Add support for Curve25519 using the public domain code that is found

in OpenSSH.  The "private use" DH group 1034 is based on the value
that was picked by strongswan recently.

OK mikeb@ markus@

1 files changed, 265 insertions, 0 deletions

diff --git a/sbin/iked/smult_curve25519_ref.c b/sbin/iked/smult_curve25519_ref.c
new file mode 100644
index 00000000000..71c106a2c8d
--- /dev/null
+++ b/sbin/iked/smult_curve25519_ref.c
@@ -0,0 +1,265 @@
+/* $OpenBSD: smult_curve25519_ref.c,v 1.1 2014/08/27 10:28:57 reyk 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;
+}