net: Add fuzzer for HostResolverImpl.

net/dns/fuzzed_host_resolver.cc

Index: net/dns/fuzzed_host_resolver.cc
diff --git a/net/dns/fuzzed_host_resolver.cc b/net/dns/fuzzed_host_resolver.cc
new file mode 100644
index 0000000000000000000000000000000000000000..41fedd1cb8de04976abcd367f0628d82d1978cde
--- /dev/null
+++ b/net/dns/fuzzed_host_resolver.cc
@@ -0,0 +1,238 @@
+// Copyright 2016 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#include "net/dns/fuzzed_host_resolver.h"
+
+#include <stdint.h>
+
+#include <limits>
+#include <string>
+
+#include "base/bind.h"
+#include "base/logging.h"
+#include "base/macros.h"
+#include "base/memory/ref_counted.h"
+#include "base/single_thread_task_runner.h"
+#include "base/threading/thread_task_runner_handle.h"
+#include "net/base/address_list.h"
+#include "net/base/fuzzed_data_provider.h"
+#include "net/base/ip_address.h"
+#include "net/base/ip_endpoint.h"
+#include "net/base/net_errors.h"
+#include "net/dns/dns_client.h"
+#include "net/dns/dns_config_service.h"
+#include "net/dns/dns_hosts.h"
+
+namespace net {
+
+namespace {
+
+// Returns a fuzzed non-zero port number.
+uint16_t FuzzPort(FuzzedDataProvider* data_provider) {
+  uint16_t port = data_provider->ConsumeUint16();
+  // Port 0 is magic.

[eroman, 2016/06/01 01:47:21]

but shouldn't be

[mmenke, 2016/06/01 21:21:51]

It's a reserved port, so presumably it should be?  This test may work if I
allowed port 0, but connecting to port 0 seemed too weird, hence this line.

INADDR_ANY is also generally defined as 0, I believe - admittedly, it's only for
creating listen sockets, but still makes "port 0" freak me out a bit.

[eroman, 2016/06/01 21:46:06]

Sorry I should have been clearer.

My comment was about layering -- from the perspective of DnsConfig, is it
expected that port cannot be 0 for a nameserver? If it doesn't care, then should
probably just feed in 0 as a possibility and let it do its magic.

Looking at the windows implementation of dnsconfigservice at least, doesn't look
like it will allow port 0.

Yes, I agree port 0 can be treated in magic ways by APIs, which is why testing
for it can be useful.

That said, I don't think fuzzing or not fuzzing the port for this input is going
to be that interesting, since it won't be doing much with it anyway.

[mmenke, 2016/06/01 21:53:28]

I've removed the check - I think it was inspired by the belief that
DnsConfigService can't return ports of 0, though perhaps I was wrong - and even
if not, we probably shouldn't fail badly if that happens.  If the bots run into
issues with port 0, can reconsider it.

[mmenke, 2016/06/01 21:54:26]

Actually, it was inspired by the belief that *connections* to port 0 should
fail, so it seemed weird that our mock classes would allow them.  Anyhow, I'll
still remove the check.

+  if (port == 0)
+    return 53;
+  return port;
+}
+
+// Returns a fuzzed IPv4 address.  Can return invalid / reserved addresses.
+IPAddress FuzzIPv4Address(FuzzedDataProvider* data_provider) {
+  return IPAddress(data_provider->ConsumeUint8(), data_provider->ConsumeUint8(),
+                   data_provider->ConsumeUint8(),
+                   data_provider->ConsumeUint8());
+}
+
+// Returns a fuzzed IPv6 address.  Can return invalid / reserved addresses.
+IPAddress FuzzIPv6Address(FuzzedDataProvider* data_provider) {
+  return IPAddress(data_provider->ConsumeUint8(), data_provider->ConsumeUint8(),
+                   data_provider->ConsumeUint8(), data_provider->ConsumeUint8(),
+                   data_provider->ConsumeUint8(), data_provider->ConsumeUint8(),
+                   data_provider->ConsumeUint8(), data_provider->ConsumeUint8(),
+                   data_provider->ConsumeUint8(), data_provider->ConsumeUint8(),
+                   data_provider->ConsumeUint8(), data_provider->ConsumeUint8(),
+                   data_provider->ConsumeUint8(), data_provider->ConsumeUint8(),
+                   data_provider->ConsumeUint8(),
+                   data_provider->ConsumeUint8());
+}
+
+// Returns a fuzzed address, which can be either IPv4 or IPv6.  Can return
+// invalid / reserved addresses.
+IPAddress FuzzIPAddress(FuzzedDataProvider* data_provider) {
+  if (data_provider->ConsumeBool())
+    return FuzzIPv4Address(data_provider);
+  return FuzzIPv6Address(data_provider);
+}
+
+// HostResolverProc that returns a random set of results, and can succeed or
+// fail. Must only be run on the thread it's created on.
+class FuzzedHostResolverProc : public HostResolverProc {
+ public:
+  // Can safely be used after the destruction of |data_provider|. This can
+  // happen if a request is issued but the code never waits for the result
+  // before the test ends.
+  explicit FuzzedHostResolverProc(
+      base::WeakPtr<FuzzedDataProvider> data_provider)
+      : HostResolverProc(nullptr),
+        data_provider_(data_provider),
+        network_task_runner_(base::ThreadTaskRunnerHandle::Get()) {}
+
+  int Resolve(const std::string& host,
+              AddressFamily address_family,
+              HostResolverFlags host_resolver_flags,
+              AddressList* addrlist,
+              int* os_error) override {
+    DCHECK(network_task_runner_->BelongsToCurrentThread());
+
+    if (os_error)
+      *os_error = 0;
+
+    // If the data provider is no longer avaiable, just fail. The HostResolver
+    // has already been deleted by this point, anyways.
+    if (!data_provider_)
+      return ERR_FAILED;
+
+    AddressList result;
+
+    // Put IPv6 addresses before IPv4 ones. This code doesn't sort addresses
+    // correctly, but when sorted according to spec, IPv6 addresses are
+    // generally before IPv4 ones.
+    if (address_family == ADDRESS_FAMILY_UNSPECIFIED ||
+        address_family == ADDRESS_FAMILY_IPV6) {
+      uint16_t num_ipv6_addresses = data_provider_->ConsumeUint8();

[eroman, 2016/06/01 01:47:21]

nit: any reason to use uint16 here (rather than uint8, or a size_t) ?

[mmenke, 2016/06/01 21:21:51]

I initially used uint16_t for number of addresses, and forgot to update it when
I switched the range.  I've gone ahead and switch to size_t, but I think uint8_t
works just as well.  size_t just indicates it's related to a memory allocation a
bit more clearly, though that's not exactly ambiguous here.

+      for (uint16_t i = 0; i < num_ipv6_addresses; ++i) {
+        result.push_back(
+            net::IPEndPoint(FuzzIPv6Address(data_provider_.get()), 0));
+      }
+    }
+
+    if (address_family == ADDRESS_FAMILY_UNSPECIFIED ||
+        address_family == ADDRESS_FAMILY_IPV4) {
+      uint16_t num_ipv4_addresses = data_provider_->ConsumeUint8();

[eroman, 2016/06/01 01:47:21]

ditto

[mmenke, 2016/06/01 21:21:51]

Done.

+      for (uint16_t i = 0; i < num_ipv4_addresses; ++i) {
+        result.push_back(
+            net::IPEndPoint(FuzzIPv4Address(data_provider_.get()), 0));
+      }
+    }
+
+    if (result.empty())
+      return ERR_NAME_NOT_RESOLVED;
+
+    if (host_resolver_flags & HOST_RESOLVER_CANONNAME) {
+      // Don't bother to fuzz this - almost nothing cares.
+      result.set_canonical_name("foo.com");
+    }
+
+    *addrlist = result;
+    return OK;
+  }
+
+ private:
+  ~FuzzedHostResolverProc() override {}
+
+  base::WeakPtr<FuzzedDataProvider> data_provider_;
+
+  // Just used for thread-safety checks.
+  scoped_refptr<base::SingleThreadTaskRunner> network_task_runner_;
+
+  DISALLOW_COPY_AND_ASSIGN(FuzzedHostResolverProc);
+};
+
+}  // namespace
+
+FuzzedHostResolver::FuzzedHostResolver(const Options& options,
+                                       NetLog* net_log,
+                                       FuzzedDataProvider* data_provider)
+    : HostResolverImpl(options, net_log, base::ThreadTaskRunnerHandle::Get()),
+      data_provider_(data_provider),
+      socket_factory_(data_provider),
+      is_ipv6_reachable_(data_provider->ConsumeBool()),
+      net_log_(net_log),
+      data_provider_weak_factory_(data_provider) {
+  HostResolverImpl::ProcTaskParams proc_task_params(
+      new FuzzedHostResolverProc(data_provider_weak_factory_.GetWeakPtr()),
+      // Retries are only used when the original request hangs, which this class
+      // currently can't simulate.
+      0 /* max_retry_attempts */);
+  set_proc_params_for_test(proc_task_params);
+}
+
+FuzzedHostResolver::~FuzzedHostResolver() {}
+
+void FuzzedHostResolver::SetDnsClientEnabled(bool enabled) {
+  if (!enabled) {
+    HostResolverImpl::SetDnsClientEnabled(false);
+    return;
+  }
+
+  // Fuzz DNS configuration.
+
+  DnsConfig config;
+
+  // Fuzz name servers.
+  uint32_t num_nameservers = data_provider_->ConsumeUint32InRange(0, 4);
+  for (uint32_t i = 0; i < num_nameservers; ++i) {
+    config.nameservers.push_back(
+        IPEndPoint(FuzzIPAddress(data_provider_), FuzzPort(data_provider_)));
+  }
+
+  // Fuzz suffix search list. Each case deliberately falls through.
+  switch (data_provider_->ConsumeUint32InRange(0, 3)) {
+    case 3:
+      config.search.push_back("foo.com");
+    case 2:
+      config.search.push_back("bar");
+    case 1:
+      config.search.push_back("com");
+    default:
+      break;
+  }
+
+  net::DnsHosts hosts;
+  // Fuzz hosts file.
+  uint8_t num_hosts_entries = data_provider_->ConsumeUint8();
+  for (uint8_t i = 0; i < num_hosts_entries; ++i) {
+    const char* kHostnames[] = {"foo", "foo.com",   "a.foo.com",
+                                "bar", "localhost", "localhost6"};
+    const char* hostname = data_provider_->PickArrayEntry(kHostnames);
+    net::IPAddress address = FuzzIPAddress(data_provider_);
+    config.hosts[net::DnsHostsKey(hostname, net::GetAddressFamily(address))] =
+        address;
+  }
+
+  config.unhandled_options = data_provider_->ConsumeBool();
+  config.append_to_multi_label_name = data_provider_->ConsumeBool();
+  config.randomize_ports = data_provider_->ConsumeBool();
+  config.ndots = data_provider_->ConsumeInt32InRange(0, 3);
+  config.attempts = data_provider_->ConsumeInt32InRange(1, 3);
+
+  // Timeouts don't really work for fuzzing. Even a timeout of 0 milliseconds
+  // will be increased after the first timeout, resulting in inconsistent
+  // behavior.
+  config.timeout = base::TimeDelta::FromDays(10);
+
+  config.rotate = data_provider_->ConsumeBool();
+
+  // Doesn't currently seem to do anything.
+  config.edns0 = false;
+
+  config.use_local_ipv6 = data_provider_->ConsumeBool();
+
+  std::unique_ptr<DnsClient> dns_client = DnsClient::CreateClientForTesting(
+      net_log_, &socket_factory_,
+      base::Bind(&FuzzedDataProvider::ConsumeInt32InRange,
+                 base::Unretained(data_provider_)));
+  dns_client->SetConfig(config);
+  SetDnsClient(std::move(dns_client));
+}
+
+bool FuzzedHostResolver::IsIPv6Reachable(const BoundNetLog& net_log) {
+  return is_ipv6_reachable_;
+}
+
+void FuzzedHostResolver::RunLoopbackProbeJob() {
+  SetHaveOnlyLoopbackAddresses(data_provider_->ConsumeBool());
+}
+
+}  // namespace net