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Add ITE-9 SCAI Attribute Assertion proposal
Signed-off-by: Marcela Melara <[email protected]> Add link to spec document
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| # Predicate type: Software Supply Chain Attribute Integrity (SCAI) | ||
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| Type URI: scai/attribute-assertion/v0.1 | ||
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| Version: 0.1 | ||
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| Author: Marcela Melara <[email protected]> | ||
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| ## Purpose | ||
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| The Software Supply Chain Attribute Integrity, or SCAI (pronounced "sky"), specification proposes a data | ||
| format for capturing functional attribute and integrity information about software artifacts and their supply | ||
| chain. SCAI data can be associated with executable binaries, statically- or dynamically-linked libraries, | ||
| software packages, container images, software toolchains, and compute environments. | ||
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| Existing supply chain data formats do not capture any information about the security functionality or | ||
| behavior of the resulting software artifact, nor do they provide sufficient evidence to support any claims of | ||
| integrity of the supply chain processes they describe. The SCAI data format is designed to bridge this gap. | ||
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| For more details, see the [SCAI v0.1 specification document](https://arxiv.org/pdf/2210.05813.pdf) | ||
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| ## Prerequisites | ||
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| In addition to the in-toto attestation framework, | ||
| SCAI assumes that implementers have appropriate processes and tooling in place for | ||
| capturing other types of software supply chain metadata, which can be extended to add support for SCAI. | ||
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| ## Model | ||
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| SCAI metadata, referred to as **Attribute Assertions**, comprises a set of statements that describe functional | ||
| attributes of a software artifact and its supply chain, capable of covering the full software stack of the | ||
| toolchain that produced the artifact down to the hardware platform. SCAI Attribute Assertions include | ||
| information about the conditions under which certain functional attributes arise, as well as (authenticated) | ||
| evidence for the asserted attributes. | ||
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| SCAI is intended to be implemented as part of an existing software supply chain attestation | ||
| framework by software development tools or services (e.g., builders, CI/CD pipelines, software analysis tools) | ||
| seeking to capture more granular information about the attributes and behavior of the software artifacts they | ||
| produce. As such, we envision SCAI metadata being explicitly bound to, or embedded within, other metadata | ||
| objects. | ||
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| ## Schema | ||
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| ``` | ||
| { | ||
| "predicateType": "scai/attribute-assertion/v0.1", | ||
| "predicate": { | ||
| "attributes": [{ | ||
| "attribute": "<ATTRIBUTE>", | ||
| "target": { // optional | ||
| "name": "<NAME>", | ||
| "digest": { "<ALGORITHM>": "<HEX VALUE>", ... }, | ||
| "locationURI": "<URI>", | ||
| "objectType": "<OBJECT TYPE>" // optional | ||
| }, | ||
| "conditions": { /*object */ }, // optional | ||
| "evidence": { /* object */ } // optional | ||
| }] | ||
| } | ||
| } | ||
| ``` | ||
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| This predicate has been adapted from the [SCAI v0.1 specification](https://arxiv.org/pdf/2210.05813.pdf) for greater interoperability. | ||
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| ### Parsing Rules | ||
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| At a high-level, Attribute Assertions MUST allow humans and programs to easily parse the asserted | ||
| attributes. Additional fields MUST enable program-based consumers to automatically parse and evaluate | ||
| the given information. | ||
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| The following parsing rules apply in addition: | ||
| * Consumers MUST ignore unrecognized fields. | ||
| * Producers SHOULD omit _optional_ fields when unused to avoid ambiguity. | ||
| * Acceptable formats of the `attribute`, `conditions` and `evidence` fields are up to the producer and consumer. | ||
| * Because consumers evaluate this predicate against a policy, the semantics SHOULD be consistent and monotonic between Attestations (see in-toto Attestation Spec [parsing rules](https://github.com/in-toto/attestation/tree/main/spec#parsing-rules)). | ||
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| ### Fields | ||
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| `predicateType` _string ([TypeURI](https://github.com/in-toto/attestation/blob/main/spec/field_types.md#TypeURI)), required_ | ||
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| > Identifier for the schema of the Assertion. Always | ||
| > `scai/attribute-assertion/v0.1` for this version of the spec. | ||
| `predicate.attributes` _array of objects, required_ | ||
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| > An array of one or more SCAI Attribute Assertions about the subject. | ||
| `predicate.attributes[*].attribute` _string, required_ | ||
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| > A string describing a specific functional feature of the Attestation subject. | ||
| > | ||
| > Attributes are expected to be domain- or application-specific. | ||
| `predicate.attributes[*].target` _object ([SCAI Object Reference](https://arxiv.org/pdf/2210.05813.pdf), optional_ | ||
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| > An object reference to a specific artifact or metadata object to which the `attribute` field applies. | ||
| > | ||
| > The semantics of the optional `objectType` field are up to the producer and consumer. | ||
| `predicate.attributes[*].conditions` _object, optional_ | ||
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| > An object representing specific conditions under which the associated attribute arises. | ||
| `predicate.attributes[*].evidence` _object, optional_ | ||
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| > An object representing (authenticated) evidence for the asserted `attribute`. | ||
| > | ||
| > Regardless of format, the `evidence` object MUST be self-describing (i.e, have a [TypeURI](https://github.com/in-toto/attestation/blob/main/spec/field_types.md#TypeURI)) to | ||
| > enable the consumer to evaluate the object against a policy. | ||
| > | ||
| > When omitted, a consumer may choose to evaluate the Attestation | ||
| > on the basis of the producer's identity. | ||
| ## Examples | ||
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| #### Attestation for gcc compiler attributes | ||
| ``` | ||
| { | ||
| // Standard attestation fields | ||
| "_type": "https://in-toto.io/Statement/v0.1", | ||
| "subject": [{ | ||
| "name": "gcc9.3.0", | ||
| "digest": { "sha256": "78ab6a8..." }, | ||
| "locationURI": "http://us.archive.ubuntu.com/ubuntu/pool/main/g/gcc-defaults/gcc_9.3.0-1ubuntu2_amd64.deb" | ||
| }], | ||
| "predicateType": "scai/attribute-assertion/v0.1", | ||
| "predicate": { | ||
| "attributes": [{ | ||
| "attribute": "WITH_STACK_PROTECTION", | ||
| "conditions": { "flags": "-fstack-protector*" } | ||
| }, | ||
| { | ||
| "attribute": "REPRODUCIBLE", | ||
| "evidence": { | ||
| "name": "rebuilderd-attestation", | ||
| "digest": { "sha256": "abcdabcde..." }, | ||
| "locationURI": "http://example.com/rebuilderd-instance/gcc_9.3.0-1ubuntu2_amd64.att", | ||
| "objectType": "https://in-toto.io/link/v0.1" | ||
| } | ||
| }] | ||
| } | ||
| } | ||
| ``` | ||
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| #### Attestation for gcc compilation with *endorsed* compiler flags | ||
| ``` | ||
| { | ||
| // Standard attestation fields | ||
| "_type": "https://in-toto.io/Statement/v0.1", | ||
| "subject": [{ | ||
| "name": "hello-world", | ||
| "digest": { "sha256": "78ab6a8..." }, | ||
| "locationURI": "http://example.com/binaries/hello-world" | ||
| }], | ||
| "predicateType": "scai/attribute-assertion/v0.1", | ||
| "predicate": { | ||
| "attributes": [{ | ||
| "attribute": "WITH_STACK_PROTECTION", | ||
| "conditions": { "flags": "-fstack-protector*" }, | ||
| "evidence": { | ||
| "_type": "https://github.com/secure-systems-lab/dsse", | ||
| "payloadType": "application/vnd.in-toto+json", | ||
| "payload": "eyJfdHlwZSI6ICJodHRwczovL2l...", | ||
| "signatures": [{ "sig": "MEQCIAZjdOJnQddF14Rpq..." }] | ||
| } | ||
| }] | ||
| } | ||
| } | ||
| ``` | ||
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| #### Attestation for build with SLSA Provenance (hypothetical) | ||
| ``` | ||
| { | ||
| // Standard attestation fields | ||
| "_type": "https://in-toto.io/Statement/v0.1", | ||
| "subject": [{ | ||
| "name": "hello-world", | ||
| "digest": { "sha256": "78ab6a8..." }, | ||
| "locationURI": "http://example.com/binaries/hello-world" | ||
| }], | ||
| "predicateType": "https://slsa.dev/provenance/vX" | ||
| "predicate": { | ||
| "buildType": "https://example.com/sources/Makefile", | ||
| "builder": { "id": "mailto:[email protected]" }, | ||
| "invocation": { | ||
| "configSource": { | ||
| "uri": "https://example.com/sources/", | ||
| "digest": { "sha256": "cdcdcdc..." } | ||
| }, | ||
| "parameters": { "CFLAGS": "-fstack-protector" } | ||
| }, | ||
| "materials": [{ | ||
| "uri": "https://example.com/sources/hello-world.c", | ||
| "digest": { "sha256": "e5564d4..." } | ||
| }], | ||
| // hypothetical field for SCAI | ||
| "subjectAttributes": [{ | ||
| "attribute": "WITH_STACK_PROTECTION", | ||
| "conditions": { "flags": "-fstack-protector*" }, | ||
| "evidence": { | ||
| "_type": "https://github.com/secure-systems-lab/dsse", | ||
| "payloadType": "application/vnd.in-toto+json", | ||
| "payload": "eyJfdHlwZSI6ICJodHRwczovL2l...", | ||
| "signatures": [{ "sig": "MEQCIAZjdOJnQddF14Rpq..." }] | ||
| } | ||
| }] | ||
| } | ||
| } | ||
| ``` | ||
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| #### Attestation for build on Intel(R) SGX hardware with SLSA Provenance (hypothetical) | ||
| ``` | ||
| { | ||
| // Standard attestation fields | ||
| "_type": "https://in-toto.io/Statement/v0.1", | ||
| "subject": [{ | ||
| "name": "some-security-critical-app", | ||
| "digest": { "sha256": "abcdefa..." }, | ||
| "locationURI": "http://example.com/binaries/some-security-critical-app" | ||
| }], | ||
| "predicateType": "https://slsa.dev/provenance/vX" | ||
| "predicate": { | ||
| "buildType": "https://example.com/sources/Makefile", | ||
| "builder": { "id": "mailto:[email protected]" }, | ||
| "invocation": { | ||
| "configSource": { | ||
| "uri": "https://example.com/sources/", | ||
| "digest": { "sha256": "cdcdcdc..." } | ||
| }, | ||
| "parameters": { "CFLAGS": "-fstack-protector" } | ||
| }, | ||
| "materials": [{ | ||
| "uri": "https://example.com/sources/some-app.c", | ||
| "digest": { "sha256": "e456f78..." } | ||
| }], | ||
| // hypothetical field for SCAI | ||
| "metadata": { | ||
| "attribute": "ATTESTED_HARDWARE", | ||
| "target": { | ||
| "name": "enclave.signed.so", | ||
| "digest": { "sha256": "e3b0c44..." }, | ||
| "locationURI": "http://example.com/enclaves/enclave.signed.so", | ||
| }, | ||
| "evidence": { | ||
| "_type": "https://download.01.org/intel-sgx/sgx-dcap/1.14/linux", | ||
| // Intel SGX DCAP attestation | ||
| "quote_body": { | ||
| "version": 3, | ||
| "sign_type": 2, | ||
| "..." | ||
| }, | ||
| "report_body": { | ||
| "cpu_svn": "0c0dfff...", | ||
| "mr_enclave": "0a1b2c3...", | ||
| "mr_signer": "a1b2c3d...", | ||
| "report_data":"9876543...", | ||
| "..." | ||
| }, | ||
| "signature_size": 4163, | ||
| "signature": "0123456..." | ||
| } | ||
| } | ||
| } | ||
| } | ||
| ``` |