[v4,0/9] TPM 2.0 trusted keys with attached policy
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Message ID 20191230173802.8731-1-James.Bottomley@HansenPartnership.com
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  • TPM 2.0 trusted keys with attached policy
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James Bottomley Dec. 30, 2019, 5:37 p.m. UTC
This is basically a respin to update the ASN.1 interface to pass
pointers in and out instead of updating in place.  The remainder of
the patches haven't changed in substance, but have changed to support
the new ASN.1 encoder API.

General Cover letter description:

I've changed the output format to use the standardised ASN.1 coding
for TPM2 keys, meaning they should interoperate with userspace TPM2
key implementations.  Apart from interoperability, another advantage
of the existing key format is that it carries all parameters like
parent and hash with it and it is capable of carrying policy
directives in a way that mean they're tied permanently to the key (no
having to try to remember what the policy was and reconstruct it from
userspace).  This actually allows us to support the TPM 1.2 commands
like pcrinfo easily in 2.0.

Using the TPM2_PolicyPassword trick, this series now combines
authorization with policy in a flexible way that would allow us to
move to HMAC based authorizations later for TPM security.  In getting
passwords to work, I fixed the tpm2 password format in a separate
patch.  TPM 1.2 only allows fixed length authorizations, but TPM 2.0
allows for variable length passphrases, so we should support that in
the keys.

James

---

James Bottomley (9):
  lib: add asn.1 encoder
  oid_registry: Add TCG defined OIDS for TPM keys
  security: keys: trusted fix tpm2 authorizations
  security: keys: trusted: use ASN.1 tpm2 key format for the blobs
  security: keys: trusted: Make sealed key properly interoperable
  security: keys: trusted: add PCR policy to TPM2 keys
  security: keys: trusted: add ability to specify arbitrary policy
  security: keys: trusted: implement counter/timer policy
  security: keys: trusted: add password based authorizations to policy
    keys

 Documentation/security/keys/trusted-encrypted.rst |  64 +++-
 include/keys/trusted-type.h                       |   7 +-
 include/linux/asn1_encoder.h                      |  32 ++
 include/linux/oid_registry.h                      |   5 +
 include/linux/tpm.h                               |   8 +
 lib/Makefile                                      |   2 +-
 lib/asn1_encoder.c                                | 391 +++++++++++++++++++
 security/keys/Kconfig                             |   2 +
 security/keys/trusted-keys/Makefile               |   2 +-
 security/keys/trusted-keys/tpm2-policy.c          | 433 ++++++++++++++++++++++
 security/keys/trusted-keys/tpm2-policy.h          |  31 ++
 security/keys/trusted-keys/tpm2key.asn1           |  23 ++
 security/keys/trusted-keys/trusted_tpm1.c         |  46 ++-
 security/keys/trusted-keys/trusted_tpm2.c         | 360 ++++++++++++++++--
 14 files changed, 1370 insertions(+), 36 deletions(-)
 create mode 100644 include/linux/asn1_encoder.h
 create mode 100644 lib/asn1_encoder.c
 create mode 100644 security/keys/trusted-keys/tpm2-policy.c
 create mode 100644 security/keys/trusted-keys/tpm2-policy.h
 create mode 100644 security/keys/trusted-keys/tpm2key.asn1

Comments

Jarkko Sakkinen Dec. 31, 2019, 4:05 p.m. UTC | #1
On Mon, Dec 30, 2019 at 09:37:53AM -0800, James Bottomley wrote:
> This is basically a respin to update the ASN.1 interface to pass
> pointers in and out instead of updating in place.  The remainder of
> the patches haven't changed in substance, but have changed to support
> the new ASN.1 encoder API.
> 
> General Cover letter description:
> 
> I've changed the output format to use the standardised ASN.1 coding
> for TPM2 keys, meaning they should interoperate with userspace TPM2
> key implementations.  Apart from interoperability, another advantage
> of the existing key format is that it carries all parameters like
> parent and hash with it and it is capable of carrying policy
> directives in a way that mean they're tied permanently to the key (no
> having to try to remember what the policy was and reconstruct it from
> userspace).  This actually allows us to support the TPM 1.2 commands
> like pcrinfo easily in 2.0.
> 
> Using the TPM2_PolicyPassword trick, this series now combines
> authorization with policy in a flexible way that would allow us to
> move to HMAC based authorizations later for TPM security.  In getting
> passwords to work, I fixed the tpm2 password format in a separate
> patch.  TPM 1.2 only allows fixed length authorizations, but TPM 2.0
> allows for variable length passphrases, so we should support that in
> the keys.
> 
> James

I'll finally go deep with this as soon as we land the fixes for

https://bugzilla.kernel.org/show_bug.cgi?id=205935.

I'm sorry for ignorance but there's been multiple factors that have
delayed the review (the bug mentioned, kind of sudden steep ramp up to
keyring maintenance as David had to focus on other things, SGX
upstreaming and generally time seems to dissappear somewhere towards the
end of the year).

This week is a bit catching up but I'm sure that next week I have space
to give the focus the patch set requires (and deserves).

/Jarkko