From 0000dca6f0e4dda212bf8adf555b68f2c7464ff8 Mon Sep 17 00:00:00 2001
From: MarcoFalke <falke.marco@gmail.com>
Date: Fri, 10 Sep 2021 17:54:38 +0200
Subject: [PATCH] fuzz: Cleanup muhash fuzz target

Can be reviewed with -W --ignore-all-space

Fixes:
* Calling ConsumeRandomLengthByteVector 4 times, when 2 is enough.
* Slow execution speed: Finalize is expensive because it invokes
  division. Speed up the target by calling Finalize() at most twice per
  fuzz input.
---
 src/test/fuzz/muhash.cpp | 71 +++++++++++++++++++---------------------
 1 file changed, 33 insertions(+), 38 deletions(-)

diff --git a/src/test/fuzz/muhash.cpp b/src/test/fuzz/muhash.cpp
index 4ea95118704..8304e6fdb87 100644
--- a/src/test/fuzz/muhash.cpp
+++ b/src/test/fuzz/muhash.cpp
@@ -12,52 +12,47 @@
 FUZZ_TARGET(muhash)
 {
     FuzzedDataProvider fuzzed_data_provider{buffer.data(), buffer.size()};
-    std::vector<uint8_t> data = ConsumeRandomLengthByteVector(fuzzed_data_provider);
-    std::vector<uint8_t> data2 = ConsumeRandomLengthByteVector(fuzzed_data_provider);
-    if (data.empty()) {
-        data.resize(fuzzed_data_provider.ConsumeIntegralInRange<size_t>(1, 4096), fuzzed_data_provider.ConsumeIntegral<uint8_t>());
-    }
-    if (data2.empty()) {
-        data2.resize(fuzzed_data_provider.ConsumeIntegralInRange<size_t>(1, 4096), fuzzed_data_provider.ConsumeIntegral<uint8_t>());
-    }
-
-    data = ConsumeRandomLengthByteVector(fuzzed_data_provider);
-    data2 = ConsumeRandomLengthByteVector(fuzzed_data_provider);
+    std::vector<uint8_t> data{ConsumeRandomLengthByteVector(fuzzed_data_provider)};
+    std::vector<uint8_t> data2{ConsumeRandomLengthByteVector(fuzzed_data_provider)};
 
     MuHash3072 muhash;
 
-    // Test that MuHash result is consistent independent of order of operations
     muhash.Insert(data);
     muhash.Insert(data2);
 
+    const std::string initial_state_hash{"dd5ad2a105c2d29495f577245c357409002329b9f4d6182c0af3dc2f462555c8"};
     uint256 out;
-    muhash.Finalize(out);
-
-    muhash = MuHash3072();
-    muhash.Insert(data2);
-    muhash.Insert(data);
-
     uint256 out2;
-    muhash.Finalize(out2);
+    CallOneOf(
+        fuzzed_data_provider,
+        [&] {
+            // Test that MuHash result is consistent independent of order of operations
+            muhash.Finalize(out);
 
+            muhash = MuHash3072();
+            muhash.Insert(data2);
+            muhash.Insert(data);
+            muhash.Finalize(out2);
+        },
+        [&] {
+            // Test that multiplication with the initial state never changes the finalized result
+            muhash.Finalize(out);
+            MuHash3072 muhash3;
+            muhash3 *= muhash;
+            muhash3.Finalize(out2);
+        },
+        [&] {
+            // Test that dividing a MuHash by itself brings it back to it's initial state
+            muhash /= muhash;
+            muhash.Finalize(out);
+            out2 = uint256S(initial_state_hash);
+        },
+        [&] {
+            // Test that removing all added elements brings the object back to it's initial state
+            muhash.Remove(data);
+            muhash.Remove(data2);
+            muhash.Finalize(out);
+            out2 = uint256S(initial_state_hash);
+        });
     assert(out == out2);
-    MuHash3072 muhash3;
-    muhash3 *= muhash;
-    uint256 out3;
-    muhash3.Finalize(out3);
-    assert(out == out3);
-
-    // Test that removing all added elements brings the object back to it's initial state
-    muhash /= muhash;
-    muhash.Finalize(out);
-
-    MuHash3072 muhash2;
-    muhash2.Finalize(out2);
-
-    assert(out == out2);
-
-    muhash3.Remove(data);
-    muhash3.Remove(data2);
-    muhash3.Finalize(out3);
-    assert(out == out3);
 }