3x-ui-agent/internal/web/service/probe_theme.go

package service

import (
	"crypto/sha256"
	"encoding/hex"
	"mime"
	"net/http"
	"os"
	"path/filepath"
	"strings"

	"github.com/mhsanaei/3x-ui/v3/internal/config"

	"github.com/gin-gonic/gin"
)

// Item 7 B3+B5: public theme hosting (hub frontend.rs
// serve/disk/asset port). Themes are static directory packages on
// disk — <db folder>/themes/<short>/dist — served by the panel
// process itself at the engine root, next to the contract API. A
// theme's files are only ever read as static bytes, never executed.
// What an installed theme does not answer falls through to the
// embedded fallback theme (B5: monitor-theme-default's release dist,
// vendored under probe_theme_default/), so the public page answers
// even with nothing installed. Site icons (the favicon / touch_icon
// settings) answer ahead of any theme, so the icon follows the site
// across theme switches.

// ProbeThemesRoot is the on-disk themes directory.
func ProbeThemesRoot() string {
	return filepath.Join(config.GetDBFolderPath(), "themes")
}

// ValidThemeShort mirrors the hub's valid_short: the name of a theme
// directory, so no separators and nothing empty ([A-Za-z0-9_-]+).
func ValidThemeShort(short string) bool {
	if short == "" {
		return false
	}
	for _, r := range short {
		if !(r >= 'a' && r <= 'z' || r >= 'A' && r <= 'Z' || r >= '0' && r <= '9' || r == '-' || r == '_') {
			return false
		}
	}
	return true
}

// probeExternalTheme resolves the dist directory of an installed
// theme (hub external_theme): the theme counts only when dist and
// its index.html are actually there.
func probeExternalTheme(short string) (string, bool) {
	if short == "" {
		short = "default"
	}
	if !ValidThemeShort(short) {
		return "", false
	}
	themes, err := filepath.EvalSymlinks(ProbeThemesRoot())
	if err != nil {
		return "", false
	}
	root, err := filepath.EvalSymlinks(filepath.Join(themes, short))
	if err != nil || !strings.HasPrefix(root, themes+string(os.PathSeparator)) {
		return "", false
	}
	dist, err := filepath.EvalSymlinks(filepath.Join(root, "dist"))
	if err != nil || !strings.HasPrefix(dist, root+string(os.PathSeparator)) {
		return "", false
	}
	info, err := os.Stat(filepath.Join(dist, "index.html"))
	if err != nil || info.IsDir() {
		return "", false
	}
	return dist, true
}

// ProbeThemeInstalled reports whether a theme short is selectable
// (hub selectable): an installed external theme.
func ProbeThemeInstalled(short string) bool {
	_, ok := probeExternalTheme(short)
	return ok
}

// readInsideTheme reads a regular file whose canonical path stays
// below root (hub read_inside), rejecting escapes and symlinks out.
func readInsideTheme(root, relative string) ([]byte, bool) {
	canonRoot, err := filepath.EvalSymlinks(root)
	if err != nil {
		return nil, false
	}
	file, err := filepath.EvalSymlinks(filepath.Join(canonRoot, relative))
	if err != nil || !strings.HasPrefix(file, canonRoot+string(os.PathSeparator)) {
		return nil, false
	}
	info, err := os.Stat(file)
	if err != nil || !info.Mode().IsRegular() {
		return nil, false
	}
	data, err := os.ReadFile(file)
	if err != nil {
		return nil, false
	}
	return data, true
}

func isThemeAssetPath(p string) bool { return strings.HasPrefix(p, "assets/") }

// probeThemeETag is the strong validator of a served body: half a
// SHA-256 of it, quoted (hub asset()).
func probeThemeETag(data []byte) string {
	sum := sha256.Sum256(data)
	return "\"" + hex.EncodeToString(sum[:])[:32] + "\""
}

// serveThemeAsset writes one theme file with the caching policy its
// path warrants (hub asset()): hashed files under assets/ are
// immutable for a year; everything else is the SPA shell — no-cache
// plus a strong ETag (half the SHA-256 of the body), so a theme
// switch lands on the next request at the cost of a 304.
func serveThemeAsset(c *gin.Context, path string, data []byte) {
	contentType := mime.TypeByExtension(filepath.Ext(path))
	if contentType == "" {
		contentType = "application/octet-stream"
	}
	if isThemeAssetPath(path) {
		c.Header("Cache-Control", "public, max-age=31536000, immutable")
		c.Data(http.StatusOK, contentType, data)
		return
	}
	etag := probeThemeETag(data)
	c.Header("Content-Type", contentType)
	c.Header("Cache-Control", "no-cache")
	c.Header("ETag", etag)
	if c.GetHeader("If-None-Match") == etag {
		c.AbortWithStatus(http.StatusNotModified)
		return
	}
	c.Data(http.StatusOK, contentType, data)
}

// probeThemeChainBytes resolves the bytes a path would be answered
// with, ahead of writing any response: the current theme's own file,
// then the embedded fallback's, then (for the shell paths the stamp
// pass asks about) the index.html either would fall back to.
func probeThemeChainBytes(relative string) ([]byte, bool) {
	if dist, ok := probeExternalTheme(ProbeCurrentTheme()); ok {
		if data, found := readInsideTheme(dist, relative); found {
			return data, true
		}
	}
	if data, found := probeEmbeddedFile(relative); found {
		return data, true
	}
	if !isThemeAssetPath(relative) {
		if dist, ok := probeExternalTheme(ProbeCurrentTheme()); ok {
			if data, found := readInsideTheme(dist, "index.html"); found {
				return data, true
			}
		}
		if data, found := probeEmbeddedFile("index.html"); found {
			return data, true
		}
	}
	return nil, false
}

// probeStampIconPaths are the icon URLs the shell stamp names after
// the bytes served for them (hub stamp_icons).
var probeStampIconPaths = []string{
	"favicon.svg", "admin/favicon.svg", "apple-touch-icon.png", "admin/apple-touch-icon.png",
}

// stampProbeIcons rewrites each icon URL in the HTML shell to carry
// the ETag of what that URL serves (hub stamp_icons): the URL a theme
// writes is fixed while what it serves is not — a site icon set or
// cleared, a theme switched — and browsers hold a tab's icon by its
// URL without re-asking, so a changed icon must become a new URL.
func stampProbeIcons(html []byte) []byte {
	text := string(html)
	for _, p := range probeStampIconPaths {
		quoted := "\"/" + p + "\""
		if !strings.Contains(text, quoted) {
			continue
		}
		var (
			data []byte
			ok   bool
		)
		if key, isIcon := ProbeIconSettingKey(p); isIcon {
			if v := ProbeIconSetting(key); v != "" {
				if _, iconBytes, err := ProbeSiteIcon(v); err == nil {
					data, ok = iconBytes, true
				}
			}
		}
		if !ok {
			data, ok = probeThemeChainBytes(p)
		}
		if !ok {
			continue
		}
		etag := strings.Trim(probeThemeETag(data), "\"")
		if len(etag) > 8 {
			etag = etag[:8]
		}
		text = strings.ReplaceAll(text, quoted, "\"/"+p+"?v="+etag+"\"")
	}
	return []byte(text)
}

// serveProbeThemeFile serves one resolved theme file, stamping the
// shell's icon URLs on the way out.
func serveProbeThemeFile(c *gin.Context, path string, data []byte) {
	if path == "index.html" {
		data = stampProbeIcons(data)
	}
	serveThemeAsset(c, path, data)
}

// serveProbeIcon answers a site icon under the shell's caching
// policy (hub icon()): the URL stays while the bytes change, and an
// SVG opened directly is a document at this origin, so the sandbox
// keeps any script in it from running here.
func serveProbeIcon(c *gin.Context, mimeType string, data []byte) {
	etag := probeThemeETag(data)
	c.Header("Content-Type", mimeType)
	c.Header("X-Content-Type-Options", "nosniff")
	c.Header("Content-Security-Policy", "default-src 'none'; style-src 'unsafe-inline'; sandbox")
	c.Header("Cache-Control", "no-cache")
	c.Header("ETag", etag)
	if c.GetHeader("If-None-Match") == etag {
		c.AbortWithStatus(http.StatusNotModified)
		return
	}
	c.Data(http.StatusOK, mimeType, data)
}

// ServeProbeThemePath answers one non-API root path (hub respond):
// a set site icon first (unless the request asks for the theme's own
// with ?theme), then the current theme's file, its index.html as the
// SPA fallback for non-asset paths, then the embedded fallback theme
// the same way — a missing hashed asset is a true 404 from the
// fallback, never HTML. Returns false only when nothing at all can
// answer (the embedded theme is part of the binary, so in practice
// the fallback always answers).
func ServeProbeThemePath(c *gin.Context, path string) bool {
	if key, isIcon := ProbeIconSettingKey(path); isIcon && c.Request.URL.RawQuery != "theme" {
		if v := ProbeIconSetting(key); v != "" {
			if mimeType, data, err := ProbeSiteIcon(v); err == nil {
				serveProbeIcon(c, mimeType, data)
				return true
			}
		}
	}
	rel := path
	if rel == "" {
		rel = "index.html"
	}
	if dist, ok := probeExternalTheme(ProbeCurrentTheme()); ok {
		if data, found := readInsideTheme(dist, rel); found {
			serveProbeThemeFile(c, rel, data)
			return true
		}
		if !isThemeAssetPath(rel) {
			if data, found := readInsideTheme(dist, "index.html"); found {
				serveProbeThemeFile(c, "index.html", data)
				return true
			}
		}
		// A missing asset defers to the embedded theme, which issues
		// the refusal (hub disk() returning None).
	}
	if data, found := probeEmbeddedFile(rel); found {
		serveProbeThemeFile(c, rel, data)
		return true
	}
	if isThemeAssetPath(rel) {
		c.String(http.StatusNotFound, "没有这个文件：/%s", rel)
		return true
	}
	if data, found := probeEmbeddedFile("index.html"); found {
		serveProbeThemeFile(c, "index.html", data)
		return true
	}
	return false
}