validator

grpc_validator

import "github.com/grpc-ecosystem/go-grpc-middleware/validator"

grpc_validator is a generic request contents validator server-side middleware for gRPC.

Request Validator Middleware

Validating input is important, and hard. It also causes a lot of boilerplate code. This middleware checks for the existence of a Validate method on each of the messages of a gRPC request. This includes the single request of the Unary calls, as well as each message of the inbound Stream calls. In case of a validation failure, an InvalidArgument gRPC status is returned, along with a description of the validation failure.

While it is generic, it was intended to be used with https://github.com/mwitkow/go-proto-validators, a Go protocol buffers codegen plugin that creates the Validate methods (including nested messages) based on declarative options in the .proto files themselves. For example:

syntax = "proto3";
package validator.examples;
import "github.com/mwitkow/go-proto-validators/validator.proto";

message InnerMessage {
  // some_integer can only be in range (1, 100).
  int32 some_integer = 1 [(validator.field) = {int_gt: 0, int_lt: 100}];
  // some_float can only be in range (0;1).
  double some_float = 2 [(validator.field) = {float_gte: 0, float_lte: 1}];
}

message OuterMessage {
  // important_string must be a lowercase alpha-numeric of 5 to 30 characters (RE2 syntax).
  string important_string = 1 [(validator.field) = {regex: "^[a-z]{2,5}$"}];
  // proto3 doesn't have `required`, the `msg_exist` enforces presence of InnerMessage.
  InnerMessage inner = 2 [(validator.field) = {msg_exists : true}];
}

The OuterMessage.Validate would include validation of regexes, existence of the InnerMessage and the range values within it. The grpc_validator middleware would then automatically use that to check all messages processed by the server.

Please consult https://github.com/mwitkow/go-proto-validators for details on protoc invocation and other parameters of customization.

Usage

func StreamServerInterceptor

func StreamServerInterceptor() grpc.StreamServerInterceptor

StreamServerInterceptor returns a new streaming server interceptor that validates incoming messages.

The stage at which invalid messages will be rejected with InvalidArgument varies based on the type of the RPC. For ServerStream (1:m) requests, it will happen before reaching any userspace handlers. For ClientStream (n:1) or BidiStream (n:m) RPCs, the messages will be rejected on calls to stream.Recv().

func UnaryServerInterceptor

func UnaryServerInterceptor() grpc.UnaryServerInterceptor

UnaryServerInterceptor returns a new unary server interceptor that validates incoming messages.

Invalid messages will be rejected with InvalidArgument before reaching any userspace handlers.