From fa4b52bd16189d40761c5976b8427e30779aba23 Mon Sep 17 00:00:00 2001
From: MarcoFalke <*~=`'#}+{/-|&$^_@721217.xyz>
Date: Thu, 30 Oct 2025 10:40:14 +0100
Subject: [PATCH] fuzz: refactor memcpy to std::ranges::copy to work around
 ubsan warn

Using std::ranges::copy from the C++ standard library has a few benefits
here:

* It has the additional benefit of being a bit more type safe and
  document the byte cast explicitly.
* The compiler will likely optimize it to the same asm, but performance
  doesn't really matter here anyway.
* It works around an UB-Sanitizer bug, when the source range is empty.

Fixes https://github.com/bitcoin/bitcoin/issues/33643
---
 src/test/fuzz/util/net.cpp | 11 ++++++-----
 1 file changed, 6 insertions(+), 5 deletions(-)

diff --git a/src/test/fuzz/util/net.cpp b/src/test/fuzz/util/net.cpp
index e49c043364e..ba17e4e9360 100644
--- a/src/test/fuzz/util/net.cpp
+++ b/src/test/fuzz/util/net.cpp
@@ -1,4 +1,4 @@
-// Copyright (c) 2009-2022 The Bitcoin Core developers
+// Copyright (c) 2009-present The Bitcoin Core developers
 // Distributed under the MIT software license, see the accompanying
 // file COPYING or http://www.opensource.org/licenses/mit-license.php.
 
@@ -20,6 +20,7 @@
 #include <cstdint>
 #include <cstdlib>
 #include <cstring>
+#include <ranges>
 #include <thread>
 #include <vector>
 
@@ -322,8 +323,8 @@ std::unique_ptr<Sock> FuzzedSock::Accept(sockaddr* addr, socklen_t* addr_len) co
                 *addr_len = write_len;
                 auto addr4 = reinterpret_cast<sockaddr_in*>(addr);
                 addr4->sin_family = AF_INET;
-                const auto sin_addr_bytes = m_fuzzed_data_provider.ConsumeBytes<uint8_t>(sizeof(addr4->sin_addr));
-                memcpy(&addr4->sin_addr, sin_addr_bytes.data(), sin_addr_bytes.size());
+                const auto sin_addr_bytes{m_fuzzed_data_provider.ConsumeBytes<std::byte>(sizeof(addr4->sin_addr))};
+                std::ranges::copy(sin_addr_bytes, reinterpret_cast<std::byte*>(&addr4->sin_addr));
                 addr4->sin_port = m_fuzzed_data_provider.ConsumeIntegralInRange<uint16_t>(1, 65535);
             }
         } else {
@@ -333,8 +334,8 @@ std::unique_ptr<Sock> FuzzedSock::Accept(sockaddr* addr, socklen_t* addr_len) co
                 *addr_len = write_len;
                 auto addr6 = reinterpret_cast<sockaddr_in6*>(addr);
                 addr6->sin6_family = AF_INET6;
-                const auto sin_addr_bytes = m_fuzzed_data_provider.ConsumeBytes<uint8_t>(sizeof(addr6->sin6_addr));
-                memcpy(&addr6->sin6_addr, sin_addr_bytes.data(), sin_addr_bytes.size());
+                const auto sin_addr_bytes{m_fuzzed_data_provider.ConsumeBytes<std::byte>(sizeof(addr6->sin6_addr))};
+                std::ranges::copy(sin_addr_bytes, reinterpret_cast<std::byte*>(&addr6->sin6_addr));
                 addr6->sin6_port = m_fuzzed_data_provider.ConsumeIntegralInRange<uint16_t>(1, 65535);
             }
         }