From 4a7fd7a7124f84e010b01d0769ef0572bf031ee8 Mon Sep 17 00:00:00 2001
From: practicalswift <practicalswift@users.noreply.github.com>
Date: Mon, 13 Jan 2020 15:08:52 +0000
Subject: [PATCH 1/2] tests: Add amount compression/decompression fuzzing to
 existing fuzzing harness: test compression round-trip

---
 src/test/fuzz/integer.cpp | 10 +++++++++-
 1 file changed, 9 insertions(+), 1 deletion(-)

diff --git a/src/test/fuzz/integer.cpp b/src/test/fuzz/integer.cpp
index 723938bcdb7..b496ab53419 100644
--- a/src/test/fuzz/integer.cpp
+++ b/src/test/fuzz/integer.cpp
@@ -2,6 +2,7 @@
 // Distributed under the MIT software license, see the accompanying
 // file COPYING or http://www.opensource.org/licenses/mit-license.php.
 
+#include <amount.h>
 #include <arith_uint256.h>
 #include <compressor.h>
 #include <consensus/merkle.h>
@@ -56,7 +57,14 @@ void test_one_input(const std::vector<uint8_t>& buffer)
 
     const Consensus::Params& consensus_params = Params().GetConsensus();
     (void)CheckProofOfWork(u256, u32, consensus_params);
-    (void)CompressAmount(u64);
+    if (u64 <= MAX_MONEY) {
+        const uint64_t compressed_money_amount = CompressAmount(u64);
+        assert(u64 == DecompressAmount(compressed_money_amount));
+        static const uint64_t compressed_money_amount_max = CompressAmount(MAX_MONEY - 1);
+        assert(compressed_money_amount <= compressed_money_amount_max);
+    } else {
+        (void)CompressAmount(u64);
+    }
     static const uint256 u256_min(uint256S("0000000000000000000000000000000000000000000000000000000000000000"));
     static const uint256 u256_max(uint256S("ffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffff"));
     const std::vector<uint256> v256{u256, u256_min, u256_max};

From 7e9c7113afbed96cef80c327cc93e82000d6bb69 Mon Sep 17 00:00:00 2001
From: practicalswift <practicalswift@users.noreply.github.com>
Date: Mon, 13 Jan 2020 15:09:36 +0000
Subject: [PATCH 2/2] compressor: Make the domain of CompressAmount(...)
 explicit

---
 src/compressor.h | 10 ++++++++++
 1 file changed, 10 insertions(+)

diff --git a/src/compressor.h b/src/compressor.h
index c1eda503c8d..acb34da4a06 100644
--- a/src/compressor.h
+++ b/src/compressor.h
@@ -19,7 +19,17 @@ bool CompressScript(const CScript& script, std::vector<unsigned char> &out);
 unsigned int GetSpecialScriptSize(unsigned int nSize);
 bool DecompressScript(CScript& script, unsigned int nSize, const std::vector<unsigned char> &out);
 
+/**
+ * Compress amount.
+ *
+ * nAmount is of type uint64_t and thus cannot be negative. If you're passing in
+ * a CAmount (int64_t), make sure to properly handle the case where the amount
+ * is negative before calling CompressAmount(...).
+ *
+ * @pre Function defined only for 0 <= nAmount <= MAX_MONEY.
+ */
 uint64_t CompressAmount(uint64_t nAmount);
+
 uint64_t DecompressAmount(uint64_t nAmount);
 
 /** Compact serializer for scripts.