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

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()`.

2 files changed, 63 insertions, 25 deletions

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
 {