[0/8] openssl_tpm2_engine: Add attestation functions for primary keys

Message

James Bottomley Aug. 2, 2024, 8:25 p.m. UTC

The first 5 patches add supporting infrastructure and the next three
add the actually attestation command, its man page and its tests.

The design is to be able to store a stable copy of the signing EK
(done by name) in /etc/eksign.name, which can then be used to verify
any on the fly creation of the signing key.  The reason for using a
signing EK not an AK as the specs usually require is to have the
simplicity of a stable key that never changes as the attesting key and
because there are no privacy issues in the machine owner knowing it.
The command then provides a way to attest this key against the EK
certificate (if the TPM has one).  If there is no EK certificate, the
signing EK name is used on a trust on first use (TOFU) basis.

attest_tpm2_primary --eksign > /etc/eksign.name

Will create this file once.  If an EK certificate exists, the
eksign.name file can be attested to that certificate with

attest_tpm2_primary --attest tpm-cert.crt --name /etc/eksign.name

The above commands should only need to be done once per TPM.

Once the Signing EK is known, it can be used on every boot to create
and certify the NULL key, which is what the kernel uses and exports
from version 6.10 onwards and thus proves to the user that the
kernel's reliance on the NULL key during boot was cryptographically
justifed.  This can be done from a boot script as:

attest_tpm2_primary --certify null --name /etc/eksign.name /sys/class/tpm/tpm0/null_name

Which will return true if the certification succeeds.  If the
certification fails, all TPM functions should be considered
compromised.  Whether boot should continue even with a compromised TPM
is a user policy decision.

James

---

James Bottomley (8):
  tss: Fix handling of TPM_RH_NULL in intel-tss
  libcommon: add ability to create a signing primary key
  libcommon: add bin2hex and tmp2_get_hexname
  libcommon: add primary creation from template
  tss: add tpm2_Certify, tpm2_ActivateCredential and tpm2_PolicyOR
  tools: add new attest_tpm2_primary command
  attest_tpm2_primary: add man page
  tests: add tests for attest_tpm2_primary

 src/include/ibm-tss.h              |  84 +++
 src/include/intel-tss.h            |  95 +++-
 src/include/tpm2-common.h          |   9 +
 src/libcommon/tpm2-common.c        |  93 +++-
 src/tools/Makefile.am              |  11 +-
 src/tools/attest_tpm2_primary.1.in | 103 ++++
 src/tools/attest_tpm2_primary.c    | 842 +++++++++++++++++++++++++++++
 tests/attestation.sh               |  30 +
 tests/check_importable.sh          |   3 +-
 tests/engine/Makefile.am           |   3 +-
 tests/provider/Makefile.am         |   3 +-
 tests/seal_unseal.sh               |   3 +-
 tests/start_sw_tpm.sh              |   2 +
 13 files changed, 1230 insertions(+), 51 deletions(-)
 create mode 100644 src/tools/attest_tpm2_primary.1.in
 create mode 100644 src/tools/attest_tpm2_primary.c
 create mode 100755 tests/attestation.sh