cel: fix validation of expression result type (#3526)

* cel: fix validation of expression result type

The earlier code used the proto.Equals from github.com/gogo/protobuf, which failed to compare two messages of the same type for some reason. Switching to proto.Equal from the canonical github.com/golang/protobuf fixes the issue.

* deps: remove deprecated github.com/golang/protobuf in favor of google.golang.org/protobuf

* downgrade github.com/smallstep/nosql to resolve warning pb.proto warning

modules/caddyhttp/celmatcher_test.go

@@ -0,0 +1,51 @@
+// Copyright 2015 Matthew Holt and The Caddy Authors
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package caddyhttp
+
+import (
+	"testing"
+
+	"github.com/caddyserver/caddy/v2"
+)
+
+func TestMatchExpressionProvision(t *testing.T) {
+	tests := []struct {
+		name       string
+		expression *MatchExpression
+		wantErr    bool
+	}{
+		{
+			name: "boolean mtaches succeed",
+			expression: &MatchExpression{
+				Expr: "{http.request.uri.query} != ''",
+			},
+			wantErr: false,
+		},
+		{
+			name: "reject expressions with non-boolean results",
+			expression: &MatchExpression{
+				Expr: "{http.request.uri.query}",
+			},
+			wantErr: true,
+		},
+	}
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			if err := tt.expression.Provision(caddy.Context{}); (err != nil) != tt.wantErr {
+				t.Errorf("MatchExpression.Provision() error = %v, wantErr %v", err, tt.wantErr)
+			}
+		})
+	}
+}