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Prevent redirect to Host (2) (#19175) (#19186)

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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>
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zeripath 2022-03-23 20:01:23 +00:00 committed by GitHub
parent 6fc73a8433
commit e3d8e92bdc
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6
modules/context/context.go
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@ -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