Backport fix for CVE-2021-34558 (#80)

See: https://groups.google.com/g/golang-dev/c/5LJ2V7rd-Ag/m/YGLHVBZ6AAAJ
refraction-networking · Jul 13, 2021 · 0b2885c · 0b2885c
1 parent 2179f28
commit 0b2885c
Showing 1 changed file with 5 additions and 1 deletion.
diff --git a/key_agreement.go b/key_agreement.go
@@ -69,7 +69,11 @@ func (ka rsaKeyAgreement) generateClientKeyExchange(config *Config, clientHello
 		return nil, nil, err
 	}
 
-	encrypted, err := rsa.EncryptPKCS1v15(config.rand(), cert.PublicKey.(*rsa.PublicKey), preMasterSecret)
+	rsaKey, ok := cert.PublicKey.(*rsa.PublicKey)
+	if !ok {
+		return nil, nil, errors.New("tls: server certificate contains incorrect key type for selected ciphersuite")
+	}
+	encrypted, err := rsa.EncryptPKCS1v15(config.rand(), rsaKey, preMasterSecret)
 	if err != nil {
 		return nil, nil, err
 	}