From eb07d22b2d3ec70203412a7746b0ec73217cc974 Mon Sep 17 00:00:00 2001
From: Andrew Chow <achow101-github@achow101.com>
Date: Wed, 31 Jul 2019 18:02:24 -0400
Subject: Shuffle inputs and outputs after joining psbts

Github-Pull: #16512
Rebased-From: 6f405a1d3b38395e35571b68aae55cae50e0762a
---
 src/rpc/rawtransaction.cpp | 25 ++++++++++++++++++++++++-
 1 file changed, 24 insertions(+), 1 deletion(-)

(limited to 'src')

diff --git a/src/rpc/rawtransaction.cpp b/src/rpc/rawtransaction.cpp
index b0af7e09d4..c4b7bec052 100644
--- a/src/rpc/rawtransaction.cpp
+++ b/src/rpc/rawtransaction.cpp
@@ -19,6 +19,7 @@
 #include <policy/rbf.h>
 #include <primitives/transaction.h>
 #include <psbt.h>
+#include <random.h>
 #include <rpc/rawtransaction.h>
 #include <rpc/server.h>
 #include <rpc/util.h>
@@ -1861,8 +1862,30 @@ UniValue joinpsbts(const JSONRPCRequest& request)
         merged_psbt.unknown.insert(psbt.unknown.begin(), psbt.unknown.end());
     }
 
+    // Generate list of shuffled indices for shuffling inputs and outputs of the merged PSBT
+    std::vector<int> input_indices(merged_psbt.inputs.size());
+    std::iota(input_indices.begin(), input_indices.end(), 0);
+    std::vector<int> output_indices(merged_psbt.outputs.size());
+    std::iota(output_indices.begin(), output_indices.end(), 0);
+
+    // Shuffle input and output indicies lists
+    Shuffle(input_indices.begin(), input_indices.end(), FastRandomContext());
+    Shuffle(output_indices.begin(), output_indices.end(), FastRandomContext());
+
+    PartiallySignedTransaction shuffled_psbt;
+    shuffled_psbt.tx = CMutableTransaction();
+    shuffled_psbt.tx->nVersion = merged_psbt.tx->nVersion;
+    shuffled_psbt.tx->nLockTime = merged_psbt.tx->nLockTime;
+    for (int i : input_indices) {
+        shuffled_psbt.AddInput(merged_psbt.tx->vin[i], merged_psbt.inputs[i]);
+    }
+    for (int i : output_indices) {
+        shuffled_psbt.AddOutput(merged_psbt.tx->vout[i], merged_psbt.outputs[i]);
+    }
+    shuffled_psbt.unknown.insert(merged_psbt.unknown.begin(), merged_psbt.unknown.end());
+
     CDataStream ssTx(SER_NETWORK, PROTOCOL_VERSION);
-    ssTx << merged_psbt;
+    ssTx << shuffled_psbt;
     return EncodeBase64((unsigned char*)ssTx.data(), ssTx.size());
 }
 
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