hugo/markup/rst/convert.go
Bjørn Erik Pedersen f4389e48ce
Add some basic security policies with sensible defaults
This ommmit contains some security hardening measures for the Hugo build runtime.

There are some rarely used features in Hugo that would be good to have disabled by default. One example would be the "external helpers".

For `asciidoctor` and some others we use Go's `os/exec` package to start a new process.

These are a predefined set of binary names, all loaded from `PATH` and with a predefined set of arguments. Still, if you don't use `asciidoctor` in your project, you might as well have it turned off.

You can configure your own in the new `security` configuration section, but the defaults are configured to create a minimal amount of site breakage. And if that do happen, you will get clear instructions in the loa about what to do.

The default configuration is listed below. Note that almost all of these options are regular expression _whitelists_ (a string or a slice); the value `none` will block all.

```toml
[security]
  enableInlineShortcodes = false
  [security.exec]
    allow = ['^dart-sass-embedded$', '^go$', '^npx$', '^postcss$']
    osEnv = ['(?i)^(PATH|PATHEXT|APPDATA|TMP|TEMP|TERM)$']

  [security.funcs]
    getenv = ['^HUGO_']

  [security.http]
    methods = ['(?i)GET|POST']
    urls = ['.*']
```
2021-12-16 09:40:22 +01:00

136 lines
3.8 KiB
Go

// Copyright 2019 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 rst converts content to HTML using the RST external helper.
package rst
import (
"bytes"
"runtime"
"github.com/gohugoio/hugo/common/hexec"
"github.com/gohugoio/hugo/htesting"
"github.com/gohugoio/hugo/identity"
"github.com/gohugoio/hugo/markup/internal"
"github.com/gohugoio/hugo/markup/converter"
)
// Provider is the package entry point.
var Provider converter.ProviderProvider = provider{}
type provider struct {
}
func (p provider) New(cfg converter.ProviderConfig) (converter.Provider, error) {
return converter.NewProvider("rst", func(ctx converter.DocumentContext) (converter.Converter, error) {
return &rstConverter{
ctx: ctx,
cfg: cfg,
}, nil
}), nil
}
type rstConverter struct {
ctx converter.DocumentContext
cfg converter.ProviderConfig
}
func (c *rstConverter) Convert(ctx converter.RenderContext) (converter.Result, error) {
b, err := c.getRstContent(ctx.Src, c.ctx)
if err != nil {
return nil, err
}
return converter.Bytes(b), nil
}
func (c *rstConverter) Supports(feature identity.Identity) bool {
return false
}
// getRstContent calls the Python script rst2html as an external helper
// to convert reStructuredText content to HTML.
func (c *rstConverter) getRstContent(src []byte, ctx converter.DocumentContext) ([]byte, error) {
logger := c.cfg.Logger
binaryName, binaryPath := getRstBinaryNameAndPath()
if binaryName == "" {
logger.Println("rst2html / rst2html.py not found in $PATH: Please install.\n",
" Leaving reStructuredText content unrendered.")
return src, nil
}
logger.Infoln("Rendering", ctx.DocumentName, "with", binaryName, "...")
var result []byte
var err error
// certain *nix based OSs wrap executables in scripted launchers
// invoking binaries on these OSs via python interpreter causes SyntaxError
// invoke directly so that shebangs work as expected
// handle Windows manually because it doesn't do shebangs
if runtime.GOOS == "windows" {
pythonBinary, _ := internal.GetPythonBinaryAndExecPath()
args := []string{binaryPath, "--leave-comments", "--initial-header-level=2"}
result, err = internal.ExternallyRenderContent(c.cfg, ctx, src, pythonBinary, args)
} else {
args := []string{"--leave-comments", "--initial-header-level=2"}
result, err = internal.ExternallyRenderContent(c.cfg, ctx, src, binaryName, args)
}
if err != nil {
return nil, err
}
// TODO(bep) check if rst2html has a body only option.
bodyStart := bytes.Index(result, []byte("<body>\n"))
if bodyStart < 0 {
bodyStart = -7 // compensate for length
}
bodyEnd := bytes.Index(result, []byte("\n</body>"))
if bodyEnd < 0 || bodyEnd >= len(result) {
bodyEnd = len(result) - 1
if bodyEnd < 0 {
bodyEnd = 0
}
}
return result[bodyStart+7 : bodyEnd], err
}
var rst2Binaries = []string{"rst2html", "rst2html.py"}
func getRstBinaryNameAndPath() (string, string) {
for _, candidate := range rst2Binaries {
if pth := hexec.LookPath(candidate); pth != "" {
return candidate, pth
}
}
return "", ""
}
// Supports returns whether rst is (or should be) installed on this computer.
func Supports() bool {
name, _ := getRstBinaryNameAndPath()
hasBin := name != ""
if htesting.SupportsAll() {
if !hasBin {
panic("rst not installed")
}
return true
}
return hasBin
}