Re: [PATCH RFC 00/20] attestation: Add a common subsystem and TDX support

[Aneesh Kumar K . V]

Jiri Pirko <jiri@xxxxxxxxxxx> writes:

> From: Jiri Pirko <jiri@xxxxxxxxxx>
>
> Linux has several attestation interfaces tied to individual technologies.
> That makes evidence retrieval, measurement registers, device state and
> kernel consumers provider-specific.
>
> This series introduces a common attestation subsystem. Its goal is to
> support platform, TEE and device providers through one model, including
> TPM2, TDX, SEV-SNP, Arm CCA, FIRME, Caliptra and PCI/TSM-backed devices.
> This first series implements the common subsystem and a TDX provider.
> Existing native TDX tsm_mr and tsm_report interfaces remain independent.
>
> Attestation devices use CTLV, a schema-driven character-device TLV UAPI.
> Compared with sysfs or configfs, CTLV executes one validated request
> atomically instead of assembling a transaction through several files.
> Compared with netlink, an opened device fd directly identifies authority
> and lifetime, can be delegated normally, and owns its event queue. CTLV
> also provides:
>
>   - generated kernel metadata, UAPI constants and documentation;
>   - strict type, bounds, nesting and required-field validation;
>   - runtime operation and schema introspection;
>   - family inheritance and extension points;
>   - fragmented queries with generation checks;
>   - per-fd event subscription, overflow reporting and removal notification;
>   - large input and output blobs.
>
> The attestation family exposes capabilities, evidence, measurement-register
> topology and operations, an append-only MR journal and journal
> notifications. This first ABI contains the paths exercised by TDX. Extended
> evidence classes, dynamic registers, record payloads, verdict recording and
> device-security transitions follow with providers that need them and are out
> of scope of this initial patchset. The broader direction is illustrated here:
>
> https://github.com/jpirko/linux_mlxsw/commits/wip_attestation_all_1
>
> That branch also contains additional providers (test and sim),
> attestation core extensions, libctlv and ctlvctl. With the tools
> and kernel specifications, an attestation device can be used as follows:
>
>   # Discover CTLV devices and their family chains.
>   ctlvctl --spec-dir Documentation/ctlv/specs list
>
>   # Inspect the root-family lineage and attestation capabilities.
>   ctlvctl --spec-dir Documentation/ctlv/specs query ctlv0 families-dump
>   ctlvctl --spec-dir Documentation/ctlv/specs query ctlv0 device-get
>
>   # List the measurement registers of the attestation device.
>   ctlvctl --spec-dir Documentation/ctlv/specs query ctlv0 mr-dump
>
>   # Read RTMR0 (MR 1).
>   ctlvctl --spec-dir Documentation/ctlv/specs \
>           query ctlv0 mr-read mr.id=1
>
>   # Extend RTMR0 with 48 zero bytes (SHA-384).
>   digest=$(printf '%096d' 0)
>   ctlvctl --spec-dir Documentation/ctlv/specs \
>           exec ctlv0 mr-extend --json \
>           '{"id":1,"value":[{"hash-algo":5,"data":"hex:'"$digest"'"}]}'
>
>   # Retrieve the RTMR0 journal.
>   ctlvctl --spec-dir Documentation/ctlv/specs \
>           query ctlv0 mr-log-get --json '{"selection":[{"id":1}]}'
>
> The 20 patches are organized as follows:
>
>   1-13    add CTLV, its generator and documentation
>   14-17   add the base attestation family and implementation
>   18-20   expose the native TDX service and add the TDX family
>

I am using this to understand what the IDE setup flow would look like,
but it is unclear whether the connect flow belongs in an attestation
framework. I understand the desire to pass the certificate slot number
as part of connect, and sysfs is probably not a suitable interface for
that. However, is CTLV the interface we want to use for connect?

My patches end up doing the following. I am also unsure whether this is
the intended workflow for the attestation framework.

# ./ctlvctl/ctlvctl --spec-dir=./specs/ ops ctlv0
# ctlv/ctlv-attestation/ctlv-attestation-pci, generation 1
families-dump           query   read    fixed   request 16      reply 112..65536
ops-dump                query   read    fixed   request 16      reply 56..65536
op-schema-get           query   read    fixed   request 40      reply 552..65536
subscriptions-add       action  read    fixed   request 6160
subscriptions-remove    action  read    fixed   request 6160
event-queue-get         query   read    fixed   request 16      reply 40..65536
event-queue-set         action  read    fixed   request 40
op-changed              event   record 112
event-overflow          event   record 112
device-removed          event   record 40
device-get              action  read    fixed   request 16      reply 12984
evidence-get            action  read-write      dynamic disabled        request 26800   reply 472
device-state-changed    event   record 64
mr-log-entry-appended   event   record 73416
evidence-accept         action  read-write      dynamic disabled        request 64
evidence-accept-clear   action  read-write      dynamic disabled        request 16
devsec-state-get        query   read    dynamic disabled        request 16      reply 40..1024
devsec-run              action  read-write      dynamic disabled        request 64      reply 40
evidence-state-changed  event   record 112
state-get               action  read    fixed   request 16      reply 184
connect                 action  read-write      dynamic enabled request 88      reply 40
disconnect              action  read-write      dynamic disabled        request 40      reply 40
lock                    action  read-write      dynamic disabled        request 64      reply 40
unlock                  action  read-write      dynamic disabled        request 40      reply 40
evidence-refresh        action  read-write      dynamic disabled        request 88      reply 40

# ./ctlvctl/ctlvctl --spec-dir=./specs/ exec ctlv0 state-get
# state-get, 1 fragment, generation 0
  pci.generation 0
  pci.connected 0
  pci.locked 0
  pci.accepted 0
# 

# ./ctlvctl/ctlvctl --spec-dir=./specs/ schema ctlv0 connect                
connect (action)
request:
  root nest
    pci.generation required uint [0, 4294967295]
    pci.tsm-id required uint [0, 2147483647]
    pci.cert-slot optional uint [0, 7]
reply:
  root nest
    pci.generation required uint [0, 4294967295]
# 

# ./ctlvctl/ctlvctl --spec-dir=./specs/ exec ctlv0 connect pci.generation=0 pci.tsm-id=0

-aneesh