1 files changed, 116 insertions, 0 deletions

diff --git a/kexkems.c b/kexkems.c
new file mode 100644
index 000000000..43cf82018
--- /dev/null
+++ b/kexkems.c
@@ -0,0 +1,116 @@
+/* $OpenBSD: kexkems.c,v 1.1 2019/01/21 10:20:12 djm Exp $ */
+/*
+ * Copyright (c) 2019 Markus Friedl.  All rights reserved.
+ *
+ * modification, are permitted provided that the following conditions
+ * are met:
+ * 1. Redistributions of source code must retain the above copyright
+ *    notice, this list of conditions and the following disclaimer.
+ * 2. Redistributions in binary form must reproduce the above copyright
+ *    notice, this list of conditions and the following disclaimer in the
+ *    documentation and/or other materials provided with the distribution.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
+ * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
+ * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
+ * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
+ * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
+ * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+ * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+ * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+ * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
+ * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+ */
+
+#include <sys/types.h>
+#include <stdio.h>
+#include <string.h>
+#include <signal.h>
+
+#include "sshkey.h"
+#include "digest.h"
+#include "kex.h"
+#include "log.h"
+#include "packet.h"
+#include "ssh2.h"
+#include "sshbuf.h"
+#include "ssherr.h"
+
+static int input_kex_kem_init(int, u_int32_t, struct ssh *);
+
+int
+kex_kem_server(struct ssh *ssh)
+{
+        debug("expecting SSH2_MSG_KEX_ECDH_INIT");
+        ssh_dispatch_set(ssh, SSH2_MSG_KEX_ECDH_INIT, &input_kex_kem_init);
+        return 0;
+}
+
+static int
+input_kex_kem_init(int type, u_int32_t seq, struct ssh *ssh)
+{
+        struct kex *kex = ssh->kex;
+        struct sshkey *server_host_private, *server_host_public;
+        struct sshbuf *shared_secret = NULL;
+        struct sshbuf *server_pubkey = NULL;
+        u_char *server_host_key_blob = NULL, *signature = NULL;
+        u_char *client_pubkey = NULL;
+        u_char hash[SSH_DIGEST_MAX_LENGTH];
+        size_t slen, pklen, sbloblen, hashlen;
+        int r;
+
+        if ((r = kex_load_hostkey(ssh, &server_host_private,
+            &server_host_public)) != 0)
+                goto out;
+
+        if ((r = sshpkt_get_string(ssh, &client_pubkey, &pklen)) != 0 ||
+            (r = sshpkt_get_end(ssh)) != 0)
+                goto out;
+
+        /* compute shared secret */
+        if ((r = kex_kem_sntrup4591761x25519_enc(kex, client_pubkey, pklen,
+            &server_pubkey, &shared_secret)) != 0)
+                goto out;
+
+        /* calc H */
+        if ((r = sshkey_to_blob(server_host_public, &server_host_key_blob,
+            &sbloblen)) != 0)
+                goto out;
+        hashlen = sizeof(hash);
+        if ((r = kex_c25519_hash(
+            kex->hash_alg,
+            kex->client_version,
+            kex->server_version,
+            sshbuf_ptr(kex->peer), sshbuf_len(kex->peer),
+            sshbuf_ptr(kex->my), sshbuf_len(kex->my),
+            server_host_key_blob, sbloblen,
+            client_pubkey, pklen,
+            sshbuf_ptr(server_pubkey), sshbuf_len(server_pubkey),
+            sshbuf_ptr(shared_secret), sshbuf_len(shared_secret),
+            hash, &hashlen)) != 0)
+                goto out;
+
+        /* sign H */
+        if ((r = kex->sign(ssh, server_host_private, server_host_public,
+            &signature, &slen, hash, hashlen, kex->hostkey_alg)) != 0)
+                goto out;
+
+        /* send server hostkey, ECDH pubkey 'Q_S' and signed H */
+        if ((r = sshpkt_start(ssh, SSH2_MSG_KEX_ECDH_REPLY)) != 0 ||
+            (r = sshpkt_put_string(ssh, server_host_key_blob, sbloblen)) != 0 ||
+            (r = sshpkt_put_stringb(ssh, server_pubkey)) != 0 ||
+            (r = sshpkt_put_string(ssh, signature, slen)) != 0 ||
+            (r = sshpkt_send(ssh)) != 0)
+                goto out;
+
+        if ((r = kex_derive_keys(ssh, hash, hashlen, shared_secret)) == 0)
+                r = kex_send_newkeys(ssh);
+out:
+        explicit_bzero(hash, sizeof(hash));
+        free(server_host_key_blob);
+        free(signature);
+        free(client_pubkey);
+        sshbuf_free(shared_secret);
+        sshbuf_free(server_pubkey);
+        return r;
+}