Get rid of ecdhRaw and export ecdh with custom hash func

.gitignore

@@ -7,3 +7,5 @@ nimble.paths
 ci/build_nim.sh
 ci/NimBinaries/
 ci/nim/
+
+*.exe

secp256k1.nim

@@ -72,9 +72,6 @@ const
   SkEdchSecretSize* = 32
     ## ECDH-agreed key size
 
-  SkEcdhRawSecretSize* = 33
-    ## ECDH-agreed raw key size
-
 type
   SkPublicKey* {.requiresInit.} = object
     ## Representation of public key.
@@ -116,10 +113,7 @@ type
     ## Representation of ECDH shared secret
     data*: array[SkEdchSecretSize, byte]
 
-  SkEcdhRawSecret* {.requiresInit.} = object
+  SkEcdhHashFunc* = secp256k1_ecdh_hash_function
-    ## Representation of ECDH shared secret, with leading `y` byte
-    # (`y` is 0x02 when pubkey.y is even or 0x03 when odd)
-    data*: array[SkEcdhRawSecretSize, byte]
 
   SkResult*[T] = Result[T, cstring]
 
@@ -607,26 +601,26 @@ func recover*(sig: SkRecoverableSignature, msg: SkMessage): SkResult[SkPublicKey
 
   ok(SkPublicKey(data: data))
 
-func ecdh*(seckey: SkSecretKey, pubkey: SkPublicKey): SkEcdhSecret =
+func ecdh*(seckey: SkSecretKey, pubkey: SkPublicKey): SkResult[SkEcdhSecret] =
   ## Calculate ECDH shared secret.
   var secret {.noinit.}: array[SkEdchSecretSize, byte]
-  let res = secp256k1_ecdh(
+  if secp256k1_ecdh(
       secp256k1_context_no_precomp, secret.baseAddr, unsafeAddr pubkey.data,
-      seckey.data.baseAddr)
+      seckey.data.baseAddr) != 1:
-  doAssert res == 1, "cannot compute ECDH secret, keys invalid?"
+    return err("cannot compute ECDH secret, keys invalid?")
 
-  SkEcdhSecret(data: secret)
+  ok(SkEcdhSecret(data: secret))
 
-func ecdhRaw*(seckey: SkSecretKey, pubkey: SkPublicKey): SkEcdhRawSecret =
+func ecdh*[N: static[int]](seckey: SkSecretKey, pubkey: SkPublicKey,
-  ## Calculate ECDH shared secret, ethereum style
+           hashfn: SkEcdhHashFunc, data: pointer): SkResult[array[N, byte]] =
-  # TODO - deprecate: https://github.com/status-im/nim-eth/issues/222
+  ## Calculate ECDH shared secret using custom hash function.
-  var secret {.noinit.}: array[SkEcdhRawSecretSize, byte]
+  var secret {.noinit.}: array[N, byte]
-  let res = secp256k1_ecdh_raw(
+  if secp256k1_ecdh(
       secp256k1_context_no_precomp, secret.baseAddr, unsafeAddr pubkey.data,
-    seckey.data.baseAddr)
+      seckey.data.baseAddr, hashfn, data) != 1:
-  doAssert res == 1, "cannot compute raw ECDH secret, keys invalid?"
+    return err("cannot compute ECDH secret, keys invalid?")
 
-  SkEcdhRawSecret(data: secret)
+  ok(secret)
 
 func clear*(v: var SkSecretKey) =
   ## Wipe and clear memory of Secp256k1 `private key`.
@@ -640,12 +634,6 @@ func clear*(v: var SkEcdhSecret) =
   ## result in undefined behaviour or Defect
   burnMem(v.data)
 
-func clear*(v: var SkEcdhRawSecret) =
-  ## Wipe and clear memory of ECDH `shared secret`.
-  ## After calling this function, the key is invalid and using it elsewhere will
-  ## result in undefined behaviour or Defect
-  burnMem(v.data)
-
 func `$`*(
     v: SkPublicKey | SkSecretKey | SkXOnlyPublicKey | SkSignature | SkRecoverableSignature | SkSchnorrSignature): string =
   toHex(v)
@@ -665,7 +653,6 @@ proc default*(T: type SkSignature): T {.error: "loophole".}
 proc default*(T: type SkRecoverableSignature): T {.error: "loophole".}
 proc default*(T: type SkSchnorrSignature): T {.error: "loophole".}
 proc default*(T: type SkEcdhSecret): T {.error: "loophole".}
-proc default*(T: type SkEcdhRawSecret): T {.error: "loophole".}
 
 func tweakAdd*(secretKey: var SkSecretKey, tweak: openArray[byte]): SkResult[void] =
   let res = secp256k1_ec_privkey_tweak_add(

secp256k1/abi.nim

@@ -35,7 +35,7 @@ type
 
   secp256k1_ecdh_hash_function* = proc (output: ptr byte,
                                         x32, y32: ptr byte,
-                                        data: pointer) {.cdecl, raises: [].}
+                                        data: pointer): cint {.cdecl, raises: [].}
 
   secp256k1_context* = object
   secp256k1_scratch_space* = object
@@ -312,23 +312,6 @@ template secp256k1_ecdh*(ctx: ptr secp256k1_context; output32: ptr byte;
   secp256k1_ecdh(ctx, output32, pubkey, privkey,
     secp256k1_ecdh_hash_function_default(), nil)
 
-proc secp256k1_ecdh_raw*(ctx: ptr secp256k1_context; output32: ptr byte;
-                         pubkey: ptr secp256k1_pubkey;
-                         input32: ptr byte): cint {.secp.}
-  ## Compute an EC Diffie-Hellman secret in constant time
-  ## Returns: 1: exponentiation was successful
-  ##         0: scalar was invalid (zero or overflow)
-  ## Args:    ctx:        pointer to a context object (cannot be NULL)
-  ## Out:     result:     a 33-byte array which will be populated by an ECDH
-  ##                      secret computed from the point and scalar in form
-  ##                      of compressed point
-  ## In:      pubkey:     a pointer to a secp256k1_pubkey containing an
-  ##                      initialized public key
-  ##          privkey:    a 32-byte scalar with which to multiply the point
-  ##
-
-## Multikey interface follows
-
 type
   secp256k1_xonly_pubkey* = object
     ## Opaque data structure that holds a parsed and valid "x-only" public key.

tests/test_secp256k1.nim

@@ -1,4 +1,7 @@
-import ../secp256k1, unittest
+import
+  ../secp256k1,
+  unittest,
+  stew/ptrops
 
 {.used.}
 
@@ -15,13 +18,13 @@ const
     1'u8, 0, 0, 0, 0, 0, 0, 0,
     1'u8, 0, 0, 0, 0, 0, 0, 0,
   ])
-  msg2 = array[40, byte]([
+  msg2: array[40, byte] = [
     0'u8, 0, 0, 0, 0, 0, 0, 0,
     0'u8, 0, 0, 0, 0, 0, 0, 0,
     0'u8, 0, 0, 0, 0, 0, 0, 0,
     0'u8, 0, 0, 0, 0, 0, 0, 0,
     0'u8, 0, 0, 0, 0, 0, 0, 0,
-  ])
+  ]
 
 proc workingRng(data: var openArray[byte]): bool =
   data[0] += 1
@@ -72,3 +75,34 @@ suite "secp256k1":
       SkMessage.fromBytes([]).isErr()
       SkMessage.fromBytes([0'u8]).isErr()
       SkMessage.fromBytes(array[32, byte](msg0)).isOk()
+
+  test "Custom hash function":
+    proc customHash(output: ptr byte, x32, y32: ptr byte, data: pointer): cint
+                    {.cdecl, raises: [].} =
+      # Save x and y as uncompressed public key
+      output[] = 0x04
+      copyMem(output.offset(1), x32, 32)
+      copyMem(output.offset(33), y32, 32)
+      return 1
+
+    proc skone(_: type SkSecretKey): SkSecretKey =
+      # silence noisy warning: Cannot prove that 'result' is initialized.
+      result = SkSecretKey.random(workingRng)[]
+      var data: array[SkRawSecretKeySize, byte]
+      zeroMem(data[0].addr, data.len)
+      data[31] = 1
+      copyMem(result.addr, data[0].addr, data.len)
+
+    let
+      sone = SkSecretKey.skone()
+      sb32 = SkSecretKey.random(workingRng)[]
+      pk0  = sone.toPublicKey
+      pk1  = sb32.toPublicKey
+
+    var
+      # compute using ECDH function with custom hash function
+      outputEcdh = ecdh[65](sb32, pk0, customHash, nil).get
+      # compute "explicitly"
+      pointSer = pk1.toRaw
+
+    check equalMem(outputEcdh.addr, pointSer.addr, 65)