From a3d1158d5ea6274bce89ce2addef0161a142c60b Mon Sep 17 00:00:00 2001 From: Yi Zha Date: Fri, 4 Aug 2023 07:30:44 +0800 Subject: [PATCH] doc: update signature specification for v1 release (#256) * doc: update signature specification for v1 release Signed-off-by: Yi Zha --- media/signature-specification.svg | 4 +- specs/signature-specification.md | 191 ++++++++++++------------------ 2 files changed, 78 insertions(+), 117 deletions(-) diff --git a/media/signature-specification.svg b/media/signature-specification.svg index e009f6c6..dc124bc4 100644 --- a/media/signature-specification.svg +++ b/media/signature-specification.svg @@ -1,2 +1,4 @@ + + -
Registry
[Not supported by viewer]
Manifest
[Not supported by viewer]
Blobs
[Not supported by viewer]
Artifact Type
[Not supported by viewer]
Annotations
[Not supported by viewer]
Notary Signature Manifest
[Not supported by viewer]
Subject
(Manifest Descriptor)
[Not supported by viewer]
Payload
(Manifest Descriptor)
[Not supported by viewer]
Signed Attributes
[Not supported by viewer]
Unsigned Attributes
[Not supported by viewer]
Signature
<div>Signature</div>
Signature Envelope

[Not supported by viewer] \ No newline at end of file +
Registry
Regist...
Manifest
Manifest
Layers
Layers
config.mediaType
config.mediaType
Annotations
Annotations
The Notary Project Signature Manifest
The Notary Project Signature Mani...
Subject
(Manifest Descriptor)
Subject...
Payload
(Manifest Descriptor)
Payload(Manifest Des...
Signed Attributes
Signed Attributes
Unsigned Attributes
Unsigned Attributes
Signature
Signature
Signature Envelope

Signature Envelope...Text is not SVG - cannot display \ No newline at end of file diff --git a/specs/signature-specification.md b/specs/signature-specification.md index 0651e63a..1b7d29ca 100644 --- a/specs/signature-specification.md +++ b/specs/signature-specification.md @@ -1,60 +1,18 @@ # Signature Specification -This document provides the following details for Notary v2 signatures: +This document provides the following details for Notary Project signature: - **[Storage](#storage)**: Describes how signatures are stored and retrieved from an OCI registry. -- **[Signature Envelope](#signature-envelope)**: Describes the structure of a Notary v2 signature. +- **[Signature Envelope](#signature-envelope)**: Describes the structure of the Notary Project signature. ## Storage -This section describes how Notary v2 signatures are stored in the OCI Distribution conformant registry. -Notary v2 uses [OCI artifact manifest][oci-artifact-manifest] to store signatures in the registry. -The media type of the signature manifest is `application/vnd.oci.artifact.manifest.v1+json`. -The signature manifest has an artifact type that specifies it's a Notary V2 signature, a reference to the manifest of the artifact being signed, a blob referencing the signature, and a collection of annotations. +This section describes how a Notary Project signature is stored in an OCI Distribution conformant registry. +OCI image manifest is used to store signatures in the registry, see [OCI image spec v1.1.0-rc3][oci-image-manifest] for details. +The signature manifest has a configuration media type that specifies it's a Notary Project signature, a subject referencing the manifest of the artifact being signed, a layer referencing the signature, and a collection of annotations. ![Signature storage inside registry](../media/signature-specification.svg) -Signature manifest example per OCI artifact manifest - -```jsonc -{ - "mediaType": "application/vnd.oci.artifact.manifest.v1+json", - "artifactType": "application/vnd.cncf.notary.signature", - "blobs": [ - { - "mediaType": "application/jose+json", - "digest": "sha256:9834876dcfb05cb167a5c24953eba58c4ac89b1adf57f28f2f9d09af107ee8f0", - "size": 32654 - } - ], - "subject": { - "mediaType": "application/vnd.oci.image.manifest.v1+json", - "digest": "sha256:73c803930ea3ba1e54bc25c2bdc53edd0284c62ed651fe7b00369da519a3c333", - "size": 16724 - }, - "annotations": { - "io.cncf.notary.x509chain.thumbprint#S256": - "[\"B7A69A70992AE4F9FF103EBE04A2C3BA6C777E439253CE36562E6E98375068C3\",\"932EB6F5598435D4EF23F97B0B5ACB515FAE2B8D8FAC046AB813DDC419DD5E89\"]" - } -} -``` - -- **`artifactType`** (*string*): This REQUIRED property references the Notary version of the signature: `application/vnd.cncf.notary.signature`. -- **`blobs`** (*array of objects*): This REQUIRED property contains collection of only one [OCI descriptor][oci-descriptor] referencing signature envelope. - - **`mediaType`** (*string*): This REQUIRED property contains media type of signature envelope blob. Following values are supported - - `application/jose+json` - - `application/cose` -- **`subject`** (*descriptor*): A REQUIRED artifact descriptor referencing the signed manifest, including, but not limited to image manifest, image index, OCI artifact manifest. -- **`annotations`** (*string-string map*): This REQUIRED property contains metadata for the artifact manifest. - It is being used to store information about the signature. - Keys using the `io.cncf.notary` namespace are reserved for use in Notary and MUST NOT be used by other specifications. - - **`io.cncf.notary.x509chain.thumbprint#S256`**: A REQUIRED annotation whose value contains the list of SHA-256 fingerprint of signing certificate and certificate chain (including root) used for signature generation. The annotation name contains the hash algorithm as a suffix (`#S256`) and can be extended to support other hashing algorithms in future. - The list of fingerprints is present as a JSON array string, corresponding to ordered certificates in [*Certificate Chain* unsigned attribute](#unsigned-attributes) in the signature envelope. - -### Backward Compatibility - -Notary v2 MAY support using `OCI image manifest` to store signatures in the registries that implement partial of the [OCI image specification v1.1][oci-image-manifest]. - Signature manifest example per OCI image manifest: ```jsonc @@ -88,7 +46,7 @@ Signature manifest example per OCI image manifest: Besides the [image manifest property requirements][image-manifest-property-descriptions], the properties have the following additional restrictions: - **`mediaType`** (*string*): This REQUIRED property MUST be `application/vnd.oci.image.manifest.v1+json`. -- **`config`** (*descriptor*): This property is REQUIRED to be compatible with [OCI image specification][oci-image-manifest]. Notary v2 doesn't require any configuration for a signature, and the configuration content is not consumed by Notary v2. +- **`config`** (*descriptor*): This property is REQUIRED to be compatible with [OCI image specification][oci-image-manifest]. The Notary Project signature specification doesn't require any configuration for a signature, and the configuration content is not consumed by implementations of the Notary Project signature specification. - **`mediaType`** (*string*): This REQUIRED property MUST be `application/vnd.cncf.notary.signature`. - **`digest`** (*string*): This REQUIRED property is the digest of the config content. - **`size`** (*int64*): This REQUIRED property specifies the size, in bytes, of the raw config content. @@ -96,24 +54,23 @@ Besides the [image manifest property requirements][image-manifest-property-descr - **`mediaType`** (*string*): This REQUIRED property contains media type of signature envelope blob. Following values are supported - `application/jose+json` - `application/cose` -- **`subject`** (*descriptor*): A REQUIRED artifact descriptor referencing the signed manifest, including, but not limited to image manifest, image index, OCI artifact manifest. -- **`annotations`** (*string-string map*): This REQUIRED property contains metadata for the artifact manifest. +- **`subject`** (*descriptor*): A REQUIRED artifact descriptor referencing the signed manifest. +- **`annotations`** (*string-string map*): This REQUIRED property contains metadata for the image manifest. It is being used to store information about the signature. - Keys using the `io.cncf.notary` namespace are reserved for use in Notary and MUST NOT be used by other specifications. - - **`io.cncf.notary.x509chain.thumbprint#S256`**: A REQUIRED annotation whose value contains the list of SHA-256 fingerprint of signing certificate and certificate chain (including root) used for signature generation. The annotation name contains the hash algorithm as a suffix (`#S256`) and can be extended to support other hashing algorithms in future. - The list of fingerprints is present as a JSON array string, corresponding to ordered certificates in [*Certificate Chain* unsigned attribute](#unsigned-attributes) in the signature envelope. + Keys using the `io.cncf.notary` namespace are reserved for use in the Notary Project signature specification and MUST NOT be used by other specifications. + - **`io.cncf.notary.x509chain.thumbprint#S256`**: A REQUIRED annotation whose value contains the list of SHA-256 fingerprints of signing certificate and certificate chain (including root) used for signature generation. The list of fingerprints is present as a JSON array string, corresponding to ordered certificates in [*Certificate Chain* unsigned attribute](#unsigned-attributes) in the signature envelope. The annotation name contains the hash algorithm as a suffix (`#S256`) and can be extended to support other hashing algorithms in future. ### Signature Discovery The client should be able to discover all the signatures belonging to an artifact (such as image manifest) by using [OCI Distribution Referrers API][oci-distribution-referrers]. OCI Distribution Referrers API returns a paginated list of all artifacts belonging to a target artifact (such as container images, SBoMs). -The implementation can filter Notary signature artifacts by either using OCI Distribution Referrers API or using custom logic on the client. -Each Notary signature artifact refers to a signature envelope blob. +The implementation can filter Notary Project signatures by either using OCI Distribution Referrers API or using custom logic on the client. +Each Notary Project signature refers to a signature envelope blob. ### Signature Filtering -An OCI artifact can have multiple signatures, Notary v2 uses annotations of the signature artifact to filter relevant signatures based on the applicable trust policy. -The Notary v2 signature artifact's `io.cncf.notary.x509chain.thumbprint#S256` annotations key MUST contain the list of SHA-256 fingerprints of certificate and certificate chain used for signing. +An OCI artifact can have multiple signatures, implementations of the Notary Project signature specification uses annotations of the signature manifest to filter relevant signatures based on the applicable trust policy. +The Notary Project signature manifest's `io.cncf.notary.x509chain.thumbprint#S256` annotation key MUST contain the list of SHA-256 fingerprints of certificate and certificate chain used for signing. ## Signature Envelope @@ -127,33 +84,30 @@ A signature envelope consists of the following components: A signature envelope is `e = {m, v, u, s}` where `s` is signature. -This specification defines the set of signed and unsigned attributes that make up a valid The Notary v2 signature. This specification aims to be be agnostic of signature envelope format (e.g. COSE, JWS), details of encoding the envelope in a specific signature envelope format are covered in in separate specs. +This specification defines the set of signed and unsigned attributes that make up a valid Notary Project signature. This specification aims to be be agnostic of signature envelope format (e.g. COSE, JWS), details of encoding the envelope in a specific signature envelope format are covered in in separate specs. -Notary v2 supports the following envelope formats: +The Notary Project signature supports the following envelope formats: - [JWS](./signature-envelope-jws.md) -- [COSE Sign1](./signature-envelope-cose.md) +- [COSE](./signature-envelope-cose.md) ### Payload -Notary v2 payload is a JSON document with media type `application/vnd.cncf.notary.payload.v1+json` and has following properties. +The Notary Project signature payload is a JSON document with media type `application/vnd.cncf.notary.payload.v1+json` and has following properties. - `targetArtifact` : Required property whose value is the descriptor of the target artifact manifest that is being signed. Only [OCI descriptor][oci-descriptor] is supported. - - Descriptor MUST contain `mediaType`, `digest`, `size` fields. - - Descriptor MAY contain `annotations` and if present it MUST follow the [annotation rules][annotation-rules]. Notary v2 uses annotations for storing both Notary specific and user defined metadata. The prefix `io.cncf.notary` in annotation keys is reserved for use in Notary v2 and MUST NOT be used outside this specification. - - Descriptor MAY contain `artifactType` field for artifact manifests, or the `config.mediaType` for `oci.image` based manifests. + - Descriptor MUST contain `mediaType`, `digest`, and `size` fields. + - Descriptor MAY contain `annotations` and if present it MUST follow the [annotation rules][annotation-rules]. The Notary Project signature uses annotations for storing both Notary Project specific and user defined metadata. The prefix `io.cncf.notary` in annotation keys is reserved for use in Notary Project signature and MUST NOT be used outside this specification. + - Descriptor MAY contain `artifactType` field for the `config.mediaType` of OCI image manifests. #### Examples ```jsonc { "targetArtifact": { - "mediaType": "application/vnd.oci.image.manifest.v1+json", - "digest": "sha256:73c803930ea3ba1e54bc25c2bdc53edd0284c62ed651fe7b00369da519a3c333", - "size": 16724, - "annotations": { - "io.wabbit-networks.buildId": "123" // user defined metadata - } + "mediaType": "sbom/example", + "digest": "sha256:9834876dcfb05cb167a5c24953eba58c4ac89b1adf57f28f2f9d09af107ee8f0", + "size": 32654 } } ``` @@ -161,9 +115,13 @@ Notary v2 payload is a JSON document with media type `application/vnd.cncf.notar ```jsonc { "targetArtifact": { - "mediaType": "sbom/example", - "digest": "sha256:9834876dcfb05cb167a5c24953eba58c4ac89b1adf57f28f2f9d09af107ee8f0", - "size": 32654 + "mediaType": "application/vnd.oci.image.manifest.v1+json", + "digest": "sha256:73c803930ea3ba1e54bc25c2bdc53edd0284c62ed651fe7b00369da519a3c333", + "size": 16724, + "artifactType": "application/vnd.oci.image.config.v1+json", + "annotations": { + "io.wabbit-networks.buildId": "123" // user defined metadata + } } } ``` @@ -177,31 +135,33 @@ Signed attributes/claims are additional metadata apart from the payload, which a - Claims that MUST be processed by a verifier MUST be marked as critical. Some claims may be optional and critical, i.e. they MUST be processed by a verifier only if they are present. - Claims which are informational and do not influence signature verification MUST NOT be marked critical. -Notary v2 requires the signature envelope to support the following signed attributes/claims. +The Notary Project signature specification requires the signature envelope to support the following signed attributes/claims. #### Standard attributes -- **Signing Scheme** (critical): A REQUIRED claim that defines the [Notary v2 Signing Scheme](./signing-scheme.md) used by the signature. This attribute dictates the rest of signature schema - the set of signed and unsigned attributes to be included in the signature. Supported values are `notary.x509` and `notary.x509.signingAuthority`. -- **Signing Time**: A claim that indicates the time at which the signature was generated. Though this claim is signed by the signing key, it’s considered unauthenticated as a signer can modify local time and manipulate this claim. More details [here](#signing-time). This claim is REQUIRED and only valid when signing scheme is `notary.x509` . -- **Authentic Signing Time** (critical): The authenticated time at which the signature was generated. This claim is REQUIRED and only valid when signing scheme is `notary.x509.signingAuthority` . More details [here](#signing-time). -- **Expiry** (critical): An OPTIONAL claim that provides a “best by use” time for the artifact, as defined by the signer. More details [here](#expiry). +- **Signing Scheme** (critical): A REQUIRED claim that defines the [Notary Project Signing Scheme](./signing-scheme.md) used by the signature. This attribute dictates the rest of signature schema - the set of signed and unsigned attributes to be included in the signature. Supported values are `notary.x509` and `notary.x509.signingAuthority`. +- **Signing Time**: A claim that indicates the time at which the signature was generated. Though this claim is signed by the signing key, it's considered unauthenticated as a signer can modify local time and manipulate this claim. More details [here](#signing-time). This claim is REQUIRED and only valid when signing scheme is `notary.x509`. +- **Authentic Signing Time** (critical): The authenticated time at which the signature was generated. This claim allows a verifier to determine if the signature was generated when the certificate was valid. This claim is REQUIRED and only valid when signing scheme is `notary.x509.signingAuthority`. More details [here](#signing-time). +- **Expiry** (critical): An OPTIONAL claim that provides a "best by use" time for the artifact, as defined by the signer. More details [here](#expiry). - **Content Type** (critical): A REQUIRED claim that indicates the content type of the [payload](#payload). The supported value is `application/vnd.cncf.notary.payload.v1+json`. Other payload types MAY be supported in future. #### Extended attributes -Implementations of Notary v2 signature spec MAY include additional signed attributes in the signature envelope. +Implementations of the Notary Project signature specification MAY include additional signed attributes in the signature envelope. These attributes MAY be marked critical, i.e. the attribute MUST be understood and processed by a verifier, unknown critical attributes MUST cause signature verification to fail. Usage of extended signed attributes which are marked critical in signature will have implications on portability of the signature, these are discussed in [Signature Portability](#signature-portability) section. #### Extended attributes for *Notation* Plugins -This section documents extended attributes used by Notary v2 reference implementation *Notation* to support plugins. +[Notation](https://github.com/notaryproject/notation) is a CLI and has set of libraries that offer an implementation of the Notary Project signature specification. Notation allows you to sign as well as verify artifacts against Notary Project signatures. + +This section documents extended attributes used by Notation to support plugins. Plugins is a *Notation* concept that allows parts of signing and verification logic to be performed by an external provider. -*Signing plugins* allow *Notation* to be extended for integration with remote keys remote key management services and signing services, where as *verification plugins* allow for customization of verification logic. +*Signing plugins* allow *Notation* to be extended for integration with remote keys, remote key management services, and signing services, where as *verification plugins* allow for customization of verification logic. Detailed specification for plugins can be found [here](https://github.com/notaryproject/notaryproject/blob/main/specs/plugin-extensibility.md#notation-extensibility-for-signing-and-verification). -These extended attributes are documented in this spec, as other Notary V2 implementations may encounter these attributes if they verify a signature that indicated it required a verification plugin for complete signature verification. +This specification documents these extended attributes, as implementations of the Notary Project signature specification may encounter these attributes, if they verify a signature that requires a verification plugin for complete signature verification. -- **Verification Plugin** (critical): An OPTIONAL attribute that specifies the name of the verification plugin that MAY be used to verify the signature e.g. “com.example.nv2plugin”. +- **Verification Plugin** (critical): An OPTIONAL attribute that specifies the name of the verification plugin that MAY be used to verify the signature e.g. "com.example.nv2plugin". [Notation plugin](https://github.com/notaryproject/notaryproject/blob/main/specs/plugin-extensibility.md#plugin-contract) aware implementations use this attribute to load and execute a *Notation* compliant plugin. The plugin participates in the overall signature verification workflow and performs specific steps in it. - **Verification Plugin Minimum Version** (critical): An OPTIONAL attribute that specifies the minimum version of the verification plugin that MUST be used to verify the signature. @@ -209,15 +169,15 @@ A Notation plugin aware implementations MUST use this attribute to verify the si The plugin MUST use [Semantic Versioning](https://semver.org/) (SemVer) to use this feature i.e the `get-plugin-metadata` plugin command MUST return a SemVer compliant version in the response. A use case for this feature is for a plugin publisher to address security bug in older plugin version, by setting the minimum version to the plugin version with fixes. -See [Guidelines for Notary v2 Implementors](#guidelines-for-notary-v2-implementors) for options to handle these attributes during signature verification. +See [Guidelines for implementations of the Notary Project signature specification](#guidelines-for-notary-project-signature-implementors) for options to handle these attributes during signature verification. ### Unsigned Attributes -These attributes are considered unsigned with respect to the signing key that generates the signature. These attributes are typically signed by a third party (e.g. CA, TSA). +These attributes are considered unsigned with respect to the signing key that generates the signature. -- **Certificate Chain**: This is a REQUIRED attribute that contains the ordered list of X.509 public certificates associated with the signing key used to generate the signature. The ordered list starts with the signing certificates, any intermediate certificates and ends with the root certificate. The certificate chain MUST be authenticated against a trust store as part of signature validation. Specific requirements for the certificates in the chain are provided [here](#certificate-requirements). -- **Timestamp signature** : An OPTIONAL counter signature which provides [authentic timestamp](#signing-time)e.g. Time Stamp Authority (TSA) generated timestamp signature. Only [RFC3161](ietf-rfc3161) compliant TimeStampToken are currently supported. -- **Signing Agent**: An OPTIONAL claim that provides the identifier of the software (e.g. Notation) that produced the signature on behalf of the user. It is an opaque string set by the software that produces the signature. It's intended primarily for diagnostic and troubleshooting purposes, this attribute is unsigned, the verifier MUST NOT validate formatting, or fail validation based on the content of this claim. The suggested format is one or more tokens of the form `{id}/{version}` containing identifier and version of the software, seperated by spaces. E.g. “notation/1.0.0”, “notation/1.0.0 com.example.nv2plugin/0.8”. +- **Certificate Chain**: This is a REQUIRED attribute that contains the ordered list of X.509 public certificates associated with the signing key used to generate the signature. The ordered list starts with the signing certificate, any intermediate certificates and ends with the root certificate. The certificate chain MUST be authenticated against a trust store as part of signature validation. Specific requirements for the certificates in the chain are provided [here](#certificate-requirements). +- **Timestamp signature** : An OPTIONAL counter signature which provides [authentic timestamp](#signing-time)e.g. Time Stamp Authority (TSA) generated timestamp signature. Only [RFC3161][ietf-rfc3161] compliant TimeStampToken are currently supported. +- **Signing Agent**: An OPTIONAL claim that provides the identifier of the software (e.g. Notation) that produced the signature on behalf of the user. It is an opaque string set by the software that produces the signature. It's intended primarily for diagnostic and troubleshooting purposes, this attribute is unsigned, the verifier MUST NOT validate formatting, or fail validation based on the content of this claim. The suggested format is one or more tokens of the form `{id}/{version}` containing identifier and version of the software, separated by spaces. E.g. "notation/1.0.0", "notation/1.0.0 myplugin/0.8". ## Signature Algorithm Requirements @@ -281,18 +241,18 @@ The `keyUsage` extension MUST be present and MUST be marked critical. Bit positi - The certificate MUST NOT chain to multiple parents/roots. - The certificate chain MUST NOT contain a certificate that is unrelated to the certificate chain. 1. Any certificate in the certificate chain MUST NOT use SHA1WithRSA and ECDSAWithSHA1 signatures. -1. Only Basic Constraints, Key Usage, and Extended Key Usage extensions of X.509 certificates are honored. For rest of the extensions, Notary MUST fail open i.e. they MUST NOT be evaluated or honored. -1. The certificates in the certificate chain MUST be valid at signing time. Notary MUST NOT enforce validity period nesting, i.e the validity period for a given certificate may not fall entirely within the validity period of that certificate's issuer certificate. -1. In the absence of an Authentic Timestamp, each and every certificate in the certificate chain i.e. signing certificate, intermediate certificates, and the root certificate must be valid i.e. not expired at the time of signature verification. +2. Only Basic Constraints, Key Usage, and Extended Key Usage extensions of X.509 certificates are honored. For rest of the extensions, implementations of the Notary Project signature specification MUST fail open i.e. rest of the extensions MUST NOT be evaluated or honored. +3. The certificates in the certificate chain MUST be valid at signing time. Implementations of the Notary Project signature specification MUST NOT enforce validity period nesting, i.e the validity period for a given certificate may not fall entirely within the validity period of that certificate's issuer certificate. +4. In the absence of an Authentic Timestamp, each and every certificate in the certificate chain i.e. signing certificate, intermediate certificates, and the root certificate must be valid i.e. not expired at the time of signature verification. ## FAQ -**Q: How will Notary v2 support multiple signature envelope formats?** +**Q: How will Notary Project signature specification support multiple signature envelope formats?** -**A:** The `mediaType` of artifact manifest's blob identifies the signature envelope type. +**A:** The `mediaType` of image manifest's layer identifies the signature envelope type. The client implementation can use the aforementioned `mediaType` to parse the signature envelope. -**Q: How will Notary v2 support multiple payload formats?** +**Q: How will Notary Project signature specification support multiple payload formats?** **A:** The Signature envelope MUST have a versioning mechanism to support multiple payload formats. @@ -307,7 +267,7 @@ The signing time denotes the time at which the signature was generated. A X509 c ### Expiry -This is an optional feature that provides a “best by use” time for the artifact, as defined by the signer. Notary v2 allows users to include an optional expiry time when they generate a signature. The expiry time is not set by default and requires explicit configuration by users at the time of signature generation. The artifact is considered expired when the current time is greater than or equal to expiry time, users performing verification can either configure their trust policies to fail the verification or even accept the artifact with expiry date in the past using policy. This is an advanced feature that allows implementing controls for user defined semantics like deprecation for older artifacts, or block older artifacts in a production environment. Users should only include an expiry time in the signed artifact after considering the behavior they expect for consumers of the artifact after it expires. Users can choose to consume an artifact even after the expiry time based on their specific needs. +This is an optional feature that provides a "best by use" time for the artifact, as defined by the signer. The Notary Project signature specification allows users to include an optional expiry time when they generate a signature. The expiry time is not set by default and requires explicit configuration by users at the time of signature generation. The artifact is considered expired when the current time is greater than or equal to expiry time, users performing verification can either configure their trust policies to fail the verification or even accept the artifact with expiry date in the past using policy. This is an advanced feature that allows implementing controls for user defined semantics like deprecation for older artifacts, or block older artifacts in a production environment. Users should only include an expiry time in the signed artifact after considering the behavior they expect for consumers of the artifact after it expires. Users can choose to consume an artifact even after the expiry time based on their specific needs. ### Signature Portability @@ -323,44 +283,43 @@ Signatures associated with these artifacts require broad portability. E.g. Images for containerized applications and services used within an organization, or shared with limited authorized parties. Based on user requirements a private artifact can have different levels of portability, the signature’s portability should at least match the the artifact’s portability. -*Notary v2 signature portability* is based on the following +*The Notary Project signature portability* is based on the following -**Signature discovery** +#### Signature discovery -Notary v2 addressed signature discovery by storing signatures in the same registry (location) where an artifact is present. +The Notary Project signature specification addressed signature discovery by storing signatures in the same registry (location) where an artifact is present. This is supported through [OCI Distribution Referrers API][oci-distribution-referrers] which allows reference artifacts such as signatures, SBOMs to be associated with existing artifacts like Images. -Notary v2 allows multiple signatures to be associated with an artifact, and clients may automatically push signatures for an artifact to a destination registry when a signed artifact moves from one registry to other. +The Notary Project signature specification allows multiple signatures to be associated with an artifact, and clients may automatically push signatures for an artifact to a destination registry when a signed artifact moves from one registry to other. -**Verification requirements** +#### Verification requirements -Notary v2 supports a range of signed artifacts intended for public and private distribution. -Signatures generated by Notary v2 without extended signature attributes marked critical can be verified in any environment where Notation client or another Notary v2 standards compliant verification tool is available, without any additional dependencies. +The Notary Project signature specification supports a range of signed artifacts intended for public and private distribution. +Signatures generated without extended signature attributes marked critical can be verified in any environment where Notation or another Notary Project signature specification compliant verification tool is available, without any additional dependencies. It should be noted that revocations checks, which usually relies on an external mechanism such as CRL/OCSP may require the verification environment to have access to local network or public internet, to have access to the CRL/OCSP endpoint. -Notary v2 also supports signatures generated using compliant signing plugins, which allow vendors to optionally provide additional features on top of Notary v2 standard features. -Verification of these signatures may require additional dependencies like Notary v2 compliant verification plugin, making these signatures more appropriate to use where broad portability may not be required for the associated signed artifact. +The Notary Project signature specification also supports signatures generated using compliant signing plugins, which allow vendors to optionally provide additional features on top of Notation standard features. +Verification of these signatures may require additional dependencies like Notation compliant verification plugin, making these signatures more appropriate to use where broad portability may not be required for the associated signed artifact. This allows users to implement security controls required for their organizations, that are not broadly applicable and may take time to standardize. E.g. Integration with a signature transparency log as part of signature verification. Based on user’s requirements, a user can select appropriate signing mechanism that produces signatures with desired portability. -Notation signatures without any critical extended attributes do not impose any additional dependency requirements for verifiers as these can be validated with just the Notation client. -Whereas, Notation signatures that contain critical extended attributes will require additional dependencies for signature validation, either on Notary v2 compliant plugins or equivalent tooling which may not be available in all environments. -Similarly, Notary v2 compliant plugin vendors should be aware that usage of extended signed attributes which are marked critical in signature will have implications on portability of the signature. +The Notary Project signatures without any critical extended attributes do not impose any additional dependency requirements for verifiers as these can be validated with just Notation. +Whereas, the Notary Project signatures that contain critical extended attributes will require additional dependencies for signature validation, either on Notation compliant plugins or equivalent tooling which may not be available in all environments. +Similarly, Notation compliant plugin vendors should be aware that usage of extended signed attributes which are marked critical in signature will have implications on portability of the signature. -### Guidelines for Notary v2 Implementors +### Guidelines for implementations of the Notary Project signature specification -Implementations of Notary v2, can choose to be [Notation plugin protocol](./plugin-extensibility.md#plugin-contract) aware or not. If an implementation chooses to be plugin protocol aware, and it encounters the Verification Plugin and Verification Plugin minimum version attributes during signature verification, it MUST process these attributes. This involves finding the appropriate plugin and the version to use, and executing `verify-signature` plugin command with correct inputs and processing the plugin response, as per the [Verification Plugin interface](./plugin-extensibility.md#verification-extensibility). +Implementations of the Notary Project signature specification, can choose to be [Notation plugin protocol](./plugin-extensibility.md#plugin-contract) aware or not. If an implementation chooses to be plugin protocol aware, and it encounters the Verification Plugin and Verification Plugin minimum version attributes during signature verification, it MUST process these attributes. This involves finding the appropriate plugin and the version to use, and executing `verify-signature` plugin command with correct inputs and processing the plugin response, as per the [Verification Plugin interface](./plugin-extensibility.md#verification-extensibility). -Alternatively, an implementation of Notary v2 can choose not to implement plugin protocol. +Alternatively, an implementation of the Notary Project signature specification can choose not to implement plugin protocol. - The implementation MUST itself perform equivalent verification logic that is usually performed by plugin specified in the signature. - An implementation MUST fail signature verification if it cannot perform the equivalent verification logic, as skipping the plugin equivalent verification logic will cause incorrect and inconsistent signature verification behavior. - An implementation MAY choose to support a set of known plugin’s verification logic and fail others. -[annotation-rules]: https://github.com/opencontainers/image-spec/blob/main/annotations.md#rules -[oci-descriptor]: https://github.com/opencontainers/image-spec/blob/main/descriptor.md +[annotation-rules]: https://github.com/opencontainers/image-spec/blob/v1.0.0/annotations.md#rules +[oci-descriptor]: https://github.com/opencontainers/image-spec/blob/v1.0.0/descriptor.md [ietf-rfc3161]: https://datatracker.ietf.org/doc/html/rfc3161#section-2.4.2 -[oci-artifact-manifest]: https://github.com/opencontainers/image-spec/blob/v1.1.0-rc2/artifact.md -[oci-distribution-referrers]: https://github.com/opencontainers/distribution-spec/blob/v1.1.0-rc1/spec.md#listing-referrers -[oci-image-manifest]: https://github.com/opencontainers/image-spec/blob/v1.1.0-rc2/manifest.md -[image-manifest-property-descriptions]: https://github.com/opencontainers/image-spec/blob/v1.1.0-rc2/manifest.md#image-manifest-property-descriptions +[oci-distribution-referrers]: https://github.com/opencontainers/distribution-spec/blob/v1.0.0/spec.md#listing-referrers +[oci-image-manifest]: https://github.com/opencontainers/image-spec/blob/v1.1.0-rc3/manifest.md +[image-manifest-property-descriptions]: https://github.com/opencontainers/image-spec/blob/v1.1.0-rc3/manifest.md#image-manifest-property-descriptions