xds: Support deprecated xDS TLS fields for Istio compat (1.77.x backport) #12508
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## Problem When using xDS with Istio's grpc-agent in proxyless mode, Java gRPC fails with: ``` LDS response Listener validation error: tls_certificate_provider_instance is required in downstream-tls-context ``` **Root Cause:** Istio sends deprecated certificate provider fields for backward compatibility with older Envoy versions. Java gRPC currently only reads the current fields, causing validation failures. Specifically, Istio uses these deprecated fields: 1. **Field 11**: `tls_certificate_certificate_provider_instance` (deprecated) instead of field 14 (`tls_certificate_provider_instance`) 2. **Field 4**: `validation_context_certificate_provider_instance` in `CombinedValidationContext` (deprecated) instead of `ca_certificate_provider_instance` in `default_validation_context` ## Fix Istio is adding support for the new fields in istio/istio#58257. Add fallback logic to support deprecated certificate provider fields before that is rolled out: **For identity certificates:** 1. Try current field 14 (`tls_certificate_provider_instance`) first 2. Fall back to deprecated field 11 (`tls_certificate_certificate_provider_instance`) **For validation context in CombinedValidationContext:** 1. Try `ca_certificate_provider_instance` in `default_validation_context` first 2. Fall back to deprecated field 4 (`validation_context_certificate_provider_instance`) This matches the behavior of [grpc-cpp](https://github.com/grpc/grpc/blob/master/src/core/xds/grpc/xds_common_types_parser.cc#L435-L474) and [grpc-go](https://github.com/grpc/grpc-go/blob/master/internal/xds/xdsclient/xdsresource/unmarshal_cds.go#L310-L344) implementations. ## Testing * Added new tests for both deprecated field paths (field 11 and field 4) * All existing tests pass * Manual local testing with Istio in proxyless mode verified the compatibility fix works --------- Co-authored-by: Amp <amp@ampcode.com>
kannanjgithub
approved these changes
Nov 13, 2025
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Problem
When using xDS with Istio's grpc-agent in proxyless mode, Java gRPC fails with:
Root Cause:
Istio sends deprecated certificate provider fields for backward compatibility with older Envoy versions. Java gRPC currently only reads the current fields, causing validation failures.
Specifically, Istio uses these deprecated fields:
tls_certificate_certificate_provider_instance(deprecated) instead of field 14 (tls_certificate_provider_instance)validation_context_certificate_provider_instanceinCombinedValidationContext(deprecated) instead ofca_certificate_provider_instanceindefault_validation_contextFix
Add fallback logic to support deprecated certificate provider fields:
For identity certificates:
tls_certificate_provider_instance) firsttls_certificate_certificate_provider_instance)For validation context in CombinedValidationContext:
ca_certificate_provider_instanceindefault_validation_contextfirstvalidation_context_certificate_provider_instance)This matches the behavior of grpc-cpp and grpc-go implementations.
Testing
Backport of #12435
CC @laz-canva