Secret inside TLVPayload is PaymentSecret

Secret field inside TLVPayload's PaymentData is PaymentSecret
and not PaymentPreimage and It's used for mpp.

Author: aarani

src/DotNetLightning.Core/Serialization/TLVs.fs

@@ -167,7 +167,7 @@ type HopPayloadTLV =
     | AmountToForward of LNMoney
     | OutgoingCLTV of uint32
     | ShortChannelId of ShortChannelId
-    | PaymentData of paymentSecret: PaymentPreimage * totalMsat: LNMoney
+    | PaymentData of paymentSecret: PaymentSecret * totalMsat: LNMoney
     | Unknown of GenericTLV
     with
     static member FromGenericTLV(tlv: GenericTLV) =
@@ -183,8 +183,8 @@ type HopPayloadTLV =
             ShortChannelId.From8Bytes tlv.Value
             |> ShortChannelId
         | 8UL ->
-            let secret = tlv.Value.[0..PaymentPreimage.LENGTH - 1] |> PaymentPreimage.Create
-            let totalMSat = UInt64.FromTruncatedBytes tlv.Value.[PaymentPreimage.LENGTH..] |> LNMoney.MilliSatoshis
+            let secret = tlv.Value.[0..PaymentSecret.LENGTH - 1] |> PaymentSecret.FromByteArray
+            let totalMSat = UInt64.FromTruncatedBytes tlv.Value.[PaymentSecret.LENGTH..] |> LNMoney.MilliSatoshis
             (secret, totalMSat) |> PaymentData
         | _ -> Unknown tlv
 

src/DotNetLightning.Core/Utils/Primitives.fs

@@ -215,6 +215,33 @@ module Primitives =
                 member this.ToPubKey() =
                     this.ToPrivKey().PubKey
 
+    type PaymentSecret =
+        private PaymentSecret of uint256
+            with
+                // as per BOLT-2:
+                static member LENGTH = 32
+
+                static member Create(secret: uint256) =
+                    PaymentSecret secret
+
+                static member FromByteArray(secretBytes: array<byte>) =
+                    uint256(secretBytes, false)
+                    |> PaymentSecret
+
+                member this.Value =
+                    let (PaymentSecret v) = this in v
+
+                member this.ToHex() =
+                    let h = NBitcoin.DataEncoders.HexEncoder()
+                    let ba: byte[] = this.ToByteArray()
+                    ba |> h.EncodeData
+
+                member this.ToBytes() =
+                    this.Value.ToBytes(false)
+
+                member this.ToByteArray() =
+                    this.Value.ToBytes(false) |> Array.ofSeq
+
     let (|PaymentPreimage|) x =
         match x with
         | PaymentPreimage x -> x

tests/DotNetLightning.Core.Tests/Generators/Msgs.fs

@@ -601,7 +601,7 @@ let gossipTimestampFilterGen: Gen<GossipTimestampFilterMsg> = gen {
 
 let private hopPayloadTlvGen =
     let paymentDataGen: Gen<_ * _> =
-        ((PaymentPreimage.Create <!> bytesOfNGen(32)), (lnMoneyGen))
+        ((PaymentSecret.Create <!> uint256Gen), (lnMoneyGen))
         ||> Gen.map2(fun a b -> (a, b))
     Gen.frequency
         [(1, AmountToForward <!> lnMoneyGen)