend the policy on signature check failure (2012-09-24 20:51:59 +0100)

----------------------------------------------------------------
(from the branch description for modsign-post-KS local branch)

post Kernel-Summit module signing
----------------------------------------------------------------
David Howells (26):
KEYS: Add payload preparsing opportunity prior to key instantiate or update
MPILIB: Provide count_leading/trailing_zeros() based on arch functions
KEYS: Document asymmetric key type
KEYS: Implement asymmetric key type
KEYS: Asymmetric key pluggable data parsers
KEYS: Asymmetric public-key algorithm crypto key subtype
KEYS: Provide signature verification with an asymmetric key
MPILIB: Reinstate mpi_cmp[_ui]() and export for RSA signature verification
RSA: Implement signature verification algorithm [PKCS#1 / RFC3447]
RSA: Fix signature verification for shorter signatures
X.509: Implement simple static OID registry
X.509: Add utility functions to render OIDs as strings
X.509: Add simple ASN.1 grammar compiler
X.509: Add an ASN.1 decoder
MPILIB: Provide a function to read raw data into an MPI
X.509: Add a crypto key parser for binary (DER) X.509 certificates
Merge Rusty's module signature checking hook into modsign-post-KS
MOD: Fix Rusty's module_sig_check()
MODSIGN: Provide gitignore and make clean rules for extra files
MODSIGN: Provide Kconfig options
MODSIGN: Automatically generate module signing keys if missing
MODSIGN: Provide module signing public keys to the kernel
MODSIGN: Implement module signature checking
MODSIGN: Provide a script for generating a key ID from an X.509 cert
MODSIGN: Sign modules during the build process
MODSIGN: Extend the policy on signature check failure

Rusty Russell (1):
module: signature checking hook

.gitignore | 13 +
Documentation/crypto/asymmetric-keys.txt | 312 ++++++
Documentation/kernel-parameters.txt | 6 +
Documentation/security/keys.txt | 50 +-
Makefile | 1 +
crypto/Kconfig | 1 +
crypto/Makefile | 1 +
crypto/asymmetric_keys/.gitignore | 1 +
crypto/asymmetric_keys/Kconfig | 38 +
crypto/asymmetric_keys/Makefile | 27 +
crypto/asymmetric_keys/asymmetric_keys.h | 15 +
crypto/asymmetric_keys/asymmetric_type.c | 274 +++++
crypto/asymmetric_keys/public_key.c | 108 ++
crypto/asymmetric_keys/public_key.h | 30 +
crypto/asymmetric_keys/rsa.c | 277 ++++++
crypto/asymmetric_keys/signature.c | 49 +
crypto/asymmetric_keys/x509.asn1 | 60 ++
crypto/asymmetric_keys/x509_cert_parser.c | 497 ++++++++++
crypto/asymmetric_keys/x509_parser.h | 36 +
crypto/asymmetric_keys/x509_public_key.c | 207 ++++
crypto/asymmetric_keys/x509_rsakey.asn1 | 4 +
fs/cifs/cifs_spnego.c | 6 +-
fs/cifs/cifsacl.c | 8 +-
include/asm-generic/bitops/count_zeros.h | 57 ++
include/crypto/public_key.h | 108 ++
include/keys/asymmetric-parser.h | 37 +
include/keys/asymmetric-subtype.h | 55 +
include/keys/asymmetric-type.h | 25 +
include/keys/user-type.h | 6 +-
include/linux/asn1.h | 67 ++
include/linux/asn1_ber_bytecode.h | 87 ++
include/linux/asn1_decoder.h | 24 +
include/linux/key-type.h | 35 +-
include/linux/module.h | 8 +
include/linux/mpi.h | 1 +
include/linux/oid_registry.h | 92 ++
init/Kconfig | 68 ++
kernel/Makefile | 57 ++
kernel/modsign_pubkey.c | 112 +++
kernel/module-internal.h | 16 +
kernel/module.c | 100 +-
kernel/module_signing.c | 247 +++++
lib/.gitignore | 2 +-
lib/Kconfig | 5 +
lib/Makefile | 18 +
lib/asn1_decoder.c | 477 +++++++++
lib/build_OID_registry | 209 ++++
lib/mpi/Makefile | 1 +
lib/mpi/longlong.h | 138 +--
lib/mpi/mpi-bit.c | 2 +-
lib/mpi/mpi-cmp.c | 70 ++
lib/mpi/mpi-pow.c | 4 +-
lib/mpi/mpicoder.c | 55 +
lib/oid_registry.c | 170 ++++
net/ceph/crypto.c | 9 +-
net/dns_resolver/dns_key.c | 6 +-
net/rxrpc/ar-key.c | 40 +-
scripts/.gitignore | 1 +
scripts/Makefile | 2 +
scripts/Makefile.build | 11 +
scripts/Makefile.modpost | 75 +-
scripts/asn1_compiler.c | 1545 +++++++++++++++++++++++++++++
scripts/sign-file | 115 +++
scripts/x509keyid | 268 +++++
security/keys/encrypted-keys/encrypted.c | 16 +-
security/keys/key.c | 114 ++-
security/keys/keyctl.c | 18 +-
security/keys/keyring.c | 6 +-
security/keys/request_key_auth.c | 8 +-
security/keys/trusted.c | 16 +-
security/keys/user_defined.c | 14 +-
71 files changed, 6394 insertions(+), 244 deletions(-)
create mode 100644 Documentation/crypto/asymmetric-keys.txt
create mode 100644 crypto/asymmetric_keys/.gitignore
create mode 100644 crypto/asymmetric_keys/Kconfig
create mode 100644 crypto/asymmetric_keys/Makefile
create mode 100644 crypto/asymmetric_keys/asymmetric_keys.h
create mode 100644 crypto/asymmetric_keys/asymmetric_type.c
create mode 100644 crypto/asymmetric_keys/public_key.c
create mode 100644 crypto/asymmetric_keys/public_key.h
create mode 100644 crypto/asymmetric_keys/rsa.c
create mode 100644 crypto/asymmetric_keys/signature.c
create mode 100644 crypto/asymmetric_keys/x509.asn1
create mode 100644 crypto/asymmetric_keys/x509_cert_parser.c
create mode 100644 crypto/asymmetric_keys/x509_parser.h
create mode 100644 crypto/asymmetric_keys/x509_public_key.c
create mode 100644 crypto/asymmetric_keys/x509_rsakey.asn1
create mode 100644 include/asm-generic/bitops/count_zeros.h
create mode 100644 include/crypto/public_key.h
create mode 100644 include/keys/asymmetric-parser.h
create mode 100644 include/keys/asymmetric-subtype.h
create mode 100644 include/keys/asymmetric-type.h
create mode 100644 include/linux/asn1.h
create mode 100644 include/linux/asn1_ber_bytecode.h
create mode 100644 include/linux/asn1_decoder.h
create mode 100644 include/linux/oid_registry.h
create mode 100644 kernel/modsign_pubkey.c
create mode 100644 kernel/module-internal.h
create mode 100644 kernel/module_signing.c
create mode 100644 lib/asn1_decoder.c
create mode 100755 lib/build_OID_registry
create mode 100644 lib/mpi/mpi-cmp.c
create mode 100644 lib/oid_registry.c
create mode 100644 scripts/asn1_compiler.c
create mode 100644 scripts/sign-file
create mode 100755 scripts/x509keyid
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at http://vger.kernel.org/majordomo-info.html
Please read the FAQ at http://www.tux.org/lkml/

Next message: David Howells: "Re: [GIT PULL] Asymmetric keys and module signing"
Previous message: Sebastian Hesselbarth: "[PATCH 4/6] ARM: dove: Restructure SoC device tree descriptor"
Next in thread: David Howells: "Re: [GIT PULL] Asymmetric keys and module signing"
Messages sorted by: [ date ] [ thread ] [ subject ] [ author ]