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[release-1.11] [CVE-2023-44487] Disable http2 for webhooks #2875

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merged 2 commits into from
Oct 23, 2023
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[release-1.11] [CVE-2023-44487] Disable http2 for webhooks #2875

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e09b940
disable http2 for webhooks
skonto Oct 20, 2023
8b6fb5a
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skonto Oct 23, 2023
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18 changes: 18 additions & 0 deletions webhook/webhook.go
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Original file line number Diff line number Diff line change
Expand Up @@ -74,6 +74,17 @@ type Options struct {
// ControllerOptions encapsulates options for creating a new controller,
// including throttling and stats behavior.
ControllerOptions *controller.ControllerOptions

// EnableHTTP2 enables HTTP2 for webhooks.
// Mitigate CVE-2023-44487 by disabling HTTP2 by default until the Go
// standard library and golang.org/x/net are fully fixed.
// Right now, it is possible for authenticated and unauthenticated users to
// hold open HTTP2 connections and consume huge amounts of memory.
// See:
// * https://github.com/kubernetes/kubernetes/pull/121120
// * https://github.com/kubernetes/kubernetes/issues/121197
// * https://github.com/golang/go/issues/63417#issuecomment-1758858612
EnableHTTP2 bool
}

// Operation is the verb being operated on
Expand Down Expand Up @@ -237,12 +248,19 @@ func (wh *Webhook) Run(stop <-chan struct{}) error {
QuietPeriod: wh.Options.GracePeriod,
}

// If TLSNextProto is not nil, HTTP/2 support is not enabled automatically.
nextProto := map[string]func(*http.Server, *tls.Conn, http.Handler){}
if wh.Options.EnableHTTP2 {
nextProto = nil
}

server := &http.Server{
ErrorLog: log.New(&zapWrapper{logger}, "", 0),
Handler: drainer,
Addr: fmt.Sprint(":", wh.Options.Port),
TLSConfig: wh.tlsConfig,
ReadHeaderTimeout: time.Minute, //https://medium.com/a-journey-with-go/go-understand-and-mitigate-slowloris-attack-711c1b1403f6
TLSNextProto: nextProto,
}

var serve = server.ListenAndServe
Expand Down
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