From: David Benjamin <davidben@google.com>
Date: Tue, 23 Jul 2019 18:14:48 +0000 (-0400)
Subject: Don't generate an unnecessary Diffie-Hellman key in TLS 1.3 clients.
X-Git-Tag: openssl-3.0.0-alpha1~1717
X-Git-Url: https://git.openssl.org/gitweb/?p=openssl.git;a=commitdiff_plain;h=166c0b98fd6e8b1bb341397642527a9396468f6c

Don't generate an unnecessary Diffie-Hellman key in TLS 1.3 clients.

tls_parse_stoc_key_share was generating a new EVP_PKEY public/private
keypair and then overrides it with the server public key, so the
generation was a waste anyway. Instead, it should create a
parameters-only EVP_PKEY.

(This is a consequence of OpenSSL using the same type for empty key,
empty key with key type, empty key with key type + parameters, public
key, and private key. As a result, it's easy to mistakenly mix such
things up, as happened here.)

Reviewed-by: Matt Caswell <matt@openssl.org>
Reviewed-by: Kurt Roeckx <kurt@roeckx.be>
(Merged from https://github.com/openssl/openssl/pull/9445)
---

diff --git a/ssl/statem/extensions_clnt.c b/ssl/statem/extensions_clnt.c
index b6e96ae56f..e6b674cebe 100644
--- a/ssl/statem/extensions_clnt.c
+++ b/ssl/statem/extensions_clnt.c
@@ -1900,8 +1900,8 @@ int tls_parse_stoc_key_share(SSL *s, PACKET *pkt, unsigned int context, X509 *x,
         return 0;
     }
 
-    skey = ssl_generate_pkey(ckey);
-    if (skey == NULL) {
+    skey = EVP_PKEY_new();
+    if (skey == NULL || EVP_PKEY_copy_parameters(skey, ckey) <= 0) {
         SSLfatal(s, SSL_AD_INTERNAL_ERROR, SSL_F_TLS_PARSE_STOC_KEY_SHARE,
                  ERR_R_MALLOC_FAILURE);
         return 0;