test: Add fuzzer support functions for internal toxcore objects.

These help creating fuzzer fixtures with non-trivially constructed
objects and takes care of cleaning them up afterwards so the fuzzer code
can focus on the system under test.

testing/fuzzing/BUILD.bazel

@@ -15,6 +15,13 @@ cc_library(
     visibility = ["//c-toxcore:__subpackages__"],
 )
 
+cc_library(
+    name = "fuzz_tox",
+    hdrs = ["fuzz_tox.h"],
+    visibility = ["//c-toxcore:__subpackages__"],
+    deps = [":fuzz_support"],
+)
+
 cc_fuzz_test(
     name = "bootstrap_fuzz_test",
     srcs = ["bootstrap_harness.cc"],

testing/fuzzing/fuzz_support.cc

@@ -1 +1,5 @@
+/* SPDX-License-Identifier: GPL-3.0-or-later
+ * Copyright © 2021-2022 The TokTok team.
+ */
+
 #include "fuzz_support.h"

testing/fuzzing/fuzz_support.h

@@ -1,5 +1,5 @@
 /* SPDX-License-Identifier: GPL-3.0-or-later
- * Copyright © 2021 The TokTok team.
+ * Copyright © 2021-2022 The TokTok team.
  */
 
 #ifndef C_TOXCORE_TESTING_FUZZING_FUZZ_SUPPORT_H
@@ -7,19 +7,29 @@
 
 #include <cstdint>
 #include <cstdlib>
+#include <utility>
 
 struct Fuzz_Data {
     const uint8_t *data;
     std::size_t size;
 
-    uint8_t consume1() {
+    Fuzz_Data(const uint8_t *input_data, std::size_t input_size)
+        : data(input_data), size(input_size)
+    {}
+
+    Fuzz_Data &operator=(const Fuzz_Data &rhs) = delete;
+    Fuzz_Data(const Fuzz_Data &rhs) = delete;
+
+    uint8_t consume1()
+    {
         const uint8_t val = data[0];
         ++data;
         --size;
         return val;
     }
 
-    const uint8_t *consume(std::size_t count) {
+    const uint8_t *consume(std::size_t count)
+    {
         const uint8_t *val = data;
         data += count;
         size -= count;
@@ -60,28 +70,28 @@ struct Fuzz_Data {
     }                                        \
     DECL = INPUT.consume(SIZE)
 
-inline void fuzz_select_target(uint8_t selector, Fuzz_Data input)
+inline void fuzz_select_target(uint8_t selector, Fuzz_Data &input)
 {
     // The selector selected no function, so we do nothing and rely on the
     // fuzzer to come up with a better selector.
 }
 
 template <typename Arg, typename... Args>
-void fuzz_select_target(uint8_t selector, Fuzz_Data input, Arg fn, Args ...args)
+void fuzz_select_target(uint8_t selector, Fuzz_Data &input, Arg &&fn, Args &&... args)
 {
     if (selector == sizeof...(Args)) {
         return fn(input);
     }
-    return fuzz_select_target(selector - 1, input, args...);
+    return fuzz_select_target(selector - 1, input, std::forward<Args>(args)...);
 }
 
 template <typename... Args>
-void fuzz_select_target(const uint8_t *data, std::size_t size, Args ...args)
+void fuzz_select_target(const uint8_t *data, std::size_t size, Args &&... args)
 {
     Fuzz_Data input{data, size};
 
     CONSUME1_OR_RETURN(uint8_t selector, input);
-    return fuzz_select_target(selector, input, args...);
+    return fuzz_select_target(selector, input, std::forward<Args>(args)...);
 }
 
 #endif  // C_TOXCORE_TESTING_FUZZING_FUZZ_SUPPORT_H

testing/fuzzing/fuzz_tox.h

@@ -0,0 +1,95 @@
+/* SPDX-License-Identifier: GPL-3.0-or-later
+ * Copyright © 2022 The TokTok team.
+ */
+
+#ifndef C_TOXCORE_TESTING_FUZZING_FUZZ_TOX_H
+#define C_TOXCORE_TESTING_FUZZING_FUZZ_TOX_H
+
+#include <cassert>
+#include <memory>
+
+#include "../../toxcore/DHT.h"
+#include "../../toxcore/logger.h"
+#include "../../toxcore/network.h"
+#include "fuzz_support.h"
+
+constexpr uint16_t SIZE_IP_PORT = SIZE_IP6 + sizeof(uint16_t);
+
+template <typename T>
+using Ptr = std::unique_ptr<T, void (*)(T *)>;
+
+/** @brief Construct any Tox resource using fuzzer input data.
+ *
+ * Constructs (or fails by returning) a valid object of type T and passes it to
+ * a function specified on the rhs of `>>`. Takes care of cleaning up the
+ * resource after the specified function returns.
+ *
+ * Some `with` instances require additional inputs such as the `Fuzz_Data`
+ * reference or a logger.
+ */
+template <typename T>
+struct with;
+
+/** @brief Construct a Logger without logging callback.
+ */
+template <>
+struct with<Logger> {
+    template <typename F>
+    void operator>>(F &&f)
+    {
+        Ptr<Logger> logger(logger_new(), logger_kill);
+        assert(logger != nullptr);
+        f(std::move(logger));
+    }
+};
+
+/** @brief Construct an IP_Port by unpacking fuzzer input with `unpack_ip_port`.
+ */
+template <>
+struct with<IP_Port> {
+    Fuzz_Data &input_;
+
+    template <typename F>
+    void operator>>(F &&f)
+    {
+        CONSUME_OR_RETURN(const uint8_t *ipp_packed, input_, SIZE_IP_PORT);
+        IP_Port ipp;
+        unpack_ip_port(&ipp, ipp_packed, SIZE_IP6, true);
+
+        f(ipp);
+    }
+};
+
+/** @brief Construct a Networking_Core object using the Network vtable passed.
+ *
+ * Use `with<Logger>{} >> with<Networking_Core>{input, ns} >> ...` to construct
+ * a logger and pass it to the Networking_Core constructor function.
+ */
+template <>
+struct with<Networking_Core> {
+    Fuzz_Data &input_;
+    const Network *ns_;
+    Ptr<Logger> logger_{nullptr, logger_kill};
+
+    friend with operator>>(with<Logger> f, with self)
+    {
+        f >> [&self](Ptr<Logger> logger) { self.logger_ = std::move(logger); };
+        return self;
+    }
+
+    template <typename F>
+    void operator>>(F &&f)
+    {
+        with<IP_Port>{input_} >> [&f, this](const IP_Port &ipp) {
+            Ptr<Networking_Core> net(
+                new_networking_ex(logger_.get(), ns_, &ipp.ip, ipp.port, ipp.port + 100, nullptr),
+                kill_networking);
+            if (net == nullptr) {
+                return;
+            }
+            f(std::move(net));
+        };
+    }
+};
+
+#endif  // C_TOXCORE_TESTING_FUZZING_FUZZ_TOX_H

toxcore/DHT_fuzz_test.cc

@@ -7,7 +7,7 @@
 
 namespace {
 
-void TestHandleRequest(Fuzz_Data input)
+void TestHandleRequest(Fuzz_Data &input)
 {
     CONSUME_OR_RETURN(const uint8_t *self_public_key, input, CRYPTO_PUBLIC_KEY_SIZE);
     CONSUME_OR_RETURN(const uint8_t *self_secret_key, input, CRYPTO_SECRET_KEY_SIZE);
@@ -19,7 +19,7 @@ void TestHandleRequest(Fuzz_Data input)
         self_public_key, self_secret_key, public_key, request, &request_id, input.data, input.size);
 }
 
-void TestUnpackNodes(Fuzz_Data input)
+void TestUnpackNodes(Fuzz_Data &input)
 {
     CONSUME1_OR_RETURN(const bool tcp_enabled, input);
 

toxcore/group_moderation_fuzz_test.cc

@@ -4,7 +4,7 @@
 
 namespace {
 
-void TestModListUnpack(Fuzz_Data input)
+void TestModListUnpack(Fuzz_Data &input)
 {
     CONSUME1_OR_RETURN(const uint16_t num_mods, input);
     Moderation mods{};
@@ -12,7 +12,7 @@ void TestModListUnpack(Fuzz_Data input)
     mod_list_cleanup(&mods);
 }
 
-void TestSanctionsListUnpack(Fuzz_Data input)
+void TestSanctionsListUnpack(Fuzz_Data &input)
 {
     Mod_Sanction sanctions[10];
     Mod_Sanction_Creds creds;
@@ -20,7 +20,7 @@ void TestSanctionsListUnpack(Fuzz_Data input)
     sanctions_list_unpack(sanctions, &creds, 10, input.data, input.size, &processed_data_len);
 }
 
-void TestSanctionCredsUnpack(Fuzz_Data input)
+void TestSanctionCredsUnpack(Fuzz_Data &input)
 {
     CONSUME_OR_RETURN(const uint8_t *data, input, MOD_SANCTIONS_CREDS_SIZE);
     Mod_Sanction_Creds creds;