grpc: restrict status codes from control plane (gRFC A54)

credentials/credentials.go

@@ -36,16 +36,16 @@ import (
 // PerRPCCredentials defines the common interface for the credentials which need to
 // attach security information to every RPC (e.g., oauth2).
 type PerRPCCredentials interface {
-	// GetRequestMetadata gets the current request metadata, refreshing
-	// tokens if required. This should be called by the transport layer on
-	// each request, and the data should be populated in headers or other
-	// context. If a status code is returned, it will be used as the status
-	// for the RPC. uri is the URI of the entry point for the request.
-	// When supported by the underlying implementation, ctx can be used for
-	// timeout and cancellation. Additionally, RequestInfo data will be
-	// available via ctx to this call.
-	// TODO(zhaoq): Define the set of the qualified keys instead of leaving
-	// it as an arbitrary string.
+	// GetRequestMetadata gets the current request metadata, refreshing tokens
+	// if required. This should be called by the transport layer on each
+	// request, and the data should be populated in headers or other
+	// context. If a status code is returned, it will be used as the status for
+	// the RPC (restricted to an allowable set of codes as defined by gRFC
+	// A54). uri is the URI of the entry point for the request.  When supported
+	// by the underlying implementation, ctx can be used for timeout and
+	// cancellation. Additionally, RequestInfo data will be available via ctx
+	// to this call.  TODO(zhaoq): Define the set of the qualified keys instead
+	// of leaving it as an arbitrary string.
 	GetRequestMetadata(ctx context.Context, uri ...string) (map[string]string, error)
 	// RequireTransportSecurity indicates whether the credentials requires
 	// transport security.

internal/status/status.go

@@ -164,3 +164,13 @@ func (e *Error) Is(target error) bool {
 	}
 	return proto.Equal(e.s.s, tse.s.s)
 }
+
+// IsRestrictedControlPlaneCode returns whether the status includes a code
+// restricted for control plane usage as defined by gRFC A54.
+func IsRestrictedControlPlaneCode(s *Status) bool {
+	switch s.Code() {
+	case codes.InvalidArgument, codes.NotFound, codes.AlreadyExists, codes.FailedPrecondition, codes.Aborted, codes.OutOfRange, codes.DataLoss:
+		return true
+	}
+	return false
+}

internal/transport/http2_client.go

@@ -40,6 +40,7 @@ import (
 	icredentials "google.golang.org/grpc/internal/credentials"
 	"google.golang.org/grpc/internal/grpcutil"
 	imetadata "google.golang.org/grpc/internal/metadata"
+	istatus "google.golang.org/grpc/internal/status"
 	"google.golang.org/grpc/internal/syscall"
 	"google.golang.org/grpc/internal/transport/networktype"
 	"google.golang.org/grpc/keepalive"
@@ -589,7 +590,11 @@ func (t *http2Client) getTrAuthData(ctx context.Context, audience string) (map[s
 	for _, c := range t.perRPCCreds {
 		data, err := c.GetRequestMetadata(ctx, audience)
 		if err != nil {
-			if _, ok := status.FromError(err); ok {
+			if st, ok := status.FromError(err); ok {
+				// Restrict the code to the list allowed by gRFC A54.
+				if istatus.IsRestrictedControlPlaneCode(st) {
+					err = status.Errorf(codes.Internal, "transport: received per-RPC creds error with illegal status: %v", err)
+				}
 				return nil, err
 			}
 
@@ -618,7 +623,14 @@ func (t *http2Client) getCallAuthData(ctx context.Context, audience string, call
 		}
 		data, err := callCreds.GetRequestMetadata(ctx, audience)
 		if err != nil {
-			return nil, status.Errorf(codes.Internal, "transport: %v", err)
+			if st, ok := status.FromError(err); ok {
+				// Restrict the code to the list allowed by gRFC A54.
+				if istatus.IsRestrictedControlPlaneCode(st) {
+					err = status.Errorf(codes.Internal, "transport: received per-RPC creds error with illegal status: %v", err)
+				}
+				return nil, err
+			}
+			return nil, status.Errorf(codes.Internal, "transport: per-RPC creds failed due to error: %v", err)
 		}
 		callAuthData = make(map[string]string, len(data))
 		for k, v := range data {

picker_wrapper.go

@@ -26,6 +26,7 @@ import (
 	"google.golang.org/grpc/balancer"
 	"google.golang.org/grpc/codes"
 	"google.golang.org/grpc/internal/channelz"
+	istatus "google.golang.org/grpc/internal/status"
 	"google.golang.org/grpc/internal/transport"
 	"google.golang.org/grpc/status"
 )
@@ -129,8 +130,12 @@ func (pw *pickerWrapper) pick(ctx context.Context, failfast bool, info balancer.
 			if err == balancer.ErrNoSubConnAvailable {
 				continue
 			}
-			if _, ok := status.FromError(err); ok {
+			if st, ok := status.FromError(err); ok {
 				// Status error: end the RPC unconditionally with this status.
+				// First restrict the code to the list allowed by gRFC A54.
+				if istatus.IsRestrictedControlPlaneCode(st) {
+					err = status.Errorf(codes.Internal, "received picker error with illegal status: %v", err)
+				}
 				return nil, nil, dropError{error: err}
 			}
 			// For all other errors, wait for ready RPCs should block and other

stream.go

@@ -39,6 +39,7 @@ import (
 	imetadata "google.golang.org/grpc/internal/metadata"
 	iresolver "google.golang.org/grpc/internal/resolver"
 	"google.golang.org/grpc/internal/serviceconfig"
+	istatus "google.golang.org/grpc/internal/status"
 	"google.golang.org/grpc/internal/transport"
 	"google.golang.org/grpc/metadata"
 	"google.golang.org/grpc/peer"
@@ -195,6 +196,13 @@ func newClientStream(ctx context.Context, desc *StreamDesc, cc *ClientConn, meth
 	rpcInfo := iresolver.RPCInfo{Context: ctx, Method: method}
 	rpcConfig, err := cc.safeConfigSelector.SelectConfig(rpcInfo)
 	if err != nil {
+		if st, ok := status.FromError(err); ok {
+			// Restrict the code to the list allowed by gRFC A54.
+			if istatus.IsRestrictedControlPlaneCode(st) {
+				err = status.Errorf(codes.Internal, "config selector returned illegal status: %v", err)
+			}
+			return nil, err
+		}
 		return nil, toRPCErr(err)
 	}