use curve25519 for default key exchange (curve25519-sha256@libssh.org);

initial patch from Aris Adamantiadis; ok djm@

12 files changed, 666 insertions, 10 deletions

diff --git a/usr.bin/ssh/kex.c b/usr.bin/ssh/kex.c
index bc1d6f9ba61..d356a680882 100644
--- a/usr.bin/ssh/kex.c
+++ b/usr.bin/ssh/kex.c
@@ -1,4 +1,4 @@
-/* $OpenBSD: kex.c,v 1.91 2013/05/17 00:13:13 djm Exp $ */
+/* $OpenBSD: kex.c,v 1.92 2013/11/02 21:59:15 markus Exp $ */
 /*
  * Copyright (c) 2000, 2001 Markus Friedl.  All rights reserved.
  *
@@ -65,6 +65,7 @@ static const struct kexalg kexalgs[] = {
 	{ KEX_ECDH_SHA2_NISTP256, KEX_ECDH_SHA2, NID_X9_62_prime256v1, EVP_sha256 },
 	{ KEX_ECDH_SHA2_NISTP384, KEX_ECDH_SHA2, NID_secp384r1, EVP_sha384 },
 	{ KEX_ECDH_SHA2_NISTP521, KEX_ECDH_SHA2, NID_secp521r1, EVP_sha512 },
+	{ KEX_CURVE25519_SHA256, KEX_C25519_SHA256, 0, EVP_sha256 },
 	{ NULL, -1, -1, NULL},
 };
 
diff --git a/usr.bin/ssh/kex.h b/usr.bin/ssh/kex.h
index 6d8252c1290..bab9c8d7324 100644
--- a/usr.bin/ssh/kex.h
+++ b/usr.bin/ssh/kex.h
@@ -1,4 +1,4 @@
-/* $OpenBSD: kex.h,v 1.56 2013/07/19 07:37:48 markus Exp $ */
+/* $OpenBSD: kex.h,v 1.57 2013/11/02 21:59:15 markus Exp $ */
 
 /*
  * Copyright (c) 2000, 2001 Markus Friedl.  All rights reserved.
@@ -40,6 +40,7 @@
 #define	KEX_ECDH_SHA2_NISTP256	"ecdh-sha2-nistp256"
 #define	KEX_ECDH_SHA2_NISTP384	"ecdh-sha2-nistp384"
 #define	KEX_ECDH_SHA2_NISTP521	"ecdh-sha2-nistp521"
+#define	KEX_CURVE25519_SHA256	"curve25519-sha256@libssh.org"
 
 #define COMP_NONE	0
 #define COMP_ZLIB	1
@@ -71,6 +72,7 @@ enum kex_exchange {
 	KEX_DH_GEX_SHA1,
 	KEX_DH_GEX_SHA256,
 	KEX_ECDH_SHA2,
+	KEX_C25519_SHA256,
 	KEX_MAX
 };
 
@@ -158,6 +160,8 @@ void	 kexgex_client(Kex *);
 void	 kexgex_server(Kex *);
 void	 kexecdh_client(Kex *);
 void	 kexecdh_server(Kex *);
+void	 kexc25519_client(Kex *);
+void	 kexc25519_server(Kex *);
 
 void
 kex_dh_hash(char *, char *, char *, int, char *, int, u_char *, int,
@@ -170,6 +174,19 @@ void
 kex_ecdh_hash(const EVP_MD *, const EC_GROUP *, char *, char *, char *, int,
     char *, int, u_char *, int, const EC_POINT *, const EC_POINT *,
     const BIGNUM *, u_char **, u_int *);
+void
+kex_c25519_hash(const EVP_MD *, char *, char *, char *, int,
+    char *, int, u_char *, int, const u_char *, const u_char *,
+    const BIGNUM *, u_char **, u_int *);
+
+#define CURVE25519_SIZE 32
+void	kexc25519_keygen(u_char[CURVE25519_SIZE], u_char[CURVE25519_SIZE])
+	__attribute__((__bounded__(__minbytes__, 1, CURVE25519_SIZE)))
+	__attribute__((__bounded__(__minbytes__, 2, CURVE25519_SIZE)));
+BIGNUM *kexc25519_shared_key(const u_char[CURVE25519_SIZE],
+    const u_char[CURVE25519_SIZE])
+	__attribute__((__bounded__(__minbytes__, 1, CURVE25519_SIZE)))
+	__attribute__((__bounded__(__minbytes__, 2, CURVE25519_SIZE)));
 
 void
 derive_ssh1_session_id(BIGNUM *, BIGNUM *, u_int8_t[8], u_int8_t[16]);
diff --git a/usr.bin/ssh/kexc25519.c b/usr.bin/ssh/kexc25519.c
new file mode 100644
index 00000000000..991a06f7c04
--- /dev/null
+++ b/usr.bin/ssh/kexc25519.c
@@ -0,0 +1,124 @@
+/*
+ * Copyright (c) 2001, 2013 Markus Friedl.  All rights reserved.
+ * Copyright (c) 2010 Damien Miller.  All rights reserved.
+ * Copyright (c) 2013 Aris Adamantiadis.  All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * 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 <signal.h>
+#include <string.h>
+
+#include <openssl/bn.h>
+#include <openssl/evp.h>
+
+#include "buffer.h"
+#include "ssh2.h"
+#include "key.h"
+#include "cipher.h"
+#include "kex.h"
+#include "log.h"
+
+extern int crypto_scalarmult_curve25519(u_char a[CURVE25519_SIZE],
+    const u_char b[CURVE25519_SIZE], const u_char c[CURVE25519_SIZE])
+	__attribute__((__bounded__(__minbytes__, 1, CURVE25519_SIZE)))
+	__attribute__((__bounded__(__minbytes__, 2, CURVE25519_SIZE)))
+	__attribute__((__bounded__(__minbytes__, 3, CURVE25519_SIZE)));
+
+void
+kexc25519_keygen(u_char key[CURVE25519_SIZE], u_char pub[CURVE25519_SIZE])
+{
+	static const u_char basepoint[CURVE25519_SIZE] = {9};
+
+	arc4random_buf(key, CURVE25519_SIZE);
+	crypto_scalarmult_curve25519(pub, key, basepoint);
+}
+
+BIGNUM *
+kexc25519_shared_key(const u_char key[CURVE25519_SIZE],
+    const u_char pub[CURVE25519_SIZE])
+{
+	u_char shared_key[CURVE25519_SIZE];
+	BIGNUM *shared_secret;
+
+	crypto_scalarmult_curve25519(shared_key, key, pub);
+#ifdef DEBUG_KEXECDH
+	dump_digest("shared secret", shared_key, CURVE25519_SIZE);
+#endif
+	if ((shared_secret = BN_new()) == NULL)
+		fatal("%s: BN_new failed", __func__);
+	if (BN_bin2bn(shared_key, sizeof(shared_key), shared_secret) == NULL)
+		fatal("%s: BN_bin2bn failed", __func__);
+	memset(shared_key, 0, CURVE25519_SIZE);	/* XXX explicit_bzero() */
+	return (shared_secret);
+}
+
+void
+kex_c25519_hash(
+    const EVP_MD *evp_md,
+    char *client_version_string,
+    char *server_version_string,
+    char *ckexinit, int ckexinitlen,
+    char *skexinit, int skexinitlen,
+    u_char *serverhostkeyblob, int sbloblen,
+    const u_char client_dh_pub[CURVE25519_SIZE],
+    const u_char server_dh_pub[CURVE25519_SIZE],
+    const BIGNUM *shared_secret,
+    u_char **hash, u_int *hashlen)
+{
+	Buffer b;
+	EVP_MD_CTX md;
+	static u_char digest[EVP_MAX_MD_SIZE];
+
+	buffer_init(&b);
+	buffer_put_cstring(&b, client_version_string);
+	buffer_put_cstring(&b, server_version_string);
+
+	/* kexinit messages: fake header: len+SSH2_MSG_KEXINIT */
+	buffer_put_int(&b, ckexinitlen+1);
+	buffer_put_char(&b, SSH2_MSG_KEXINIT);
+	buffer_append(&b, ckexinit, ckexinitlen);
+	buffer_put_int(&b, skexinitlen+1);
+	buffer_put_char(&b, SSH2_MSG_KEXINIT);
+	buffer_append(&b, skexinit, skexinitlen);
+
+	buffer_put_string(&b, serverhostkeyblob, sbloblen);
+	buffer_put_string(&b, client_dh_pub, CURVE25519_SIZE);
+	buffer_put_string(&b, server_dh_pub, CURVE25519_SIZE);
+	buffer_put_bignum2(&b, shared_secret);
+
+#ifdef DEBUG_KEX
+	buffer_dump(&b);
+#endif
+	EVP_DigestInit(&md, evp_md);
+	EVP_DigestUpdate(&md, buffer_ptr(&b), buffer_len(&b));
+	EVP_DigestFinal(&md, digest, NULL);
+
+	buffer_free(&b);
+
+#ifdef DEBUG_KEX
+	dump_digest("hash", digest, EVP_MD_size(evp_md));
+#endif
+	*hash = digest;
+	*hashlen = EVP_MD_size(evp_md);
+}
diff --git a/usr.bin/ssh/kexc25519c.c b/usr.bin/ssh/kexc25519c.c
new file mode 100644
index 00000000000..b208817bb1d
--- /dev/null
+++ b/usr.bin/ssh/kexc25519c.c
@@ -0,0 +1,125 @@
+/*
+ * Copyright (c) 2001 Markus Friedl.  All rights reserved.
+ * Copyright (c) 2010 Damien Miller.  All rights reserved.
+ * Copyright (c) 2013 Aris Adamantiadis.  All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * 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 "xmalloc.h"
+#include "buffer.h"
+#include "key.h"
+#include "cipher.h"
+#include "kex.h"
+#include "log.h"
+#include "packet.h"
+#include "ssh2.h"
+
+void
+kexc25519_client(Kex *kex)
+{
+	BIGNUM *shared_secret;
+	Key *server_host_key;
+	u_char client_key[CURVE25519_SIZE];
+	u_char client_pubkey[CURVE25519_SIZE];
+	u_char *server_pubkey = NULL;
+	u_char *server_host_key_blob = NULL, *signature = NULL;
+	u_char *hash;
+	u_int slen, sbloblen, hashlen;
+
+	kexc25519_keygen(client_key, client_pubkey);
+
+	packet_start(SSH2_MSG_KEX_ECDH_INIT);
+	packet_put_string(client_pubkey, sizeof(client_pubkey));
+	packet_send();
+	debug("sending SSH2_MSG_KEX_ECDH_INIT");
+
+#ifdef DEBUG_KEXECDH
+	dump_digest("client private key:", client_key, sizeof(client_key));
+#endif
+
+	debug("expecting SSH2_MSG_KEX_ECDH_REPLY");
+	packet_read_expect(SSH2_MSG_KEX_ECDH_REPLY);
+
+	/* hostkey */
+	server_host_key_blob = packet_get_string(&sbloblen);
+	server_host_key = key_from_blob(server_host_key_blob, sbloblen);
+	if (server_host_key == NULL)
+		fatal("cannot decode server_host_key_blob");
+	if (server_host_key->type != kex->hostkey_type)
+		fatal("type mismatch for decoded server_host_key_blob");
+	if (kex->verify_host_key == NULL)
+		fatal("cannot verify server_host_key");
+	if (kex->verify_host_key(server_host_key) == -1)
+		fatal("server_host_key verification failed");
+
+	/* Q_S, server public key */
+	server_pubkey = packet_get_string(&slen);
+	if (slen != CURVE25519_SIZE)
+		fatal("Incorrect size for server Curve25519 pubkey: %d", slen);
+
+#ifdef DEBUG_KEXECDH
+	dump_digest("server public key:", server_pubkey, CURVE25519_SIZE);
+#endif
+
+	/* signed H */
+	signature = packet_get_string(&slen);
+	packet_check_eom();
+
+	shared_secret = kexc25519_shared_key(client_key, server_pubkey);
+
+	/* calc and verify H */
+	kex_c25519_hash(
+	    kex->evp_md,
+	    kex->client_version_string,
+	    kex->server_version_string,
+	    buffer_ptr(&kex->my), buffer_len(&kex->my),
+	    buffer_ptr(&kex->peer), buffer_len(&kex->peer),
+	    server_host_key_blob, sbloblen,
+	    client_pubkey,
+	    server_pubkey,
+	    shared_secret,
+	    &hash, &hashlen
+	);
+	free(server_host_key_blob);
+	free(server_pubkey);
+	if (key_verify(server_host_key, signature, slen, hash, hashlen) != 1)
+		fatal("key_verify failed for server_host_key");
+	key_free(server_host_key);
+	free(signature);
+
+	/* save session id */
+	if (kex->session_id == NULL) {
+		kex->session_id_len = hashlen;
+		kex->session_id = xmalloc(kex->session_id_len);
+		memcpy(kex->session_id, hash, kex->session_id_len);
+	}
+
+	kex_derive_keys(kex, hash, hashlen, shared_secret);
+	BN_clear_free(shared_secret);
+	kex_finish(kex);
+}
diff --git a/usr.bin/ssh/kexc25519s.c b/usr.bin/ssh/kexc25519s.c
new file mode 100644
index 00000000000..28463d03f50
--- /dev/null
+++ b/usr.bin/ssh/kexc25519s.c
@@ -0,0 +1,120 @@
+/*
+ * Copyright (c) 2001 Markus Friedl.  All rights reserved.
+ * Copyright (c) 2010 Damien Miller.  All rights reserved.
+ * Copyright (c) 2013 Aris Adamantiadis.  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 <string.h>
+#include <signal.h>
+
+#include "xmalloc.h"
+#include "buffer.h"
+#include "key.h"
+#include "cipher.h"
+#include "kex.h"
+#include "log.h"
+#include "packet.h"
+#include "ssh2.h"
+
+void
+kexc25519_server(Kex *kex)
+{
+	BIGNUM *shared_secret;
+	Key *server_host_private, *server_host_public;
+	u_char *server_host_key_blob = NULL, *signature = NULL;
+	u_char server_key[CURVE25519_SIZE];
+	u_char *client_pubkey = NULL;
+	u_char server_pubkey[CURVE25519_SIZE];
+	u_char *hash;
+	u_int slen, sbloblen, hashlen;
+
+	/* generate private key */
+	kexc25519_keygen(server_key, server_pubkey);
+#ifdef DEBUG_KEXECDH
+	dump_digest("server private key:", server_key, sizeof(server_key));
+#endif
+
+	if (kex->load_host_public_key == NULL ||
+	    kex->load_host_private_key == NULL)
+		fatal("Cannot load hostkey");
+	server_host_public = kex->load_host_public_key(kex->hostkey_type);
+	if (server_host_public == NULL)
+		fatal("Unsupported hostkey type %d", kex->hostkey_type);
+	server_host_private = kex->load_host_private_key(kex->hostkey_type);
+
+	debug("expecting SSH2_MSG_KEX_ECDH_INIT");
+	packet_read_expect(SSH2_MSG_KEX_ECDH_INIT);
+	client_pubkey = packet_get_string(&slen);
+	if (slen != CURVE25519_SIZE)
+		fatal("Incorrect size for server Curve25519 pubkey: %d", slen);
+	packet_check_eom();
+
+#ifdef DEBUG_KEXECDH
+	dump_digest("client public key:", client_pubkey, CURVE25519_SIZE);
+#endif
+
+	shared_secret = kexc25519_shared_key(server_key, client_pubkey);
+
+	/* calc H */
+	key_to_blob(server_host_public, &server_host_key_blob, &sbloblen);
+	kex_c25519_hash(
+	    kex->evp_md,
+	    kex->client_version_string,
+	    kex->server_version_string,
+	    buffer_ptr(&kex->peer), buffer_len(&kex->peer),
+	    buffer_ptr(&kex->my), buffer_len(&kex->my),
+	    server_host_key_blob, sbloblen,
+	    client_pubkey,
+	    server_pubkey,
+	    shared_secret,
+	    &hash, &hashlen
+	);
+
+	/* save session id := H */
+	if (kex->session_id == NULL) {
+		kex->session_id_len = hashlen;
+		kex->session_id = xmalloc(kex->session_id_len);
+		memcpy(kex->session_id, hash, kex->session_id_len);
+	}
+
+	/* sign H */
+	kex->sign(server_host_private, server_host_public, &signature, &slen,
+	    hash, hashlen);
+
+	/* destroy_sensitive_data(); */
+
+	/* send server hostkey, ECDH pubkey 'Q_S' and signed H */
+	packet_start(SSH2_MSG_KEX_ECDH_REPLY);
+	packet_put_string(server_host_key_blob, sbloblen);
+	packet_put_string(server_pubkey, sizeof(server_pubkey));
+	packet_put_string(signature, slen);
+	packet_send();
+
+	free(signature);
+	free(server_host_key_blob);
+	/* have keys, free server key */
+	free(client_pubkey);
+	kex_derive_keys(kex, hash, hashlen, shared_secret);
+	BN_clear_free(shared_secret);
+	kex_finish(kex);
+}
diff --git a/usr.bin/ssh/lib/Makefile b/usr.bin/ssh/lib/Makefile
index c4bc546cd21..81f069f1a9a 100644
--- a/usr.bin/ssh/lib/Makefile
+++ b/usr.bin/ssh/lib/Makefile
@@ -1,4 +1,4 @@
-#	$OpenBSD: Makefile,v 1.67 2013/01/17 23:00:01 djm Exp $
+#	$OpenBSD: Makefile,v 1.68 2013/11/02 21:59:15 markus Exp $
 
 .PATH:		${.CURDIR}/..
 .include "${.CURDIR}/../Makefile.inc"
@@ -13,7 +13,7 @@ SRCS=	authfd.c authfile.c bufaux.c bufec.c bufbn.c buffer.c canohost.c \
 	ssh-dss.c ssh-rsa.c ssh-ecdsa.c dh.c kexdh.c kexgex.c kexecdh.c \
 	kexdhc.c kexgexc.c kexecdhc.c msg.c progressmeter.c dns.c \
 	monitor_fdpass.c umac.c addrmatch.c schnorr.c jpake.c ssh-pkcs11.c \
-	krl.c
+	krl.c smult_curve25519_ref.c kexc25519.c kexc25519c.c
 
 SRCS+=	umac128.c
 CLEANFILES+=   umac128.c
diff --git a/usr.bin/ssh/myproposal.h b/usr.bin/ssh/myproposal.h
index 22a4f3998e7..9a0cc63d218 100644
--- a/usr.bin/ssh/myproposal.h
+++ b/usr.bin/ssh/myproposal.h
@@ -1,4 +1,4 @@
-/* $OpenBSD: myproposal.h,v 1.32 2013/01/08 18:49:04 markus Exp $ */
+/* $OpenBSD: myproposal.h,v 1.33 2013/11/02 21:59:15 markus Exp $ */
 
 /*
  * Copyright (c) 2000 Markus Friedl.  All rights reserved.
@@ -25,6 +25,7 @@
  */
 
 #define KEX_DEFAULT_KEX		\
+	"curve25519-sha256@libssh.org," \
 	"ecdh-sha2-nistp256," \
 	"ecdh-sha2-nistp384," \
 	"ecdh-sha2-nistp521," \
diff --git a/usr.bin/ssh/smult_curve25519_ref.c b/usr.bin/ssh/smult_curve25519_ref.c
new file mode 100644
index 00000000000..036d6e733d1
--- /dev/null
+++ b/usr.bin/ssh/smult_curve25519_ref.c
@@ -0,0 +1,264 @@
+/*
+version 20081011
+Matthew Dempsky
+Public domain.
+Derived from public domain code by D. J. Bernstein.
+*/
+
+int crypto_scalarmult_curve25519(unsigned char *, const unsigned char *, const unsigned char *);
+
+static void add(unsigned int out[32],const unsigned int a[32],const unsigned int b[32])
+{
+  unsigned int j;
+  unsigned int u;
+  u = 0;
+  for (j = 0;j < 31;++j) { u += a[j] + b[j]; out[j] = u & 255; u >>= 8; }
+  u += a[31] + b[31]; out[31] = u;
+}
+
+static void sub(unsigned int out[32],const unsigned int a[32],const unsigned int b[32])
+{
+  unsigned int j;
+  unsigned int u;
+  u = 218;
+  for (j = 0;j < 31;++j) {
+    u += a[j] + 65280 - b[j];
+    out[j] = u & 255;
+    u >>= 8;
+  }
+  u += a[31] - b[31];
+  out[31] = u;
+}
+
+static void squeeze(unsigned int a[32])
+{
+  unsigned int j;
+  unsigned int u;
+  u = 0;
+  for (j = 0;j < 31;++j) { u += a[j]; a[j] = u & 255; u >>= 8; }
+  u += a[31]; a[31] = u & 127;
+  u = 19 * (u >> 7);
+  for (j = 0;j < 31;++j) { u += a[j]; a[j] = u & 255; u >>= 8; }
+  u += a[31]; a[31] = u;
+}
+
+static const unsigned int minusp[32] = {
+ 19, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 128
+} ;
+
+static void freeze(unsigned int a[32])
+{
+  unsigned int aorig[32];
+  unsigned int j;
+  unsigned int negative;
+
+  for (j = 0;j < 32;++j) aorig[j] = a[j];
+  add(a,a,minusp);
+  negative = -((a[31] >> 7) & 1);
+  for (j = 0;j < 32;++j) a[j] ^= negative & (aorig[j] ^ a[j]);
+}
+
+static void mult(unsigned int out[32],const unsigned int a[32],const unsigned int b[32])
+{
+  unsigned int i;
+  unsigned int j;
+  unsigned int u;
+
+  for (i = 0;i < 32;++i) {
+    u = 0;
+    for (j = 0;j <= i;++j) u += a[j] * b[i - j];
+    for (j = i + 1;j < 32;++j) u += 38 * a[j] * b[i + 32 - j];
+    out[i] = u;
+  }
+  squeeze(out);
+}
+
+static void mult121665(unsigned int out[32],const unsigned int a[32])
+{
+  unsigned int j;
+  unsigned int u;
+
+  u = 0;
+  for (j = 0;j < 31;++j) { u += 121665 * a[j]; out[j] = u & 255; u >>= 8; }
+  u += 121665 * a[31]; out[31] = u & 127;
+  u = 19 * (u >> 7);
+  for (j = 0;j < 31;++j) { u += out[j]; out[j] = u & 255; u >>= 8; }
+  u += out[j]; out[j] = u;
+}
+
+static void square(unsigned int out[32],const unsigned int a[32])
+{
+  unsigned int i;
+  unsigned int j;
+  unsigned int u;
+
+  for (i = 0;i < 32;++i) {
+    u = 0;
+    for (j = 0;j < i - j;++j) u += a[j] * a[i - j];
+    for (j = i + 1;j < i + 32 - j;++j) u += 38 * a[j] * a[i + 32 - j];
+    u *= 2;
+    if ((i & 1) == 0) {
+      u += a[i / 2] * a[i / 2];
+      u += 38 * a[i / 2 + 16] * a[i / 2 + 16];
+    }
+    out[i] = u;
+  }
+  squeeze(out);
+}
+
+static void select(unsigned int p[64],unsigned int q[64],const unsigned int r[64],const unsigned int s[64],unsigned int b)
+{
+  unsigned int j;
+  unsigned int t;
+  unsigned int bminus1;
+
+  bminus1 = b - 1;
+  for (j = 0;j < 64;++j) {
+    t = bminus1 & (r[j] ^ s[j]);
+    p[j] = s[j] ^ t;
+    q[j] = r[j] ^ t;
+  }
+}
+
+static void mainloop(unsigned int work[64],const unsigned char e[32])
+{
+  unsigned int xzm1[64];
+  unsigned int xzm[64];
+  unsigned int xzmb[64];
+  unsigned int xzm1b[64];
+  unsigned int xznb[64];
+  unsigned int xzn1b[64];
+  unsigned int a0[64];
+  unsigned int a1[64];
+  unsigned int b0[64];
+  unsigned int b1[64];
+  unsigned int c1[64];
+  unsigned int r[32];
+  unsigned int s[32];
+  unsigned int t[32];
+  unsigned int u[32];
+  unsigned int j;
+  unsigned int b;
+  int pos;
+
+  for (j = 0;j < 32;++j) xzm1[j] = work[j];
+  xzm1[32] = 1;
+  for (j = 33;j < 64;++j) xzm1[j] = 0;
+
+  xzm[0] = 1;
+  for (j = 1;j < 64;++j) xzm[j] = 0;
+
+  for (pos = 254;pos >= 0;--pos) {
+    b = e[pos / 8] >> (pos & 7);
+    b &= 1;
+    select(xzmb,xzm1b,xzm,xzm1,b);
+    add(a0,xzmb,xzmb + 32);
+    sub(a0 + 32,xzmb,xzmb + 32);
+    add(a1,xzm1b,xzm1b + 32);
+    sub(a1 + 32,xzm1b,xzm1b + 32);
+    square(b0,a0);
+    square(b0 + 32,a0 + 32);
+    mult(b1,a1,a0 + 32);
+    mult(b1 + 32,a1 + 32,a0);
+    add(c1,b1,b1 + 32);
+    sub(c1 + 32,b1,b1 + 32);
+    square(r,c1 + 32);
+    sub(s,b0,b0 + 32);
+    mult121665(t,s);
+    add(u,t,b0);
+    mult(xznb,b0,b0 + 32);
+    mult(xznb + 32,s,u);
+    square(xzn1b,c1);
+    mult(xzn1b + 32,r,work);
+    select(xzm,xzm1,xznb,xzn1b,b);
+  }
+
+  for (j = 0;j < 64;++j) work[j] = xzm[j];
+}
+
+static void recip(unsigned int out[32],const unsigned int z[32])
+{
+  unsigned int z2[32];
+  unsigned int z9[32];
+  unsigned int z11[32];
+  unsigned int z2_5_0[32];
+  unsigned int z2_10_0[32];
+  unsigned int z2_20_0[32];
+  unsigned int z2_50_0[32];
+  unsigned int z2_100_0[32];
+  unsigned int t0[32];
+  unsigned int t1[32];
+  int i;
+
+  /* 2 */ square(z2,z);
+  /* 4 */ square(t1,z2);
+  /* 8 */ square(t0,t1);
+  /* 9 */ mult(z9,t0,z);
+  /* 11 */ mult(z11,z9,z2);
+  /* 22 */ square(t0,z11);
+  /* 2^5 - 2^0 = 31 */ mult(z2_5_0,t0,z9);
+
+  /* 2^6 - 2^1 */ square(t0,z2_5_0);
+  /* 2^7 - 2^2 */ square(t1,t0);
+  /* 2^8 - 2^3 */ square(t0,t1);
+  /* 2^9 - 2^4 */ square(t1,t0);
+  /* 2^10 - 2^5 */ square(t0,t1);
+  /* 2^10 - 2^0 */ mult(z2_10_0,t0,z2_5_0);
+
+  /* 2^11 - 2^1 */ square(t0,z2_10_0);
+  /* 2^12 - 2^2 */ square(t1,t0);
+  /* 2^20 - 2^10 */ for (i = 2;i < 10;i += 2) { square(t0,t1); square(t1,t0); }
+  /* 2^20 - 2^0 */ mult(z2_20_0,t1,z2_10_0);
+
+  /* 2^21 - 2^1 */ square(t0,z2_20_0);
+  /* 2^22 - 2^2 */ square(t1,t0);
+  /* 2^40 - 2^20 */ for (i = 2;i < 20;i += 2) { square(t0,t1); square(t1,t0); }
+  /* 2^40 - 2^0 */ mult(t0,t1,z2_20_0);
+
+  /* 2^41 - 2^1 */ square(t1,t0);
+  /* 2^42 - 2^2 */ square(t0,t1);
+  /* 2^50 - 2^10 */ for (i = 2;i < 10;i += 2) { square(t1,t0); square(t0,t1); }
+  /* 2^50 - 2^0 */ mult(z2_50_0,t0,z2_10_0);
+
+  /* 2^51 - 2^1 */ square(t0,z2_50_0);
+  /* 2^52 - 2^2 */ square(t1,t0);
+  /* 2^100 - 2^50 */ for (i = 2;i < 50;i += 2) { square(t0,t1); square(t1,t0); }
+  /* 2^100 - 2^0 */ mult(z2_100_0,t1,z2_50_0);
+
+  /* 2^101 - 2^1 */ square(t1,z2_100_0);
+  /* 2^102 - 2^2 */ square(t0,t1);
+  /* 2^200 - 2^100 */ for (i = 2;i < 100;i += 2) { square(t1,t0); square(t0,t1); }
+  /* 2^200 - 2^0 */ mult(t1,t0,z2_100_0);
+
+  /* 2^201 - 2^1 */ square(t0,t1);
+  /* 2^202 - 2^2 */ square(t1,t0);
+  /* 2^250 - 2^50 */ for (i = 2;i < 50;i += 2) { square(t0,t1); square(t1,t0); }
+  /* 2^250 - 2^0 */ mult(t0,t1,z2_50_0);
+
+  /* 2^251 - 2^1 */ square(t1,t0);
+  /* 2^252 - 2^2 */ square(t0,t1);
+  /* 2^253 - 2^3 */ square(t1,t0);
+  /* 2^254 - 2^4 */ square(t0,t1);
+  /* 2^255 - 2^5 */ square(t1,t0);
+  /* 2^255 - 21 */ mult(out,t1,z11);
+}
+
+int crypto_scalarmult_curve25519(unsigned char *q,
+  const unsigned char *n,
+  const unsigned char *p)
+{
+  unsigned int work[96];
+  unsigned char e[32];
+  unsigned int i;
+  for (i = 0;i < 32;++i) e[i] = n[i];
+  e[0] &= 248;
+  e[31] &= 127;
+  e[31] |= 64;
+  for (i = 0;i < 32;++i) work[i] = p[i];
+  mainloop(work,e);
+  recip(work + 32,work + 32);
+  mult(work + 64,work,work + 32);
+  freeze(work + 64);
+  for (i = 0;i < 32;++i) q[i] = work[64 + i];
+  return 0;
+}
diff --git a/usr.bin/ssh/ssh-keyscan.c b/usr.bin/ssh/ssh-keyscan.c
index 660e4e06efa..137674cf69b 100644
--- a/usr.bin/ssh/ssh-keyscan.c
+++ b/usr.bin/ssh/ssh-keyscan.c
@@ -1,4 +1,4 @@
-/* $OpenBSD: ssh-keyscan.c,v 1.87 2013/05/17 00:13:14 djm Exp $ */
+/* $OpenBSD: ssh-keyscan.c,v 1.88 2013/11/02 21:59:15 markus Exp $ */
 /*
  * Copyright 1995, 1996 by David Mazieres <dm@lcs.mit.edu>.
  *
@@ -239,6 +239,7 @@ keygrab_ssh2(con *c)
 	c->c_kex->kex[KEX_DH_GEX_SHA1] = kexgex_client;
 	c->c_kex->kex[KEX_DH_GEX_SHA256] = kexgex_client;
 	c->c_kex->kex[KEX_ECDH_SHA2] = kexecdh_client;
+	c->c_kex->kex[KEX_C25519_SHA256] = kexc25519_client;
 	c->c_kex->verify_host_key = hostjump;
 
 	if (!(j = setjmp(kexjmp))) {
diff --git a/usr.bin/ssh/sshconnect2.c b/usr.bin/ssh/sshconnect2.c
index a5e621ea81b..1572fe457f6 100644
--- a/usr.bin/ssh/sshconnect2.c
+++ b/usr.bin/ssh/sshconnect2.c
@@ -1,4 +1,4 @@
-/* $OpenBSD: sshconnect2.c,v 1.198 2013/06/05 12:52:38 dtucker Exp $ */
+/* $OpenBSD: sshconnect2.c,v 1.199 2013/11/02 21:59:15 markus Exp $ */
 /*
  * Copyright (c) 2000 Markus Friedl.  All rights reserved.
  * Copyright (c) 2008 Damien Miller.  All rights reserved.
@@ -202,6 +202,7 @@ ssh_kex2(char *host, struct sockaddr *hostaddr, u_short port)
 	kex->kex[KEX_DH_GEX_SHA1] = kexgex_client;
 	kex->kex[KEX_DH_GEX_SHA256] = kexgex_client;
 	kex->kex[KEX_ECDH_SHA2] = kexecdh_client;
+	kex->kex[KEX_C25519_SHA256] = kexc25519_client;
 	kex->client_version_string=client_version_string;
 	kex->server_version_string=server_version_string;
 	kex->verify_host_key=&verify_host_key_callback;
diff --git a/usr.bin/ssh/sshd.c b/usr.bin/ssh/sshd.c
index 006a90a529e..09ba9d8c6d6 100644
--- a/usr.bin/ssh/sshd.c
+++ b/usr.bin/ssh/sshd.c
@@ -1,4 +1,4 @@
-/* $OpenBSD: sshd.c,v 1.409 2013/10/23 23:35:32 djm Exp $ */
+/* $OpenBSD: sshd.c,v 1.410 2013/11/02 21:59:15 markus Exp $ */
 /*
  * Author: Tatu Ylonen <ylo@cs.hut.fi>
  * Copyright (c) 1995 Tatu Ylonen <ylo@cs.hut.fi>, Espoo, Finland
@@ -2305,6 +2305,7 @@ do_ssh2_kex(void)
 	kex->kex[KEX_DH_GEX_SHA1] = kexgex_server;
 	kex->kex[KEX_DH_GEX_SHA256] = kexgex_server;
 	kex->kex[KEX_ECDH_SHA2] = kexecdh_server;
+	kex->kex[KEX_C25519_SHA256] = kexc25519_server;
 	kex->server = 1;
 	kex->client_version_string=client_version_string;
 	kex->server_version_string=server_version_string;
diff --git a/usr.bin/ssh/sshd/Makefile b/usr.bin/ssh/sshd/Makefile
index d59607c9417..c9f0b8e853c 100644
--- a/usr.bin/ssh/sshd/Makefile
+++ b/usr.bin/ssh/sshd/Makefile
@@ -1,4 +1,4 @@
-#	$OpenBSD: Makefile,v 1.79 2013/08/10 10:19:35 ajacoutot Exp $
+#	$OpenBSD: Makefile,v 1.80 2013/11/02 21:59:15 markus Exp $
 
 .PATH:		${.CURDIR}/..
 
@@ -16,7 +16,8 @@ SRCS=	sshd.c auth-rhosts.c auth-passwd.c auth-rsa.c auth-rh-rsa.c \
 	auth2-none.c auth2-passwd.c auth2-pubkey.c \
 	monitor_mm.c monitor.c monitor_wrap.c \
 	kexdhs.c kexgexs.c kexecdhs.c sftp-server.c sftp-common.c \
-	roaming_common.c roaming_serv.c sandbox-systrace.c
+	roaming_common.c roaming_serv.c sandbox-systrace.c \
+	kexc25519s.c
 
 .include <bsd.own.mk> # for KERBEROS and AFS