/*
 * Copyright 2023 Signal Messenger, LLC
 * SPDX-License-Identifier: AGPL-3.0-only
 */

syntax = "proto3";

option java_multiple_files = true;

package org.signal.chat.keys;

import "google/protobuf/empty.proto";

import "org/signal/chat/common.proto";
import "org/signal/chat/errors.proto";
import "org/signal/chat/require.proto";
import "org/signal/chat/tag.proto";

// Provides methods for working with pre-keys.
service Keys {
  option (require.auth) = AUTH_ONLY_AUTHENTICATED;

  // Retrieves an approximate count of the number of the various kinds of
  // pre-keys stored for the authenticated device.
  rpc GetPreKeyCount (GetPreKeyCountRequest) returns (GetPreKeyCountResponse) {}

  // Retrieves a set of pre-keys for establishing a session with the targeted
  // device or devices. Note that callers with an unidentified access key for
  // the targeted account should use the version of this method in
  // `KeysAnonymous` instead.
  rpc GetPreKeys(GetPreKeysRequest) returns (GetPreKeysResponse) {}

  // Uploads a new set of one-time EC pre-keys for the authenticated device,
  // clearing any previously-stored pre-keys. Note that all keys submitted via
  // a single call to this method _must_ have the same identity type (i.e. if
  // the first key has an ACI identity type, then all other keys in the same
  // stream must also have an ACI identity type). The provided list of pre-keys
  // must be non-empty.
  rpc SetOneTimeEcPreKeys (SetOneTimeEcPreKeysRequest) returns (SetPreKeyResponse) {}

  // Uploads a new set of one-time KEM pre-keys for the authenticated device,
  // clearing any previously-stored pre-keys. Note that all keys submitted via
  // a single call to this method _must_ have the same identity type (i.e. if
  // the first key has an ACI identity type, then all other keys in the same
  // stream must also have an ACI identity type). The provided list of pre-keys
  // must be non-empty.
  rpc SetOneTimeKemSignedPreKeys (SetOneTimeKemSignedPreKeysRequest) returns (SetPreKeyResponse) {}

  // Sets the signed EC pre-key for one identity (i.e. ACI or PNI) associated
  // with the authenticated device.
  rpc SetEcSignedPreKey (SetEcSignedPreKeyRequest) returns (SetPreKeyResponse) {}

  // Sets the last-resort KEM pre-key for one identity (i.e. ACI or PNI)
  // associated with the authenticated device.
  rpc SetKemLastResortPreKey (SetKemLastResortPreKeyRequest) returns (SetPreKeyResponse) {}
}

// Provides methods for working with pre-keys using "unidentified access"
// credentials.
service KeysAnonymous {
  option (require.auth) = AUTH_ONLY_ANONYMOUS;

  // Retrieves a set of pre-keys for establishing a session with the targeted
  // device or devices. Callers must not submit any self-identifying credentials
  // when calling this method and must instead present the targeted account's
  // unidentified access key as an anonymous authentication mechanism. Callers
  // without an unidentified access key should use the equivalent, authenticated
  // method in `Keys` instead.
  rpc GetPreKeys(GetPreKeysAnonymousRequest) returns (GetPreKeysAnonymousResponse) {}

  // Checks identity key fingerprints of the target accounts.
  //
  // Returns a stream of elements, each one representing an account that had a mismatched
  // identity key fingerprint with the server and the corresponding identity key stored by the server.
  rpc CheckIdentityKeys(stream CheckIdentityKeyRequest) returns (stream CheckIdentityKeyResponse) {}
}

message GetPreKeyCountRequest {
}

message GetPreKeyCountResponse {
  // The approximate number of one-time EC pre-keys stored for the
  // authenticated device and associated with the caller's ACI.
  uint32 aci_ec_pre_key_count = 1;

  // The approximate number of one-time Kyber pre-keys stored for the
  // authenticated device and associated with the caller's ACI.
  uint32 aci_kem_pre_key_count = 2;

  // The approximate number of one-time EC pre-keys stored for the
  // authenticated device and associated with the caller's PNI. 0 if
  // the account does not possess a phone number.
  uint32 pni_ec_pre_key_count = 3;

  // The approximate number of one-time KEM pre-keys stored for the
  // authenticated device and associated with the caller's PNI. 0 if
  // the account does not possess a phone number.
  uint32 pni_kem_pre_key_count = 4;
}

message GetPreKeysRequest {
  // The service identifier of the account for which to retrieve pre-keys.
  common.ServiceIdentifier target_identifier = 1;

  // The ID of the device associated with the targeted account for which to
  // retrieve pre-keys. If not set, pre-keys are returned for all devices
  // associated with the targeted account.
  optional uint32 device_id = 2;
}

message GetPreKeysAnonymousRequest {
  // The request to retrieve pre-keys for a specific account/device(s).
  GetPreKeysRequest request = 1;

  // A means to authorize the request.
  oneof authorization {
    // The unidentified access key (UAK) for the targeted account.
    bytes unidentified_access_key = 2;

    // A group send endorsement token for the targeted account.
    bytes group_send_token = 3;

    // The destination account allows unrestricted unidentified access
    google.protobuf.Empty unrestricted_access = 4;
  }
}

message DevicePreKeyBundle {
  // The EC signed pre-key associated with the targeted
  // account/device/identity.
  common.EcSignedPreKey ec_signed_pre_key = 1;

  // A one-time EC pre-key for the targeted account/device/identity. May not
  // be set if no one-time EC pre-keys are available.
  common.EcPreKey ec_one_time_pre_key = 2;

  // A one-time KEM pre-key (or a last-resort KEM pre-key) for the targeted
  // account/device/identity.
  common.KemSignedPreKey kem_one_time_pre_key = 3;

  // The registration ID for the targeted account/device/identity.
  uint32 registration_id = 4;
}

message AccountPreKeyBundles {
  // The identity key associated with the targeted account/identity.
  bytes identity_key = 1;

  // A map of device IDs to pre-key "bundles" for the targeted account.
  map<uint32, DevicePreKeyBundle> device_pre_keys = 2;

  // Whether the account has enabled sealed sender from anyone. Always false
  // if the request was for a PNI, which does not allow any unidentified access.
  bool unrestricted_unidentified_access = 3;

  // If the target supports unidentified access and has an unidentified access
  // key, a fingerprint of the target's UAK. This may be used to detect a change
  // in the UAK that the sender has for the target before actually sending a message. Otherwise, empty.
  bytes unidentified_access_key_fingerprint = 4;
}

message GetPreKeysResponse {
  oneof response {
    // The requested pre-key bundles
    AccountPreKeyBundles pre_keys = 1;

    // Either the target account was not found, no active device with the given
    // ID (if specified) was found on the target account.
    errors.NotFound target_not_found = 2 [(tag.reason) = "not_found"];
  }
}

message GetPreKeysAnonymousResponse {
  oneof response {
    // The requested pre-key bundles
    AccountPreKeyBundles pre_keys = 1;

    // Either the target account was not found, no active device with the given
    // ID (if specified) was found on the target account.
    errors.NotFound target_not_found = 2 [(tag.reason) = "not_found"];

    // The provided unidentified authorization credential was invalid
    errors.FailedUnidentifiedAuthorization failed_unidentified_authorization = 3 [(tag.reason) = "failed_unidentified_authorization"];
  }
}

message SetOneTimeEcPreKeysRequest {
  // The identity type (i.e. ACI/PNI) with which the keys in this request are
  // associated.
  common.IdentityType identity_type = 1;

  // The unsigned EC pre-keys to be stored.
  repeated common.EcPreKey pre_keys = 2 [(require.size) = {min: 1, max: 100}];
}

message SetOneTimeKemSignedPreKeysRequest {
  // The identity type (i.e. ACI/PNI) with which the keys in this request are
  // associated.
  common.IdentityType identity_type = 1;

  // The KEM pre-keys to be stored.
  repeated common.KemSignedPreKey pre_keys = 2 [(require.size) = {min: 1, max: 100}];
}

message SetEcSignedPreKeyRequest {
  // The identity type (i.e. ACI/PNI) with which this key is associated.
  common.IdentityType identity_type = 1;

  // The signed EC pre-key itself.
  common.EcSignedPreKey signed_pre_key = 2 [(require.present) = true];
}

message SetKemLastResortPreKeyRequest {
  // The identity type (i.e. ACI/PNI) with which this key is associated.
  common.IdentityType identity_type = 1;

  // The signed KEM pre-key itself.
  common.KemSignedPreKey signed_pre_key = 2 [(require.present) = true];
}

message SetPreKeyResponse {
}

message CheckIdentityKeyRequest {
  // The service identifier of the account for which we want to check the associated identity key fingerprint.
  common.ServiceIdentifier target_identifier = 1;
  // The most significant 4 bytes of the SHA-256 hash of the identity key associated with the target account/identity type.
  bytes fingerprint = 2 [(require.exactlySize) = 4];
}

message CheckIdentityKeyResponse {
  // The service identifier of the account for which there is a mismatch between the client and server identity key fingerprints.
  common.ServiceIdentifier target_identifier = 1;
  // The identity key that is stored by the server for the target account/identity type.
  bytes identity_key = 2;
}