// Copyright 2018 The Grafeas Authors. All rights reserved.
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
//    http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.

syntax = "proto3";

package grafeas.v1beta1.attestation;

import "google/devtools/containeranalysis/v1beta1/common/common.proto";

option go_package = "cloud.google.com/go/containeranalysis/apiv1beta1/containeranalysispb;containeranalysispb";
option java_multiple_files = true;
option java_package = "io.grafeas.v1beta1.attestation";
option objc_class_prefix = "GRA";

// An attestation wrapper with a PGP-compatible signature. This message only
// supports `ATTACHED` signatures, where the payload that is signed is included
// alongside the signature itself in the same file.
message PgpSignedAttestation {
  // Required. The raw content of the signature, as output by GNU Privacy Guard
  // (GPG) or equivalent. Since this message only supports attached signatures,
  // the payload that was signed must be attached. While the signature format
  // supported is dependent on the verification implementation, currently only
  // ASCII-armored (`--armor` to gpg), non-clearsigned (`--sign` rather than
  // `--clearsign` to gpg) are supported. Concretely, `gpg --sign --armor
  // --output=signature.gpg payload.json` will create the signature content
  // expected in this field in `signature.gpg` for the `payload.json`
  // attestation payload.
  string signature = 1;

  // Type (for example schema) of the attestation payload that was signed.
  enum ContentType {
    // `ContentType` is not set.
    CONTENT_TYPE_UNSPECIFIED = 0;
    // Atomic format attestation signature. See
    // https://github.com/containers/image/blob/8a5d2f82a6e3263290c8e0276c3e0f64e77723e7/docs/atomic-signature.md
    // The payload extracted from `signature` is a JSON blob conforming to the
    // linked schema.
    SIMPLE_SIGNING_JSON = 1;
  }

  // Type (for example schema) of the attestation payload that was signed.
  // The verifier must ensure that the provided type is one that the verifier
  // supports, and that the attestation payload is a valid instantiation of that
  // type (for example by validating a JSON schema).
  ContentType content_type = 3;

  // This field is used by verifiers to select the public key used to validate
  // the signature. Note that the policy of the verifier ultimately determines
  // which public keys verify a signature based on the context of the
  // verification. There is no guarantee validation will succeed if the
  // verifier has no key matching this ID, even if it has a key under a
  // different ID that would verify the signature. Note that this ID should also
  // be present in the signature content above, but that is not expected to be
  // used by the verifier.
  oneof key_id {
    // The cryptographic fingerprint of the key used to generate the signature,
    // as output by, e.g. `gpg --list-keys`. This should be the version 4, full
    // 160-bit fingerprint, expressed as a 40 character hexidecimal string. See
    // https://tools.ietf.org/html/rfc4880#section-12.2 for details.
    // Implementations may choose to acknowledge "LONG", "SHORT", or other
    // abbreviated key IDs, but only the full fingerprint is guaranteed to work.
    // In gpg, the full fingerprint can be retrieved from the `fpr` field
    // returned when calling --list-keys with --with-colons.  For example:
    // ```
    // gpg --with-colons --with-fingerprint --force-v4-certs \
    //     --list-keys attester@example.com
    // tru::1:1513631572:0:3:1:5
    // pub:...<SNIP>...
    // fpr:::::::::24FF6481B76AC91E66A00AC657A93A81EF3AE6FB:
    // ```
    // Above, the fingerprint is `24FF6481B76AC91E66A00AC657A93A81EF3AE6FB`.
    string pgp_key_id = 2;
  }
}

// An attestation wrapper that uses the Grafeas `Signature` message.
// This attestation must define the `serialized_payload` that the `signatures`
// verify and any metadata necessary to interpret that plaintext.  The
// signatures should always be over the `serialized_payload` bytestring.
message GenericSignedAttestation {
  // Type of the attestation plaintext that was signed.
  enum ContentType {
    // `ContentType` is not set.
    CONTENT_TYPE_UNSPECIFIED = 0;
    // Atomic format attestation signature. See
    // https://github.com/containers/image/blob/8a5d2f82a6e3263290c8e0276c3e0f64e77723e7/docs/atomic-signature.md
    // The payload extracted in `plaintext` is a JSON blob conforming to the
    // linked schema.
    SIMPLE_SIGNING_JSON = 1;
  }

  // Type (for example schema) of the attestation payload that was signed.
  // The verifier must ensure that the provided type is one that the verifier
  // supports, and that the attestation payload is a valid instantiation of that
  // type (for example by validating a JSON schema).
  ContentType content_type = 1;

  // The serialized payload that is verified by one or more `signatures`.
  // The encoding and semantic meaning of this payload must match what is set in
  // `content_type`.
  bytes serialized_payload = 2;

  // One or more signatures over `serialized_payload`.  Verifier implementations
  // should consider this attestation message verified if at least one
  // `signature` verifies `serialized_payload`.  See `Signature` in common.proto
  // for more details on signature structure and verification.
  repeated Signature signatures = 3;
}

// Note kind that represents a logical attestation "role" or "authority". For
// example, an organization might have one `Authority` for "QA" and one for
// "build". This note is intended to act strictly as a grouping mechanism for
// the attached occurrences (Attestations). This grouping mechanism also
// provides a security boundary, since IAM ACLs gate the ability for a principle
// to attach an occurrence to a given note. It also provides a single point of
// lookup to find all attached attestation occurrences, even if they don't all
// live in the same project.
message Authority {
  // This submessage provides human-readable hints about the purpose of the
  // authority. Because the name of a note acts as its resource reference, it is
  // important to disambiguate the canonical name of the Note (which might be a
  // UUID for security purposes) from "readable" names more suitable for debug
  // output. Note that these hints should not be used to look up authorities in
  // security sensitive contexts, such as when looking up attestations to
  // verify.
  message Hint {
    // Required. The human readable name of this attestation authority, for
    // example "qa".
    string human_readable_name = 1;
  }

  // Hint hints at the purpose of the attestation authority.
  Hint hint = 1;
}

// Details of an attestation occurrence.
message Details {
  // Required. Attestation for the resource.
  Attestation attestation = 1;
}

// Occurrence that represents a single "attestation". The authenticity of an
// attestation can be verified using the attached signature. If the verifier
// trusts the public key of the signer, then verifying the signature is
// sufficient to establish trust. In this circumstance, the authority to which
// this attestation is attached is primarily useful for look-up (how to find
// this attestation if you already know the authority and artifact to be
// verified) and intent (which authority was this attestation intended to sign
// for).
message Attestation {
  // Required. The signature, generally over the `resource_url`, that verifies
  // this attestation. The semantics of the signature veracity are ultimately
  // determined by the verification engine.
  oneof signature {
    // A PGP signed attestation.
    PgpSignedAttestation pgp_signed_attestation = 1;
    GenericSignedAttestation generic_signed_attestation = 2;
  }
}