9 files changed, 299 insertions, 8 deletions

diff --git a/ChangeLog b/ChangeLog
index 75a300584..4c4d8eeb1 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -4,6 +4,10 @@
      [ssh-pkcs11.c]
      support pkcs#11 tokes that only provide x509 zerts instead of raw pubkeys;
      fixes bz#1908; based on patch from Laurent Barbe; ok djm
+   - markus@cvs.openbsd.org 2013/11/02 21:59:15
+     [kex.c kex.h myproposal.h ssh-keyscan.c sshconnect2.c sshd.c]
+     use curve25519 for default key exchange (curve25519-sha256@libssh.org);
+     initial patch from Aris Adamantiadis; ok djm@
 
 20131103
  - (dtucker) [openbsd-compat/bsd-misc.c] Include time.h for nanosleep.
diff --git a/Makefile.in b/Makefile.in
index 92c95a928..797aa3e0c 100644
--- a/Makefile.in
+++ b/Makefile.in
@@ -1,4 +1,4 @@
-# $Id: Makefile.in,v 1.340 2013/06/11 01:26:10 dtucker Exp $
+# $Id: Makefile.in,v 1.341 2013/11/03 21:26:53 djm Exp $
 
 # uncomment if you run a non bourne compatable shell. Ie. csh
 #SHELL = @SH@
@@ -73,7 +73,7 @@ LIBSSH_OBJS=authfd.o authfile.o bufaux.o bufbn.o buffer.o \
         monitor_fdpass.o rijndael.o ssh-dss.o ssh-ecdsa.o ssh-rsa.o dh.o \
         kexdh.o kexgex.o kexdhc.o kexgexc.o bufec.o kexecdh.o kexecdhc.o \
         msg.o progressmeter.o dns.o entropy.o gss-genr.o umac.o umac128.o \
-        jpake.o schnorr.o ssh-pkcs11.o krl.o
+        jpake.o schnorr.o ssh-pkcs11.o krl.o smult_curve25519_ref.o
 
 SSHOBJS= ssh.o readconf.o clientloop.o sshtty.o \
         sshconnect.o sshconnect1.o sshconnect2.o mux.o \
diff --git a/kex.c b/kex.c
index 54bd1a438..07f25e2e2 100644
--- a/kex.c
+++ b/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.
  *
@@ -80,6 +80,7 @@ static const struct kexalg kexalgs[] = {
         { KEX_ECDH_SHA2_NISTP384, KEX_ECDH_SHA2, NID_secp384r1, EVP_sha384 },
         { KEX_ECDH_SHA2_NISTP521, KEX_ECDH_SHA2, NID_secp521r1, EVP_sha512 },
 #endif
+        { KEX_CURVE25519_SHA256, KEX_C25519_SHA256, 0, EVP_sha256 },
         { NULL, -1, -1, NULL},
 };
 
diff --git a/kex.h b/kex.h
index 9f1e1adb3..0f67f5934 100644
--- a/kex.h
+++ b/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.
@@ -43,6 +43,7 @@
 #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
@@ -74,6 +75,7 @@ enum kex_exchange {
         KEX_DH_GEX_SHA1,
         KEX_DH_GEX_SHA256,
         KEX_ECDH_SHA2,
+        KEX_C25519_SHA256,
         KEX_MAX
 };
 
@@ -161,6 +163,8 @@ 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,
@@ -175,6 +179,19 @@ 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 *);
 #endif
+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/myproposal.h b/myproposal.h
index 4e913e3ce..0820749a8 100644
--- a/myproposal.h
+++ b/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.
@@ -66,6 +66,7 @@
 #endif
 
 # define KEX_DEFAULT_KEX \
+        "curve25519-sha256@libssh.org," \
         KEX_ECDH_METHODS \
         KEX_SHA256_METHODS \
         "diffie-hellman-group-exchange-sha1," \
diff --git a/smult_curve25519_ref.c b/smult_curve25519_ref.c
new file mode 100644
index 000000000..2e69934d4
--- /dev/null
+++ b/smult_curve25519_ref.c
@@ -0,0 +1,265 @@
+/* $OpenBSD: smult_curve25519_ref.c,v 1.2 2013/11/02 22:02:14 markus Exp $ */
+/*
+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/ssh-keyscan.c b/ssh-keyscan.c
index 8b807c10a..c5f658d77 100644
--- a/ssh-keyscan.c
+++ b/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>.
  *
@@ -254,6 +254,7 @@ 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/sshconnect2.c b/sshconnect2.c
index 70e3cd8c9..1f6160e86 100644
--- a/sshconnect2.c
+++ b/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.
@@ -208,6 +208,7 @@ 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/sshd.c b/sshd.c
index d4349f618..8a62fc1a6 100644
--- a/sshd.c
+++ b/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
@@ -2451,6 +2451,7 @@ 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;