Re: [PATCH RFC 15/20] attestation: Prepare provider and instance core

[Sergii Dmytruk]

On Thu, Oct 15, 2026 at 04:50:48PM +0200, Jiri Pirko wrote:
> From: Jiri Pirko <jiri@xxxxxxxxxx>
> 
> Add provider validation, instance registration and lifecycle management for
> the attestation family.
> 
> The provider descriptor is one immutable evidence and MR contract; journal
> storage follows in the next patch. The core object can be compile-checked
> here. CONFIG_ATTESTATION remains unwired until the CTLV handlers land.
> 
> Assisted-by: Cursor: GPT-5.6 Sol
> Assisted-by: Cursor: Claude Opus 5.5
> Signed-off-by: Jiri Pirko <jiri@xxxxxxxxxx>
> ---
>  Documentation/driver-api/attestation.rst |  36 +++
>  Documentation/driver-api/index.rst       |   1 +
>  MAINTAINERS                              |   2 +
>  drivers/attestation/Kconfig              |  12 +
>  drivers/attestation/Makefile             |   4 +
>  drivers/attestation/core/core.c          | 280 +++++++++++++++++++++++
>  drivers/attestation/core/internal.h      |  35 +++
>  include/linux/attestation.h              | 138 +++++++++++
>  8 files changed, 508 insertions(+)
>  create mode 100644 Documentation/driver-api/attestation.rst
>  create mode 100644 drivers/attestation/Kconfig
>  create mode 100644 drivers/attestation/Makefile
>  create mode 100644 drivers/attestation/core/core.c
>  create mode 100644 drivers/attestation/core/internal.h
>  create mode 100644 include/linux/attestation.h

[...]

> diff --git a/include/linux/attestation.h b/include/linux/attestation.h
> new file mode 100644
> index 000000000000..0fd806ea77d8
> --- /dev/null
> +++ b/include/linux/attestation.h
> @@ -0,0 +1,138 @@
> +/* SPDX-License-Identifier: GPL-2.0-only */
> +#ifndef _LINUX_ATTESTATION_H
> +#define _LINUX_ATTESTATION_H
> +
> +#include <crypto/hash.h>
> +#include <linux/types.h>
> +
> +#include <uapi/linux/ctlv_attestation_gen.h>
> +#include <uapi/linux/hash_info.h>
> +
> +struct attestation;
> +struct ctlv_blob;
> +
> +/**
> + * struct attestation_digest - One MR digest.
> + * @algorithm: hash algorithm
> + * @data: digest bytes
> + */
> +struct attestation_digest {
> +	enum hash_algo algorithm;
> +	u8 data[HASH_MAX_DIGESTSIZE];
> +};
> +
> +/**
> + * struct attestation_digest_set - Digests ordered as the MR algorithms.
> + * @values_count: number of digests
> + * @values: digest array
> + */
> +struct attestation_digest_set {
> +	size_t values_count;
> +	struct attestation_digest *values;
> +};
> +
> +/**
> + * struct attestation_mr_props - Immutable MR properties.
> + * @id: provider-unique MR ID
> + * @name: MR name
> + * @algorithms: ordered hash algorithms

Why do these need to be sorted?  Is it just to make indexing easier?

I see that the number of algorithms is also checked on extending.  Does
it mean that a situation when not all PCR banks are extended at the same
time is considered an invalid one?  That may be a problem at least for
DRTM which may extend only one bank even if several are active.

> + * @algorithms_count: number of algorithms
> + * @has_register_index: whether @register_index is valid
> + * @register_index: native register index
> + * @readable: MR can be read
> + * @extendable: MR can be extended

At least with TPMs, whether a PCR can be extended depends on locality,
so this isn't necessarily a static property.  Is this flag expected to
always be accurate or it would be OK for a provider to declare an
extendable MR but then deny doing it?

> + */
> +struct attestation_mr_props {
> +	unsigned int id;
> +	const char *name;
> +	const enum hash_algo *algorithms;
> +	size_t algorithms_count;
> +	bool has_register_index;
> +	unsigned int register_index;
> +	bool readable;
> +	bool extendable;
> +};
> +
> +/**
> + * struct attestation_evidence_supported_object - Evidence output description.
> + * @format: evidence format name
> + * @max_length: maximum output bytes
> + * @binds_mrs: evidence validity depends on MR state
> + */
> +struct attestation_evidence_supported_object {
> +	const char *format;
> +	size_t max_length;
> +	bool binds_mrs;
> +};
> +
> +/**
> + * struct attestation_evidence_caps - Immutable evidence capabilities.
> + * @min_challenge_length: minimum challenge bytes
> + * @max_challenge_length: maximum challenge bytes
> + * @max_total_output_length: maximum bytes across all objects
> + * @objects: supported evidence objects
> + * @objects_count: number of objects
> + */
> +struct attestation_evidence_caps {
> +	size_t min_challenge_length;
> +	size_t max_challenge_length;
> +	size_t max_total_output_length;
> +	const struct attestation_evidence_supported_object *objects;
> +	size_t objects_count;
> +};
> +
> +/**
> + * struct attestation_evidence_object_request - One resolved output object.
> + * @supported_object: matching capability entry
> + * @output: resolved output blob
> + */
> +struct attestation_evidence_object_request {
> +	const struct attestation_evidence_supported_object *supported_object;
> +	struct ctlv_blob *output;
> +};
> +
> +/**
> + * struct attestation_evidence_request - Validated evidence request.
> + * @challenge: challenge bytes
> + * @challenge_length: challenge length
> + * @objects: requested output objects
> + * @objects_count: number of objects
> + */
> +struct attestation_evidence_request {
> +	const u8 *challenge;
> +	size_t challenge_length;
> +	const struct attestation_evidence_object_request *objects;
> +	size_t objects_count;
> +};
> +
> +/**
> + * struct attestation_evidence_result - Provider evidence result.
> + * @object_lengths: produced length for every requested object
> + */
> +struct attestation_evidence_result {
> +	size_t *object_lengths;

No number of objects?  That would make this structure more
self-contained.  Copying `objects` from the request would allow passing
it around to handle results, but there may not be too much value in
doing it this way.

> +};
> +
> +/**
> + * struct attestation_provider - Immutable provider operations and properties.
> + * @evidence_get: produce requested evidence
> + * @mr_read: read one MR
> + * @mr_extend: extend one MR
> + * @evidence_caps: evidence capabilities, or NULL
> + * @mrs: fixed MR properties
> + * @mrs_count: number of fixed MRs
> + */
> +struct attestation_provider {
> +	int (*evidence_get)(struct attestation *att,
> +			    const struct attestation_evidence_request *request,
> +			    struct attestation_evidence_result *result);
> +	int (*mr_read)(struct attestation *att, unsigned int mr_id,
> +		       struct attestation_digest_set *values);
> +	int (*mr_extend)(struct attestation *att, unsigned int mr_id,
> +			 const struct attestation_digest_set *values);
> +	const struct attestation_evidence_caps *evidence_caps;
> +	const struct attestation_mr_props *mrs;
> +	size_t mrs_count;
> +};
> +
> +#endif /* _LINUX_ATTESTATION_H */
> -- 
> 2.56.0