main.go

package main

import (
  "context"
  "fmt"
  "net"
  "strings"

  core "github.com/envoyproxy/go-control-plane/envoy/api/v2/core"
  auth "github.com/envoyproxy/go-control-plane/envoy/service/auth/v2"
  envoy_type "github.com/envoyproxy/go-control-plane/envoy/type"
  "github.com/gogo/googleapis/google/rpc"
  status "google.golang.org/genproto/googleapis/rpc/status"

  "google.golang.org/grpc"
)

type authorizationServer struct{}

func (a *authorizationServer) Check(ctx context.Context, req *auth.CheckRequest) (*auth.CheckResponse, error) {
  headers := req.GetAttributes().GetRequest().GetHttp().GetHeaders()
  authHeader := headers["authorization"]
  fmt.Printf("authHeader: %v", authHeader)
  fmt.Println("\n==============")

  var splitToken []string
  if authHeader != "" {
    splitToken = strings.Split(authHeader, "Bearer ")
  }

  if len(splitToken) == 2 {
    token := splitToken[1]

    if len(token) == 3 {
      return &auth.CheckResponse{
        Status: &status.Status{
          Code: int32(rpc.OK),
        },
        HttpResponse: &auth.CheckResponse_OkResponse{
          OkResponse: &auth.OkHttpResponse{
            Headers: []*core.HeaderValueOption{
              {
                Header: &core.HeaderValue{
                  Key:   "my-credential-header",
                  Value: "permission6,permission9",
                },
              },
            },
          },
        },
      }, nil
    }
  }

  return &auth.CheckResponse{
    Status: &status.Status{
      Code: int32(rpc.UNAUTHENTICATED),
    },
    HttpResponse: &auth.CheckResponse_DeniedResponse{
      DeniedResponse: &auth.DeniedHttpResponse{
        Status: &envoy_type.HttpStatus{Code: 401},
        Body:   "Authorization header must be formatted as Authorization: Bearer TOKEN, where TOKEN is a three-character string",
      },
    },
  }, nil
}

func main() {
  lis, _ := net.Listen("tcp", ":4040")
  grpcServer := grpc.NewServer()
  authServer := &authorizationServer{}
  auth.RegisterAuthorizationServer(grpcServer, authServer)
  grpcServer.Serve(lis)
}