Expose the peer ephemeral public key used for TLSv1.3 key exchange.

SSL_get_server_tmp_key() provides the peer ephemeral public key used
for key exchange. In the case of TLSv1.3 this is essentially the peer
public key from the key share used for TLSv1.3 key exchange, hence make it
availaable via SSL_get_server_tmp_key().

ok inoguchi@ tb@

1 files changed, 16 insertions, 32 deletions

diff --git a/src/lib/libssl/s3_lib.c b/src/lib/libssl/s3_lib.c
index dfd5893a2f..87b43a3521 100644
--- a/src/lib/libssl/s3_lib.c
+++ b/src/lib/libssl/s3_lib.c
@@ -1,4 +1,4 @@
-/* $OpenBSD: s3_lib.c,v 1.191 2020/02/16 14:33:04 inoguchi Exp $ */
+/* $OpenBSD: s3_lib.c,v 1.192 2020/04/18 14:07:56 jsing Exp $ */
 /* Copyright (C) 1995-1998 Eric Young (eay@cryptsoft.com)
  * All rights reserved.
  *
@@ -1652,10 +1652,6 @@ static long
 ssl_ctrl_get_server_tmp_key(SSL *s, EVP_PKEY **pkey_tmp)
 {
         EVP_PKEY *pkey = NULL;
-        EC_GROUP *group = NULL;
-        EC_POINT *point = NULL;
-        EC_KEY *ec_key = NULL;
-        BIGNUM *order = NULL;
         SESS_CERT *sc;
         int ret = 0;
 
@@ -1672,41 +1668,29 @@ ssl_ctrl_get_server_tmp_key(SSL *s, EVP_PKEY **pkey_tmp)
                 return 0;
 
         if (sc->peer_dh_tmp != NULL) {
-                ret = EVP_PKEY_set1_DH(pkey, sc->peer_dh_tmp);
-        } else if (sc->peer_ecdh_tmp) {
-                ret = EVP_PKEY_set1_EC_KEY(pkey, sc->peer_ecdh_tmp);
-        } else if (sc->peer_x25519_tmp != NULL) {
-                /* Fudge up an EC_KEY that looks like X25519... */
-                if ((group = EC_GROUP_new_by_curve_name(
-                    NID_X9_62_prime256v1)) == NULL)
-                        goto err;
-                if ((point = EC_POINT_new(group)) == NULL)
-                        goto err;
-                if ((order = BN_new()) == NULL)
+                if (!EVP_PKEY_set1_DH(pkey, sc->peer_dh_tmp))
                         goto err;
-                if (!BN_set_bit(order, 252))
-                        goto err;
-                if (!EC_GROUP_set_generator(group, point, order, NULL))
+        } else if (sc->peer_ecdh_tmp) {
+                if (!EVP_PKEY_set1_EC_KEY(pkey, sc->peer_ecdh_tmp))
                         goto err;
-                EC_GROUP_set_curve_name(group, NID_X25519);
-                if ((ec_key = EC_KEY_new()) == NULL)
+        } else if (sc->peer_x25519_tmp != NULL) {
+                if (!ssl_kex_dummy_ecdhe_x25519(pkey))
                         goto err;
-                if (!EC_KEY_set_group(ec_key, group))
+        } else if (S3I(s)->hs_tls13.key_share != NULL) {
+                if (!tls13_key_share_peer_pkey(S3I(s)->hs_tls13.key_share,
+                    pkey))
                         goto err;
-                ret = EVP_PKEY_set1_EC_KEY(pkey, ec_key);
+        } else {
+                goto err;
         }
 
-        if (ret == 1) {
-                *pkey_tmp = pkey;
-                pkey = NULL;
-        }
+        *pkey_tmp = pkey;
+        pkey = NULL;
 
-  err:
+        ret = 1;
+
+ err:
         EVP_PKEY_free(pkey);
-        EC_GROUP_free(group);
-        EC_POINT_free(point);
-        EC_KEY_free(ec_key);
-        BN_free(order);
 
         return (ret);
 }