Provide configuration to allow camo-media proxying

custom/conf/app.example.ini

@@ -514,6 +514,10 @@ PASSWORD_HASH_ALGO = argon2
 CSRF_COOKIE_HTTP_ONLY = true
 ; Validate against https://haveibeenpwned.com/Passwords to see if a password has been exposed
 PASSWORD_CHECK_PWN = false
+; Use a camo image proxy - leave empty to not use
+CAMO_SERVER_URL =
+; HMAC to encode urls with
+CAMO_HMAC_KEY = 
 
 [openid]
 ;

docs/content/doc/advanced/config-cheat-sheet.en-us.md

@@ -345,6 +345,8 @@ set name for unique queues. Individual queues will default to
     - spec - use one or more special characters as ``!"#$%&'()*+,-./:;<=>?@[\\]^_`{|}~``
     - off - do not check password complexity
 - `PASSWORD_CHECK_PWN`: **false**: Check [HaveIBeenPwned](https://haveibeenpwned.com/Passwords) to see if a password has been exposed.
+- `CAMO_SERVER_URL`: **<empty>**: If you would like to use a camo proxy to proxy images from rendered content, set the camo server url here
+- `CAMO_HMAC_KEY`: **<empty>**: Provide the HMAC key for encoding urls
 
 ## OpenID (`openid`)
 

modules/markup/camo.go

@@ -0,0 +1,35 @@
+// Copyright 2020 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"
+	"crypto/hmac"
+	"crypto/sha1"
+	"encoding/base64"
+	"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
+func CamoEncode(link []byte) []byte {
+	if bytes.HasPrefix(link, []byte(setting.CamoServerURL)) || len(setting.CamoHMACKey) == 0 {
+		return link
+	}
+
+	hmacKey := []byte(setting.CamoHMACKey)
+	mac := hmac.New(sha1.New, hmacKey)
+	_, _ = mac.Write(link) // hmac does not return errors
+	macSum := b64encode(mac.Sum(nil))
+	encodedURL := b64encode(link)
+
+	return []byte(util.URLJoin(setting.CamoServerURL, macSum, encodedURL))
+}
+
+func b64encode(data []byte) string {
+	return strings.TrimRight(base64.URLEncoding.EncodeToString(data), "=")
+}

modules/markup/html.go

@@ -377,8 +377,17 @@ func (ctx *postProcessCtx) visitNode(node *html.Node, visitText bool) {
 
 					lnk := string(link)
 					lnk = util.URLJoin(prefix, lnk)
+
 					link = []byte(lnk)
 				}
+				if setting.CamoServerURL != "" {
+					lnk := string(link)
+					lnkURL, _ := url.Parse(lnk)
+					if lnkURL.IsAbs() && !strings.HasPrefix(lnk, setting.AppURL) {
+						// We should camo this url
+						link = CamoEncode(link)
+					}
+				}
 				node.Attr[idx].Val = string(link)
 			}
 		} else if node.Data == "a" {

modules/setting/setting.go

@@ -147,6 +147,8 @@ var (
 	PasswordComplexity                 []string
 	PasswordHashAlgo                   string
 	PasswordCheckPwn                   bool
+	CamoServerURL                      string
+	CamoHMACKey                        string
 
 	// UI settings
 	UI = struct {
@@ -746,6 +748,8 @@ func NewContext() {
 	PasswordHashAlgo = sec.Key("PASSWORD_HASH_ALGO").MustString("argon2")
 	CSRFCookieHTTPOnly = sec.Key("CSRF_COOKIE_HTTP_ONLY").MustBool(true)
 	PasswordCheckPwn = sec.Key("PASSWORD_CHECK_PWN").MustBool(false)
+	CamoServerURL = sec.Key("CAMO_SERVER_URL").MustString("")
+	CamoHMACKey = sec.Key("CAMO_HMAC_KEY").MustString("")
 
 	InternalToken = loadInternalToken(sec)