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// Copyright 2018 The Hugo Authors. All rights reserved.
//
// 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 security
import (
"bytes"
"encoding/json"
"errors"
"fmt"
"reflect"
"strings"
"github.com/gohugoio/hugo/common/herrors"
"github.com/gohugoio/hugo/common/types"
"github.com/gohugoio/hugo/config"
"github.com/gohugoio/hugo/parser"
"github.com/gohugoio/hugo/parser/metadecoders"
"github.com/mitchellh/mapstructure"
)
const securityConfigKey = "security"
// DefaultConfig holds the default security policy.
var DefaultConfig = Config{
Exec: Exec{
Allow: NewWhitelist(
"^dart-sass-embedded$",
"^go$", // for Go Modules
"^npx$", // used by all Node tools (Babel, PostCSS).
"^postcss$",
),
// These have been tested to work with Hugo's external programs
// on Windows, Linux and MacOS.
OsEnv: NewWhitelist("(?i)^(PATH|PATHEXT|APPDATA|HOME|TMP|TEMP|TERM)$"),
},
Funcs: Funcs{
Getenv: NewWhitelist("^HUGO_"),
},
HTTP: HTTP{
URLs: NewWhitelist(".*"),
Methods: NewWhitelist("(?i)GET|POST"),
},
}
// Config is the top level security config.
type Config struct {
// Restricts access to os.Exec.
Exec Exec `json:"exec"`
// Restricts access to certain template funcs.
Funcs Funcs `json:"funcs"`
// Restricts access to resources.Get, getJSON, getCSV.
HTTP HTTP `json:"http"`
// Allow inline shortcodes
EnableInlineShortcodes bool `json:"enableInlineShortcodes"`
}
// Exec holds os/exec policies.
type Exec struct {
Allow Whitelist `json:"allow"`
OsEnv Whitelist `json:"osEnv"`
}
// Funcs holds template funcs policies.
type Funcs struct {
// OS env keys allowed to query in os.Getenv.
Getenv Whitelist `json:"getenv"`
}
type HTTP struct {
// URLs to allow in remote HTTP (resources.Get, getJSON, getCSV).
URLs Whitelist `json:"urls"`
// HTTP methods to allow.
Methods Whitelist `json:"methods"`
}
// ToTOML converts c to TOML with [security] as the root.
func (c Config) ToTOML() string {
sec := c.ToSecurityMap()
var b bytes.Buffer
if err := parser.InterfaceToConfig(sec, metadecoders.TOML, &b); err != nil {
panic(err)
}
return strings.TrimSpace(b.String())
}
func (c Config) CheckAllowedExec(name string) error {
if !c.Exec.Allow.Accept(name) {
return &AccessDeniedError{
name: name,
path: "security.exec.allow",
policies: c.ToTOML(),
}
}
return nil
}
func (c Config) CheckAllowedGetEnv(name string) error {
if !c.Funcs.Getenv.Accept(name) {
return &AccessDeniedError{
name: name,
path: "security.funcs.getenv",
policies: c.ToTOML(),
}
}
return nil
}
func (c Config) CheckAllowedHTTPURL(url string) error {
if !c.HTTP.URLs.Accept(url) {
return &AccessDeniedError{
name: url,
path: "security.http.urls",
policies: c.ToTOML(),
}
}
return nil
}
func (c Config) CheckAllowedHTTPMethod(method string) error {
if !c.HTTP.Methods.Accept(method) {
return &AccessDeniedError{
name: method,
path: "security.http.method",
policies: c.ToTOML(),
}
}
return nil
}
// ToSecurityMap converts c to a map with 'security' as the root key.
func (c Config) ToSecurityMap() map[string]interface{} {
// Take it to JSON and back to get proper casing etc.
asJson, err := json.Marshal(c)
herrors.Must(err)
m := make(map[string]interface{})
herrors.Must(json.Unmarshal(asJson, &m))
// Add the root
sec := map[string]interface{}{
"security": m,
}
return sec
}
// DecodeConfig creates a privacy Config from a given Hugo configuration.
func DecodeConfig(cfg config.Provider) (Config, error) {
sc := DefaultConfig
if cfg.IsSet(securityConfigKey) {
m := cfg.GetStringMap(securityConfigKey)
dec, err := mapstructure.NewDecoder(
&mapstructure.DecoderConfig{
WeaklyTypedInput: true,
Result: &sc,
DecodeHook: stringSliceToWhitelistHook(),
},
)
if err != nil {
return sc, err
}
if err = dec.Decode(m); err != nil {
return sc, err
}
}
if !sc.EnableInlineShortcodes {
// Legacy
sc.EnableInlineShortcodes = cfg.GetBool("enableInlineShortcodes")
}
return sc, nil
}
func stringSliceToWhitelistHook() mapstructure.DecodeHookFuncType {
return func(
f reflect.Type,
t reflect.Type,
data interface{}) (interface{}, error) {
if t != reflect.TypeOf(Whitelist{}) {
return data, nil
}
wl := types.ToStringSlicePreserveString(data)
return NewWhitelist(wl...), nil
}
}
// AccessDeniedError represents a security policy conflict.
type AccessDeniedError struct {
path string
name string
policies string
}
func (e *AccessDeniedError) Error() string {
return fmt.Sprintf("access denied: %q is not whitelisted in policy %q; the current security configuration is:\n\n%s\n\n", e.name, e.path, e.policies)
}
// IsAccessDenied reports whether err is an AccessDeniedError
func IsAccessDenied(err error) bool {
var notFoundErr *AccessDeniedError
return errors.As(err, ¬FoundErr)
}
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