use KEM API for vanilla c25519 KEX

usr.bin/ssh/Makefile.inc

@@ -1,4 +1,4 @@
-#	$OpenBSD: Makefile.inc,v 1.62 2019/01/21 10:20:12 djm Exp $
+#	$OpenBSD: Makefile.inc,v 1.63 2019/01/21 10:24:09 djm Exp $
 
 .include <bsd.own.mk>
 
@@ -58,8 +58,6 @@ SRCS_KEXS+=	kexgexs.c
 .endif
 SRCS_KEX+=	kexc25519.c
 SRCS_KEX+=	smult_curve25519_ref.c
-SRCS_KEXC+=	kexc25519c.c
-SRCS_KEXS+=	kexc25519s.c
 
 SRCS_KEY+=	sshkey.c
 SRCS_KEY+=	sshbuf-misc.c

usr.bin/ssh/kex.h

@@ -1,4 +1,4 @@
-/* $OpenBSD: kex.h,v 1.99 2019/01/21 10:20:12 djm Exp $ */
+/* $OpenBSD: kex.h,v 1.100 2019/01/21 10:24:09 djm Exp $ */
 
 /*
  * Copyright (c) 2000, 2001 Markus Friedl.  All rights reserved.
@@ -195,6 +195,11 @@ int	 kexc25519_server(struct ssh *);
 int	 kex_kem_client(struct ssh *);
 int	 kex_kem_server(struct ssh *);
 
+int	 kex_c25519_keypair(struct kex *);
+int	 kex_c25519_enc(struct kex *, const u_char *, size_t, struct sshbuf **,
+    struct sshbuf **);
+int	 kex_c25519_dec(struct kex *, const u_char *, size_t, struct sshbuf **);
+
 int	 kex_kem_sntrup4591761x25519_keypair(struct kex *);
 int	 kex_kem_sntrup4591761x25519_enc(struct kex *, const u_char *, size_t,
     struct sshbuf **, struct sshbuf **);

usr.bin/ssh/kexc25519.c

@@ -1,6 +1,6 @@
-/* $OpenBSD: kexc25519.c,v 1.13 2019/01/21 10:20:12 djm Exp $ */
+/* $OpenBSD: kexc25519.c,v 1.14 2019/01/21 10:24:09 djm Exp $ */
 /*
- * Copyright (c) 2001, 2013 Markus Friedl.  All rights reserved.
+ * Copyright (c) 2019 Markus Friedl.  All rights reserved.
  * Copyright (c) 2010 Damien Miller.  All rights reserved.
  * Copyright (c) 2013 Aris Adamantiadis.  All rights reserved.
  *
@@ -27,20 +27,16 @@
 
 #include <sys/types.h>
 
-#include <signal.h>
+#include <stdio.h>
 #include <string.h>
+#include <signal.h>
 
-#include <openssl/bn.h>
-#include <openssl/evp.h>
-
-#include "sshbuf.h"
-#include "ssh2.h"
 #include "sshkey.h"
-#include "cipher.h"
 #include "kex.h"
-#include "log.h"
+#include "sshbuf.h"
 #include "digest.h"
 #include "ssherr.h"
+#include "ssh2.h"
 
 extern int crypto_scalarmult_curve25519(u_char a[CURVE25519_SIZE],
     const u_char b[CURVE25519_SIZE], const u_char c[CURVE25519_SIZE])
@@ -140,3 +136,109 @@ kex_c25519_hash(
 #endif
 	return 0;
 }
+
+int
+kex_c25519_keypair(struct kex *kex)
+{
+	struct sshbuf *buf = NULL;
+	u_char *cp = NULL;
+	int r;
+
+	if ((buf = sshbuf_new()) == NULL)
+		return SSH_ERR_ALLOC_FAIL;
+	if ((r = sshbuf_reserve(buf, CURVE25519_SIZE, &cp)) != 0)
+		goto out;
+	kexc25519_keygen(kex->c25519_client_key, cp);
+#ifdef DEBUG_KEXECDH
+	dump_digest("client public key c25519:", cp, CURVE25519_SIZE);
+#endif
+	kex->kem_client_pub = buf;
+	buf = NULL;
+ out:
+	sshbuf_free(buf);
+	return r;
+}
+
+int
+kex_c25519_enc(struct kex *kex, const u_char *pkblob,
+   size_t pklen, struct sshbuf **server_blobp, struct sshbuf **shared_secretp)
+{
+	struct sshbuf *server_blob = NULL;
+	struct sshbuf *buf = NULL;
+	u_char *server_pub;
+	u_char server_key[CURVE25519_SIZE];
+	int r;
+
+	*server_blobp = NULL;
+	*shared_secretp = NULL;
+
+	if (pklen != CURVE25519_SIZE) {
+		r = SSH_ERR_SIGNATURE_INVALID;
+		goto out;
+	}
+#ifdef DEBUG_KEXECDH
+	dump_digest("client public key 25519:", pkblob, CURVE25519_SIZE);
+#endif
+	/* allocate space for encrypted KEM key and ECDH pub key */
+	if ((server_blob = sshbuf_new()) == NULL) {
+		r = SSH_ERR_ALLOC_FAIL;
+		goto out;
+	}
+	if ((r = sshbuf_reserve(server_blob, CURVE25519_SIZE, &server_pub)) != 0)
+		goto out;
+	kexc25519_keygen(server_key, server_pub);
+	/* allocate shared secret */
+	if ((buf = sshbuf_new()) == NULL) {
+		r = SSH_ERR_ALLOC_FAIL;
+		goto out;
+	}
+	if ((r = kexc25519_shared_key_ext(server_key, pkblob, buf, 0)) < 0)
+		goto out;
+#ifdef DEBUG_KEXECDH
+	dump_digest("server public key 25519:", server_pub, CURVE25519_SIZE);
+	dump_digest("encoded shared secret:", sshbuf_ptr(buf), sshbuf_len(buf));
+#endif
+	*server_blobp = server_blob;
+	*shared_secretp = buf;
+	server_blob = NULL;
+	buf = NULL;
+ out:
+	explicit_bzero(server_key, sizeof(server_key));
+	sshbuf_free(server_blob);
+	sshbuf_free(buf);
+	return r;
+}
+
+int
+kex_c25519_dec(struct kex *kex, const u_char *pkblob,
+    size_t pklen, struct sshbuf **shared_secretp)
+{
+	struct sshbuf *buf = NULL;
+	int r;
+
+	*shared_secretp = NULL;
+
+	if (pklen != CURVE25519_SIZE) {
+		r = SSH_ERR_SIGNATURE_INVALID;
+		goto out;
+	}
+#ifdef DEBUG_KEXECDH
+	dump_digest("server public key c25519:", pkblob, CURVE25519_SIZE);
+#endif
+	/* shared secret */
+	if ((buf = sshbuf_new()) == NULL) {
+		r = SSH_ERR_ALLOC_FAIL;
+		goto out;
+	}
+	if ((r = kexc25519_shared_key_ext(kex->c25519_client_key, pkblob,
+	    buf, 0)) < 0)
+		goto out;
+#ifdef DEBUG_KEXECDH
+	dump_digest("encoded shared secret:", sshbuf_ptr(buf), sshbuf_len(buf));
+#endif
+	*shared_secretp = buf;
+	buf = NULL;
+ out:
+	sshbuf_free(buf);
+	return r;
+}