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forgejo/modules/markup/camo.go

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// Copyright 2022 The Gitea Authors. All rights reserved.
// SPDX-License-Identifier: MIT
package markup
import (
"crypto/hmac"
"crypto/sha1"
"encoding/base64"
"net/url"
"strings"
"code.gitea.io/gitea/modules/setting"
"code.gitea.io/gitea/modules/util"
)
// CamoEncode encodes a lnk to fit with the go-camo and camo proxy links. The purposes of camo-proxy are:
// 1. Allow accessing "http://" images on a HTTPS site by using the "https://" URLs provided by camo-proxy.
// 2. Hide the visitor's real IP (protect privacy) when accessing external images.
func CamoEncode(link string) string {
if strings.HasPrefix(link, setting.Camo.ServerURL) {
return link
}
mac := hmac.New(sha1.New, []byte(setting.Camo.HMACKey))
_, _ = mac.Write([]byte(link)) // hmac does not return errors
macSum := b64encode(mac.Sum(nil))
encodedURL := b64encode([]byte(link))
return util.URLJoin(setting.Camo.ServerURL, macSum, encodedURL)
}
func b64encode(data []byte) string {
return strings.TrimRight(base64.URLEncoding.EncodeToString(data), "=")
}
func camoHandleLink(link string) string {
if setting.Camo.Enabled {
lnkURL, err := url.Parse(link)
if err == nil && lnkURL.IsAbs() && !strings.HasPrefix(link, setting.AppURL) &&
(setting.Camo.Allways || lnkURL.Scheme != "https") {
return CamoEncode(link)
}
}
return link
}