Prevent redirect to Host (2) (#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 <[email protected]>
go-gitea · Mar 23, 2022 · 0b1686b · 0b1686b
1 parent 81b5bef
commit 0b1686b
Showing 1 changed file with 6 additions and 0 deletions.
diff --git 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