tls: allow cert validation by only leaf trusted CA's CRL (#18289)

Commit Message: Allow cert validation by only leaf trusted CAs CRL
Additional Description: Close #18268. In the previous implementation, we don't have availability to validate certs when all trusted CAs don't have their own CRLs if any trusted CAs have that. This feature allows validating even if all trusted CAs don't have CRLs.
Risk Level: Low
Testing: Unit
Docs Changes: Required
Release Notes: Required

Signed-off-by: Shikugawa <rei@tetrate.io>

Mirrored from https://github.com/envoyproxy/envoy @ 56e8c45b1b340c4a4f8f02ec2488354c31806d59

envoy/extensions/transport_sockets/tls/v3/common.proto

@@ -253,7 +253,7 @@ message CertificateProviderPluginInstance {
   string certificate_name = 2;
 }
 
-// [#next-free-field: 14]
+// [#next-free-field: 15]
 message CertificateValidationContext {
   option (udpa.annotations.versioning).previous_message_type =
       "envoy.api.v2.auth.CertificateValidationContext";
@@ -292,6 +292,9 @@ message CertificateValidationContext {
   // 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 if any do 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.
@@ -417,7 +420,9 @@ message CertificateValidationContext {
   // 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.
+  // 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.
@@ -433,4 +438,8 @@ message CertificateValidationContext {
   // 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;
 }