From e3d8e92bdc67562783de9a76b5b7842b68daeb48 Mon Sep 17 00:00:00 2001
From: zeripath <art27@cantab.net>
Date: Wed, 23 Mar 2022 20:01:23 +0000
Subject: [PATCH] Prevent redirect to Host (2) (#19175) (#19186)
Backport #19175
Unhelpfully Locations starting with `/\` will be converted by the
browser to `//` because ... well I do not fully understand. Certainly
the RFCs and MDN do not indicate that this would be expected. Providing
"compatibility" with the (mis)behaviour of a certain proprietary OS is
my suspicion. However, we clearly have to protect against this.
Therefore we should reject redirection locations that match the regular
expression: `^/[\\\\/]+`
Reference #9678
Signed-off-by: Andrew Thornton <art27@cantab.net>
---
modules/context/context.go | 6 ++++++
1 file changed, 6 insertions(+)
diff --git a/modules/context/context.go b/modules/context/context.go
index fe49094479..7fae0b110f 100644
--- a/modules/context/context.go
+++ b/modules/context/context.go
@@ -181,6 +181,12 @@ func (ctx *Context) RedirectToFirst(location ...string) {
continue
}
+ // Unfortunately browsers consider a redirect Location with preceding "//" and "/\" as meaning redirect to "http(s)://REST_OF_PATH"
+ // Therefore we should ignore these redirect locations to prevent open redirects
+ if len(loc) > 1 && loc[0] == '/' && (loc[1] == '/' || loc[1] == '\\') {
+ continue
+ }
+
u, err := url.Parse(loc)
if err != nil || ((u.Scheme != "" || u.Host != "") && !strings.HasPrefix(strings.ToLower(loc), strings.ToLower(setting.AppURL))) {
continue