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Thu, 29 Oct 2026 12:38:54 -0700 (PDT) Received: from localhost ([208.127.45.21]) by smtp.gmail.com with ESMTPSA id 2adb3069b0e04-5bfd7ef0c2esm69050e87.50.2026.10.29.12.38.53 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Thu, 29 Oct 2026 12:38:53 -0700 (PDT) Date: Thu, 29 Oct 2026 20:38:49 +0100 From: Jiri Pirko To: Jason Gunthorpe Cc: linux-coco@lists.linux.dev, linux-kernel@vger.kernel.org, linux-api@vger.kernel.org, x86@kernel.org, kvm@vger.kernel.org, linux-doc@vger.kernel.org, david.quigley@intel.com, lukas@wunner.de, ksinyuk@kernel.org, rodrigo.vivi@intel.com, cedric.xing@intel.com, sameo@meta.com, drdeeglaze@gmail.com, James.Bottomley@hansenpartnership.com, aik@amd.com, jpiotrowski@nvidia.com, qinkun@google.com, pgonda@google.com, jic23@kernel.org, alistair.francis@wdc.com, ankita@nvidia.com, suzuki.poulose@arm.com, kas@kernel.org, rick.p.edgecombe@intel.com, elena.reshetova@intel.com, dave.hansen@linux.intel.com, sathyanarayanan.kuppuswamy@linux.intel.com, peter.fang@intel.com Subject: Re: [PATCH RFC 14/20] attestation: Add the base family specification and generated files Message-ID: References: <20261015145053.3664509-1-jiri@resnulli.us> <20261015145053.3664509-15-jiri@resnulli.us> <179302367452.58760.3782556786585774917.b4-review@b4> <20261029184324.GE3734323@nvidia.com> X-Mailing-List: linux-api@vger.kernel.org List-Id: List-Post: List-Help: List-Subscribe: List-Unsubscribe: List-Owner: Precedence: list MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20261029184324.GE3734323@nvidia.com> Thu, Oct 29, 2026 at 07:43:24PM +0100, jgg@nvidia.com wrote: >On Thu, Oct 29, 2026 at 11:04:58AM +0100, Jiri Pirko wrote: >> Mon, Oct 26, 2026 at 03:07:54PM +0100, jgg@nvidia.com wrote: >> >> [..] >> >> > >> >======= >> > >> >device-get: >> > request: {} >> > reply: >> > caps: >> > evidence?: >> > min-challenge-length: uint >> > max-challenge-length: uint >> > >> >Did anyone implement a variable length challenge? That seems a bit >> >strange. There is also a very important crypto warning here that the >> >> Yes. TPM2_Quote accepts variable-length qualifyingData, represented by >> TPM2B_DATA with an explicit length. This varies per request on the same >> TPM: >> >> [1] TPM Library Part 2, section 10.3.3, page 136: TPM2B_DATA. >> https://medias.cdn.trustedcomputinggroup.org/production/Trusted_Platform_Module_2_0_Library_Part_2_Structures_Version_185_pub_c0a962a931.pdf#page=136 >> >> [2] Part 3, section 18.4.2, page 158: TPM2_Quote qualifyingData. >> https://medias.cdn.trustedcomputinggroup.org/production/Trusted_Platform_Module_2_0_Library_Part_3_Commands_Version_185_pub_87a5c10230.pdf#page=158 >> >> The PSA Attestation API, section 4.4, also requires one implementation to >> support 32-, 48-, and 64-byte challenges: >> https://arm-software.github.io/psa-api/attestation/1.0/api/api.html >> >> FIRME DEN0149 1.0 ALP2, section 8.12, Table 8.23, page 100, likewise >> defines an explicit Platform challenge size parameter in x4[31:0]. >> FIRME itself does not mandate the specific 32/48/64-byte set: >> https://documentation-service.arm.com/static/699c3b70b60ef220b14ec14d?token=#page=100 > >I feel like userspace needs to know the difference between 'any size >between 0 and 100 and 'exactly one of 32, 64, 128' ? True.