Merge bitcoin/bitcoin#26859: fuzz: extend ConsumeNetAddr() to return I2P and CJDNS addresses

b851c5385d0a0acec4493be1561cea285065d5dc fuzz: extend ConsumeNetAddr() to return I2P and CJDNS addresses (Vasil Dimov)

Pull request description:

  In the process of doing so, refactor `ConsumeNetAddr()` to generate the addresses from IPv4, IPv6, Tor, I2P and CJDNS networks in the same way - by preparing some random stream and deserializing from it. Similar code was already found in `RandAddr()`.

ACKs for top commit:
  achow101:
    ACK b851c5385d0a0acec4493be1561cea285065d5dc
  mzumsande:
    ACK b851c5385d0a0acec4493be1561cea285065d5dc
  brunoerg:
    utACK b851c5385d0a0acec4493be1561cea285065d5dc

Tree-SHA512: 9905acff0e996f30ddac0c14e5ee9e1db926c7751472c06d6441111304242b563f7c942b162b209d80e8fb65a97249792eef9ae0a96100419565bf7f59f59676

6 files changed, 100 insertions, 61 deletions

diff --git a/src/netaddress.h b/src/netaddress.h
index 08dd77c0ff..0bbde43dd7 100644
--- a/src/netaddress.h
+++ b/src/netaddress.h
@@ -261,6 +261,18 @@ public:
         }
     }
 
+    /**
+     * BIP155 network ids recognized by this software.
+     */
+    enum BIP155Network : uint8_t {
+        IPV4 = 1,
+        IPV6 = 2,
+        TORV2 = 3,
+        TORV3 = 4,
+        I2P = 5,
+        CJDNS = 6,
+    };
+
     friend class CSubNet;
 
 private:
@@ -283,18 +295,6 @@ private:
     bool SetI2P(const std::string& addr);
 
     /**
-     * BIP155 network ids recognized by this software.
-     */
-    enum BIP155Network : uint8_t {
-        IPV4 = 1,
-        IPV6 = 2,
-        TORV2 = 3,
-        TORV3 = 4,
-        I2P = 5,
-        CJDNS = 6,
-    };
-
-    /**
      * Size of CNetAddr when serialized as ADDRv1 (pre-BIP155) (in bytes).
      */
     static constexpr size_t V1_SERIALIZATION_SIZE = ADDR_IPV6_SIZE;
diff --git a/src/test/fuzz/addrman.cpp b/src/test/fuzz/addrman.cpp
index ece396aadf..8a54cc656d 100644
--- a/src/test/fuzz/addrman.cpp
+++ b/src/test/fuzz/addrman.cpp
@@ -64,26 +64,13 @@ FUZZ_TARGET(data_stream_addr_man, .init = initialize_addrman)
 CNetAddr RandAddr(FuzzedDataProvider& fuzzed_data_provider, FastRandomContext& fast_random_context)
 {
     CNetAddr addr;
-    if (fuzzed_data_provider.remaining_bytes() > 1 && fuzzed_data_provider.ConsumeBool()) {
-        addr = ConsumeNetAddr(fuzzed_data_provider);
-    } else {
-        // The networks [1..6] correspond to CNetAddr::BIP155Network (private).
-        static const std::map<uint8_t, uint8_t> net_len_map = {{1, ADDR_IPV4_SIZE},
-                                                               {2, ADDR_IPV6_SIZE},
-                                                               {4, ADDR_TORV3_SIZE},
-                                                               {5, ADDR_I2P_SIZE},
-                                                               {6, ADDR_CJDNS_SIZE}};
-        uint8_t net = fast_random_context.randrange(5) + 1; // [1..5]
-        if (net == 3) {
-            net = 6;
+    assert(!addr.IsValid());
+    for (size_t i = 0; i < 8 && !addr.IsValid(); ++i) {
+        if (fuzzed_data_provider.remaining_bytes() > 1 && fuzzed_data_provider.ConsumeBool()) {
+            addr = ConsumeNetAddr(fuzzed_data_provider);
+        } else {
+            addr = ConsumeNetAddr(fuzzed_data_provider, &fast_random_context);
         }
-
-        DataStream s{};
-
-        s << net;
-        s << fast_random_context.randbytes(net_len_map.at(net));
-
-        s >> CAddress::V2_NETWORK(addr);
     }
 
     // Return a dummy IPv4 5.5.5.5 if we generated an invalid address.
diff --git a/src/test/fuzz/banman.cpp b/src/test/fuzz/banman.cpp
index 4a040c56de..b26151f63c 100644
--- a/src/test/fuzz/banman.cpp
+++ b/src/test/fuzz/banman.cpp
@@ -70,11 +70,13 @@ FUZZ_TARGET(banman, .init = initialize_banman)
                 fuzzed_data_provider,
                 [&] {
                     CNetAddr net_addr{ConsumeNetAddr(fuzzed_data_provider)};
-                    const std::optional<CNetAddr>& addr{LookupHost(net_addr.ToStringAddr(), /*fAllowLookup=*/false)};
-                    if (addr.has_value() && addr->IsValid()) {
-                        net_addr = *addr;
-                    } else {
-                        contains_invalid = true;
+                    if (!net_addr.IsCJDNS() || !net_addr.IsValid()) {
+                        const std::optional<CNetAddr>& addr{LookupHost(net_addr.ToStringAddr(), /*fAllowLookup=*/false)};
+                        if (addr.has_value() && addr->IsValid()) {
+                            net_addr = *addr;
+                        } else {
+                            contains_invalid = true;
+                        }
                     }
                     ban_man.Ban(net_addr, ConsumeBanTimeOffset(fuzzed_data_provider), fuzzed_data_provider.ConsumeBool());
                 },
diff --git a/src/test/fuzz/netaddress.cpp b/src/test/fuzz/netaddress.cpp
index 5141d3362d..4803cdccad 100644
--- a/src/test/fuzz/netaddress.cpp
+++ b/src/test/fuzz/netaddress.cpp
@@ -26,6 +26,12 @@ FUZZ_TARGET(netaddress)
     if (net_addr.GetNetwork() == Network::NET_ONION) {
         assert(net_addr.IsTor());
     }
+    if (net_addr.GetNetwork() == Network::NET_I2P) {
+        assert(net_addr.IsI2P());
+    }
+    if (net_addr.GetNetwork() == Network::NET_CJDNS) {
+        assert(net_addr.IsCJDNS());
+    }
     if (net_addr.GetNetwork() == Network::NET_INTERNAL) {
         assert(net_addr.IsInternal());
     }
@@ -69,6 +75,12 @@ FUZZ_TARGET(netaddress)
     if (net_addr.IsTor()) {
         assert(net_addr.GetNetwork() == Network::NET_ONION);
     }
+    if (net_addr.IsI2P()) {
+        assert(net_addr.GetNetwork() == Network::NET_I2P);
+    }
+    if (net_addr.IsCJDNS()) {
+        assert(net_addr.GetNetwork() == Network::NET_CJDNS);
+    }
     (void)net_addr.IsValid();
     (void)net_addr.ToStringAddr();
 
diff --git a/src/test/fuzz/util/net.cpp b/src/test/fuzz/util/net.cpp
index eb0f14ede0..99151bb84d 100644
--- a/src/test/fuzz/util/net.cpp
+++ b/src/test/fuzz/util/net.cpp
@@ -25,33 +25,63 @@
 
 class CNode;
 
-CNetAddr ConsumeNetAddr(FuzzedDataProvider& fuzzed_data_provider) noexcept
+CNetAddr ConsumeNetAddr(FuzzedDataProvider& fuzzed_data_provider, FastRandomContext* rand) 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 = {};
-            auto addr_bytes = fuzzed_data_provider.ConsumeBytes<uint8_t>(16);
-            if (addr_bytes[0] == CJDNS_PREFIX) { // Avoid generating IPv6 addresses that look like CJDNS.
-                addr_bytes[0] = 0x55; // Just an arbitrary number, anything != CJDNS_PREFIX would do.
-            }
-            memcpy(v6_addr.s6_addr, addr_bytes.data(), 16);
-            net_addr = CNetAddr{v6_addr, fuzzed_data_provider.ConsumeIntegral<uint32_t>()};
+    struct NetAux {
+        Network net;
+        CNetAddr::BIP155Network bip155;
+        size_t len;
+    };
+
+    static constexpr std::array<NetAux, 6> nets{
+        NetAux{.net = Network::NET_IPV4, .bip155 = CNetAddr::BIP155Network::IPV4, .len = ADDR_IPV4_SIZE},
+        NetAux{.net = Network::NET_IPV6, .bip155 = CNetAddr::BIP155Network::IPV6, .len = ADDR_IPV6_SIZE},
+        NetAux{.net = Network::NET_ONION, .bip155 = CNetAddr::BIP155Network::TORV3, .len = ADDR_TORV3_SIZE},
+        NetAux{.net = Network::NET_I2P, .bip155 = CNetAddr::BIP155Network::I2P, .len = ADDR_I2P_SIZE},
+        NetAux{.net = Network::NET_CJDNS, .bip155 = CNetAddr::BIP155Network::CJDNS, .len = ADDR_CJDNS_SIZE},
+        NetAux{.net = Network::NET_INTERNAL, .bip155 = CNetAddr::BIP155Network{0}, .len = 0},
+    };
+
+    const size_t nets_index{rand == nullptr
+        ? fuzzed_data_provider.ConsumeIntegralInRange<size_t>(0, nets.size() - 1)
+        : static_cast<size_t>(rand->randrange(nets.size()))};
+
+    const auto& aux = nets[nets_index];
+
+    CNetAddr addr;
+
+    if (aux.net == Network::NET_INTERNAL) {
+        if (rand == nullptr) {
+            addr.SetInternal(fuzzed_data_provider.ConsumeBytesAsString(32));
+        } else {
+            const auto v = rand->randbytes(32);
+            addr.SetInternal(std::string{v.begin(), v.end()});
         }
-    } 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 addr;
+    }
+
+    DataStream s;
+
+    s << static_cast<uint8_t>(aux.bip155);
+
+    std::vector<uint8_t> addr_bytes;
+    if (rand == nullptr) {
+        addr_bytes = fuzzed_data_provider.ConsumeBytes<uint8_t>(aux.len);
+        addr_bytes.resize(aux.len);
+    } else {
+        addr_bytes = rand->randbytes(aux.len);
     }
-    return net_addr;
+    if (aux.net == NET_IPV6 && addr_bytes[0] == CJDNS_PREFIX) { // Avoid generating IPv6 addresses that look like CJDNS.
+        addr_bytes[0] = 0x55; // Just an arbitrary number, anything != CJDNS_PREFIX would do.
+    }
+    if (aux.net == NET_CJDNS) { // Avoid generating CJDNS addresses that don't start with CJDNS_PREFIX because those are !IsValid().
+        addr_bytes[0] = CJDNS_PREFIX;
+    }
+    s << addr_bytes;
+
+    s >> CAddress::V2_NETWORK(addr);
+
+    return addr;
 }
 
 CAddress ConsumeAddress(FuzzedDataProvider& fuzzed_data_provider) noexcept
diff --git a/src/test/fuzz/util/net.h b/src/test/fuzz/util/net.h
index 47e4a2fac0..a6c9e23f2e 100644
--- a/src/test/fuzz/util/net.h
+++ b/src/test/fuzz/util/net.h
@@ -24,7 +24,15 @@
 #include <optional>
 #include <string>
 
-CNetAddr ConsumeNetAddr(FuzzedDataProvider& fuzzed_data_provider) noexcept;
+/**
+ * Create a CNetAddr. It may have `addr.IsValid() == false`.
+ * @param[in,out] fuzzed_data_provider Take data for the address from this, if `rand` is `nullptr`.
+ * @param[in,out] rand If not nullptr, take data from it instead of from `fuzzed_data_provider`.
+ * Prefer generating addresses using `fuzzed_data_provider` because it is not uniform. Only use
+ * `rand` if `fuzzed_data_provider` is exhausted or its data is needed for other things.
+ * @return a "random" network address.
+ */
+CNetAddr ConsumeNetAddr(FuzzedDataProvider& fuzzed_data_provider, FastRandomContext* rand = nullptr) noexcept;
 
 class FuzzedSock : public Sock
 {