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forgejo/modules/markup/renderer.go

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// Copyright 2017 The Gitea Authors. All rights reserved.
// Use of this source code is governed by a MIT-style
// license that can be found in the LICENSE file.
package markup
import (
"bytes"
"context"
"errors"
"fmt"
"io"
"net/url"
"path/filepath"
"strings"
"sync"
"code.gitea.io/gitea/modules/git"
"code.gitea.io/gitea/modules/setting"
)
// Init initialize regexps for markdown parsing
func Init() {
NewSanitizer()
if len(setting.Markdown.CustomURLSchemes) > 0 {
CustomLinkURLSchemes(setting.Markdown.CustomURLSchemes)
}
// since setting maybe changed extensions, this will reload all renderer extensions mapping
extRenderers = make(map[string]Renderer)
for _, renderer := range renderers {
for _, ext := range renderer.Extensions() {
extRenderers[strings.ToLower(ext)] = renderer
}
}
}
// Header holds the data about a header.
type Header struct {
Level int
Text string
ID string
}
// RenderContext represents a render context
type RenderContext struct {
Ctx context.Context
RelativePath string // relative path from tree root of the branch
Type string
IsWiki bool
URLPrefix string
Metas map[string]string
DefaultLink string
GitRepo *git.Repository
ShaExistCache map[string]bool
cancelFn func()
TableOfContents []Header
InStandalonePage bool // used by external render. the router "/org/repo/render/..." will output the rendered content in a standalone page
}
// Cancel runs any cleanup functions that have been registered for this Ctx
func (ctx *RenderContext) Cancel() {
if ctx == nil {
return
}
ctx.ShaExistCache = map[string]bool{}
if ctx.cancelFn == nil {
return
}
ctx.cancelFn()
}
// AddCancel adds the provided fn as a Cleanup for this Ctx
func (ctx *RenderContext) AddCancel(fn func()) {
if ctx == nil {
return
}
oldCancelFn := ctx.cancelFn
if oldCancelFn == nil {
ctx.cancelFn = fn
return
}
ctx.cancelFn = func() {
defer oldCancelFn()
fn()
}
}
// Renderer defines an interface for rendering markup file to HTML
type Renderer interface {
Name() string // markup format name
Extensions() []string
SanitizerRules() []setting.MarkupSanitizerRule
Render(ctx *RenderContext, input io.Reader, output io.Writer) error
}
// PostProcessRenderer defines an interface for renderers who need post process
type PostProcessRenderer interface {
NeedPostProcess() bool
}
// PostProcessRenderer defines an interface for external renderers
type ExternalRenderer interface {
// SanitizerDisabled disabled sanitize if return true
SanitizerDisabled() bool
// DisplayInIFrame represents whether render the content with an iframe
DisplayInIFrame() bool
}
// RendererContentDetector detects if the content can be rendered
// by specified renderer
type RendererContentDetector interface {
CanRender(filename string, input io.Reader) bool
}
var (
extRenderers = make(map[string]Renderer)
renderers = make(map[string]Renderer)
)
// RegisterRenderer registers a new markup file renderer
func RegisterRenderer(renderer Renderer) {
renderers[renderer.Name()] = renderer
for _, ext := range renderer.Extensions() {
extRenderers[strings.ToLower(ext)] = renderer
}
}
// GetRendererByFileName get renderer by filename
func GetRendererByFileName(filename string) Renderer {
extension := strings.ToLower(filepath.Ext(filename))
return extRenderers[extension]
}
// GetRendererByType returns a renderer according type
func GetRendererByType(tp string) Renderer {
return renderers[tp]
}
// DetectRendererType detects the markup type of the content
func DetectRendererType(filename string, input io.Reader) string {
buf, err := io.ReadAll(input)
if err != nil {
return ""
}
for _, renderer := range renderers {
if detector, ok := renderer.(RendererContentDetector); ok && detector.CanRender(filename, bytes.NewReader(buf)) {
return renderer.Name()
}
}
return ""
}
// Render renders markup file to HTML with all specific handling stuff.
func Render(ctx *RenderContext, input io.Reader, output io.Writer) error {
if ctx.Type != "" {
return renderByType(ctx, input, output)
} else if ctx.RelativePath != "" {
return renderFile(ctx, input, output)
}
return errors.New("Render options both filename and type missing")
}
// RenderString renders Markup string to HTML with all specific handling stuff and return string
func RenderString(ctx *RenderContext, content string) (string, error) {
var buf strings.Builder
if err := Render(ctx, strings.NewReader(content), &buf); err != nil {
return "", err
}
return buf.String(), nil
}
type nopCloser struct {
io.Writer
}
func (nopCloser) Close() error { return nil }
func renderIFrame(ctx *RenderContext, output io.Writer) error {
// set height="0" ahead, otherwise the scrollHeight would be max(150, realHeight)
// at the moment, only "allow-scripts" is allowed for sandbox mode.
// "allow-same-origin" should never be used, it leads to XSS attack, and it makes the JS in iframe can access parent window's config and CSRF token
// TODO: when using dark theme, if the rendered content doesn't have proper style, the default text color is black, which is not easy to read
_, err := io.WriteString(output, fmt.Sprintf(`
<iframe src="%s/%s/%s/render/%s/%s"
name="giteaExternalRender"
onload="this.height=giteaExternalRender.document.documentElement.scrollHeight"
width="100%%" height="0" scrolling="no" frameborder="0" style="overflow: hidden"
sandbox="allow-scripts"
></iframe>`,
setting.AppSubURL,
url.PathEscape(ctx.Metas["user"]),
url.PathEscape(ctx.Metas["repo"]),
ctx.Metas["BranchNameSubURL"],
url.PathEscape(ctx.RelativePath),
))
return err
}
func render(ctx *RenderContext, renderer Renderer, input io.Reader, output io.Writer) error {
var wg sync.WaitGroup
var err error
pr, pw := io.Pipe()
defer func() {
_ = pr.Close()
_ = pw.Close()
}()
var pr2 io.ReadCloser
var pw2 io.WriteCloser
var sanitizerDisabled bool
if r, ok := renderer.(ExternalRenderer); ok {
sanitizerDisabled = r.SanitizerDisabled()
}
if !sanitizerDisabled {
pr2, pw2 = io.Pipe()
defer func() {
_ = pr2.Close()
_ = pw2.Close()
}()
wg.Add(1)
go func() {
err = SanitizeReader(pr2, renderer.Name(), output)
_ = pr2.Close()
wg.Done()
}()
} else {
pw2 = nopCloser{output}
}
wg.Add(1)
go func() {
if r, ok := renderer.(PostProcessRenderer); ok && r.NeedPostProcess() {
err = PostProcess(ctx, pr, pw2)
} else {
_, err = io.Copy(pw2, pr)
}
_ = pr.Close()
_ = pw2.Close()
wg.Done()
}()
if err1 := renderer.Render(ctx, input, pw); err1 != nil {
return err1
}
_ = pw.Close()
wg.Wait()
return err
}
// ErrUnsupportedRenderType represents
type ErrUnsupportedRenderType struct {
Type string
}
func (err ErrUnsupportedRenderType) Error() string {
return fmt.Sprintf("Unsupported render type: %s", err.Type)
}
func renderByType(ctx *RenderContext, input io.Reader, output io.Writer) error {
if renderer, ok := renderers[ctx.Type]; ok {
return render(ctx, renderer, input, output)
}
return ErrUnsupportedRenderType{ctx.Type}
}
// ErrUnsupportedRenderExtension represents the error when extension doesn't supported to render
type ErrUnsupportedRenderExtension struct {
Extension string
}
func (err ErrUnsupportedRenderExtension) Error() string {
return fmt.Sprintf("Unsupported render extension: %s", err.Extension)
}
func renderFile(ctx *RenderContext, input io.Reader, output io.Writer) error {
extension := strings.ToLower(filepath.Ext(ctx.RelativePath))
if renderer, ok := extRenderers[extension]; ok {
if r, ok := renderer.(ExternalRenderer); ok && r.DisplayInIFrame() {
if !ctx.InStandalonePage {
// for an external render, it could only output its content in a standalone page
// otherwise, a <iframe> should be outputted to embed the external rendered page
return renderIFrame(ctx, output)
}
}
return render(ctx, renderer, input, output)
}
return ErrUnsupportedRenderExtension{extension}
}
// Type returns if markup format via the filename
func Type(filename string) string {
if parser := GetRendererByFileName(filename); parser != nil {
return parser.Name()
}
return ""
}
// IsMarkupFile reports whether file is a markup type file
func IsMarkupFile(name, markup string) bool {
if parser := GetRendererByFileName(name); parser != nil {
return parser.Name() == markup
}
return false
}
// IsReadmeFile reports whether name looks like a README file
// based on its name.
func IsReadmeFile(name string) bool {
name = strings.ToLower(name)
if len(name) < 6 {
return false
} else if len(name) == 6 {
return name == "readme"
}
return name[:7] == "readme."
}
// IsReadmeFileExtension reports whether name looks like a README file
// based on its name. It will look through the provided extensions and check if the file matches
// one of the extensions and provide the index in the extension list.
// If the filename is `readme.` with an unmatched extension it will match with the index equaling
// the length of the provided extension list.
// Note that the '.' should be provided in ext, e.g ".md"
func IsReadmeFileExtension(name string, ext ...string) (int, bool) {
if len(name) < 6 || name[:6] != "readme" {
return 0, false
}
for i, extension := range ext {
if name[6:] == extension {
return i, true
}
}
if name[6] == '.' {
return len(ext), true
}
return 0, false
}