139 lines
4.2 KiB
Go
139 lines
4.2 KiB
Go
/*
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GoToSocial
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Copyright (C) 2021-2022 GoToSocial Authors admin@gotosocial.org
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This program is free software: you can redistribute it and/or modify
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it under the terms of the GNU Affero General Public License as published by
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the Free Software Foundation, either version 3 of the License, or
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(at your option) any later version.
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This program is distributed in the hope that it will be useful,
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but WITHOUT ANY WARRANTY; without even the implied warranty of
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MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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GNU Affero General Public License for more details.
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You should have received a copy of the GNU Affero General Public License
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along with this program. If not, see <http://www.gnu.org/licenses/>.
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*/
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package web
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import (
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// nolint:gosec
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"crypto/sha1"
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"encoding/hex"
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"fmt"
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"io"
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"net/http"
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"path"
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"strings"
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"time"
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"github.com/gin-gonic/gin"
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"github.com/superseriousbusiness/gotosocial/internal/log"
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)
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type eTagCacheEntry struct {
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eTag string
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fileLastModified time.Time
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}
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// generateEtag generates a strong (byte-for-byte) etag using
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// the entirety of the provided reader.
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func generateEtag(r io.Reader) (string, error) {
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// nolint:gosec
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hash := sha1.New()
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if _, err := io.Copy(hash, r); err != nil {
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return "", err
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}
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b := make([]byte, 0, sha1.Size)
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b = hash.Sum(b)
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return `"` + hex.EncodeToString(b) + `"`, nil
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}
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// getAssetFileInfo tries to fetch the ETag for the given filePath from the module's
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// assetsETagCache. If it can't be found there, it uses the provided http.FileSystem
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// to generate a new ETag to go in the cache, which it then returns.
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func (m *Module) getAssetETag(filePath string, fs http.FileSystem) (string, error) {
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file, err := fs.Open(filePath)
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if err != nil {
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return "", fmt.Errorf("error opening %s: %s", filePath, err)
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}
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defer file.Close()
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fileInfo, err := file.Stat()
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if err != nil {
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return "", fmt.Errorf("error statting %s: %s", filePath, err)
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}
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fileLastModified := fileInfo.ModTime()
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if cachedETag, ok := m.assetsETagCache.Get(filePath); ok && !fileLastModified.After(cachedETag.fileLastModified) {
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// only return our cached etag if the file wasn't
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// modified since last time, otherwise generate a
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// new one; eat fresh!
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return cachedETag.eTag, nil
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}
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eTag, err := generateEtag(file)
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if err != nil {
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return "", fmt.Errorf("error generating etag: %s", err)
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}
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// put new entry in cache before we return
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m.assetsETagCache.Set(filePath, eTagCacheEntry{
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eTag: eTag,
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fileLastModified: fileLastModified,
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})
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return eTag, nil
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}
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// cacheControlMiddleware implements Cache-Control header setting, and checks for
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// files inside the given http.FileSystem.
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//
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// The middleware checks if the file has been modified using If-None-Match etag,
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// if present. If the file hasn't been modified, the middleware returns 304.
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//
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// See: https://developer.mozilla.org/en-US/docs/Web/HTTP/Headers/If-None-Match
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// and: https://developer.mozilla.org/en-US/docs/Web/HTTP/Headers/Cache-Control
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func (m *Module) cacheControlMiddleware(fs http.FileSystem) gin.HandlerFunc {
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return func(c *gin.Context) {
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// no-cache prevents clients using default caching or heuristic caching,
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// and also ensures that clients will validate their cached version against
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// the version stored on the server to keep up to date.
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c.Header("Cache-Control", "no-cache")
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ifNoneMatch := c.Request.Header.Get("If-None-Match")
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// derive the path of the requested asset inside the provided filesystem
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upath := c.Request.URL.Path
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if !strings.HasPrefix(upath, "/") {
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upath = "/" + upath
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}
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assetFilePath := strings.TrimPrefix(path.Clean(upath), assetsPath)
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// either fetch etag from ttlcache or generate it
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eTag, err := m.getAssetETag(assetFilePath, fs)
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if err != nil {
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log.Errorf("error getting ETag for %s: %s", assetFilePath, err)
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return
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}
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// Regardless of what happens further down, set the etag header
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// so that the client has the up-to-date version.
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c.Header("Etag", eTag)
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// If client already has latest version of the asset, 304 + bail.
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if ifNoneMatch == eTag {
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c.AbortWithStatus(http.StatusNotModified)
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return
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}
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// else let the rest of the request be processed normally
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}
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}
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