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, 42 insertions, 1 deletions

diff --git a/src/lib/libssl/ssl_kex.c b/src/lib/libssl/ssl_kex.c
index 439c1702b3..9f05fd60c9 100644
--- a/src/lib/libssl/ssl_kex.c
+++ b/src/lib/libssl/ssl_kex.c
@@ -1,4 +1,4 @@
-/* $OpenBSD: ssl_kex.c,v 1.1 2020/01/30 16:25:09 jsing Exp $ */
+/* $OpenBSD: ssl_kex.c,v 1.2 2020/04/18 14:07:56 jsing Exp $ */
 /*
  * Copyright (c) 2020 Joel Sing <jsing@openbsd.org>
  *
@@ -19,10 +19,51 @@
 
 #include <openssl/ec.h>
 #include <openssl/ecdh.h>
+#include <openssl/evp.h>
+#include <openssl/objects.h>
 
 #include "bytestring.h"
 
 int
+ssl_kex_dummy_ecdhe_x25519(EVP_PKEY *pkey)
+{
+        EC_GROUP *group = NULL;
+        EC_POINT *point = NULL;
+        EC_KEY *ec_key = NULL;
+        BIGNUM *order = NULL;
+        int ret = 0;
+
+        /* 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)
+                goto err;
+        if (!BN_set_bit(order, 252))
+                goto err;
+        if (!EC_GROUP_set_generator(group, point, order, NULL))
+                goto err;
+        EC_GROUP_set_curve_name(group, NID_X25519);
+        if ((ec_key = EC_KEY_new()) == NULL)
+                goto err;
+        if (!EC_KEY_set_group(ec_key, group))
+                goto err;
+        if (!EVP_PKEY_set1_EC_KEY(pkey, ec_key))
+                goto err;
+
+        ret = 1;
+
+ err:
+        EC_GROUP_free(group);
+        EC_POINT_free(point);
+        EC_KEY_free(ec_key);
+        BN_free(order);
+
+        return ret;
+}
+
+int
 ssl_kex_generate_ecdhe_ecp(EC_KEY *ecdh, int nid)
 {
         EC_GROUP *group;