merge bitcoin#26909: prevent peers.dat corruptions by only serializing once

Author: kwvg

src/addrdb.cpp

@@ -33,10 +33,9 @@ bool SerializeDB(Stream& stream, const Data& data)
 {
     // Write and commit header, data
     try {
-        CHashWriter hasher(stream.GetType(), stream.GetVersion());
-        stream << Params().MessageStart() << data;
-        hasher << Params().MessageStart() << data;
-        stream << hasher.GetHash();
+        HashedSourceWriter hashwriter{stream};
+        hashwriter << Params().MessageStart() << data;
+        stream << hashwriter.GetHash();
     } catch (const std::exception& e) {
         return error("%s: Serialize or I/O error - %s", __func__, e.what());
     }

src/addrman.cpp

@@ -1168,8 +1168,7 @@ void AddrMan::Unserialize(Stream& s_)
 }
 
 // explicit instantiation
-template void AddrMan::Serialize(CHashWriter& s) const;
-template void AddrMan::Serialize(CAutoFile& s) const;
+template void AddrMan::Serialize(HashedSourceWriter<CAutoFile>& s) const;
 template void AddrMan::Serialize(CDataStream& s) const;
 template void AddrMan::Unserialize(CAutoFile& s);
 template void AddrMan::Unserialize(CHashVerifier<CAutoFile>& s);

src/hash.h

@@ -201,6 +201,30 @@ class CHashVerifier : public CHashWriter
     }
 };
 
+/** Writes data to an underlying source stream, while hashing the written data. */
+template <typename Source>
+class HashedSourceWriter : public CHashWriter
+{
+private:
+    Source& m_source;
+
+public:
+    explicit HashedSourceWriter(Source& source LIFETIMEBOUND) : CHashWriter{source.GetType(), source.GetVersion()}, m_source{source} {}
+
+    void write(Span<const std::byte> src)
+    {
+        m_source.write(src);
+        CHashWriter::write(src);
+    }
+
+    template <typename T>
+    HashedSourceWriter& operator<<(const T& obj)
+    {
+        ::Serialize(*this, obj);
+        return *this;
+    }
+};
+
 /** Compute the 256-bit hash of an object's serialization. */
 template<typename T>
 uint256 SerializeHash(const T& obj, int nType=SER_GETHASH, int nVersion=PROTOCOL_VERSION)

src/test/streams_tests.cpp

@@ -437,4 +437,18 @@ BOOST_AUTO_TEST_CASE(streams_buffered_file_rand)
     fs::remove("streams_test_tmp");
 }
 
+BOOST_AUTO_TEST_CASE(streams_hashed)
+{
+    CDataStream stream(SER_NETWORK, INIT_PROTO_VERSION);
+    HashedSourceWriter hash_writer{stream};
+    const std::string data{"bitcoin"};
+    hash_writer << data;
+
+    CHashVerifier hash_verifier{&stream};
+    std::string result;
+    hash_verifier >> result;
+    BOOST_CHECK_EQUAL(data, result);
+    BOOST_CHECK_EQUAL(hash_writer.GetHash(), hash_verifier.GetHash());
+}
+
 BOOST_AUTO_TEST_SUITE_END()