Audit curve fixes part2 (#298)

* refactor and fix mulgen (curve25519)

* crypto tests fixing

* fix some confusion in curve25519 mul

* removing ForbiddenCurveValues table and checks

* fix remaining merge issues

libp2p/crypto/curve25519.nim

@@ -37,22 +37,6 @@ proc intoCurve25519Key*(s: openarray[byte]): Curve25519Key =
 
 proc getBytes*(key: Curve25519Key): seq[byte] = @key
 
-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],
-        ]
-
 proc byteswap(buf: var Curve25519Key) {.inline.} =
   for i in 0..<16:
     let
@@ -60,27 +44,23 @@ proc byteswap(buf: var Curve25519Key) {.inline.} =
     buf[i] = buf[31 - i]
     buf[31 - i] = x
 
-proc mul*(_: type[Curve25519], dst: var Curve25519Key, scalar: Curve25519Key, point: Curve25519Key) =
+proc mul*(_: type[Curve25519], point: var Curve25519Key, multiplier: Curve25519Key) =
   let defaultBrEc = brEcGetDefault()
 
-  # The source point is provided in array G (of size Glen bytes);
+  # multiplier needs to be big-endian
-  # the multiplication result is written over it.
-  dst = scalar
-
-  # point needs to be big-endian
   var
-    rpoint = point
+    multiplierBs = multiplier
-  rpoint.byteswap()
+  multiplierBs.byteswap()
   let
     res = defaultBrEc.mul(
-      cast[pcuchar](addr dst[0]),
+      cast[pcuchar](addr point[0]),
       Curve25519KeySize,
-      cast[pcuchar](addr rpoint[0]),
+      cast[pcuchar](addr multiplierBs[0]),
       Curve25519KeySize,
       EC_curve25519)
   assert res == 1
 
-proc mulgen(_: type[Curve25519], dst: var Curve25519Key, point: Curve25519Key): bool =
+proc mulgen(_: type[Curve25519], dst: var Curve25519Key, point: Curve25519Key) =
   let defaultBrEc = brEcGetDefault()
 
   var
@@ -96,17 +76,8 @@ proc mulgen(_: type[Curve25519], dst: var Curve25519Key, point: Curve25519Key):
   
   assert size == Curve25519KeySize
 
-  if dst in ForbiddenCurveValues:
+proc public*(private: Curve25519Key): Curve25519Key =
-    false
+  Curve25519.mulgen(result, private)
-  else:
-    true
-
-proc public*(private: Curve25519Key): Result[Curve25519Key, cstring] =
-  var res: Curve25519Key
-  if Curve25519.mulgen(res, private):
-    ok(res)
-  else:
-    err("mulgen produced a forbidden key")
 
 proc random*(_: type[Curve25519Key], rng: var BrHmacDrbgContext): Curve25519Key =
   var res: Curve25519Key

libp2p/protocols/secure/noise.nim

@@ -90,7 +90,7 @@ type
 
 proc genKeyPair(rng: var BrHmacDrbgContext): KeyPair =
   result.privateKey = Curve25519Key.random(rng)
-  result.publicKey = result.privateKey.public().tryGet()
+  result.publicKey = result.privateKey.public()
 
 proc hashProtocol(name: string): MDigest[256] =
   # If protocol_name is less than or equal to HASHLEN bytes in length,
@@ -103,7 +103,8 @@ proc hashProtocol(name: string): MDigest[256] =
     result = sha256.digest(name)
 
 proc dh(priv: Curve25519Key, pub: Curve25519Key): Curve25519Key =
-  Curve25519.mul(result, pub, priv)
+  result = pub
+  Curve25519.mul(result, priv)
 
 # Cipherstate
 

tests/testcrypto.nim

@@ -485,42 +485,40 @@ suite "Key interface test suite":
   test "Curve25519":
     # from bearssl test_crypto.c
     var
-      res: Curve25519Key
+      bearOp = fromHex("A546E36BF0527C9D3B16154B82465EDD62144C0AC1FC5A18506A2244BA449AC4").intoCurve25519Key()
-      bearOp = fromHex("A546E36BF0527C9D3B16154B82465EDD62144C0AC1FC5A18506A2244BA449AC4")
+      bearIn = fromHex("E6DB6867583030DB3594C1A424B15F7C726624EC26B3353B10A903A6D0AB1C4C").intoCurve25519Key()
-      bearIn = fromHex("E6DB6867583030DB3594C1A424B15F7C726624EC26B3353B10A903A6D0AB1C4C")
+      bearOut = fromHex("C3DA55379DE9C6908E94EA4DF28D084F32ECCF03491C71F754B4075577A28552").intoCurve25519Key()
-      bearOut = fromHex("C3DA55379DE9C6908E94EA4DF28D084F32ECCF03491C71F754B4075577A28552")
 
-    Curve25519.mul(res, bearIn.intoCurve25519Key, bearOp.intoCurve25519Key)
+    Curve25519.mul(bearIn, bearOp)
-    check res == bearOut
+    check bearIn == bearOut
 
     # from https://github.com/golang/crypto/blob/1d94cc7ab1c630336ab82ccb9c9cda72a875c382/curve25519/vectors_test.go#L26
     var
       private1: Curve25519Key = [0x66.byte, 0x8f, 0xb9, 0xf7, 0x6a, 0xd9, 0x71, 0xc8, 0x1a, 0xc9, 0x0, 0x7, 0x1a, 0x15, 0x60, 0xbc, 0xe2, 0xca, 0x0, 0xca, 0xc7, 0xe6, 0x7a, 0xf9, 0x93, 0x48, 0x91, 0x37, 0x61, 0x43, 0x40, 0x14]
       base: Curve25519Key = [0xdb.byte, 0x5f, 0x32, 0xb7, 0xf8, 0x41, 0xe7, 0xa1, 0xa0, 0x9, 0x68, 0xef, 0xfd, 0xed, 0x12, 0x73, 0x5f, 0xc4, 0x7a, 0x3e, 0xb1, 0x3b, 0x57, 0x9a, 0xac, 0xad, 0xea, 0xe8, 0x9, 0x39, 0xa7, 0xdd]
-      public1: Curve25519Key
       public1Test: Curve25519Key = [0x9.byte, 0xd, 0x85, 0xe5, 0x99, 0xea, 0x8e, 0x2b, 0xee, 0xb6, 0x13, 0x4, 0xd3, 0x7b, 0xe1, 0xe, 0xc5, 0xc9, 0x5, 0xf9, 0x92, 0x7d, 0x32, 0xf4, 0x2a, 0x9a, 0xa, 0xfb, 0x3e, 0xb, 0x40, 0x74]
 
-    Curve25519.mul(public1, base, private1)
+    Curve25519.mul(base, private1)
-    check public1.toHex == public1Test.toHex
+    check base.toHex == public1Test.toHex
 
     # RFC vectors
     private1 = fromHex("a8abababababababababababababababababababababababababababababab6b").intoCurve25519Key
-    check private1.public().get().toHex  == "E3712D851A0E5D79B831C5E34AB22B41A198171DE209B8B8FACA23A11C624859"
+    check private1.public().toHex  == "E3712D851A0E5D79B831C5E34AB22B41A198171DE209B8B8FACA23A11C624859"
     private1 = fromHex("c8cdcdcdcdcdcdcdcdcdcdcdcdcdcdcdcdcdcdcdcdcdcdcdcdcdcdcdcdcdcd4d").intoCurve25519Key
-    check private1.public().get().toHex  == "B5BEA823D9C9FF576091C54B7C596C0AE296884F0E150290E88455D7FBA6126F"
+    check private1.public().toHex  == "B5BEA823D9C9FF576091C54B7C596C0AE296884F0E150290E88455D7FBA6126F"
     private1 = fromHex("77076d0a7318a57d3c16c17251b26645df4c2f87ebc0992ab177fba51db92c2a").intoCurve25519Key
     var
       private2 = fromHex("5dab087e624a8a4b79e17f8b83800ee66f3bb1292618b6fd1c2f8b27ff88e0eb").intoCurve25519Key
-      p1Pub = private1.public().get()
+      p1Pub = private1.public()
-      p2Pub = private2.public().get()
+      p2Pub = private2.public()
     check p1Pub.toHex  == "8520F0098930A754748B7DDCB43EF75A0DBF3A0D26381AF4EBA4A98EAA9B4E6A"
     check p2Pub.toHex  == "DE9EDB7D7B7DC1B4D35B61C2ECE435373F8343C85B78674DADFC7E146F882B4F"
 
     var
-      secret1: Curve25519Key
+      secret1 = p2Pub
-      secret2: Curve25519Key
+      secret2 = p1Pub
-    Curve25519.mul(secret1, p2Pub, private1)
+    Curve25519.mul(secret1, private1)
-    Curve25519.mul(secret2, p1Pub, private2)
+    Curve25519.mul(secret2, private2)
     check secret1.toHex == secret2.toHex