Fix some leaks in opa policies (networkservicemesh#1624)

* Fix some leaks in opa policies

Signed-off-by: NikitaSkrynnik <nikita.skrynnik@xored.com>

* fix go linter issues

Signed-off-by: NikitaSkrynnik <nikita.skrynnik@xored.com>

---------

Signed-off-by: NikitaSkrynnik <nikita.skrynnik@xored.com>

pkg/tools/opa/policy.go

@@ -1,6 +1,6 @@
 // Copyright (c) 2020-2022 Doc.ai and/or its affiliates.
 //
-// Copyright (c) 2023 Cisco and/or its affiliates.
+// Copyright (c) 2023-2024 Cisco and/or its affiliates.
 //
 // SPDX-License-Identifier: Apache-2.0
 //
@@ -20,10 +20,10 @@ package opa
 
 import (
 	"context"
+	"fmt"
 	"os"
 	"path/filepath"
 	"strings"
-	"sync"
 
 	"github.com/open-policy-agent/opa/rego"
 	"github.com/pkg/errors"
@@ -77,15 +77,12 @@ func WithNamedPolicyFromSource(name, source, query string, checkQuery CheckQuery
 
 // AuthorizationPolicy checks that passed tokens are valid
 type AuthorizationPolicy struct {
-	initErr        error
 	name           string
 	policyFilePath string
 	policySource   string
 	pkg            string
 	query          string
-	evalQuery      *rego.PreparedEvalQuery
 	checker        CheckAccessFunc
-	once           sync.Once
 }
 
 // Name returns AuthorizationPolicy name
@@ -99,10 +96,11 @@ func (d *AuthorizationPolicy) Check(ctx context.Context, model interface{}) erro
 	if err != nil {
 		return err
 	}
-	if intErr := d.init(); intErr != nil {
+	evalQuery, intErr := d.init()
+	if intErr != nil {
 		return intErr
 	}
-	rs, err := d.evalQuery.Eval(ctx, rego.EvalInput(input))
+	rs, err := evalQuery.Eval(ctx, rego.EvalInput(input))
 	if err != nil {
 		return status.Error(codes.Internal, err.Error())
 	}
@@ -116,33 +114,23 @@ func (d *AuthorizationPolicy) Check(ctx context.Context, model interface{}) erro
 	return nil
 }
 
-func (d *AuthorizationPolicy) init() error {
-	d.once.Do(func() {
-		if d.query == "" {
-			d.query = strings.TrimSuffix(filepath.Base(d.policyFilePath), filepath.Ext(d.policyFilePath))
-		}
-		if d.initErr = d.loadSource(); d.initErr != nil {
-			return
-		}
-		if d.initErr = d.checkModule(); d.initErr != nil {
-			return
-		}
-		var r rego.PreparedEvalQuery
-		r, d.initErr = rego.New(
-			rego.Query(strings.Join([]string{"data", d.pkg, d.query}, ".")),
-			rego.Module(d.pkg, d.policySource)).PrepareForEval(context.Background())
-		if d.initErr != nil {
-			return
-		}
-		d.evalQuery = &r
-	})
-	if d.initErr != nil {
-		return d.initErr
+func (d *AuthorizationPolicy) init() (*rego.PreparedEvalQuery, error) {
+	if d.query == "" {
+		d.query = strings.TrimSuffix(filepath.Base(d.policyFilePath), filepath.Ext(d.policyFilePath))
 	}
-	if d.evalQuery == nil {
-		return errors.Errorf("policy %v is not compiled", d.policySource)
+	if err := d.loadSource(); err != nil {
+		return nil, err
 	}
-	return nil
+	if err := d.checkModule(); err != nil {
+		return nil, err
+	}
+	r, err := rego.New(
+		rego.Query(strings.Join([]string{"data", d.pkg, d.query}, ".")),
+		rego.Module(d.pkg, d.policySource)).PrepareForEval(context.Background())
+	if err != nil {
+		return nil, errors.Wrap(err, fmt.Sprintf("policy %v is not compiled", d.policySource))
+	}
+	return &r, nil
 }
 
 func (d *AuthorizationPolicy) loadSource() error {