data-plane-api/envoy/extensions/transport_sockets/tls/v3/common.proto

syntax = "proto3";

package envoy.extensions.transport_sockets.tls.v3;

import "envoy/config/core/v3/base.proto";
import "envoy/config/core/v3/extension.proto";
import "envoy/type/matcher/v3/string.proto";

import "google/protobuf/any.proto";
import "google/protobuf/wrappers.proto";

import "envoy/annotations/deprecation.proto";
import "udpa/annotations/migrate.proto";
import "udpa/annotations/sensitive.proto";
import "udpa/annotations/status.proto";
import "udpa/annotations/versioning.proto";
import "validate/validate.proto";

option java_package = "io.envoyproxy.envoy.extensions.transport_sockets.tls.v3";
option java_outer_classname = "CommonProto";
option java_multiple_files = true;
option go_package = "github.com/envoyproxy/go-control-plane/envoy/extensions/transport_sockets/tls/v3;tlsv3";
option (udpa.annotations.file_status).package_version_status = ACTIVE;

// [#protodoc-title: Common TLS configuration]

// [#next-free-field: 6]
message TlsParameters {
  option (udpa.annotations.versioning).previous_message_type = "envoy.api.v2.auth.TlsParameters";

  enum TlsProtocol {
    // Envoy will choose the optimal TLS version.
    TLS_AUTO = 0;

    // TLS 1.0
    TLSv1_0 = 1;

    // TLS 1.1
    TLSv1_1 = 2;

    // TLS 1.2
    TLSv1_2 = 3;

    // TLS 1.3
    TLSv1_3 = 4;
  }

  // Minimum TLS protocol version. By default, it's ``TLSv1_2`` for both clients and servers.
  //
  // TLS protocol versions below TLSv1_2 require setting compatible ciphers with the
  // ``cipher_suites`` setting as the default ciphers no longer include compatible ciphers.
  //
  // .. attention::
  //
  //   Using TLS protocol versions below TLSv1_2 has serious security considerations and risks.
  TlsProtocol tls_minimum_protocol_version = 1 [(validate.rules).enum = {defined_only: true}];

  // Maximum TLS protocol version. By default, it's ``TLSv1_2`` for clients and ``TLSv1_3`` for
  // servers.
  TlsProtocol tls_maximum_protocol_version = 2 [(validate.rules).enum = {defined_only: true}];

  // If specified, the TLS listener will only support the specified `cipher list
  // <https://commondatastorage.googleapis.com/chromium-boringssl-docs/ssl.h.html#Cipher-suite-configuration>`_
  // when negotiating TLS 1.0-1.2 (this setting has no effect when negotiating TLS 1.3).
  //
  // If not specified, a default list will be used. Defaults are different for server (downstream) and
  // client (upstream) TLS configurations.
  // Defaults will change over time in response to security considerations; If you care, configure
  // it instead of using the default.
  //
  // In non-FIPS builds, the default server cipher list is:
  //
  // .. code-block:: none
  //
  //   [ECDHE-ECDSA-AES128-GCM-SHA256|ECDHE-ECDSA-CHACHA20-POLY1305]
  //   [ECDHE-RSA-AES128-GCM-SHA256|ECDHE-RSA-CHACHA20-POLY1305]
  //   ECDHE-ECDSA-AES256-GCM-SHA384
  //   ECDHE-RSA-AES256-GCM-SHA384
  //
  // In builds using :ref:`BoringSSL FIPS <arch_overview_ssl_fips>`, the default server cipher list is:
  //
  // .. code-block:: none
  //
  //   ECDHE-ECDSA-AES128-GCM-SHA256
  //   ECDHE-RSA-AES128-GCM-SHA256
  //   ECDHE-ECDSA-AES256-GCM-SHA384
  //   ECDHE-RSA-AES256-GCM-SHA384
  //
  // In non-FIPS builds, the default client cipher list is:
  //
  // .. code-block:: none
  //
  //   [ECDHE-ECDSA-AES128-GCM-SHA256|ECDHE-ECDSA-CHACHA20-POLY1305]
  //   [ECDHE-RSA-AES128-GCM-SHA256|ECDHE-RSA-CHACHA20-POLY1305]
  //   ECDHE-ECDSA-AES256-GCM-SHA384
  //   ECDHE-RSA-AES256-GCM-SHA384
  //
  // In builds using :ref:`BoringSSL FIPS <arch_overview_ssl_fips>`, the default client cipher list is:
  //
  // .. code-block:: none
  //
  //   ECDHE-ECDSA-AES128-GCM-SHA256
  //   ECDHE-RSA-AES128-GCM-SHA256
  //   ECDHE-ECDSA-AES256-GCM-SHA384
  //   ECDHE-RSA-AES256-GCM-SHA384
  repeated string cipher_suites = 3;

  // If specified, the TLS connection will only support the specified ECDH
  // curves. If not specified, the default curves will be used.
  //
  // In non-FIPS builds, the default curves are:
  //
  // .. code-block:: none
  //
  //   X25519
  //   P-256
  //
  // In builds using :ref:`BoringSSL FIPS <arch_overview_ssl_fips>`, the default curve is:
  //
  // .. code-block:: none
  //
  //   P-256
  repeated string ecdh_curves = 4;

  // If specified, the TLS connection will only support the specified signature algorithms.
  // The list is ordered by preference.
  // If not specified, the default signature algorithms defined by BoringSSL will be used.
  //
  // Default signature algorithms selected by BoringSSL (may be out of date):
  //
  // .. code-block:: none
  //
  //   ecdsa_secp256r1_sha256
  //   rsa_pss_rsae_sha256
  //   rsa_pkcs1_sha256
  //   ecdsa_secp384r1_sha384
  //   rsa_pss_rsae_sha384
  //   rsa_pkcs1_sha384
  //   rsa_pss_rsae_sha512
  //   rsa_pkcs1_sha512
  //   rsa_pkcs1_sha1
  //
  // Signature algorithms supported by BoringSSL (may be out of date):
  //
  // .. code-block:: none
  //
  //   rsa_pkcs1_sha256
  //   rsa_pkcs1_sha384
  //   rsa_pkcs1_sha512
  //   ecdsa_secp256r1_sha256
  //   ecdsa_secp384r1_sha384
  //   ecdsa_secp521r1_sha512
  //   rsa_pss_rsae_sha256
  //   rsa_pss_rsae_sha384
  //   rsa_pss_rsae_sha512
  //   ed25519
  //   rsa_pkcs1_sha1
  //   ecdsa_sha1
  repeated string signature_algorithms = 5;
}

// BoringSSL private key method configuration. The private key methods are used for external
// (potentially asynchronous) signing and decryption operations. Some use cases for private key
// methods would be TPM support and TLS acceleration.
message PrivateKeyProvider {
  option (udpa.annotations.versioning).previous_message_type =
      "envoy.api.v2.auth.PrivateKeyProvider";

  reserved 2;

  reserved "config";

  // Private key method provider name. The name must match a
  // supported private key method provider type.
  string provider_name = 1 [(validate.rules).string = {min_len: 1}];

  // Private key method provider specific configuration.
  oneof config_type {
    google.protobuf.Any typed_config = 3 [(udpa.annotations.sensitive) = true];
  }
}

// [#next-free-field: 9]
message TlsCertificate {
  option (udpa.annotations.versioning).previous_message_type = "envoy.api.v2.auth.TlsCertificate";

  // The TLS certificate chain.
  //
  // If ``certificate_chain`` is a filesystem path, a watch will be added to the
  // parent directory for any file moves to support rotation. This currently
  // only applies to dynamic secrets, when the ``TlsCertificate`` is delivered via
  // SDS.
  config.core.v3.DataSource certificate_chain = 1;

  // The TLS private key.
  //
  // If ``private_key`` is a filesystem path, a watch will be added to the parent
  // directory for any file moves to support rotation. This currently only
  // applies to dynamic secrets, when the ``TlsCertificate`` is delivered via SDS.
  config.core.v3.DataSource private_key = 2 [(udpa.annotations.sensitive) = true];

  // ``Pkcs12`` data containing TLS certificate, chain, and private key.
  //
  // If ``pkcs12`` is a filesystem path, the file will be read, but no watch will
  // be added to the parent directory, since ``pkcs12`` isn't used by SDS.
  // This field is mutually exclusive with ``certificate_chain``, ``private_key`` and ``private_key_provider``.
  // This can't be marked as ``oneof`` due to API compatibility reasons. Setting
  // both :ref:`private_key <envoy_v3_api_field_extensions.transport_sockets.tls.v3.TlsCertificate.private_key>`,
  // :ref:`certificate_chain <envoy_v3_api_field_extensions.transport_sockets.tls.v3.TlsCertificate.certificate_chain>`,
  // or :ref:`private_key_provider <envoy_v3_api_field_extensions.transport_sockets.tls.v3.TlsCertificate.private_key_provider>`
  // and :ref:`pkcs12 <envoy_v3_api_field_extensions.transport_sockets.tls.v3.TlsCertificate.pkcs12>`
  // fields will result in an error. Use :ref:`password
  // <envoy_v3_api_field_extensions.transport_sockets.tls.v3.TlsCertificate.password>`
  // to specify the password to unprotect the ``PKCS12`` data, if necessary.
  config.core.v3.DataSource pkcs12 = 8 [(udpa.annotations.sensitive) = true];

  // If specified, updates of file-based ``certificate_chain`` and ``private_key``
  // sources will be triggered by this watch. The certificate/key pair will be
  // read together and validated for atomic read consistency (i.e. no
  // intervening modification occurred between cert/key read, verified by file
  // hash comparisons). This allows explicit control over the path watched, by
  // default the parent directories of the filesystem paths in
  // ``certificate_chain`` and ``private_key`` are watched if this field is not
  // specified. This only applies when a ``TlsCertificate`` is delivered by SDS
  // with references to filesystem paths. See the :ref:`SDS key rotation
  // <sds_key_rotation>` documentation for further details.
  config.core.v3.WatchedDirectory watched_directory = 7;

  // BoringSSL private key method provider. This is an alternative to :ref:`private_key
  // <envoy_v3_api_field_extensions.transport_sockets.tls.v3.TlsCertificate.private_key>` field. This can't be
  // marked as ``oneof`` due to API compatibility reasons. Setting both :ref:`private_key
  // <envoy_v3_api_field_extensions.transport_sockets.tls.v3.TlsCertificate.private_key>` and
  // :ref:`private_key_provider
  // <envoy_v3_api_field_extensions.transport_sockets.tls.v3.TlsCertificate.private_key_provider>` fields will result in an
  // error.
  PrivateKeyProvider private_key_provider = 6;

  // The password to decrypt the TLS private key. If this field is not set, it is assumed that the
  // TLS private key is not password encrypted.
  config.core.v3.DataSource password = 3 [(udpa.annotations.sensitive) = true];

  // The OCSP response to be stapled with this certificate during the handshake.
  // The response must be DER-encoded and may only be  provided via ``filename`` or
  // ``inline_bytes``. The response may pertain to only one certificate.
  config.core.v3.DataSource ocsp_staple = 4;

  // [#not-implemented-hide:]
  repeated config.core.v3.DataSource signed_certificate_timestamp = 5;
}

message TlsSessionTicketKeys {
  option (udpa.annotations.versioning).previous_message_type =
      "envoy.api.v2.auth.TlsSessionTicketKeys";

  // Keys for encrypting and decrypting TLS session tickets. The
  // first key in the array contains the key to encrypt all new sessions created by this context.
  // All keys are candidates for decrypting received tickets. This allows for easy rotation of keys
  // by, for example, putting the new key first, and the previous key second.
  //
  // If :ref:`session_ticket_keys <envoy_v3_api_field_extensions.transport_sockets.tls.v3.DownstreamTlsContext.session_ticket_keys>`
  // is not specified, the TLS library will still support resuming sessions via tickets, but it will
  // use an internally-generated and managed key, so sessions cannot be resumed across hot restarts
  // or on different hosts.
  //
  // Each key must contain exactly 80 bytes of cryptographically-secure random data. For
  // example, the output of ``openssl rand 80``.
  //
  // .. attention::
  //
  //   Using this feature has serious security considerations and risks. Improper handling of keys
  //   may result in loss of secrecy in connections, even if ciphers supporting perfect forward
  //   secrecy are used. See https://www.imperialviolet.org/2013/06/27/botchingpfs.html for some
  //   discussion. To minimize the risk, you must:
  //
  //   * Keep the session ticket keys at least as secure as your TLS certificate private keys
  //   * Rotate session ticket keys at least daily, and preferably hourly
  //   * Always generate keys using a cryptographically-secure random data source
  repeated config.core.v3.DataSource keys = 1
      [(validate.rules).repeated = {min_items: 1}, (udpa.annotations.sensitive) = true];
}

// Indicates a certificate to be obtained from a named CertificateProvider plugin instance.
// The plugin instances are defined in the client's bootstrap file.
// The plugin allows certificates to be fetched/refreshed over the network asynchronously with
// respect to the TLS handshake.
// [#not-implemented-hide:]
message CertificateProviderPluginInstance {
  // Provider instance name. If not present, defaults to "default".
  //
  // Instance names should generally be defined not in terms of the underlying provider
  // implementation (e.g., "file_watcher") but rather in terms of the function of the
  // certificates (e.g., "foo_deployment_identity").
  string instance_name = 1;

  // Opaque name used to specify certificate instances or types. For example, "ROOTCA" to specify
  // a root-certificate (validation context) or "example.com" to specify a certificate for a
  // particular domain. Not all provider instances will actually use this field, so the value
  // defaults to the empty string.
  string certificate_name = 2;
}

// Matcher for subject alternative names, to match both type and value of the SAN.
message SubjectAltNameMatcher {
  // Indicates the choice of GeneralName as defined in section 4.2.1.5 of RFC 5280 to match
  // against.
  enum SanType {
    SAN_TYPE_UNSPECIFIED = 0;
    EMAIL = 1;
    DNS = 2;
    URI = 3;
    IP_ADDRESS = 4;
  }

  // Specification of type of SAN. Note that the default enum value is an invalid choice.
  SanType san_type = 1 [(validate.rules).enum = {defined_only: true not_in: 0}];

  // Matcher for SAN value.
  type.matcher.v3.StringMatcher matcher = 2 [(validate.rules).message = {required: true}];
}

// [#next-free-field: 17]
message CertificateValidationContext {
  option (udpa.annotations.versioning).previous_message_type =
      "envoy.api.v2.auth.CertificateValidationContext";

  // Peer certificate verification mode.
  enum TrustChainVerification {
    // Perform default certificate verification (e.g., against CA / verification lists)
    VERIFY_TRUST_CHAIN = 0;

    // Connections where the certificate fails verification will be permitted.
    // For HTTP connections, the result of certificate verification can be used in route matching. (
    // see :ref:`validated <envoy_v3_api_field_config.route.v3.RouteMatch.TlsContextMatchOptions.validated>` ).
    ACCEPT_UNTRUSTED = 1;
  }

  reserved 4, 5;

  reserved "verify_subject_alt_name";

  // TLS certificate data containing certificate authority certificates to use in verifying
  // a presented peer certificate (e.g. server certificate for clusters or client certificate
  // for listeners). If not specified and a peer certificate is presented it will not be
  // verified. By default, a client certificate is optional, unless one of the additional
  // options (:ref:`require_client_certificate
  // <envoy_v3_api_field_extensions.transport_sockets.tls.v3.DownstreamTlsContext.require_client_certificate>`,
  // :ref:`verify_certificate_spki
  // <envoy_v3_api_field_extensions.transport_sockets.tls.v3.CertificateValidationContext.verify_certificate_spki>`,
  // :ref:`verify_certificate_hash
  // <envoy_v3_api_field_extensions.transport_sockets.tls.v3.CertificateValidationContext.verify_certificate_hash>`, or
  // :ref:`match_typed_subject_alt_names
  // <envoy_v3_api_field_extensions.transport_sockets.tls.v3.CertificateValidationContext.match_typed_subject_alt_names>`) is also
  // specified.
  //
  // It can optionally contain certificate revocation lists, in which case Envoy will verify
  // that the presented peer certificate has not been revoked by one of the included CRLs. Note
  // that if a CRL is provided for any certificate authority in a trust chain, a CRL must be
  // provided for all certificate authorities in that chain. Failure to do so will result in
  // verification failure for both revoked and unrevoked certificates from that chain.
  // The behavior of requiring all certificates to contain CRLs can be altered by
  // setting :ref:`only_verify_leaf_cert_crl <envoy_v3_api_field_extensions.transport_sockets.tls.v3.CertificateValidationContext.only_verify_leaf_cert_crl>`
  // true. If set to true, only the final certificate in the chain undergoes CRL verification.
  //
  // See :ref:`the TLS overview <arch_overview_ssl_enabling_verification>` for a list of common
  // system CA locations.
  //
  // If ``trusted_ca`` is a filesystem path, a watch will be added to the parent
  // directory for any file moves to support rotation. This currently only
  // applies to dynamic secrets, when the ``CertificateValidationContext`` is
  // delivered via SDS.
  //
  // X509_V_FLAG_PARTIAL_CHAIN is set by default, so non-root/intermediate ca certificate in ``trusted_ca``
  // can be treated as trust anchor as well. It allows verification with building valid partial chain instead
  // of a full chain.
  //
  // Only one of ``trusted_ca`` and ``ca_certificate_provider_instance`` may be specified.
  //
  // [#next-major-version: This field and watched_directory below should ideally be moved into a
  // separate sub-message, since there's no point in specifying the latter field without this one.]
  config.core.v3.DataSource trusted_ca = 1
      [(udpa.annotations.field_migrate).oneof_promotion = "ca_cert_source"];

  // Certificate provider instance for fetching TLS certificates.
  //
  // Only one of ``trusted_ca`` and ``ca_certificate_provider_instance`` may be specified.
  // [#not-implemented-hide:]
  CertificateProviderPluginInstance ca_certificate_provider_instance = 13
      [(udpa.annotations.field_migrate).oneof_promotion = "ca_cert_source"];

  // If specified, updates of a file-based ``trusted_ca`` source will be triggered
  // by this watch. This allows explicit control over the path watched, by
  // default the parent directory of the filesystem path in ``trusted_ca`` is
  // watched if this field is not specified. This only applies when a
  // ``CertificateValidationContext`` is delivered by SDS with references to
  // filesystem paths. See the :ref:`SDS key rotation <sds_key_rotation>`
  // documentation for further details.
  config.core.v3.WatchedDirectory watched_directory = 11;

  // An optional list of base64-encoded SHA-256 hashes. If specified, Envoy will verify that the
  // SHA-256 of the DER-encoded Subject Public Key Information (SPKI) of the presented certificate
  // matches one of the specified values.
  //
  // A base64-encoded SHA-256 of the Subject Public Key Information (SPKI) of the certificate
  // can be generated with the following command:
  //
  // .. code-block:: bash
  //
  //   $ openssl x509 -in path/to/client.crt -noout -pubkey
  //     | openssl pkey -pubin -outform DER
  //     | openssl dgst -sha256 -binary
  //     | openssl enc -base64
  //   NvqYIYSbgK2vCJpQhObf77vv+bQWtc5ek5RIOwPiC9A=
  //
  // This is the format used in HTTP Public Key Pinning.
  //
  // When both:
  // :ref:`verify_certificate_hash
  // <envoy_v3_api_field_extensions.transport_sockets.tls.v3.CertificateValidationContext.verify_certificate_hash>` and
  // :ref:`verify_certificate_spki
  // <envoy_v3_api_field_extensions.transport_sockets.tls.v3.CertificateValidationContext.verify_certificate_spki>` are specified,
  // a hash matching value from either of the lists will result in the certificate being accepted.
  //
  // .. attention::
  //
  //   This option is preferred over :ref:`verify_certificate_hash
  //   <envoy_v3_api_field_extensions.transport_sockets.tls.v3.CertificateValidationContext.verify_certificate_hash>`,
  //   because SPKI is tied to a private key, so it doesn't change when the certificate
  //   is renewed using the same private key.
  repeated string verify_certificate_spki = 3
      [(validate.rules).repeated = {items {string {min_len: 44 max_bytes: 44}}}];

  // An optional list of hex-encoded SHA-256 hashes. If specified, Envoy will verify that
  // the SHA-256 of the DER-encoded presented certificate matches one of the specified values.
  //
  // A hex-encoded SHA-256 of the certificate can be generated with the following command:
  //
  // .. code-block:: bash
  //
  //   $ openssl x509 -in path/to/client.crt -outform DER | openssl dgst -sha256 | cut -d" " -f2
  //   df6ff72fe9116521268f6f2dd4966f51df479883fe7037b39f75916ac3049d1a
  //
  // A long hex-encoded and colon-separated SHA-256 (a.k.a. "fingerprint") of the certificate
  // can be generated with the following command:
  //
  // .. code-block:: bash
  //
  //   $ openssl x509 -in path/to/client.crt -noout -fingerprint -sha256 | cut -d"=" -f2
  //   DF:6F:F7:2F:E9:11:65:21:26:8F:6F:2D:D4:96:6F:51:DF:47:98:83:FE:70:37:B3:9F:75:91:6A:C3:04:9D:1A
  //
  // Both of those formats are acceptable.
  //
  // When both:
  // :ref:`verify_certificate_hash
  // <envoy_v3_api_field_extensions.transport_sockets.tls.v3.CertificateValidationContext.verify_certificate_hash>` and
  // :ref:`verify_certificate_spki
  // <envoy_v3_api_field_extensions.transport_sockets.tls.v3.CertificateValidationContext.verify_certificate_spki>` are specified,
  // a hash matching value from either of the lists will result in the certificate being accepted.
  repeated string verify_certificate_hash = 2
      [(validate.rules).repeated = {items {string {min_len: 64 max_bytes: 95}}}];

  // An optional list of Subject Alternative name matchers. If specified, Envoy will verify that the
  // Subject Alternative Name of the presented certificate matches one of the specified matchers.
  // The matching uses "any" semantics, that is to say, the SAN is verified if at least one matcher is
  // matched.
  //
  // When a certificate has wildcard DNS SAN entries, to match a specific client, it should be
  // configured with exact match type in the :ref:`string matcher <envoy_v3_api_msg_type.matcher.v3.StringMatcher>`.
  // For example if the certificate has "\*.example.com" as DNS SAN entry, to allow only "api.example.com",
  // it should be configured as shown below.
  //
  // .. code-block:: yaml
  //
  //  match_typed_subject_alt_names:
  //  - san_type: DNS
  //    matcher:
  //      exact: "api.example.com"
  //
  // .. attention::
  //
  //   Subject Alternative Names are easily spoofable and verifying only them is insecure,
  //   therefore this option must be used together with :ref:`trusted_ca
  //   <envoy_v3_api_field_extensions.transport_sockets.tls.v3.CertificateValidationContext.trusted_ca>`.
  repeated SubjectAltNameMatcher match_typed_subject_alt_names = 15;

  // This field is deprecated in favor of
  // :ref:`match_typed_subject_alt_names
  // <envoy_v3_api_field_extensions.transport_sockets.tls.v3.CertificateValidationContext.match_typed_subject_alt_names>`.
  // Note that if both this field and :ref:`match_typed_subject_alt_names
  // <envoy_v3_api_field_extensions.transport_sockets.tls.v3.CertificateValidationContext.match_typed_subject_alt_names>`
  // are specified, the former (deprecated field) is ignored.
  repeated type.matcher.v3.StringMatcher match_subject_alt_names = 9
      [deprecated = true, (envoy.annotations.deprecated_at_minor_version) = "3.0"];

  // [#not-implemented-hide:] Must present signed certificate time-stamp.
  google.protobuf.BoolValue require_signed_certificate_timestamp = 6;

  // An optional `certificate revocation list
  // <https://en.wikipedia.org/wiki/Certificate_revocation_list>`_
  // (in PEM format). If specified, Envoy will verify that the presented peer
  // certificate has not been revoked by this CRL. If this DataSource contains
  // multiple CRLs, all of them will be used. Note that if a CRL is provided
  // for any certificate authority in a trust chain, a CRL must be provided
  // for all certificate authorities in that chain. Failure to do so will
  // result in verification failure for both revoked and unrevoked certificates
  // from that chain. This default behavior can be altered by setting
  // :ref:`only_verify_leaf_cert_crl <envoy_v3_api_field_extensions.transport_sockets.tls.v3.CertificateValidationContext.only_verify_leaf_cert_crl>` to
  // true.
  config.core.v3.DataSource crl = 7;

  // If specified, Envoy will not reject expired certificates.
  bool allow_expired_certificate = 8;

  // Certificate trust chain verification mode.
  TrustChainVerification trust_chain_verification = 10
      [(validate.rules).enum = {defined_only: true}];

  // The configuration of an extension specific certificate validator.
  // If specified, all validation is done by the specified validator,
  // and the behavior of all other validation settings is defined by the specified validator (and may be entirely ignored, unused, and unvalidated).
  // Refer to the documentation for the specified validator. If you do not want a custom validation algorithm, do not set this field.
  // [#extension-category: envoy.tls.cert_validator]
  config.core.v3.TypedExtensionConfig custom_validator_config = 12;

  // If this option is set to true, only the certificate at the end of the
  // certificate chain will be subject to validation by :ref:`CRL <envoy_v3_api_field_extensions.transport_sockets.tls.v3.CertificateValidationContext.crl>`.
  bool only_verify_leaf_cert_crl = 14;

  // Defines maximum depth of a certificate chain accepted in verification, the default limit is 100, though this can be system-dependent.
  // This number does not include the leaf, so a depth of 1 allows the leaf and one CA certificate. If a trusted issuer appears in the chain,
  // but in a depth larger than configured, the certificate validation will fail.
  // See `BoringSSL SSL_CTX_set_verify_depth <https://commondatastorage.googleapis.com/chromium-boringssl-docs/ssl.h.html#SSL_CTX_set_verify_depth>`
  // If you use OpenSSL, its behavior is different from BoringSSL, this will define a limit on the number of certificates between the end-entity and trust-anchor certificates.
  // Neither the end-entity nor the trust-anchor certificates count against depth.
  // See `OpenSSL SSL set_verify_depth <https://www.openssl.org/docs/man1.1.1/man3/SSL_CTX_set_verify_depth.html>`_.
  // Trusted issues are specified by setting :ref:`trusted_ca <envoy_v3_api_field_extensions.transport_sockets.tls.v3.CertificateValidationContext.trusted_ca>`
  google.protobuf.UInt32Value max_verify_depth = 16 [(validate.rules).uint32 = {lte: 100}];
}