From a98589711da5e9d935e8d690cfca92892e86d557 Mon Sep 17 00:00:00 2001 From: Roland Shoemaker Date: Wed, 9 Jun 2021 11:31:27 -0700 Subject: [PATCH] crypto/tls: test key type when casting When casting the certificate public key in generateClientKeyExchange, check the type is appropriate. This prevents a panic when a server agrees to a RSA based key exchange, but then sends an ECDSA (or other) certificate. Fixes #47143 Fixes CVE-2021-34558 Thanks to Imre Rad for reporting this issue. Change-Id: Iabccacca6052769a605cccefa1216a9f7b7f6aea Reviewed-on: https://team-review.git.corp.google.com/c/golang/go-private/+/1116723 Reviewed-by: Filippo Valsorda Reviewed-by: Katie Hockman Reviewed-on: https://go-review.googlesource.com/c/go/+/334031 Trust: Filippo Valsorda Run-TryBot: Filippo Valsorda TryBot-Result: Go Bot Reviewed-by: Dmitri Shuralyov Upstream-Status: Backport https://github.com/golang/go/commit/a98589711da5e9d935e8d690cfca92892e86d557 CVE: CVE-2021-34558 Signed-off-by: Armin Kuster --- src/crypto/tls/key_agreement.go | 6 +++++- 1 file changed, 5 insertions(+), 1 deletion(-) Index: go/src/crypto/tls/key_agreement.go =================================================================== --- go.orig/src/crypto/tls/key_agreement.go +++ go/src/crypto/tls/key_agreement.go @@ -67,7 +67,11 @@ func (ka rsaKeyAgreement) generateClient 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 }