From 8dec3688781b2e15ffaad05ce23aba7d0c378230 Mon Sep 17 00:00:00 2001
From: Giovanni Petrantoni <giovanni@fragcolor.xyz>
Date: Fri, 14 Feb 2020 11:56:05 +0900
Subject: [PATCH] Add Curve25519 (BearSSL) required operations for noise

---
 libp2p/crypto/chacha20poly1305.nim |  2 +-
 libp2p/crypto/curve25519.nim       | 82 ++++++++++++++++++++++++++++++
 2 files changed, 83 insertions(+), 1 deletion(-)
 create mode 100644 libp2p/crypto/curve25519.nim

diff --git a/libp2p/crypto/chacha20poly1305.nim b/libp2p/crypto/chacha20poly1305.nim
index fc09a2b..bdc9a84 100644
--- a/libp2p/crypto/chacha20poly1305.nim
+++ b/libp2p/crypto/chacha20poly1305.nim
@@ -23,7 +23,7 @@ const
   ChaChaPolyTagSize = 16
   
 type
-  ChaChaPoly = object
+  ChaChaPoly* = object
   ChaChaPolyKey* = array[ChaChaPolyKeySize, byte]
   ChaChaPolyNonce* = array[ChaChaPolyNonceSize, byte]
   ChaChaPolyTag* = array[ChaChaPolyTagSize, byte]
diff --git a/libp2p/crypto/curve25519.nim b/libp2p/crypto/curve25519.nim
new file mode 100644
index 0000000..a9a18c2
--- /dev/null
+++ b/libp2p/crypto/curve25519.nim
@@ -0,0 +1,82 @@
+## Nim-Libp2p
+## Copyright (c) 2020 Status Research & Development GmbH
+## Licensed under either of
+##  * Apache License, version 2.0, ([LICENSE-APACHE](LICENSE-APACHE))
+##  * MIT license ([LICENSE-MIT](LICENSE-MIT))
+## at your option.
+## This file may not be copied, modified, or distributed except according to
+## those terms.
+
+## This module integrates BearSSL ChaCha20+Poly1305
+##
+## This module uses unmodified parts of code from
+## BearSSL library <https://bearssl.org/>
+## Copyright(C) 2018 Thomas Pornin <pornin@bolet.org>.
+
+# RFC @ https://tools.ietf.org/html/rfc7748
+
+import bearssl
+
+const
+  Curve25519KeySize = 32
+  
+type
+  Curve25519* = object
+  Curve25519Key* = array[Curve25519KeySize, byte]
+  pcuchar = ptr cuchar
+
+
+const
+  ForbiddenCurveValues: array[12, Curve25519Key] = [
+                [0.byte, 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, 0],
+                [1.byte, 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, 0],
+                [224.byte, 235, 122, 124, 59, 65, 184, 174, 22, 86, 227, 250, 241, 159, 196, 106, 218, 9, 141, 235, 156, 50, 177, 253, 134, 98, 5, 22, 95, 73, 184, 0],
+                [95.byte, 156, 149, 188, 163, 80, 140, 36, 177, 208, 177, 85, 156, 131, 239, 91, 4, 68, 92, 196, 88, 28, 142, 134, 216, 34, 78, 221, 208, 159, 17, 87],
+                [236.byte, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 127],
+                [237.byte, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 127],
+                [238.byte, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 127],
+                [205.byte, 235, 122, 124, 59, 65, 184, 174, 22, 86, 227, 250, 241, 159, 196, 106, 218, 9, 141, 235, 156, 50, 177, 253, 134, 98, 5, 22, 95, 73, 184, 128],
+                [76.byte, 156, 149, 188, 163, 80, 140, 36, 177, 208, 177, 85, 156, 131, 239, 91, 4, 68, 92, 196, 88, 28, 142, 134, 216, 34, 78, 221, 208, 159, 17, 215],
+                [217.byte, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255],
+                [218.byte, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255],
+                [219.byte, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 25],
+        ]
+
+let defaultBrEc = brEcGetDefault()
+    
+proc mul*(_: type[Curve25519], dst: var Curve25519Key, scalar: Curve25519Key, point: Curve25519Key) =
+  # The source point is provided in array G (of size Glen bytes);
+  # the multiplication result is written over it. 
+  dst = scalar
+  let
+    res = defaultBrEc.mul(
+      cast[pcuchar](addr dst[0]),
+      Curve25519KeySize,
+      cast[pcuchar](unsafeAddr point[0]),
+      Curve25519KeySize,
+      EC_curve25519.cint)
+  assert res == 1
+
+proc mulgen*(_: type[Curve25519], dst: var Curve25519Key, scalar: Curve25519Key) =
+  while true:
+    let
+      size = defaultBrEc.mulgen(
+        cast[pcuchar](addr dst[0]),
+        cast[pcuchar](unsafeAddr scalar[0]),
+        Curve25519KeySize,
+        EC_curve25519.cint)
+    assert size == Curve25519KeySize
+    for forbid in ForbiddenCurveValues:
+      if dst == forbid:
+        continue
+    break
+
+when isMainModule:
+  var
+    key: Curve25519Key
+    dst: Curve25519Key
+    dst2: Curve25519Key
+  Curve25519.mulgen(dst, key)
+  echo dst
+  Curve25519.mul(dst2, dst, key)
+  echo dst2