Merge bitcoin/bitcoin#26497: fuzz: Make ConsumeNetAddr always produce valid onion addresses

0eeb9b0442fb2f2da33c04704eefe6a84d28e981 [fuzz] Move ConsumeNetAddr to fuzz/util/net.h (dergoegge)
291c8697d4be0f38635b67880107e39d3ec585ad [fuzz] Make ConsumeNetAddr produce valid onion addresses (dergoegge)
c9ba3f836e1646875d2f96f1f466f8a83634a6f7 [netaddress] Make OnionToString public (dergoegge)

Pull request description:

  The chance that the fuzzer is able to guess a valid onion address is probably slim, as they are Base32 encoded and include a checksum.  Right now, any target using `ConsumeNetAddr` would have a hard time uncovering bugs that require valid onion addresses as input.

  This PR makes `ConsumeNetAddr` produce valid onion addresses by using the 32 bytes given by the fuzzer as the pubkey for the onion address and forming a valid address according to the torv3 spec.

ACKs for top commit:
  vasild:
    ACK 0eeb9b0442fb2f2da33c04704eefe6a84d28e981
  brunoerg:
    ACK 0eeb9b0442fb2f2da33c04704eefe6a84d28e981

Tree-SHA512: 7c687a4d12f9659559be8f0c3cd4265167d1261d419cfd3d503fd7c7f207cc0db745220f02fb1737e4a5700ea7429311cfc0b42e6c15968ce6a85f8813c7e1d8

2 files changed, 50 insertions, 0 deletions

diff --git a/src/test/fuzz/util/net.cpp b/src/test/fuzz/util/net.cpp
new file mode 100644
index 0000000000..f8e996cfa5
--- /dev/null
+++ b/src/test/fuzz/util/net.cpp
@@ -0,0 +1,36 @@
+// Copyright (c) 2009-2021 The Bitcoin Core developers
+// Distributed under the MIT software license, see the accompanying
+// file COPYING or http://www.opensource.org/licenses/mit-license.php.
+
+#include <compat/compat.h>
+#include <netaddress.h>
+#include <test/fuzz/FuzzedDataProvider.h>
+#include <util/strencodings.h>
+
+#include <cstdint>
+#include <vector>
+
+CNetAddr ConsumeNetAddr(FuzzedDataProvider& fuzzed_data_provider) noexcept
+{
+    const Network network = fuzzed_data_provider.PickValueInArray({Network::NET_IPV4, Network::NET_IPV6, Network::NET_INTERNAL, Network::NET_ONION});
+    CNetAddr net_addr;
+    if (network == Network::NET_IPV4) {
+        in_addr v4_addr = {};
+        v4_addr.s_addr = fuzzed_data_provider.ConsumeIntegral<uint32_t>();
+        net_addr = CNetAddr{v4_addr};
+    } else if (network == Network::NET_IPV6) {
+        if (fuzzed_data_provider.remaining_bytes() >= 16) {
+            in6_addr v6_addr = {};
+            memcpy(v6_addr.s6_addr, fuzzed_data_provider.ConsumeBytes<uint8_t>(16).data(), 16);
+            net_addr = CNetAddr{v6_addr, fuzzed_data_provider.ConsumeIntegral<uint32_t>()};
+        }
+    } else if (network == Network::NET_INTERNAL) {
+        net_addr.SetInternal(fuzzed_data_provider.ConsumeBytesAsString(32));
+    } else if (network == Network::NET_ONION) {
+        auto pub_key{fuzzed_data_provider.ConsumeBytes<uint8_t>(ADDR_TORV3_SIZE)};
+        pub_key.resize(ADDR_TORV3_SIZE);
+        const bool ok{net_addr.SetSpecial(OnionToString(pub_key))};
+        assert(ok);
+    }
+    return net_addr;
+}
diff --git a/src/test/fuzz/util/net.h b/src/test/fuzz/util/net.h
new file mode 100644
index 0000000000..d81adab650
--- /dev/null
+++ b/src/test/fuzz/util/net.h
@@ -0,0 +1,14 @@
+// Copyright (c) 2009-2021 The Bitcoin Core developers
+// Distributed under the MIT software license, see the accompanying
+// file COPYING or http://www.opensource.org/licenses/mit-license.php.
+
+#ifndef BITCOIN_TEST_FUZZ_UTIL_NET_H
+#define BITCOIN_TEST_FUZZ_UTIL_NET_H
+
+#include <netaddress.h>
+
+class FuzzedDataProvider;
+
+CNetAddr ConsumeNetAddr(FuzzedDataProvider& fuzzed_data_provider) noexcept;
+
+#endif // BITCOIN_TEST_FUZZ_UTIL_NET_H